- Chair Karl Forster (Caltech, NuSTAR) - krl at srl.caltech.edu
- Members membership list being updated (2021-05-20)
Mission statement
The goal of this working group is to facilitate the coordination of calibration observations among operational observatories and the analysis and publication of the corresponding data. An annual cross-calibration observation of the quasar 3C 273 involving as many operational observatories as possible is undertaken in June/July each year.
This working group also supports additional opportunities for coordinated cross-calibration observations between observatories.
Activity
2021-10-22 - WG meeting on zoom
2021-05-18 - Chairs report at 2021 IACHEC Spring WG meeting is available here
2021-05-13 - WG meeting on zoom
2021 October 22nd - Working group meeting
Held on Zoom
Attending (in alphabetical order): Sunil Chandra, Hannah Earnshaw, Karl Forster, Felix Fuerst, Elisabeth Jourdain, Jamie Kennea, Renee Ludlam, Kristin Madsen, Herman Marshall, Katja Pottschmidt, Pedro Rodriguez, Celia Sanchez, Maria Santos-Lleo, Norbert Schartel, Yukikatsu Terada, Josh Wing
There were four presentations made during the working group meeting sparking a lively and constructive conversation. The meeting began with a reminder about the calibration observation information posted on the working group google sheets (https://tinyurl.com/4z94r895).
Report on recent coordinated calibration observations:
1ES 0229+200
The observations were organized to investigate the possibility of using this blazar for future cross-calibration campaigns based on the report from Norbert Schartel and Felix Fuerst presented at the last working group meeting. Coordinated observations were performed between 2021-08-08 to 14 by the following observatories:
| Observatory | Exposure time (ks) | | ...and at other wavelengths |
|---|
| Astrosat | 160 LAXPC (40 ks UVIT) | | ATOM | BVRI |
|---|
| NICER | 45.9 | | Effelsberg 100m | 2cm and 14mm bands |
|---|
| NuSTAR | 107+65+63 | | H.E.S.S | TeV 10 ks/day |
|---|
| Swift | 20 | | MAGIC | 30 GeV - 100 TeV |
|---|
| XMM-Newton | 122.6 | | | |
|---|
Crab
Coordinated observation by INTEGRAL, XMM-Newton, and NuSTAR continue with the goal of refining the NuSTAR and XMM-pn calibration. Observations coordinated with the IXPE schedule (currently 2022-02-21) are also planned.
3C 273
The annual multi-mission cross-calibration campaign will continue in 2022. Note that an IXPE observation is currently planned for 2022-06-16.
Cross-Calibrations of X-ray Satellites with Quasar 3C 273 - Corin Marasco & Kristin Chapman (
pdf)
- Kristin Madsen presented the analysis by Corin Marasco of the XMM-Newton, Chandra, NuSTAR, and Swift observations of 3C 273 that have been performed annually since 2015.
- This is an extension of the work presented in Madsen et al. (2017) AJ 153, 2 https://iopscience.iop.org/article/10.3847/1538-3881/153/1/2
- Joint fitting of the spectra from pairs of observations with matching Good Time Intervals were examined in bands:
- 3-7 keV for NuSTAR + Chandra/Swift/XMM-Newton pairs
- 1-5 keV for Chandra/Swift/XMM-Newton pairs
- Absorbed power-law model (zpow*cflux*tbabs) used to examine the measured flux relative to the model flux
- Example for 2017 observations:
 | Model parameters from the 2017 observations 
|
 | 
Cross normalization constants from the pairs of observations are shown on the left. Note: - The Swift fluxes appear relatively high - perhaps due to the extraction annulus used - the analysis will be checked wit the Swift team
- Analysis above 1 keV chosen to avoid known soft excess in 3C 273 spectrum
|
 |
- Communication with the Chandra team is underway to check the Chandra analysis
- The NuSTAR analysis will be redone with the updated calibration released this month (2021 October)
- NICER observations will also be folded into the analysis (Renee Ludlam)
- Analysis will be extended to evaluate within the concordance framework (arXiv)
- Flux ratio examined in narrow energy bands - model independent
- There is some complexity to the XMM spectrum - Felix Fuerst
- with correlated residuals between instruments
- Work is continuing and will include the 2021 XMM-Newton observations as well as the NICER observations.
NuSTAR observations of 1ES 0229+200 - Hannah Earnshaw (pdf)
- Three exposures obtained in August, 2021 (200 ks total)
- Compared to three short (~20 ks each) exposures obtained in 2013
- Spectrum can be modeled as an absorbed power law or a log-parabola continuum
- The source appears softer (gamma 2.03 -> 2.25) and fainter (about 25%) in the 2021 observations compared to 2013
- Even at historically low flux state the source is still sufficient for cross-calibration purposes
Swift-XRT monitoring of 1ES 0229+200
1ES 0229 with XMM-Newton and its impact on calibration - Felix Fuerst (pdf)
- 1ES 0229+200 observed on Oct 8-10, 2021
- 18.8 ks full frame exposure lost due to very bad background flaring
- Analysis of 60 ks small window EPIC-pn exposure presented
- can be modeled as an absorbed power law or cutoff power law
- Combined analysis with simultaneous 95 ks NuSTAR observation
- Fit improved with cutoff power law above 20 keV
- New NUSTAR calibration (CALDB20211020) improves agreement between NuSTAR FPM modules
- Analysis of joint XMM / NuSTAR observing campaign on the Crab was presented
- Observations performed every ~6 months
- Observations are used to create a correction functionfor EPIC-pn ARF
- Correction function will be vetted with more observations (calculated using MCMC)
- Analysis of joint observations of 3C 273 and 1ES 0229+200 indicate that EPIC-pn normalization is ~83% of (updated) NuSTAR FPMA
- Calibration update for EPIC-pn is being developed
- Power-law slope of 1ES 0229+200 will be evaluated with XMM-MOS+OM and Swift-XRT+UVOT data
Discussion
- It was noted that the new NuSTAR calibration appears to push the relative normalizations of XMM-pn and NuSTAR-FPM further apart
- Need to be careful to use similar extraction regions in analysis of Crab observations for cross-calibration purposes
- (extended source so observations at different epochs = different roll can sample different areas of the remnant)
- Chandra observations show spectral curvature
- however no improvement is seen when more complex models are used
Observation of 1ES 0229+200 with Astrosat - Sunil Chandra
- 1ES 0229+200 is a faint source for Astrosat-SXT, 74 ks exposure obtained in 2021 August
- Modeled as an absorbed power law
- Excess above 5 keV may be due to background and features below 0.5 keV may be residual calibration artifacts
- Astrosat-UVIT data is yet to be released
- There is also a previous observation by Astrosat (that may not be available yet)
Action Items:
- Jamie Kennea - will contact Andy B. to see if Swift-XRT 2021 data for 1ES 0229+200 will be analyzed
- Renee Ludlam - Will work with Felix F. on joint analysis of NICER observations of 1ES 0229+200
The meeting concluded after a discussion about supporting IXPE in-flight calibration
- Launch scheduled for Dec 9th, 2021
- There are many coordinated observations approved for scientific programs with INTEGRAL, XMM-Newton, NuSTAR, etc.
- Some may be useful for cross-calibration
2021 May 13th - Working group meeting
Held on Zoom
Attending (in alphabetical order):
Dipankar Bhattacharya, Karl Forster, Felix Fuerst, Jamie Kennea, Kristin Madsen, Herman Marshall, Eric Miller, Katja Pottschmidt, Celia Sanchez, Norbert Schartel, Michael Smith, Allyn Tennant, Yukikatsu Terada, Panayiotis Tzanavaris, Josh Wing
Review status of working group
- The chair has been very quiet since the last IACHEC meeting in May 2019 (apologies).
- Membership is open to all and has 60 colleagues subscribed to the WG slack channel (#coordinated-obs)
- Cross-calibration observations on 3C 273 were coordinated (thanks to Josh W. for starting the ball rolling with Chandra constraints each year)
- 2019-07-02 to 03 - Chandra, INTEGRAL, NICER, NuSTAR, Swift, XMM
- 2020-07-06 to 07 - Chandra, INTEGRAL, NICER, NuSTAR, Swift, XMM
- Communications
- There were no strong opinions about how best to communicate between WG members. Currently:
- email chair (Karl F.) krl _at_ srl.caltech.edu
- Slack channel: iachec.slack.com
- an email list server (hosted by Caltech) may be set up by Karl F. depending on what the other WG’s think (particularly the communications WG).
- Dissemination of observation scheduling information
- International standards for target visibility and observation schedules have been developed by a team at ESAC, see https://www.cosmos.esa.int/web/vovisobs_protocols/home
- A client using these standards (ObjVisSAP, ObsLocTAP) implemented for INTEGRAL, XMM-Newton, Chandra, and NuSTAR is active (TOBY), see http://integral.esa.int/toby/
- (just click on the Calculate button to get latest schedules)
- Observatories are joining the callobaration (GAIA, NOT, MAGIC, XRISM)
- All IACHEC observatories are encouraged to join
- See also SmartNet http://www.isdc.unige.ch/smartnet/index.php
- Information about calibration targets and upcoming observations collected in google sheets
A/I Request that WG chairs look at lists on the google sheets and make/suggest additions/corrections
2021 3C 273 Cross-calibration campaign
- Confirmed observations scheduled for 2021 June 9th to 11th with Chandra, INTEGRAL, NuSTAR, XMM
A/I Swift - Jamie K. thinks it likely that Swift will perform some observations - will contact Andy B. to check
A/I NICER - Karl F. will contact NICER team to see if they will join
- Kristin M. is advising two SURF students this (2021) summer in analysis of 3C 273 data taken since 2015
| Mission | 2015 | (ks) | 2016 | (ks) | 2017 | (ks) | 2018 | (ks) | 2019 | (ks) | 2020 | (ks) | 2021 |
|---|
| Chandra | 2015-07-14 | 30 | 2016-06-27 | 30 | 2017-06-26 | 27 | 2018-07-04 | 30 | 2019-07-03 | 30 | 2020-07-06 | 29 | Y |
| INTEGRAL | 2015-07-13 | 150 | 2016-06-26 | 100 | 2017-06-26 | 175 | 2018-07-04 | 100 | 2019-07-02 | 100 | 2020-07-04 | 120 | Y |
| NICER | | 2018-07-09 | 1.5 | 2019-06-30 | 38 | 2020-07-08 | 25 | ? |
| NuSTAR | 2015-07-13 | 49 | 2016-06-26 | 35 | 2017-06-26 | 35 | 2018-07-04 | 40 | 2019-07-02 | 49 | 2020-07-06 | 44 | Y |
| Swift | 2015-07-12 | 18 | 2016-06-26 | 40 | 2017-06-23 | 22 | 2018-07-14 | 17 | 2019-07-12 | 16 | 2020-07-16 | 18 | ? |
| XMM | 2015-07-13 | 72 | 2016-06-26 | 67 | 2017-06-26 | 67 | 2018-07-04 | 78 | 2019-07-02 | 69 | 2020-07-06 | 70 | Y |
A/I Kristin M. Requests the teams (Chandra, Swift, XMM, NICER) provide (processed) data ready for joint analysis
- It has always been difficult for Astrosat to join because 3C 273 is at low declination
- 3C 273 is a good target for XMM-RGS but there is pileup for EPIC instruments
A/I Karl F. will contact Konrad D. to see if SRG-eROSITA/ART-XC has survey footprint close to dates of IACHEC campaigns
Additional cross-calibration opportunities
- NuSTAR / XMM-Newton observations of the Crab in 2020/22
- Leading to revised calibration expected in 2021
- Insight-HXMT will join in future observations - Lian T.
IACHEC Support for in-flight calibration of upcoming missions
IXPE - From Allyn T.
- Launch planned for 2021 November 17th
- Science observations begin around mid-December
- Target Visibility will be 90 deg from the Sun +/- 25 deg
- For observatory verification plan to observe:
- Crab: Two half-day observations separated by about a week (due to telemetry limit)
- 1ES 1959+650: used to check alignments - good target for IXPE as it is close to NEP and not too bright or faint
A/I Begin scheduling discussions a few months before launch (discuss details at September IACHEC meeting?)
- From Herman M.
- May also use Cyg X-1 in observatory verification
- Must be careful not to perform observations that potentially step on goals of science investigations
- Other coordinations?
- Astrosat-CZTI - Dipankar B.
- Polarization seen in Crab data and possibly Cyg X-1
- However - energy range (>100 keV) not close to IXPE (< 10 keV) so cross-calibration is likely to be a science investigation
- Other polarization missions?
- POLSTAR - not launched
- polarlight - GPD
- Launch likely to be between Sep 2022 - Aug 2023
- Effective area calibration observations will need ~30 ks (or at least 20 ks of overlap with coordinating observatories)
- NuSTAR will be useful to be able to calibrate XRISM instruments up to (possibly) 25 keV
- GTI based simultaneous periods would only be possible for a short time (< 1 day) due to relative orbit precession
- so aim for overlapping start/stop coordinated scheduling of calibration targets
- Crab will be used to calibrate effective area of RESOLVE
A/I Meet to discuss details of coordinated calibration observations at least 3-months before the official launch date to give time for missions to organize targets/scheduling
The potential of 1ES 0229+200 for calibration - Norbert Schartel & Felix Fuerst
- Motivation - Calibration model differences between NuSTAR and XMM-pn - soft excess?
- Is this caused by dust on mirror (or loss of mirror shells)?
- Blazars are good calibration sources - flat spectra between 200 eV and 15 keV
- Hence 3C 273 - (Swift monitoring) but this is bright of some missions and may some complexities to spectrum in this energy range
- Mkn 421 is difficult to model SED
- 1ES 0229+200
- XMM-MOS1 and PN can be fit with very simple power law + absorption
- Good fit of Power-law extrapolated to UV-Optical (XMM-OM)
- Flux is ~ 20% of 3C 273 so exposure time allocation will be larger but this may avoid pileup in sensitive missions
- Conclusion - Unique chance to calibrate from UV to X-ray
- Caveat - Source is variable - blazer! see Swift monitoring - so would require ~simultaneous observations (within ~few days)
- Past XMM and NuSTAR observations (separated by years) does not show evidence for significant spectral change (but observed at different flux levels)
- Target is not bright enough for INTEGRAL calibration observation
- For Swift the target may be too bright for PC-mode (pileup) but too faint for WT-mode - Jamie K.
- XMM + NuSTAR observations planned for 2021 July-August
- Swift observations will be requested - maybe multiple to examine variability
- Will ask for Swift-UVOT UV filters for cross-check calibration of XMM-OM
- TeV observatories HESS, MAGIC, and VERITAS have indicated they may join the campaign (likely with radio coverage)
- We encourage all missions to join cross-calibration campaign
A/I Dipankar B. will check if this is a good target for Astrosat
A/I Karl F.+Norbert S.+Felix F. will discuss with Chandra about whether there is possibility for joining next year (this year may be difficult to organize)
A/I Jamie K. will check with Andy B. about whether Swift would be able to join (in PC-mode?)
A/I Karl F. will check with NICER team and insight-HXMT
A/I Eric M. will investigate if 1ES 0229+200 may be too bright for XRISM (pileup)
The Working Group report will be given at the Spring working group meeting on Tuesday, May 18th (1400 UT)
Attachments:
