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CRABTIME - Crab Pulsar Timing |
HEASARC Archive |
Overview
The CRABTIME database contains the Crab Pulsar Monthly Ephemeris covering the period from Feb 15 1982 (MJD=45015) to (close to) the present that was created Dr. Andrew Lyne and collaborators at Jodrell Bank Observatory. This database is periodically updated to include recent data as these become available. To assist astronomers, the HEASARC has created two new parameters which were not present in the original Jodrell Bank tables, the pulsar period and its first derivative, using the standard relations between period (P) and frequency 'Nu' (P=1./Nu) and their first derivatives (P_dot = -Nu_dot/Nu2). The assumed pulsar position used in the reductions isRA (1950.0) 05 31 31.406 DEC (1950.0) +21 58 54.391 RA (2000.0) 05 34 31.973 DEC (2000.0) +22 00 52.061
Bulletin
The CRABTIME database table was last updated on 27 August 2024.References
Lyne, A.G., Jordan, C.A., Roberts, M.E., "Jodrell Bank Crab Pulsar Timing Results, Monthly Ephemeris", http://www.jb.man.ac.uk/~pulsar/crab.html, University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire, SK11 9DL, UK.Provenance
This HEASARC version of the "Jodrell Bank Crab Pulsar Timing Results, Monthly Ephemeris" is updated within one week of any changes to the tables available on the Web at http://www.jb.man.ac.uk/pulsar/crab.html.Reduction Description
Examples of reduction of site arrival times to the Solar System barycentre and infinite frequency using the JPL Ephemeris DE200:Pulses were observed at the following places, frequencies, and times(UTC):
Wardle 609.981 MHz. 02 JULY 1983 15:26:27.521969 Wardle 609.981 MHz. 27 JULY 1983 16:02:32.558116 Jodrell 610.000 MHz. 15 JAN 1989 16:08:49.060034 Jodrell 608.000 MHz. 12 FEB 1989 14:08:36.094064
The telescope site co-ordinates are:
r x cos(lat) r x sin(lat) long(hours west)
Wardle 3836.629 kms 5078.151 kms 0.173066
Jodrell 3825.684 5086.391 0.153740
The corrections applied are as follows:
02 JULY 1983 27 JULY 1983
15:26:27.521969 16:02:32.558116
UTC to TAI +22.000000 +22.000000
TAI to TDT +32.184000 +32.184000
TDT to TDB +0.000054 -0.000639
Wardle to Earth centre +0.011222 +0.004404
Earth centre to Barycentre -8:02.243380 -6:22.406452
observed freq to infinite freq -0.633679 -0.633725
Gravitational propagation delay -0.000038 -0.000021
Corrected BC arrival time 15:19:18.840148 15:57:03.705684
BC arrival time from ephemeris 15:19:18.840180 15:57:03.705690
15 JAN 1989 12 FEB 1989
16:08:49.060034 14:08:36.094064
UTC to TAI +24.000000 +24.000000
TAI to TDT +32.184000 +32.184000
TDT to TDB +0.000348 +0.001062
Jodrell to Earth centre +0.006671 +0.006146
Earth centre to Barycentre +6:58.424915 +4:07.211028
observed freq to infinite freq -0.633435 -0.637457
Gravitational propagation delay -0.000001 -0.000003
Corrected BC arrival time 16:16:43.042532 14:13:38.858840
BC arrival time from ephemeris 16:16:43.042540 14:13:38.858881
Parameters
RA
The Right Ascension of the Crab Pulsar. The assumed pulsar position
used in the reductions is as follows:
RA (1950.0) 05 31 31.406 DEC (1950.0) +21 58 54.391
RA (J2000) 05 34 31.973 DEC (2000.0) +22 00 52.061
Dec
The Declination of the Crab Pulsar. The assumed pulsar position used
in the reductions is as follows:
RA (1950.0) 05 31 31.406 DEC (1950.0) +21 58 54.391
RA (J2000) 05 34 31.973 DEC (2000.0) +22 00 52.061
LII
The Galactic Longitude of the Crab Pulsar.
BII
The Galactic Latitude of the Crab Pulsar.
Day
The day of the ephemeris entry.
Month
The month of the ephemeris entry.
Year
The year of the ephemeris entry.
MJD
The Modified Julian Date of the ephemeris entry. The Modified Julian
Date (MJD) is the Julian Date (JD) - 2400000.5 days.
MIT_Time
'MIT Time' is the arrival time using the M.I.T.(PEP311) ephemeris
(Ash, M.E., Shapiro, I.I., & Smith, W.B. 1967, AJ, 72, 338). The arrival times
given are those of the centre of the first main pulse after midnight at
infinite frequency at the barycentre of the solar system, in seconds. The
timescale is now quoted in terms of T.D.B. To convert to T.A.I., 32.184
seconds must be subtracted. The MIT ephemeris only covers the dates up to
Feb 1990. This parameter was given to a precision of 10-6 seconds
in the original table.
JPL_Time
'JPL Time' is the arrival time obtained using the JPL (DE200)
ephemeris (Standish, M. 1982, A&A, 114, 297). The arrival times given are
those of the centre of the first main pulse after midnight at infinite
frequency at the barycentre of the solar system, in seconds. The timescale is
quoted in terms of T.D.B. To convert to T.A.I., 32.184 seconds must be
subtracted. This parameter was given to a precision of 10-6 seconds
in the original table.
T_Acc
The accuracy in microseconds with which the ephemeris defined
from these numbers is believed to describe the observed arrival times during
the whole calendar month, using the DE200 ephemeris. If the PEP311 ephemeris
is used, then the difference in 'Nu' is approximately 1 part in 1E-10,
corresponding to a maximum arrival time difference over a month of less than
250 microseconds.
Nu
The observed barycentric frequency 'Nu' in Hertz (Hz), and its first
derivative 'Nu Dot', are given at the quoted arrival time, using the DE200
ephemeris. This parameter was given to a precision of 10-10 Hz
in the original table.
Nu_Error
The uncertainty in the observed barycentric frequency 'Nu', in
Hertz (Hz).
Nu_Dot
The first derivative 'Nu Dot' of the observed barycentric
frequency 'Nu', in units of s-2, and given at the quoted arrival time, using
the DE200 ephemeris. This parameter was given to a precision of 10-17
s-2 in the original table.
Nu_Dot_Error
The uncertainty in the first derivative 'Nu Dot' of the
observed barycentric frequency 'Nu', in units of s-2.
Period
The observed period, in seconds, calculated by the HEASARC from the
reciprocal of the observed barycentric frequency 'Nu'.
Period_Dot
The first time derivative of the period, in units of s/s,
calculated by the HEASARC from the standard relation P_dot = - Nu_dot/Nu2.
DM
The dispersion measure, as observed, is usually given, the error being
typically 0.005 pc cm-3. If the value of the dm_flag parameter is 'Y', this
indicates that the quoted dispersion measure is an assumed value, extrapolated
from adjacent data.
DM_Flag
This parameter is set to 'Y' to indicate that the particular
dispersion measure is an assumed value, extrapolated from adjacent data.
DM_Dot
'DM Dot' is the first derivative of the dispersion measure 'DM', in
units of pc cm-3 s-1. This parameter was given to a precision of 10-5 in
the original table.
Delay
The assumed delay in microseconds due to interstellar scattering for
408 MHz. Where measured at other frequencies, the amount of scattering is
assumed to scale as radiofrequency to the inverse 4th power.
Note_Number
A code number indicating that there is a note for the
particular entry. The meanings of the numerical codes are as follows:
7 -- The end of the fit for AUG 1986 and the beginning of the fit for SEPT
1986 is taken as MJD 46664.0, that is midnight on 22 AUG 1986. This
is the date of a significant glitch. (See Lyne, A.G., & Pritchard,
R.S. 1987, NMRAS, 229, 223).
8 -- The end of the fit for AUG 1989 and the beginning of the fit for SEPT
1989 is taken as MJD 47767.4, that is 09:30 on 29 AUG 1989. This is
the date of a large glitch.
9 -- The fits with epochs 2 SEP, 11 SEP, and 23 SEP cover the dates 29 AUG
09:30 to 7 SEP 00:00, 7 SEP 00:00 to 15 SEP 00:00, and 15 SEP 00:00
to 1 OCT 00:00, respectively.
11 -- The end of the fit for NOV 1992 and the beginning of the fit for DEC
1992 is taken as MJD 48945.8, that is 19:30 on 19 NOV 1992. This is
the date of a significant glitch.
12 -- The end of the fit for JUN 1996 and the beginning of the fit for JULY
1996 is taken as MJD 50259.9, that is 25 JUN 1996. This is the date
of a significant glitch.
13 -- The beginning of the fit for OCT 1999 is taken as MJD 51454.1, that
is 00:00 on 3 OCT 1999. There was a significant glitch at MJD
51452.3, that is 1 OCT 1999.
14 -- The end of the fit for JULY 2000 and the beginning of the fit for AUG
2000 is taken as MJD 51739.4, that is on 14 JULY 2000. This is the
date of a significant glitch.
15 -- The end of the fit for SEPT 2000 and the beginning of the fit for OCT
2000 is taken as MJD 51804.9, that is 17 SEPT 2000. This is the date
of a significant glitch.
16 -- The end of the fit for JUNE 2001 is taken as MJD 52083.8, that is on
24 JUN 2001. This is the date of a significant glitch.
17 -- The end of the fit for AUG 2001 is taken as MJD 52146.0, that is on
24 AUG 2001. This is the date of a significant glitch.
18 -- There was a significant glitch at MJD: 52146.0 (24 AUG 2001) (Espinoza
et al. 2011b). This date was taken as the end of the fit for AUG 2001.
19 -- There was a small glitch at MJD 52497.3 (12 AUG 2002).
20 -- There was a very small glitch at MJD 52587.1 (9 NOV 2002).
21 -- There was large glitch at MJD 53067.1 (3 MAR 2004)
(Espinoza et al. 2011b). The fits with epochs 7 MAR, 15 MAR, and 26
MAR 2004 cover the dates 3 MAR 00:00 to 10 MAR 00:00, 10 MAR 00:00
to 20 MAR 00:00, and 20 MAR 00:00 to 1 APR 00:00 2004, respectively.
22 -- The fits with epochs 5 APR, 15 APR, and 25 APR 2004 cover the dates
1 APR 00:00 to 10 APR 00:00, 10 APR 00:00 to 20 APR 00:00, and 20
APR 00:00 to 1 MAY 00:00 2004, respectively.
23 -- There was a significant glitch at MJD 53254.2 (6 SEP 2004)
(Espinoza et al. 2011b). The start of the fit for SEP 2004 is taken
as MJD 53258.2 (10 SEP 2004).
24 -- There was a small glitch at MJD 53331.1 (22 NOV 2004)
(Espinoza et al. 2011b).
25 -- There was a significant glitch at MJD 53970.0 (23 AUG 2006)
(Espinoza et al. 2011b). This date was taken as the end of the fit
for AUG 2006.
26 -- There was a significant glitch at MJD 54580.0 (24 APR 2008)
(Espinoza et al. 2011b). This date was taken as the end of the fit
for APR 2008.
27 -- A significant enhancement of dispersion measure occurred during SEP
2011. For this reason, there are two fits for SEP 2011.
28 -- There was a significant glitch at MJD 55785 (10 NOV 2011). The fits
with epochs 5 NOV, 13 NOV, and 24 NOV 2011 cover the dates 31 OCT to
10 NOV, 11 NOV to 17 NOV, and 17 NOV to 30 NOV 2011, respectively
(Espinoza et al. 2011a).
29 -- Data fits from 1 DEC 2011 may include a term for DM Dot. An extra
column has been added to the table.
Contact Person
Questions regarding the CRABTIME database table can be addressed to the HEASARC Help Desk.Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:26:24 EDT
- HEASARC Director: Dr. Andy Ptak
- NASA Official: Dr. Andy Ptak
- Web Curator: J.D. Myers
- Last Modified: 16-Sep-2024