| Question | Answer |
|---|
| Would previous version of Heasoft not work to encompass the NICER analysis? say
heasoft 6.25? | We would strongly recommend that you use the most recent version of
HEASoft, which is 6.28, and an up-to-date CALDB. Note that a new version of HEASoft, 6.29,
wiill be released soon. |
| Correct, please move to heasoft 6.28 minimum |
| I was wondering what is the difference in temporal resolution between
the PI column and PI_FAST? (or energy resolution difference between the two
columns?) | Hi George. Timing: in practice there is very little difference between slow
and fast channels. We apply a calibration offset but that's about it. |
| Spectral: read noise for slow is about 30eV (1 sigma) and for fast is about
50 eV, so fast is worse by 50-70% |
| Timing: there is actually very little difference between the two
channels; |
| Energy: resolution in fast channel is worse by about 50-70%. |
| When we run nicerl2, can we save the gti file which is generated by nimaketime
internally? | nicerl2 outputs the GTIs as the 'GTI' extension (the FITS extension with
EXTNAME='GTI') in the output (cleaned) event file (the *_cl.evt file) |
| Yes. The GTI file is stored in the event file, the extension is
GTI_FILT |
| These tools (nicerarf/nicerrmf) are not yet available, right? | right - they'll
be available in heasoft 6.29 (probably available in a few weeks) |
| When are the new NICER software tools expected to be released? And will there be
threads describing their usage (specfically for nicerarf/rmf)? | Soon. The next few
weeks, we hope. |
| Hi! What exactly performs the option "miprefilter2_coltypes=base, 3c50" in the nicerl2
routine in order to use the 3c50 model? | If you plan on using the 3C50 model, you will
need to add model-specific quantities to your filter file. You can do this by running nicerl2
and specify the niprefilter2_coltypes option as “nicerl2 niprefilter2_coltypes=base,3c50'.
See the nicerl2 analysis thread
https://heasarc.gsfc.nasa.gov/docs/nicer/analysis_threads/nicerl2/ for more
information. |
| If you run with this option, nicerl2 will generate columns with the same
background metric rates that that the 3C50 model uses, which you could then - in principle -
use for screening. However, the nibackgen3C50 tool does not directly use these filter file
columns, but instead generates the rates itself from the event files. |
| According to this, I noticed that there are two different model
for modeling the background. Are there caveats for using these models accordingly to the
observed source? Or are they equivalents? Thank you again! | There will be a segment on
Background modeling tomorrow morning when those models will be discussed in more
detail. And you can see the background estimation analysis thread at
https://heasarc.gsfc.nasa.gov/docs/nicer/analysis_threads/background |
| About 'BKGD_RXTE' datasets. We are interested in properties of X-ray background only.
Does NICER have calibrated 'detector background' information? Thanks | All of the
background databases, such as the ones that will be discussed tomorrow duign the background
session, include both detector and sky background. |
| Another question about the niprefilter2_coltypes=base,3c50. If I don't specify this
option, would the background tool complain? Or are the spectra produced without that option
not reliable? | The nibackgen3C50 tool does not directly use these filter file columns,
but instead generates the rates from the event files. The extra filter file columns created by
nicerl2 niprefilter2_coltypes=base,3c50 can be useful for identifying times of high
background. |
| I am stuck after extract curve - plot device should be like in xspec or
what? | Yes, you can use:
XSELECT> cpd /xw
(as in xspec) to display to an Xwindow. |
| In the case where one is using data with all 52 modules, do you recommend using the
ARF and RMF provided in the CALDB or is it generally best to run
nicer-add-rmf/nicer-add-arf? | You should get the same result either way for all 52
modules. The one trick is that the .rmf file in CALDB might not be accessible due to a
database error. You can still retrieve the newest RMF just by searching the NICER CALDB
area. |
| Are there some caveats for the systematics errors in the XTI energy range? What do you
suggest especially for the lowest energies? Thanks | This will be covered in teh
calibration status presentation. Can you see if that answers your questions? |
| When the idea of putting NICER on ISS originated? Is any other similar type of mission
we are going to see in the future? | Around 2007, we submitted a proposal called
"NICE". It was not selected. NICER was an improvement that was selected. There maybe other
such missions going to ISS, but space on the zenith side is limited. |
| So if we change the screening criteria and get a GTI file, will the new GTI
automatically reflect in the GTI extension after nimergeclean? | if you re-run nicerl2
with updated screening criteria, then in the new cleaned event file, the GTI table will be
updated to reflect the updated criteria. |
| Are optical filters use in NICER detectors? | The XRCs have aluminized polyimide
filters and the SDDs have aluminized Si3N4 filters. The inside of the XTI is mostly black to
minimize reflections... but not perfectly |
| RXTE used ELV > 10. Isn't ELV 15 a bit too conservative? | Recall that NICER
goes to much lower energies, and atmospheric absorption is possible. Also, the Star tracker
FOV is about 15 degrees and the star tracker can be fooled by the bright limb of the earth.
The star tracker is co-aligned with the X-ray instrument. |
| How about hot detectors? How do we find them? | This question has been answered
live |
| Is it reasonable to expect all detectors have the same weight during the observation?
For example, could I create a hardness-intensity diagram using observations from the same
source, but with a different number of active detectors for each observation, or should I
select only the detectors active simultaneously in all observations? | This question has
been answered live |
| Is it possible to show using the sample data as to how one can use nifpmsel for a
detector that was partially noise within some time interval? | This question has been
answered live |
| This would be best shown as an example on Wednesday during the Q&A session.
It would be great if you could submit this suggestion through the Q&A submission form at:
https://forms.gle/Wh12E34dZmZrYJCC8 |
| Is it reasonable to expect all detectors have the same weight during the observation?
Could I create a hardness-intensity diagram using observations from the same source, but with
a different number of active detectors, or should I select only the detectors active
simultaneously in all observations? | This question has been answered live |
| How could we search and download the blank sky background observations taken by NICER
in HEASARC archive? | Go to
https://heasarc.gsfc.nasa.gov/db-perl/W3Browse/w3table.pl?tablehead=name%3Dnicermastr&Action=More+Options
and type 'BKGD_RXTE*' in the 'name' box and press the 'Start Search' button at the
bottom of the search form. |
| Note that BKGD RXTE7 is 'contaminated' by a soft X-ray source. How these
data may be used in estimating the background for a given observation will be covered in
detail tomorrow. |
| I have recently (successfully) analysed a data set, where xselect did not return
OBJECT OBSID, etc. Is that an issue? | That happens sometimes (for example if the FITS
header is missing those keywords). Generally it's not an issue. |
| Is this light curve corrected for background? | No - there's no background
correction applied. You'll need to estimate that separately - see
https://heasarc.gsfc.nasa.gov/docs/nicer/analysis_threads/background for details on how to do
this. |
| How do we extract background light curve? Is there any tool to extract bkg
LC? | There are 2 background estimation tools - see the background estimation analysis
thread https://heasarc.gsfc.nasa.gov/docs/nicer/analysis_threads/background for details. In
addition to Craig's discussion here we'll discuss these more tomorrow. |
There's experimental software to generate background lightcurves under
development in the nicergof.bkg python package - it's experimental and largely unadvertised so
please use it with caution.
To use it you can do the following:
py> from nicergof.bkg
import bkg_estimator as be
py> be.mk_bkg_lc_evt?
This will bring up the documentation for the background lightcurve estimator |
| for reprocessing with updated software/calibrations, I was wondering how large changes
tend to be? E.g., a few percent, a few tens of percent? Something more complicated than one
number? | Hi, the answer is complicated of course and depends on a particular
observation. The ARFs we released last summer (xti20200722) contain major improvements. 10s
of percent are typical. |
| Is overshooting affecting temporal properties of the events? | For the most
part, no. However, you do suffer deadtime. |
| Are the undershoot electrons concentrated in Energy? | yes - typically
undershoots are seen at E<0.4 keV |
| Is undershooting has some effects on the time series? | You do have deadtime
associated with undershoots. So, you need to be careful. |
| How do you you plot the overonly curve on top of your data? | The curve is
1.52*COR_SAX**(-0.633) |
| Hi! Can the undershooting therefore also occur due to the observation of an extremely
bright source? And if so, what is the brightness threshold? | This question has been
answered live |
| Is this the same COR_SAX that is used for the orange line in the overshooting? Are
these two different cuts made from this then? | The expression for the orange curve is:
overonly_expr=“1.5*1.52*COR_SAX**(-0.633)' |
| Might be foreshadowing Craig's slides again: As we go into solar max, are there any
NICER background filters required to screen out short-lived radiation belts induced by CMEs?
Or do we not know yet? | I use the KP index to try and filter on space weather issues.
How well that will work for CMEs will need to be determined. KP is now in th e latest MKF
files. |
| Is there a good reason to ignore detectors at the moment or is this something in case
this is necessary in the future? | at some low sun angles, I tend to ignore some
detectors as they are more sensitive to optical loading. |
| Is the nicerarf command line different from the nicer-add-arfs? | This question
has been answered live |
| In what situation per-detector ARF generation be useful? | This question has
been answered live |
| Which specific ftool/task is detlist parameter going into when using
nicerl2? | This question has been answered live |
| What is the difference between this new merging process with the existing merging
process? | The new process is smarter and keeps track of per-detector information.
Before, the user was required to keep track of configuration changes across the different
observations. |
| Can you quantify how different the NICER (per detector) response will be in this new
HEASARC version, compared to the .arf/.rmf files in used in nicer-add-arfs and
nicer-avg-rmfs? | This question has been answered live |
| I noticed that in the majority of the NICER spectra I extracted some significant
excesses are visible for energies that are lower than 1-2k keV. Are there caveats for these
energy ranges? Are there systematics issues at those energies? Do the background is well
modelled in this range? | Hopefully the information Craig is discussing now will answer
your question. If you still have questons afterward, please feel free to resubmit this
question. |
| Can you please repeat the problem with the ARF and the NH estimation that you
mentioned. | This question has been answered live |
| Could page no 10 be shown again where PSR spectrum is shown alongwith background
model? | If it helps, slides are available here:
https://heasarc.gsfc.nasa.gov/docs/nicer/data_analysis/workshops/index.html |
| About callibration: Is there any 'spill-over' of the rmf at low energies when NH is
high? This is an issue that was seen in PN/MOS as positive residuals at ~1 keV. in
highly-absorbed sources. | This question has been answered live |
| Then considering systematics for a maxium of 1% is generally enough also for energies
< 1 keV? | This question has been answered live |
| In timing analysis of sources with DDT observations (taken for several months), do you
have some tips to share (besides waiting for the upcoming software version)? | There are
no special instructions for DDT observations. They are analyzable with teh same software and
settings |
| How does PI differ from PI_FAST? | This question has been answered
live |
| If we search in NICER archieve, we can find many observation IDs with zero exposure.
Are these datasets really useful ? What is the meaning of zero exposure? | This should
be addressed in the next segment. If you still have a question then, hopefully we can address
it. |
| I noticed the session was being recorded. Will the recordings be made available later?
Do you plan to record all sessions? Thank you. | Yes, unless a presenter requests that
we don't record. |
