Question Transcript
Kristin Madsen: What is IACHEC
Michael Wolff to Everyone
What is the status of a standard model for the Crab that is a delta off of the Zombeck model for instruments to use in their calibration efforts? Is there a new Crab model that is better than Zombeck that instruments should use?
Craig Markwardt to Everyone (9:29 AM)
This is the paper I referred to:
https://www.aanda.org/articles/aa/abs/2009/13/aa7892-07/aa7892-07.html
Herman Marshall to Everyone (9:30 AM)
The model of the Crab that Zombeck published was taken from Seward’s paper in the Journal of the British Interplanetary Society (vol. 31, p. 83, 1978)
Eric Miller to Everyone (9:31 AM)
Also this paper on the Crab is useful: http://adsabs.harvard.edu/abs/2010ApJ…713..912W
Mike Corcoran to Everyone (9:31 AM)
MZ handbook http://ads.harvard.edu/books/hsaa/toc.html
Craig Markwardt to Everyone (9:33 AM)
The Weisskopf (2010) paper is great, but we perhaps know more about dust scattering halos today than then. It’s an important effect.
Jeremy Drake: Chandra
Keith Arnaud to Everyone
If HRC B-side does die can you continue ACIS observations using other space weather data ?
Me to Everyone (9:54 AM)
Yes, although some of the worry is the radiation belt passages, which other space weather data doesn’t help us with.
Obviously the HRC issues have made this a more pressing discussion.
Keith Arnaud to Everyone (9:55 AM)
So you would have to be more conservative about radiation belt passages?
Me to Everyone (9:55 AM)
Perhaps yes. We did start putting together an “ACIS return to science without HRC” plan, which we luckily didn’t have to use.
Brian W. Grefenstette to Everyone (9:56 AM)
Is the space weather issue a “data quality” issue? Or is it a “health of the instrument” issue?
Me to Everyone (9:56 AM)
Health of the instrument primarily.
Me to Everyone (9:57 AM)
At least, the worry is health and safety. You would also have data quality issues as the background increased.
Me to Everyone (9:58 AM)
ACIS is also running a flight software patch that monitors ACIS rates and can detect high particle radiation environments. It can send a signal to the on-board computer to safe the instrument. So there is some protection from that.
RIchard Mushotzky to Everyone (9:59 AM)
What is the prediction for the ACIS quantum efficiency at 1 keV for 2021?
Herman Marshall to Everyone (10:10 AM)
The new prediction for 2021.0 is an optical depth in the contaminant of 0.54 at Al-K at the center of the detector and an additional 0.22 by row 64 (for ACIS-S). To get the value at 1.0 keV would take a bit more of a calculation. Remember that these are *predictions* that depend on extrapolating a temporal model that is only validated with data up to April 2020.
Herman Marshall to Everyone (10:21 AM)
@RichardMushotzky: at 1 keV, 2021.0, the current prediction is that the contamination reduces the ACIS-S QE to 21% of the launch value in the center of the detector and 11% at row 64.
Craig Markwardt: NICER
Felix Fuerst to Everyone (10:15 AM)
Sorry if I missed it, but at what magnitude does optical loading become important in NICER?
James Steiner to Everyone (10:16 AM)
Usually, we measure it by the rate of “undershoot” resets, and when that becomes >~20/s/det, daytime effects start onsetting
Brian W. Grefenstette to Everyone (10:17 AM)
But it’s “daytime light from the Sun” and not “optical light from the source”, right?
James Steiner to Everyone (10:17 AM)
Right
RIchard Mushotzky to Everyone (10:17 AM)
At what flux level (assuming a simple gamma=-2 pl model) does background subtraction become a major issue
James Steiner to Everyone (10:18 AM)
Typical background rms is at levels around ~10uCrab
James Steiner to Everyone (10:19 AM)
Single orbit GTIs will have larger variation, but that’s about where you would push to with a typical aggregate of GTIs constituting a single observation
Mike Nowak to Everyone (10:21 AM)
Has NICER, for example, thought about doing strictly simultaneous observations HETG of HEr X-1 (no halo), for calibration???
Craig Markwardt to Everyone (10:23 AM)
Mike, we have done strictly simultaneous with NuSTAR and Swift. We of course would be interested in other cross-cal work!
Craig Markwardt to Everyone (10:41 AM)
(NICER) @Mike, probably worth having it be more than just for NICER
Mike Nowak to Everyone (10:30 AM)
Craig- XMM could be useful, too. But given no column/no halo, that removes a lot of issues. But given the super-orbital variability, strictly simultaneous would be called for. There’s bright, no line states, and fainter, more line dominated states. Not useful for “absolute” calibration, but could be good for relative calibration, line-like residuals (nor bright no line states), and gain in the line states.
Nazma Islam to Everyone (10:24 AM)
From NICER, what range of values are recommended for filtering data for magnetic rigidity cutoff (cor_range in nimaketime)?
*For NICER
Paul Ray to Everyone (10:27 AM)
There is no one right answer for filtering on COR. It depends on your application. The background conditions at low COR are quite variable with time (which is why Keith’s background model incorporates the space weather index KP)
James Steiner to Everyone (10:29 AM)
Just to add to what Paul said, if you have very faint sources, you’ll find that the background gets large at low COR and so the background systematic is accordingly a bit larger. For bright sources, there is no issues, but for faint sources I would suggest to screen by the predicted background rather than by COR directly
Craig Markwardt to Everyone (10:33 AM)
@Nazma Islam, I agree with what others have said. We use “overshoots” in the default screening as more effective than COR.
Michael Loewenstein to Everyone (10:34 AM)
(NICER) To add to what Paul and James said, one of the metrics used in Ron Remillard’s method is very tightly correlated with COR.
Jamie Kennea: Swift
Varun Bhalerao to Everyone (10:33 AM)
when proposing a target, is it better to propose with an offset? (WRT central hot column) ?
Brian W. Grefenstette to Everyone (10:34 AM)
(Swift) What fraction of the FoV is covered by hot columns?
Jamie A Kennea to Everyone (10:44 AM)
@brian columns are top to bottom about 1 to 3 pixels each, so percentage of FOV is small (like 1%)
However, as there are two near the center of the FOV, the likelihood of the source of interest landing on one is unfortunately high
RIchard Mushotzky to Everyone (10:43 AM)
Is there any info on BAT calibration??
Jamie A Kennea to Everyone (10:44 AM)
@rich I don’t have anything on BAT.
Craig Markwardt to Everyone (10:46 AM)
(Swift BAT) @Richard, we’ve been doing monitoring calibration observations with BAT and its performance has changed very little. There is some evidence of radiation damage to gain/resolution (0.5 keV shift at 60 keV), but has actually healed somewhat at lower orbital altitudes.
Varun Bhalerao to Everyone (10:45 AM)
@jamie is there a plan to deliberately place targets on the right side which seems free of hot columns?
Jamie A Kennea to Everyone (10:51 AM)
@varun – yes, we do apply an offset to try to avoid hot columns
However, the pointing accuracy stymies this sometimes
Also for WT we don’t, because it increases the chance that the source will fall out of the FOV
kristin to Everyone (10:47 AM)
(SWIFT) Optical loading in WT mode, do you know when that starts to matter?
Jamie A Kennea to Everyone (10:51 AM)
@kristin Optical loading becomes an issue for sources visible to the naked eye in WT
Andy B to Everyone (10:55 AM)
@kristin the optically loaded WT spectrum jamie showed was zeta Pup , so V 2.2 mags
Kim Page to Everyone (11:03 AM)
https://www.swift.ac.uk/analysis/xrt/optical_loading.php
^ Might be useful.
There’s an optical loading calculator linked to from that page, too.
Jamie A Kennea to Everyone (11:09 AM)
That link is in my slide too (Swift XRT optical loading)
Michael Smith: XMM-Newton
Brian W. Grefenstette to Everyone (11:04 AM)
(XMM-EPIC-pn): Is there any plan to extend the RDPHA correction for highly variable/bursting sources?
(this was answered by the speaker outside of chat)
Gulab Dwangan: AstroSAT
(ASTROSAT) The LAXPC short term background issues, what do you recommend for users? Is it automatically taken care of?
(this was answered by the speaker outside of chat)
Kallol Mukerjee to Everyone (11:46 AM)
Kristin: Short time diurnal background correction is done by laxpc pipeline itself by selection of option..
Nazma Islam to Everyone (11:40 AM)
For ASTROSAT, what is the percentage variation in cross-normalisation constant in simultaneous spectral fitting of SXT, LAXPC and CZTI?
Kallol Mukerjee to Everyone (11:46 AM)
Nazma: AstroSat normalization of SXT is 30℅ of LAXPC for its inherent fixed offset case..
Nazma Islam to Everyone (11:52 AM)
Thank you Kallol. A quick followup question: How much variation in cross normalisation constant is expected for different values of gain shift for LAXPC background spectrum?
Kallol Mukerjee to Everyone (11:59 AM)
I can check back and let u know the variation but It is taken carenby the pipeline software itself. .
Brian Grefenstette: NuSTAR
James Steiner to Everyone (11:58 AM)
(Nustar) Is there a reference flux (&/hardness) at which you recommend processing with those event flags altered?
(This question was answered by the speaker outside of chat)
kristin to Everyone (12:00 PM)
I use the status bit for the Crab
So anything crab bright needs it
Brian W. Grefenstette to Everyone (12:03 PM)
@Jack I’d also use it for sources where you might expect bursting behavior (Type I bursts, etc) where the instantaneous rate may get higher.
Felix Fuerst to Everyone (12:00 PM)
(NuSTAR) Can you give us an update on any future plans of updating the effective area?
kristin to Everyone (12:03 PM)
We are on the last stages of our effective area and RMF update. We got a little delayed because we realized that an adjustment to the RMF is also necessary, but we predict that we are probably looking for a couple of months to produce and test the next areas.