CGRO Cycle 8 Approved Program Abstracts
GRO-98-001 Mattox, John
We propose to use EGRET in cycle 8 to continue to time the
rotation of the Geminga pulsar. This observation is very
important for the following reasons: 1. Even with EGRET's
reduced sensitivity, this observation will serve to ``qualify'' t he
precise ephemeris we have developed with SAS-2, COS-B, and
1991-1997 EGRET data for continuing use. 2. The EGRET
timing residuals for 1991-1997 appear to have a sinusoidal
modulation that is consistent with a planet of mass 1.7/sin i
M_earth orbiting G eminga at a radius of 3.3 AU. The cycle 8
exposure alone cannot possibly confirm the planetary hypothesis.
However, it could serve to disprove it. 3. A braking index of 17
+/- 1 is found through a coherent analysis of the 24 yr baseline
provided by 1991-1 997 EGRET, COS-B, and SAS-2
observations. The cycle 8 observation together with the pending
June 2-16 cycle 7 EGRET observation will help to distinguish if
this is a manifestation of timing noise, or a reflection of the spin
GRO-98-003 Steinle, Helmut
In this joint proposal by all CGRO inument teams, a target of
opportunity observation with all four CGRO inuments is
proposed to measure the spectrum of the nearest active galaxy
Centaurus A in a state of ong gamma-ray emission. O bservations
of Cen A in the whole energy range covered by CGRO at such a
historically common, high intensity level, which has not been
observed by CGRO so far, would provide greatly improved
observation precision. They would provide tests of hypotheses co
ncerning intensity-dependent spectral evolution which were
advanced to explain the low and intermediate intensity level
observations made so far with CGRO. Similar proposals have
been accepted for previous cycles, but Cen A did not brighten
above the high threshold set.
GRO-98-004 Iyudin, Anatoli
The COMPTEL telescope on board the Compton Gamma-Ray
Observatory (CGRO) is capable of imaging gamma-ray line
sources in the MeV region at a sens itivity of about $10^{-5}$
photons/(cm$^2$s). Among such line emission sources of
interest an i mportant place is occupied by the classical nova,
which could produce aophysically significant fluxes of the \na
decay $\gamma$-ray line at 1.275 MeV. The nova shell expelled
by the thermonuclear runaway should be transparent to 1.275
MeV emission a few days after the nova explosion. On the basis
of Phase 1 and 2 data COMPTEL derived an average 2 \sig upper
limit for any neon-type novae in the Galactic disk o f the order of
3 $\times$ $10^{-5}$ \cms (Iyudin et al. 1995). We are confident
that we could do better, and for that reason we would like to
propose ToO observations with COMPTEL for any classical
nova with the distance $\le$1 kpc from the Sun, or with the
visual magnitude m$_V$ $\le$4.0.
GRO-98-005 van Parajijs, Jan
We propose to finish our analysis of the BATSE data base on the
Bursting Pulsar GRO J1744-28. Our results so far include
measurements of peak fluxes and fluences for all ~5500 bursts
detected during the two outbursts of the source, determi nation of
persistent and integrated burst spectra, and a detailed analysis of
the pulse phase delay during these bursts. We propose to finish
this project with detailed studies of burst spectral evolution, and
pulse phase spectroscopy and irregular variab ility within the
bursts, for the whole sample of 5500 bursts.
GRO-98-008 Catanese, Michael
We propose a Target of Opportunity Observation of a nearby
X-ray selected BL Lac object with CGRO in coordination with
the Whipple Observatory gamma-ray telescope and the Rossi
X-ray Timing Explorer when the object is in a high emission st
ate. Fifteen BL Lac objects, not previously detected above 300
GeV, will be monitored for high state activity by both the
Whipple gamma-ray telescope and the RXTE All-Sky Monitor.
The ToO would be triggered by observation of a high state in the
>300 GeV e mission as detected with the Whipple gamma-ray
telescope, if it lasts for at least one week. This technique yielded
spectacular results with Mrk 501 in 1997. By requiring an
extended high state before declaring the ToO, the probability that
a flare will b e detected with multiple telescopes is high. Such an
observation provides an excellent test of blazar emission models.
We submitted a very similar proposal in Cycle 7 that was
accepted but so far has not been initiated.
GRO-98-009 Iyudin, Anatoli
The discovery by COMPTEL of the $^{44}$Ti line emission at
1.16 MeV from the youngest known galactic SNR Cas A has
opened a new window for the investigation of SNR properties.
This discovery also shows a way that could help to uncover miss
ing remnants of young galactic SNe that might have occurred
some hundreds years ago and to improve our knowledge of the
Galactic SN rate from the past few hundred years. Contrary to
other wavelengths, in the gamma-ray band the Galaxy is almost
transparent , so that otherwise obscured supernovae remnant may
be detectable up to Av~10+3 in the gamma-ray line emission.
The direct way to complement historical observations of the
galactic SNe is to detect them by their $^{44}$Ti line emission.
Finding more SNR v ia their 44Ti line emission is important not
only for the global SN rate determination, but also provides an
excellent diagnostic of the still poorly understood SN explosion
mechanism itself.
GRO-98-013 Hurley, Kevin
We propose to use BATSE data, in conjunction with data from
the Ulysses and Near Earth Asteroid Rendezvous spacecraft, to
localize ~1 burst every 5 days throughout Cycle 8. For those
cases where only BATSE and Ulysses observe an event, the
resulting error box will consist of an annulus ~5' wide by several
degrees long on average. When NEAR also observes the burst,
we can get ~1'x20' error boxes in the best cases. We expect ~4
bursts/month to be observed by these 3 spacecraft. We will make
our results available to the wide community both by circulating
them via the Global Coordinates Network, and by posting them
on our web site.
GRO-98-014 Thompson, David
In order to extend the life of EGRET, the gas in the spark
chamber was allowed to deteriorate more than was originally
planned for the nominal two year Compton Observatory mission.
Gamma ray events are lost because the pattern recognition
software and analysis rules are not optimized for the poorer
quality data. By changing the software and analysis rules, we can
recover a significant fraction of the lost events, allowing
improved statistics for detection and study of sources. These
change s can help all users obtain maximum scientific return
from the EGRET data.
GRO-98-017 Bloemen, Hans
We propose to complete a deep COMPTEL exposure of the
Orion/Monoceros region (3 x 3 weeks). This proposal is an
update of our Cycle-6 and Cycle-7 proposals, for which 8 weeks
of observing time could not be scheduled. Two weeks were lost
du e an AGN ToO observation and the reboost in 1997. We wish
to reduce the ong asymmetry in the currently available exposure
and obtain a set of observations that is less influenced by the
Crab. The study of emission from the Orion/Monoceros region
may be ongly influenced by this exposure asymmetry because it
produces a large gradient in the inumental background in the
region of interest.\ \ Recent studies show that at least part of the
emission previously seen from Orion is due to inumental back
ground lines. Therefore, the observations proposed here are of
crucial importance now to study emission at the lower flux level.
GRO-98-019 Bertsch, Dave
EGRET observed a series of four large flares in June 1991 and
showed that gamma rays were emitted by the Sun to over 2 GeV
and the emission persisted for over 8 hours. The observations
indicate protons and electrons were produced with spec tral
indices of about 3, and that continual or episodic acceleration
with efficient storage was required. In view of the important new
information on solar flare cosmic ray production and storage
processes afforded by the early mission observations, and t he
expectation that other large flares will add new insights, we
propose to analyze all Phase 8 solar flares that occur in the field
of view of EGRET, and to investigate all flares that are detected
in the energy calorimeter. A target of opportunity is re quested
under specific circumstances.
GRO-98-020 McConnell, Mark
Although observations of soft X-ray transients with CGRO have
provided a wealth of information about the hard X-ray emission
of these sources, observations of spectra near 1 MeV are limited.
Based on experience with Cyg X-1, such observati ons would be
valuable in our efforts to understand the high energy spectrum.
Even a single significant datapoint near 1 MeV, when combined
with lower energy data, could prove useful (c.f., GRO
J0422+32). COMPTEL is capable of providing such data.
Unfortun ately, past COMPTEL observations of XRTs are
limited in number, and often so limited in exposure that no
detection was possible. We propose long exposure observations
with COMPTEL of any new XRT which becomes visible during
cycle 8 and which is likely to be detected by COMPTEL. We
also propose to continue the analysis of archival COMPTEL data
from previous XRT events, some of which show evidence for
detectable emission.
GRO-98-021 McConnell, Mark
We have previously generated the first all-sky map at 2.2 MeV
using 5 years of data from CGRO/COMPTEL. Although
generally featureless, the map does show one source (GRO
J0332-87) at a significance level of ~4 sigma. One possible
counterpar t is RE J0317-853, a unique DA white dwarf star with
both an unusually high temperature (~50,000 K) and an
unusually ong magnetic field (~340 MG). We speculate that the
2.2 MeV emission arises through some type of flaring process,
although the exact me chanism remains unclear. For Cycle 7, we
were awarded two weeks of observation time with both
COMPTEL and OSSE that will take place in June, 1998.
Meanwhile, we have been made aware of an unpublished
observation of a 6 cm radio flare from RE J0317-853 tha t
provides further evidence for episodic activity. We therefore
propose to repeat the COMPTEL/OSSE observations of this
region during cycle 8, regardless of the results from the cycle 7
GRO-98-022 Weidenspointner, Georg
A principal goal of COMPTEL is to study the Cosmic Diffuse
Gamma Ray Background (CDG). Knowledge of the energy
spectrum and the spatial homogeneity of the CDG may provide
conaints on models that attribute the CDG to a truly diffuse orig
in or to the integrated emission of unresolved point sources. The
galactic north and south pole regions are of prime importance for
the analysis of the CDG because of the low galactic diffuse
emission and the presence of only a few point sources. The expo
sure coverage of the galactic south pole is significantly lower and
far more inhomogeneous than at the galactic north pole. Three
observations with a total duration of only 11 weeks would result
in a homogeneous coverage of the galactic south pole with a
depth comparable to that at the galactic north pole. This would
significantly improve the analysis of the energy spectrum and the
homogeneity of the CDG, as well as of the galactic diffuse
emission.
GRO-98-023 Schoenfelder, Volker
A principal objective of the COMPTEL inument is to study the
large-scale Galactic emission, both diffuse and from discrete
sources, and in both continuum and lines. The presence of other
components is however likely, and it is a princip al goal to
identify correctly the aophysical origins of the observed
emission. In addition full sky mapping using the entire
COMPTEL database provides a global picture of the steady
discrete sources and is important for identifying potential new
candia te sources. The accuracy and reliability of these analyses
depend on deep and uniform exposure coverage. The combined
exposure and quality of data from Cycles 1-7 is extremely
non-uniform even in the Galactic plane.. We therefore propose a
comprehensive s et of pointings designed to yield a more
homogeneous coverage of the Galactic plane.
GRO-98-025 Sreekumar, Para
The spark-chamber tracker of EGRET has traditionally been used
to examine photons that arrive within 30 deg of the central
pointing axis (z-axis). However, the inument is capable of
detecting events incident at even larger angles. Thoug h the
effective area is significantly reduced, it is not negligible. Since
the raw data from EGRET retains photons beyond 30 deg, it can
be used to monitor and study extremely bright sources over a
much larger region of the sky. Using events with directio ns upto
50 deg from the central pointing direction, allows an increase of
~3 in the total sky coverage during the first 4.5 years of the
CGRO mission when the average EGRET detection efficiency
was high and the inument was configured to operate in the full
FOV mode. The most exciting promise of this analysis is in the
new capability to detect previously unknown large flares from
gamma-ray point sources and to generate new data for duty cycle
studies.
GRO-98-027 Hernanz, Margarita
Detection of gamma-ray emission from classical novae, in the
range between 30 and 511keV, would provide a crucial test of
the thermonuclear runaway (TNR) model. This emission is a
result of the annihilation of positrons, emitted by some ra
dioactive nuclei (such as 13N and 18F) synthesized during the
TNR; it has short duration and is produced before the optical
maximum. Therefore, it can only be analyzed "a posteriori", once
the nova has been discovered optically. The capability to observe
all the sky, together with its high sensitivity in the low-energy
range, make BATSE an ideal inument to detect this emission. In
this proposal we suggest a systematic search in BATSE
background data (for nearby novae that have exploded since
CGRO launc h) for emission in the range 30-511keV, as well as
an analysis of the new novae during the upcoming cycle. Data
analysis techniques that have been applied for BATSE
observation of 511keV transients of short duration will be ap
GRO-98-028 Kouveliotou, Chryssa
BATSE has produced a unique data base on the bright black-hole
candidates Cyg X-1, GX339-4, GRO J0422+32, GRO J1719-24,
and GRO J1655-40; new transient black-hole candidates are
discovered at a rate of about one per year. We propose (i) to
complete our study of Cug X-1 and GRO J0422+32 with the
analysis of triggered and single sweep data from these sources
(ii) to continue our successful study of the temporal (fast
variability in a frequency domain of 4mHz to 30 Hz) and spectral
(20 to 300 keV) behavior of future outbursts of the four transient
sources over a wide range of luminosities and spectral states, and
(iii) to expand this study to include new transient sources
detected with BATSE in the future. Our studies cover an
unprecedented t ime span of months to years.
GRO-98-029 Leising, Mark
We propose CGRO/OSSE observations in Vela to confirm the
COMPTEL detection of 44Ti line emission from that region, to
test whether the possible SNR G266.2-1.2 is the source of that
emission, and to help determine better the flux in the gam ma-ray
lines. We request eight weeks of OSSE exposure to achieve these
objectives.
GRO-98-030 Nemiroff, Robert
All known types of objects at cosmological distances have been
seen to undergo a gravitational lens effect except GRBs. Given
even conservative cosmological distance estimates for about
2500 BATSE detect GRBs through Cycle 8, there is abou t a
30% chance of finding a gravitational lens effect caused by the
known galaxy field. A null detection limits the maximum
average redshift of a GRB and even cosmological parameters.
Previous searches provided interesting limits on models that
indicate h igh GRB redshifts, and, assuming even conservative
redshifts, on the cosmological constant. Lens searches may be
indicating something definitive about GRBs, and useful about
our universe. We propose to continue our search for a
cosmological abundance of d ark matter ranging from 1E-15 to
1E12 solar masses. Previous CGRO searches led by the PI have
yielded methodology and software than can be used in a Cycle 8
search.
GRO-98-031 van Paradijs, Jan
We propose to make a joint spectral analysis of GRBs in the
BATSE data base which are located within the fields of view of
either the SAX WFCs or the ASM on RXTE. We have already
developed the software necessary for the proposed analysis a nd
we recently received data for two SAX and one ASM burst. The
very broad-band spectral coverage obtained this way will allow
us to test physical models of GRB spectra, determine the number
and energy diibution of spectral breaks, improve the search f or
cyclotron lines by better defining the spectral continuum, test
whether X-ray tails are a seperate emission component or result
from spectral evolution of the main component, and investigate
the relation between the spectral softening seen in many GRBs
and their recently discovered low-energy afterglow.
GRO-98-032 The, Lih, Sin
The COMPTEL detection of Ti44 1.157 MeV line flux of
(4.8+-0.9)e-5 ph/cm**2/s in the Cas A SNR is an exciting
discovery of CGRO. Gamma ray observations of Cas A provide
the unique opportunity to measure the synthesis and ejection of a
spec ific isotopes from the innermost part of a single supernova.
However, the situation regarding the line flux and therefore the
Ti44 mass synthesized appear to be unsatisfactory with OSSE
and HEXTE have not been able to confirm the COMPTEL's
detection. We p ropose a twelve week OSSE 4-detector Cas A
observation to obtain at least 3sigma detection of Ti44 decays
with a flux of 4.2e-5 ph/cm**2/s in the 68 & 78 keV and 1.16
MeV lines. We will combine all OSSE data with Cas A data
from HEXTE measurements expecti ng at the end a 1sigma
uncertainty in the flux of ~9e-6 ph/cm**2/s or ~5e-5 Msun in the
mass of Ti44.
GRO-98-034 Steinle, Helmut
We propose to monitor the Sun approaching the solar maximum
during two long duration observations, each lasting 6 weeks. We
limit our data request to the solar data (from COMPTEL,
EGRET OSSE) that are needed to analyze the gamma-ray and ne
utron emission of up to three solar flares, which occur during
each of those observation periods, leaving a wealth of solar data
to other proposers. The pointing of CGRO during those two
observations will be such, that two regions on the sky will be
obser ved which have so far not been observed with dedicated
pointings, thus completing the COMPTEL all-sky-survey.
COMPTEL will observe the two regions continuously, whereas
the EGRET spark chamber will be switched on only if major
flares occur and OSSE will b e moved to view the Sun in such
cases. By combining solar observations and the completion of the
COMPTEL sky-survey, the best use of CGRO time is made
during these long observations.
GRO-98-039 Diehl , Roland
COMPTEL 1.809 MeV measurements have shown an image of
26Al source regions along the plane of the Galaxy, where the
inner Galaxy clearly dominates the all-sky 26Al emission. But
more interesting new features have been discovered, in particu lar
substantial emission from regions not in the inner Galaxy. The
inner Galaxy and bulge may not dominate the Galactic 26Al
production as much as expected initially. Localized source
regions more nearby may provide an important clue to
contributions from secondary sources. COMPTEL's images
show promising features in the anticenter region at low
significance and intensity, which are typically indicative of
extended emission. Those may be nearby emission regions
associated with the prominent molecular clou ds of Cepheus,
Perseus, and Taurus. We propose to improve exposure in this
region far away from the confused inner-Galaxy region, and
hence more plausibly identified with source regions of rather
GRO-98-044 Collmar, Werner
The detection of gamma-ray emission from blazars by the CGRO
experiments has provided new and important insights in the
emission processes of blazars in general. It is believed that in
blazars the non-thermal continuum from X-ray to gamma- ray
energies is due to Comptonisation of soft photons by relativistic
jet electrons. However many questions remain unanswered, e.g.
the nature of the soft photons, time correlations between different
high-energy wavebands. We propose simultaneous gamma-ra y
and X-ray observations of selected, time-variable gamma-ray
blazars (3C 273, 3C 279, PKS 0528+134) to simultaneously
determine their high-energy properties. Especially to investigate
the relationship between soft X-rays, hard X-rays and
gamma-rays by co mparing measurement covering different X-
and gamma states. Such multifrequency observations should be
carried out as long as functional gamma-ray detectors are still in
operation.
GRO-98-045 Diehl, Roland
The COMPTEL 1.809 MeV measurements have shown
substantial emission from regions far away from the inner
Galaxy, the Vela and Cygnus regions: Here a unique calibration
of nucleosynthesis models for the candidate source types appears
possibl e, since the morphology and the object populations in
those regions are known to much better precision than in the
inner Galaxy. In particular, a limit on 60Fe emission could
conain SNII versus WR stars. For Cycle-7, a largely identical
proposal was ac cepted, yet only 14 out of the requested 56 days
of observation were scheduled. We propose to perform dedicated
observations of the Cygnus region. We expect to separately
identify emission from the Cygnus superbubble, and foreground
WR stars, and be able to assess the Cygnus region
nucleosynthesis history from 26Al conaints as combined with
other recent observations of the region, e.g., in CO and X rays.
GRO-98-046 Grove, Eric
We propose broadband TOO observations of the black hole
candidate GX339-4 in the X-ray high/soft state. High-sensitivity
gamma-ray observations of this source have never been made in
this spectral state. The broadband spectral studies will determine
physical processes in the source, which we will contrast with our
recent studies of simultaneous Ginga/OSSE observations of
GX339-4 and Cyg X-1 in the X-ray low/hard state. OSSE
observations alone will measure or set a lower limit on the break
energy of the gamma-ray power law expected in the high/soft
state.
GRO-98-047 McConnell, Mark
We have recently generated the first consistent broad-band
spectrum of Cyg X-1 using contemporaneous data from
COMPTEL, BATSE and OSSE, thus providing a valuable
cross-calibration of these three experiments. This gives us the
confidence to proceed with generating additional broad-band
CGRO spectra. Of particular interest is the nature of the spectrum
near 1 MeV, for which COMPTEL data is most useful. In
producing broad-band spectra, the COMPTEL statistics can be
increased considerably by r elaxing the requirement for
contemporaneous OSSE data and using only COMPTEL and
BATSE data. For this purpose, we can use BATSE spectra
generated with both standard occultation analysis and with the
JPL-EBOP analysis. We propose to generate such broad-ban d
spectra for various spectral states of Cyg X-1. These data would
provide useful input to theoretical models for the broad-band
emission and perhaps offer some insight as to the nature of the
GRO-98-048 Grove, Eric
We propose target of opportunity OSSE observations of bright
(exceeding half Crab) transient emission from X-ray pulsars.
Through phase-averaged and phase-resolved spectroscopy, we
will address the following issues. (1) Search for complex
spectral features, such as cyclotron lines and/or the emergence of
an underlying hard component. (2) Determine the pulsed
lightcurves and pulsed fraction as a function of energy. (3)
Determine the spectral and pulse-period evolution through the
peak and d ecay portion of an outburst. This is a resubmission of
an expired GRO Cycle 4-6 multiyear and Cycle 7 proposal that
resulted in the discovery of a 110 keV cyclotron line in
A0535+26 and pulsar phase lags durings bursts of GRO
J1744--28.
GRO-98-052 van Paradijs, Jan
We propose to continue our search of the BATSE data base for
gamma ray bursts (GRBs) and other transients that did not lead to
an onboard burst trigger. We have developed a complete search
and analysis system which we have used to examine 2200 days
of data. The resulting preliminary catalog of untriggered events
contains 906 GRB candidates, 13 likely bursts from SGR
1806-20 and/or SGR 1814-13, 2405 solar flares, and 318
low-energy (25--50 keV) events of unknown origin. Our off-line
search is sensitive to GRBs with peak fluxes lower by a factor of
2 than can be detected with the onboard burst trigger in its usual
(5.5 sigma, 50--300 keV) configuration. This research will
increase the number of GRBs detected with BATSE by 40--50
percent and it will provide a catalog of transients of unknown
origin. The catalogs we produce will be made available to the
public via the World Wide Web.
GRO-98-054 Thompson, David
We propose to continue analyzing both archival and new
gamma-ray burst spectra using the EGRET NaI (TASC) detector,
sensitive in the range 1 to 200 MeV. Because the TASC is
omnidirectional, bursts can be detected far beyond the nominal
EGR ET field of view; preliminary analysis indicates that the
wide-angle analysis doubles the number of bursts that EGRET
can detect at high energies. The 1-200 MeV spectra will be
studied for temporal trends within a burst and will be combined
with data from other inuments to produce broad-band spectra.
GRO-98-055 Hartman, Robert
To improve understanding of physical processes in blazar jets,
which can produce large observed luminosities of gamma rays,
we propose Targets of Opportunity (ToO's) to observe
gamma-ray emission correlated with exceptionally bright emissi
on in lower frequency bands. The objective of this work is to
determine the time delay of correlations between short-term
(~day) variations in different bands, and thus to limit possible
emission mechanisms. The objects selected for consideration
either h ave demonated previous bright high-energy gamma ray
flares, or are EGRET-detected and well-monitored at lower
frequencies. A ToO trigger could arise from an exceptionally
bright and rising state in either the optical or submm band. In
addition, we prop ose that a ToO extension be added to any
CGRO blazar observation (regardless of PI) which shows the
object to be in a very high gamma-ray state. In that case, we
propose to share the ToO extension data with the PI for the sche
GRO-98-056 Strickman, Mark
The presence of a hard X-ray tail from the bright low-mass X-ray
binary Sco X-1 has long been a source of controversy. We have
recently detected a hard X-ray tail from Sco~X-1 using OSSE on
CGRO. For CGRO Cycle 7, we proposed to study the behavior
of this tail in more detail with a longer OSSE observation,
performed in conjunction with a multiwavelength campaign.
Although highly rated, scheduling difficulties prevented
implementation of this program. Hence, we are reproposing our
plan to l earn more about the morphology of hard X-ray
variability from Sco X-1 and how it correlates to behavior in
other bands. Using this information, we will interpret the data in
the light of a number of models that currently predict hard X-ray
emission from l ow-mass X-ray binaries.
GRO-98-057 Meegan, Charles
Population studies of gamma-ray bursts are sensitive to trigger
biases in the BATSE burst catalog. Conflicting conclusions about
these biases have been published. We propose to perform a more
complete study of trigger biases arising from i numental effects,
including the effects of triggering on statistical fluctuations (the
peak counts bias) and the bias against "slow risers". We will
examine Malmquist biases to clarify the assumptions on which
they are based. The goal of the proposal i s to provide more
accurate efficiency corrections and to enable users of BATSE
data to understand how the various biases may affect their
analyses.
GRO-98-060 Wilson, Colleen
We propose to do a pulse timing study of the long period
accretion powered X-ray pulsars 4U 1145--619 and A1118-619.
We will develop an algorithm which will improve the sensitivity
for long period pulsars of the existing pulsed monitor by
reducing systematic effects produced by Earth occultations of
bright sources and bright Vela X-1 pulses. With this improved
sensitivity we will search for previously undetected outbursts
from both sources and analyze known outbursts. We will
generate puls e profiles and histories of pulse phase, frequency,
and intensity. We will search for pulse shape changes during
outbursts for both sources and among outbursts for 4U
1145--619. For both systems, we will attempt an orbital analysis
and search for correlat ions between torque and intensity.
GRO-98-061 Dingus, Brenda
We request the equivalent of approximately one week of EGRET
viewing time to study the highest energy emission from
gamma-ray bursts. EGRET will turn on the spark chamber
tracking detector for 10,000 seconds upon receipt of a BATSE
generat ed trigger of a bright burst within 40 degrees of the
EGRET axis. This mode of operation has been used since Cycle
5 with a current average rate of one BATSE trigger every 17
days. All recent COMPTEL burst detections have been observed
by EGRET with this trigger. For all bursts with spectra
determined by COMPTEL, EGRET fluxes and upper limits show
no evidence of any high energy cut off. The average spectrum
measured by EGRET is as hard as measured by COMPTEL.
Improved spectra and temporal evolution studie s are planned
with archival analysis of EGRET spark chamber events which do
not pass gamma-ray cuts but are clearly associated with bursts.
GRO-98-067 Kippen, R. Marc
The ability to localize gamma-ray bursts is one of BATSE's
greatest engths. Unfortunately, BATSE locations currently lack
the precision needed for counterpart searches and investigations
of small-angle properties. A significant part of this imprecision
is due to the fact that the localizations are approximated by
circular "error boxes." We propose to study and implement an
improved characterization that would more closely preserve the
true asymmetrical nature of BATSE burst localization s, thereby
reducing systematic errors. The improved characterization will be
provided for all past and future BATSE GRBs, and will be
incorporated into the BATSE Rapid Burst Response system for
use in rapid counterpart search efforts. A particularly impor tant
aspect of our investigation is that it will improve the locations of
weak bursts. BATSE is currently the only inument capable of
studying such events.
GRO-98-073 Ulmer, Mel
Pulsars are highly magnetized, rotating neutron stars, and
although they were discovered over 25 years ago, we still do not
understand how pulsars shine and why some pulsars are bright
gamma-ray sources. This proposal this to continue the search for
hard X-ray/gamma ray emission from isolated known radio
pulsars. This proposal is to apply this search to archival data
only. These results will be used to derive models for the
gamma-ray emission from isolated pulsars. The models will
include the dependence of the radio pulsar beaming direction
toward the earth derived from polarization measurements. We
will also delimit the beam width and beam intensity by using the
the statistics of how many pulsars are detectable versus how
many were observ ed.
GRO-98-078 Paciesas, William
We propose to continue our Cycle 7 project to produce and
maintain a comprehensive set of catalogs of BATSE gamma-ray
burst spectra that will be of general use to the aophysical
community. The catalogs will make use of the wide range of
BATSE data types and allow convenient access to deconvolved
spectra and corresponding standard model functional fit
parameters with various combinations of time and energy
resolution. The catalogs will be delivered to the CGROSSC for
dissemination, and w ill be updated regularly as new burst data
come in.
GRO-98-079 Brainerd, Jerome
We propose a continuation of the study of whether the BATSE
gamma-ray burst E-peak diibution is a consequence of inumental
effects, and whether the true diibution of E-peak has a
characteristic value of approximately 200 keV. In r esearch
conducted under CGRO Cycle 7 funding, we derived the BATSE
burst trigger efficiency as a function of E-peak for different
trigger energy ranges. Under the current proposal, we will
determine the systematic error in deriving E-peak, examine the
eff iciency of BATSE to detect soft sources such as SGRs and
hard sources such as TGFs, compare the burst characteristics
derived by BATSE to those derived by Comptel, and compare
model diibutions of E-peak with the observations to place limits
on the intr insic E-peak diibution.
GRO-98-081 Pendleton, Geoffrey
We consider several distinct models for the production of
gamma-ray bursts at cosmological distances. All of these models
are capable of producing spectra with significant high-energy
emission, as well as spectra where the high energy emis sion is
suppressed. However, these models predict distinctly different
correlations between several spectral observables during periods
of rapid high-energy spectral evolution. We propose to identify a
population of emission peaks in GRBs that exhibit spe ctral
transitions from significant emission above 300 KeV to a marked
lack of high energy flux. We will then perform spectral fits to
contiguous intervals spanning the emission peaks to quantify the
evolution of spectral parameters across the peaks. The r esulting
ensemble of high-energy spectral evolution data will be
compared to the model predictions to see which is preferred by
the data.
GRO-98-085 Kanbach, Gottfried
We propose to observe PKS 0208-512 for 3 weeks with EGRET,
COMPTEL and OSSE. PKS 0208-512, a bright, isolated
high-energy blazar, was observed previously only twice in the
central field of view. It shows ong variability, the high-energy
spectra are hard and show evidence of shape variations with
intensity up to a spectral break at 4 GeV. COMPTEL detected
PKS 0208-512 with a ong spectral excess at 1-3 MeV in several
epochs ('MeV-blazar'). OSSE has not yet observed the source.
Measurem ents at a new epoch will shed light on two competing
models which try to explain the multi-component spectra: (1) a
blue shifted, broadened annihilation line from a relativistic pair
plasma superimposed on a Compton continuum, or (2) multiple
Comptonisati on components from differently energized
particles. Both models lead to distinct predictions for the spectral
components' shape, variation, and correlation.
GRO-98-088 Mukherjee, Resmi
The proposal requests EGRET and COMPTEL data rights for the
blazar PKS 0528+134 if an observation of the galactic anticenter
region is made by EGRET. Such an observation may be
scheduled for EGRET calibration purposes. We propose to
monito r PKS 0528+134 to check for gamma-ray flares. If PKS
0528+134 is found to be flaring, we propose to request a target of
opportunity extending the EGRET observation by a week. In the
event of a gamma-ray flare in PKS 0528+134, the observations
may provide us with the last opportunity to study short time
scale flux variations correlated with observations at longer
wavelengths.
GRO-98-091 Preece, Robert
This project will examine the detailed behavior of the gamma-ray
burst low-energy continuum, by analyzing a large sample of
bright archival and Cycle 8 events, using joint spectral fits
between the BATSE Spectroscopy Detector discriminator and
LAD high energy resolution data. We wish to determine if there
exists a separate class of `low energy' bursts in the population of
low E_peak events, as suggested in observations by Ginga. With
the improved statistics available in this study, these m ay be
found to be merely an extension to the already well-determined
log-normal diibution of E_peak. Another outcome will be to
determine the existence of an additional continuum feature in the
form of a second, low-energy break. At the same time, we e
xpect to complete the Cycle 7 project investigating the
time-resolved spectroscopy of the X-ray excess that was
previously found in 15% of all bursts.
GRO-98-094 Finger, Mark
We propose a systematic study of accreting pulsars using
BATSE. The full sky will be monitored daily for pulsars with
spin frequencies between 2 mHz and 0.5 Hz. Her X-1 will be
monitored during Main High states. Quick-look estimates of the
flux and frequencies of all detectable pulsars will be provided on
the world-wide web, and refined measurements will be provided
in updates to the long-term pulsar histories and databases
currently available through the Compton Observatory science
suppor t center. We propose in-depth studies of transient pulsars,
Her X-1, Cen X-3, OAO 1657-415, and Vela X-1.
GRO-98-096 Zhang, Shuang
We propose to conduct a comprehensive multiwavelength
campaign of the peculiar candidate black hole binary system
GX339-4, which has displayed four spectral states (off, low, high
and very high), and is capable of producing multiple hard X -ray
outbursts with relatively short intervals. An unusual optical/X-ray
anti-correlation was also observed from it, similar to that seen in
the superluminal jet source GROJ1655-40. Recently a radio
jet-like feature was also seen from it. It is thus an id eal
laboratory for studying these important aophysical issues:
transient source outbursts, hard X-ray production, spectral state
transitions, and radio emission, including jet formation. The
proposed observations consist of: a) long term radio, optical ,
X-ray and hard X-ray monitoring; and b) TOO observations of
OSSE (gamma-ray), ATCA and VLBI (radio).
GRO-98-097 Connors, Alanna
We propose to maintain and continue to upgrade the ongoing
Rapid Burst Response (RBR) program of COMPTEL, CGRO's
MeV-range imaging telescope and transient spectrometer. We
provide 1-2 degree localizations (as well as MeV light-curves)
with in a few to 45 minutes after burst onset for one burst every
few months. These act as triggers for prompt repointing of other
high energy satellites, in concert with BATSE-RBR and
sometimes RXTE/ASM or IPN positions; as well as for
ground-based observatio ns. Theories of gamma-ray burst and
afterglow emission are still poorly conained. Near real-time
multi-wavelength observations can help distinguish which
physical mechanisms are key. We emphasize that these are
possible, with the help of these RBR syst ems. Not only at high
energies, but optical/IR - from the burst itself or directly after,
not the delayed afterglow tail - may be detectable ~minutes after
burst onset by systems either on-line now or soon during the
GRO-98-101 Harmon, B. Alan
The Earth Occultation Team (EOT) at Marshall Space Flight
Center routinely performs all-sky monitoring and detection tasks
for the Burst and Transient Source Experiment (BATSE). The
current effort includes monitoring $\sim$100 ong hard
X-ray/low energy gamma ray sources in the 20 keV$-$2 MeV
energy range with the Large Area Detectors, and occasional
detection and characterization of new or unusual transient
behavior. Beyond the quick-science analysis activities of the
EOT, we propose to enhance several aspects of this work during
Cycle 8: (1) Continue production of a source catalog paper, (2)
continue expansion of Web access to Earth occultation
monitoring information, (3) refine the galactic plane imaging
technique, and (4) initiate ge neral improvements to the
monitoring capability.
GRO-98-102 Fishman, Gerald
We propose to continue an approved Cycle 7 Guest Investigation
to re-point CGRO as a Target of Opportunity (ToO) in response
to ong gamma-ray bursts. The Cycle 7 ToO has not yet been
carried out. Even though the proposal was rated outst anding
(4.65), only one observation was approved, out of four requested.
In the past year six additional x-ray afterglows have been
detected from gamma-ray bursts. In addition, there have been
theoretical models published (cf. Bottcher; Vietri) that predi ct
high-energy, delayed gamma-ray burst emission from proton
synchrotron radiation and pion decay. In one model, the flux
estimates are within an order of magnitude of the EGRET
sensitivity. In view of the large model uncertainty and EGRET's
detections of delayed emission from at least two GRBs, the
prospects are moderate for a positive ToO observation. Thus, we
believe that there is new justification to continue this
investigation with three additional ToOs.
GRO-98-103 Perlmutter, Saul
BATSE has the potential to provide an order of magnitude more
OTs than are currently being discovered with the BeppoSax
satellite. With such a large sample of OTs, the diibution of
properties would challenge current models, and the brig hter and
longer OTs would likely permit breakthroughs with low-noise
spectra, detailed host studies, polarimetry, etc. BATSE/GCN
alerts also permit the study of optical emission on time scales
approaching that of GRBs. We will tap these potentials with ou r
5deg field telescope & CCD, which already respond
automatically to GRBs. Our automation for nightly operation is
nearly complete, and our sensitivity to previous OTs is already
demonated. We expect to provide 20-41 images of GRB
positions, yielding ~ 5-10 OT discoveries/year. More than 5
positions will be imaged/year within 20 sec of gamma emission
with V>17.7 mag sensitivity in 10 sec. Continued GRO support
will yield discoveries starting Sept.-Dec. 98.
GRO-98-104 Stacy, J. Gregory
Data-analysis software tools have been developed by the
CGRO/COMPTEL inument team to produce all-sky
maximum-likelihood maps using data acquired over the entire
CGRO mission. We propose to exploit this new capability to
produce a more complete set of COMPTEL
maximum-likelihood all-sky maps, using improved
inument-response functions and refined event-selection criteria.
With these all-sky maps we intend to extend our ongoing study
of the properties of active galaxies and other known a nd
candidate gamma-ray sources lying at high Galactic latitudes.
Our scientific objective is to derive the global properties of such
gamma-ray sources in the medium-energy gamma-ray regime,
and to provide cumulative fluxes or limits in the COMPTEL
energy range for all high-latitude sources of general interest.
These time-averaged results will also be compared with source
studies for individual CGRO viewing periods carried out by us
GRO-98-105 Zhang, Shuang
We propose to renew our cycle 7 proposal to continue daily
monitoring and search archival data for hard X-ray emission
from X-ray bursters using BATSE. For cycle 8, we also propose
to include all X-ray bursters discovered with the SAX/WFC. We
have discovered hard X-ray emission above 50 keV from several
X-ray bursters in previous cycles. It is now established that X-ray
bursters can also produce hard X-ray emission that is ikingly
similar to that from black hole X-ray binaries. Studying the
similarities and differences of these two classes of systems is an
integral part of our investigation. We have also been carrying out
correlated investigations with XTE, SAX and OSSE. Our
on-going monitoring program has already triggered our TOO
obse rvations with XTE and SAX. These broad band
investigations are expected to improve significantly our
understanding of the nature of hard X-ray emission from these
systems.
GRO-98-107 Tavani, Marco
We iterate for Cycle 8 our approved program for TOO
observations of new gamma-ray transients in the Galactic plane
approved for Cycle 7. We propose to study new gamma-ray
transients (GRTs) with no radio-loud blazar-like counterparts
locali zed near the Galactic plane. The nature of these sources
(Galactic vs. extragalactic) and the mechanism of high-energy
emission is currently unknown. We request non exclusive
EGRET, OSSE, COMPTEL and BATSE data rights for all GRTs
of gamma-ray flux above 1xE(-6) ph./cm**2/s within +/- 30
degrees of Galactic latitude, and exclusive data rights for the first
GRT detected during Cycle 8. EGRET quicklook analysis will be
used to trigger rapid follow-up multiwavelength studies. We will
request a GRO TOO observ ation in case EGRET detects a new
GRT of flux above 2 x E(-6) ph./cm**2/s.
GRO-98-108 McConnell, Mark
We propose to analyse and interpret gamma-ray burst (GRB) data
using both the telescope mode data and the single detector burst
mode data from COMPTEL. Collectively, these data span the
energy range from 300 keV up to 30 MeV. The first goa l of our
proposal will be to perform a standard analysis for each
significant GRB event seen by COMPTEL. This includes GRBs
that are registered by the telescope mode data as well as GRBs
that are registered only in the burst mode data. We would also
defin e a set of standard data products (including deconvolved
photon spectra) that, for each detected GRB event, would be
made available via the COMPTEL GRB Web Page. The second
goal of our proposed program will be to perform more detailed
studies of selected GRB events. This would represent a
continuation of past GRB studies by the COMPTEL team.
GRO-98-112 McCollough, Michael
We propose a target of opportunity observation (ToO) of a major
flare of the relativistic jet source Cyg X-3. We will obtain data
from BATSE, OSSE, and COMPTEL throughout the
observation. This will give us coverage from the hard X-ray to t
he soft gamma-ray for the entire ToO. In addition, during the
radio flare we will obtain hard gamma-ray measurements from
EGRET. These observations will be triggered based on hard
X-ray and radio monitoring observations.
GRO-98-116 Kouveliotou, Chryssa
During the first 7 years of its operation, BATSE detected
recurrent emission from two of the three known SGR sources,
SGR 1900+14 (once) and SGR 1806-20 (thrice). The third
reactivation of the latter source initiated a TOO with RXTE,
which resulted in the first unambiguous detection of a ongly
magnetized (B>1E14 G) pulsar associated with an SGR, which
ongly supports the magnetar model for SGRs. We propose to
continue our succesful SGR project by: (i) a search for evidence
for Global Seismic Oscillations following SGR bursts in the
BATSE data, and (ii) combining the spectral data from BATSE
and the RXTE/PCA to make a detailed time-dependent spectral
analysis of SGR events.
GRO-98-118 Barthelmy, Scott
We propose (1) to continue to operate the BATSE Coordinates
Diibution Network (BACODINE), (2) to improve the GRB
location accuracy & (3) aggressively pursue new customers &
modify the operation to meet the customer's needs. BACODINE
(no w part of GCN) is a system that calculates GRB locations
from the BATSE telemetry data in real time & diibutes those
positions to inuments to make multi-band follow-up observations
of GRBs in real time (less than 6 seconds) while the GRBs are
still bursting. The SAX observations have shown that
near-realtime follow-up observations are critical to counterpart
identification. The growing & improving ensemble of
BACODINE site inuments are setting ever more ingent upper
limits at ever shorter time delays. BACODINE facilitates
observations in the time domain shorter than are possible with
the SAX locations. Continued operations will improve these
limits & allow for more counterpart identifications.
GRO-98-120 Mitrofanov, Igor
The concept of emission time tau50 is suggested, as a
complementary temporal parameter to the classical parameter of
duration T50. It is defined as time of emission of 50\% level. We
perform the test of the bimodality of bursts using tau50 and
study the diibutions of tau50 and duty cycle tau50/T50 for
different intensity groups of bursts. Parameters tau50*, Ep* are
also implemented for each burst, as emission time measured at
spectral peak energy and peak energy measured along correspon
ding emission time. Using these parameters and the product
(tau50* x Ep*), as the cosmological invariant, we test effects of
hardness/duration/intensity correlation. The hypothesis is
checked that emitters have standard diibutions at different
red-shif ts. The luminosity dependent properties are studied in
comoving frames. The evolutionary effects of emitters at
different red-shifts are also investigated.
GRO-98-124 Briggs, Michael
Current cosmological models for the origin of gamma-ray bursts
place even the brightest bursts at redshifts affected by spatial
curvature. Consequently, cosmological signatures such as
spectral redshifting should be apparent even among the brightest
bursts, the bursts which fall on the brightness diibution's -3/2
power law component. Under the revised cosmological
interpretation, the -3/2 power law is not due to a homogeneous
diibution of sources, but rather to a balence between an e volving
source density and cosmological spatial curvature. We propose to
use BATSE data to determine whether the hardness-intensity
trend observed between the brightest and dimmest bursts
continues among the brightest bursts.
GRO-98-127 Dixon, David
Recent work has indicated that the diibution of Al26 is perhaps
not as clumpy as shown in Maximum Entropy maps of
COMPTEL 1.8 MeV data (Kn\"odlseder 1997). We propose to
continue this study, using wavelet techniques to make improved
map s and statistically quantify the smoothness of the Al26
diibution as seen by COMPTEL.
GRO-98-128 Matz, Steven
By using a rapid slewing response system to promptly (10--100s
after trigger) observe burst positions calculated on-board GRO by
BATSE, the OSSE inument has discovered persistent gamma-ray
burst emission >100 keV with power-law decays. These
detections demonate OSSE's unique capability to extend the
study of burst afterglows to the primary energy range of the burst
itself, and to times near to the trigger. We propose to continue the
operation of the rapid response system and analysis of these slew
observations (1--2 events per month) as well as any serendipitous
burst detections (0.5--1 events per month). These observations,
combined with data at other wavelengths, will form a more
comprehensive picture of the afterglow phenomenon, a nd conain
current models of burst and afterglow production.
GRO-98-130 Liang, Edison
The discovery of a new SGR 1814-13 and the announcement of
periodicities in SGR 1806-20 and SGR 1900+14 has focused
attention on these highly unusual sources. In Cycles 4-7 we have
been performing spectral fitting and theoretical studies o f the
SGR bursts seen by BATSE, and multiwavelength observations
and modeling of the highly unusual quiescent counterparts from
the millimeter through the infrared. We propose to continue both
these projects in Cycle 8. We request non-exclusive data right s
to the BATSE data from any new bursts in Cycle 8.
GRO-98-131 Liang, Edison
This is a Compton cycle 8 Guest Investigator Proposal for the
renewal of cycle 7 grant NAG 5-3840. It concerns the analysis
and modeling of gamma-ray burst (GRB) continuum spectral
evolution data obtained by BATSE. This project is an on-go ing
collaboration between Rice University and the BATSE inument
teams. Following the major developments of this past year, we
will focus in cycle 8 on GRB spectral evolution properties that
bear most on the multiwavelength (radio-X-rays) behavior of GR
Bs and their afterglows, and potential conaints on the different
cosmological scenarios. This is the core research project of our
group at Rice.
GRO-98-132 Matz, Stephen
With its high sensitivity and large but well defined field-of-view,
OSSE is the only operating satellite inument with the capability
of mapping the detailed diibution of diffuse galactic positron
annihilation radiation and continuum emission 0.05--1 MeV.
Mapping techniques developed under previous proposals can
achieve resolutions of up to ~1--2 degrees using OSSE data.
These techniques, applied to data from OSSE, SMM, and TGRS,
have led to the discovery of an unexpected asymmetry in the
galactic latitude diibution of the 511 keV annihilation line. This
proposal, which is a continuation of an approved Cycle 7
proposal, requests a sequence of observations which will be used
to 1) complete the mapping of the diffuse galactic emissio n over
the longitude range ~10--55 and 2) extend the uniform mapping
data to the other side of the disk, -55 < l < -10. These
observations will provide improved sensitivity to diffuse
emission over all previous and currently p
GRO-98-133 Connaughton, Valerie
Observations of X-ray, optical and radio counterparts to
gamma-ray bursts hours to days after the initial GRB event have
helped confirm the cosmological origin of the bursters. Recent
afterglow measurements have concentrated on emission wh ich is
softer than that seen during the prompt GRB. The most
spectacular delayed emission prior to GRB 970228, however,
came from the EGRET detection of photons 5400 seconds after
BATSE GRB 940217, including one photon of energy 18 GeV.
Following the EGRE T result, and suggestions that shocks from
GRBs may be sites for cosmic ray acceleration, we propose here
to explore afterglow emission at energies of hundreds of GeV
with the Whipple Observatory. We plan to perform observations
of 3 well-localized GRBs w ith coverage of several hours over a
period of at least 2 days each. We hope to involve other
ground-based high-energy experiments to provide a continuous
time-line for the observations.
GRO-98-134 Connoughton, Valerie
We propose to continue our hard X-ray survey of 87 BL Lacertae
objects using the source occultation method developed by the
BATSE team. A previous study of a sample of Active Galactic
Nuclei containing 4 BL Lacertae sources resulted in the deection
of 3 of these sources at a greater than 4 sigma significance level,
showing BATSE has the sensitivity to detect at least some of
these weak X-ray sources. It is proposed to investigate the
emission levels and spectra of both X-ray- and radio- se lected
BL Lac objects in an effort to examine hard X-ray differences, if
any, between two classes. We propose also to investigate a recent
claim that X-ray selected BL Lacs fall into two categories, one of
which should only be seen in hard X-rays as a fla ring source.
Recent analysis has shown that BATSE can detect flares from
these sources on time-scales of days, so that an examination of
the variability of our X-ray selected sample should be a good test
of this theory.
GRO-98-137 Phlips, Bernard
We propose an observation of the black hole candidate Cygnus
X-1 with OSSE and COMPTEL. Many such observations have
already been made, but more time is needed if one is to
accurately determine the high energy spectrum between 0.5 and 2
MeV . The detailed shape of the fall off of the spectrum near 1
MeV might be one of the few measurements available to
discriminate between the various classes of black hole models
currently in favor. The models are currently not very conained at
high energ ies because of the limited statistics available of
simultaneous times with OSSE and COMPTEL. Since the
INTEGRAL continuum sensitivity near 1 MeV will be similar to
OSSE and COMPTEL, a deep observation of Cygnus X-1 really
should be performed in the out ye ars of the CGRO program.
GRO-98-138 Phlips, Bernard
We propose a target of opportunity observation of Cygnus X-1
with OSSE and COMPTEL when it becomes very weak as
measured with BATSE, while at the same time not increasing its
low energy X-ray flux, as measured by ASM on RXTE. We
consider t his to be the definition of the state of Cygnus X-1
when enhanced MeV emission was detected during the HEAO-3
mission. Until RXTE, there was no way to differentiate between
the source going in the known X-ray high, gamma ray low state,
and a potential rar e state of X-ray low, gamma ray low emission.
The observation would be contemporaneous with an RXTE ToO
and possibly USA observations. The primary goal of this
proposal is to confirm the existence of the MeV emission if the
source goes in the defined stat e. By acquiring simultaneous
spectra over the X-ray and gamma ray band, a data set would be
available to test models of MeV emission and other black-hole
models. This is a resubmission of an approved cycle 7 proposal.
GRO-98-139 Kuiper, Lucien
Surprisingly, recent improved COMPTEL timing studies of PSR
B1509-58 using a combination of Cycle 1 to 6 observations
shows that pulsed emission is detected up to at least 10 MeV.
Above 10 MeV a significant source consistent in position wi th
the pulsar is detected in spatial analysis. Timing analysis in the
10-30 MeV energy range, however, yielded a modulation
significance of only $\sim 2\sigma$ with indications for a new
pulse (near phase 0.85) in a phase region showing no ucture at lo
wer energies. Timing analysis in the adjacent 30-100 MeV
EGRET energy range shows similar indications. Here we
propose to observe PSR B1509-58 with COMPTEL for a total
duration of 6 weeks. In combination with the analysed Cycle 1-6
and unanalysed Cycle 7 data this should be sufficient to clarify
the emission properties of PSR B1509-58 above 10 MeV.
GRO-98-140 Vestrand, W. Thomas
We propose to continue our successful search for sporadic
gamma-ray emission from X-Ray Binary Systems (XRBs). Our
preliminary analysis of COMPTEL data suggests that GX 339-04
is a source of MeV emission during hard x-ray outbursts. To con
firm the potential detections, we propose refined analysis of
archival COMPTEL data as well as a ToO campaign of joint
OSSE/COMPTEL and RXTE observations that would be
triggered by a BATSE detection of an intense hard x-ray
outburst. We request a short, one-week, EGRET observation of
Cygnus X-3 to test further the controversial claims for variable
GeV emission from the system. We also request access to any
additional EGRET/COMPTEL data gathered for a list of likely
XRB sources that we have been monitoring since Cycle 4.
GRO-98-141 Johnson, W. Neil
To date, the most accurate spectra yielding the most useful
physical information about the radiative processes in Seyfert
galaxies are provided by multiwavelength, multi-satellite
simultaneous observations. The launch of AXAF will provide us
with greatly improved X-ray data, but a meaningful interpretation
of these data will be greatly enhanced by extending the
observations to the highest possible energies. To that end, we
propose multiwavelength X-ray/gamma-ray campaigns involving
the CGR O OSSE and RXTE, to be conducted simultaneously
with AXAF. Our targets, IC 4329A, NGC 4388, and NGC 4945
(all in the GTO programs or proposed by us in the AXAF GO
program) are archetypical gamma-ray-bright Seyferts of type 1 -
2; and NGC 4151 is the brigh test radio-quiet Seyfert (type 1.5).
The resulting X-ray/gamma-ray spectra will test the unified
models of AGN, and will allow us to study the physical processes
responsible for the emission.
GRO-98-143 Ryan, James
We propose to conduct CGRO-wide ToO observations of the
Sun as we approach solar maximum, requesting up to two such
ToOs during Cycle 8. Each ToO would be triggered by NOAA
solar activity forecasts. The only other CGRO solar ToO (June
1991 ) yeilded many important new discoveries and we can
expect additional insights from any future ToO observations. The
focus of this proposal is first to obtain data from large X-class
gamma-ray emitting flares, but also to acquire data from smaller
events that would also occur during these observations. We
request all solar-related data for COMPTEL, OSSE and BATSE
from these observations. These data would be jointly analyzed
with those from EGRET obtained through a separate, but similar,
ToO proposal. The inument operating modes would be
optimized (based on past experience) for solar flare
measurements. Despite GI data rights, data and results would be
made available to other users as soon as possible via the World
GRO-98-144 Kazanas, Demos
We propose a combined spectral-temporal analysis of the black
hole candidates Cyg X-1 and GX 339-4 as well as a possible
future X-ray transient with particular emphasis in the Fourier
ucture of the lags between different energy bands. W e have
argued that such an analysis can provide, in addition to the
Thomson depth and the electron temperature of the hot corona,
also its size and radial density ucture. Earlier observations by
Ginga and RXTE have hinted for different density uctur es at
different epochs (timing states). Our goal is to confirm these
results and search for correlation between these timing states and
the well known spectral states of these sources in the OSSE
energy band too.
GRO-98-145 Dermer, Charles
We propose to search for nuclear and starburst activity in the
nearby infrared luminous merger NGC 6240 using gamma-ray
observations with the OSSE inument. This source is an example
of a class of ultra-luminous (> 10^11 L_Sun) far-infra red
galaxies (ULIGs) that emit the bulk of their radiation at
far-infrared wavelengths. ULIGs are among the most luminous
objects in the universe, and provide important clues to the
process of galaxy formation and the origin of nuclear activity in
galaxie s. Because ULIGs are obscured by gas and dust, the
detection of buried active nuclei from some of these systems may
only be possible with gamma-ray detectors. Recent ASCA
observations show variable X-ray activity in NGC 6240; thus its
nuclear origin could be confirmed with OSSE observations.
GRO-98-148 Kroeger, Richard
We propose Target of Opportunity observations with OSSE of
bright transient sources believed to be black hole candidates.
Previous observations of such transients with OSSE have
resulted in the elucidation of two gamma-ray spectral states of
BHC emission that correspond to X-ray spectral states (Grove et
al. 1997, 1998). Long TOO observations increase the likelihood
of observing spectral state transitions, which are known to have
occurred in at least four BHCs.
GRO-98-149 Kurfess, James
Purcell et al. (1997) recently reported an asymmetry in the
galactic latitude diibution of the 511 keV annihilation line
showing an enhancement extending to ~7-10 deg. above the
galactic center region. During CGRO cycle 7, OSSE observat
ions were undertaken of the "Fountain" region to better
determine the location, diibution, morphology and flux of the
positive latitude enhancement. Preliminary results from the cycle
7 observations exhibit the same high latitude excess. It is not yet
clear whether or not this this feature is directly associated with
activity in the galactic center region, although similar latitude
asymmetries are seen in radio maps of the GC region. OSSE is
the only operating satellite inument capable of studying t he
detailed diibution of this radiation. We propose cycle 8
observations observations to extend the coverage of the GC
region to negative latitudes, to determine the extent of the
asymmetry and to help clarify the origin of
GRO-98-150 Hunter, Stan
It has been 400 years since the last supernova within our Galaxy.
The closest supernova during modern times was SN1987A at a
distance of 160,000 ly in the Large Magellanic Cloud.
Supernovae, one of the most energetic aophysical phenomen a
known (possibly second only to gamma-ray bursts) and their
associated expanding remnants have long been thought to be the
accelerator, and possibly the source, of Galactic cosmic rays.
Supernovae are also the birthplace of neutron stars, and, for a
mass ive progenitor, a black hole. We propose a pointed,
target-of-opportunity observation with the EGRET inument
toward any Galactic supernova occurring during Cycle 8. The
high-energy gamma-ray data obtained from this observation,
when combined with other multi-wavelength observations,
would lead to a deeper understanding of this phenomenon.
GRO-98-151 Murphy, Ronald
OSSE has made fundamental contributions to flare science
including the following: accelerated ions contain more energy
than electrons; the accelerated alpha/proton ratio is high;
processes at >10 MeV have time scales as short as 0.1 s; and the
composition of the ambient plasma may change during the flare.
Continued progress in flare science requires increased solar
exposure which can only be achieved by dedicated observations
of the Sun. If no X-axis target with higher scientific priority is
selected, we propose that the Sun be designated the OSSE
secondary source (X- axis). We further propose to maximize
OSSE solar exposure by requesting that the Cycle 8 viewing plan
be optimized so that the Sun is positioned within 10 deg of the
X-Z plan e whenever possible, allowing OSSE to slew to the Sun
in response to a BATSE trigger. This proposal complements two
other proposals requesting CGRO-wide solar observations on the
Z axis with both dedicated and Target-of-Opport
GRO-98-155 Kinzer, Robert
Measurement of the cosmic diffuse gamma-ray background
(CGB) is one of the original science goals of OSSE. OSSE
provides a capability, unique now and into the forseeable future,
to observe this fundamentally important radiation. As outline d in
the initial multi-year proposal submitted and approved in cycle 7,
a large data base collected over the full range of background
parameter space is needed to be able to isolate the cosmic diffuse
flux from other locally produced backgrounds. The curr ent
proposal is for the second year of that multi-year proposal to
acquire an adequate data base to measure both the spectrum and
isotropy of this radiation. Preliminary results from the first
portion of the Cycle 7 observations are encouraging, and confi
rm the expectations of the proof of concept measurements made
prior to cycle 7. The inument is able to perform the complex and
extended large-offset observations using two types of shutter;
results confirm the two different
GRO-98-156 Dennis, Brian
We propose to continue providing easy on-line access to the
BATSE solar flare data at Goddard's Solar Data Analysis Center.
Our facility contains a continuously updated archive of all
BATSE solar flare data since launch together with an ex tensive
package of data analysis software. It is used extensively by the
solar physics community for scientific analysis of the X-ray
observations themselves, for correlative analysis with
observations at other wavelengths, and to identify times of hard
X -ray flares. The requested funding will be used for three
part-time people - a data technician to continue logging BATSE
data and recording flares, a programmer for software support,
and CoI Richard Schwartz to provide science support.
GRO-98-157 Vestrand, W. Thomas
We propose a Compton Observatory ToO program, in
collaboration with groups operating the leading TeV gamma-ray
telescopes in the Northern and Southern Hemispheres, to
simultaneously observe the gamma-ray properties of TeV gamma
ray emittin g Blazars during intense x-ray flares. Our targets are
four, highly variable, X-Ray-Selected BL Lacs that are known
TeV gamma-ray emitters: Mrk 421, Mrk 501, PKS 2155-304,
and PKS 2005-489. The gamma-ray observations will be
supported by simultaneous sate llite observations at x-ray
energies and by ground-based observations at radio and optical
wavelengths. The observational campaign will be triggered by
the detection of a major x-ray outburst from one of the objects
with the All-Sky Monitor on RXTE. The C ompton Observatory
measurements, in conjunction with our multiwavelength
campaign, will help resolve some of the important puzzles
associated with blazar phenomenology.
GRO-98-158 Macomb, Daryl
The second EGRET catalog and supplement list 98 sources of
high-energy gamma-rays of unknown origin. Little is known
about these sources despite their importance to gamma-ray
aonomy. We propose to explore the low-energy gamma-ray
behavi or of six of these sources using the OSSE and COMPTEL
inuments. We have used some simple criteria to identify several
candidate sources and have used the calculated high-energy
spectra to extrapolate down into the low-energy gamma-ray
range. Each of th e six candidates is likely to be detected by
OSSE and possibly by COMPTEL. Extending the observations
of these sources to lower energies is an important step in
addressing the characteristics of this class of gamma-ray source.
GRO-98-161 Valinia, Azita
We propose to determine the scale height of the Galactic diffuse
emission in the hard X-ray/soft gamma ray band via
simultaneous RXTE/OSSE observations. To understand the
origin of the diffuse emission, determination of its scale height is
necessary since comparison of the measured value with that
expected from candidate radiation mechanisms (e.g. inverse
Compton scattering, non-thermal electron/proton bremsahlung)
will provide a testbed for the different scenarios of the origin of
the emission. These observations need to be simultaneous so that
hard discrete sources (many of which are variable) can be
detected via the small fov and hard X-ray sensitivity of RXTE.
Their contribution can then be estimated and subtracted from
OSSE's spect rum. This proposal builds on our cycle 7
investigation where we performed simultaneous RXTE/OSSE
observation of the Galactic plane at zero latitude.
GRO-98-164 Miller, H. Richard
We propose an OSSE observation of the X-ray bright Seyfert 1
galaxy Akn 120, to be conducted simultaneously with our
approved RXTE pointing. These observations will yield one of
very few truly simultaneous X-ray/gamma-ray spectra for Seyfe
rt 1s. This is extremely important due to the highly variable
nature of these objects. The resulting well-determined
X-ray/gamma-ray spectrum will allow a precise measurement of
the reflection component already detected in the Ginga data, but
the extended bandpass will measure the high-energy cutoff (and
a possible non-thermal component) and to compare it with those
found for other Seyfert 1 galaxies.
GRO-98-166 Ryan, James
We propose to conduct spectroscopic analyses of COMPTEL
solar flare data and to use those results to analyze individual
flares. We can now deconvolve complex solar flare spectra from
both our telescope and our burst spectrometer inument s within
COMPTEL, using a Maximum Entropy method. We wish to
explore other Bayesian methods and to deconvolve spectra
jointly for both COMPTEL and OSSE inuments in a rigorous
fashion. The photon fluxes derived in this manner can be used to
analyze flar es that exhibit anomalously soft proton spectra. We
have contructed a photospheric, analytical, neutron transport
model that can be used effectively for low energy neutrons. The
2.223 MeV line from thermal neutron capture in the photosphere
can be combine d with the results of low-threshold-energy line
fluxes (e.g. 20Ne) to derive the proton spectra. These proton
spectra, if soft enough, can carrry far more energy than energetic
electrons in flares.
GRO-98-168 Kinzer, Robert
Simply configured deep observations of the galactic plane toward
the center with OSSE provide a direct means for mapping the
diibution of 511 keV and positronium continuum positron
annihilation components in both latitude and longitude. This
basic method provides a direct mapping approach which can
well-measure the shape of the galactic bulge and ridge. It has a
considerable sensitivity advantage over other techniques because
it uses both the half-MeV line and the ~4.5 times more intens e
positronium continuum fluxes rather than just the line flux. The
current sparse data set of properly configured and deep
measurements shows a sharp central bulge which is best
characterized as a ~24 deg.FWHM Gaussian bulge in longitude
with an ~25% cent ral discrete source contribution. The current
proposal is for deep ''basic'' observations in crucial regions at 5
deg., 355 deg,, and 335 deg. longitudes where no credible
measurements currently exist.
GRO-98-169 Esposito, Joseph
For many years it has been believed that the acceleration of
Galactic cosmic rays is due to the ong expanding shocks fronts
associated with supernovae and supernova remnants. Analysis of
the EGRET data near the Galactic plane has reveal ed that at
least seven supernova remnants are spatially correlated with
unidentified EGRET gamma-ray sources and, of these, four have
been shown to be consistent with a model of gamma-ray
emission due to cosmic ray acceleration by supernova remnants.
Thes e four remnants, plus one other, all exhibit 1720 MHz
maser emission (OH) and are of the composite supernova
remnant type. However, statistical limitations preclude
unambiguous identification of the unidentified EGRET
gamma-ray sources. We propose for non -exclusive data rights to
21 supernova remnants.
GRO-98-997 PUBLIC ToO
This is a requested target of opportunity observation of XTE J1550-564
based upon RXTE monitoring of this source.
GRO-98-998 Unowned
This is an observation, usually involving OSSE, which has been scheduled
because no other proposed source currently fits into this slot.
GRO-98-999 Instrument teams
This observation of the CRAB PULSAR is a calibration observation.