Coordinated Observations

Chair Karl Forster (Caltech, NuSTAR) - krl at srl.caltech.edu
Members
Manabu Ishida (chair; JAXA, Suzaku, Astro-H)

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
  - https://docs.google.com/spreadsheets/d/1EA_7c0J2c4kX62t-qoVDLXJiE0SkS8sqZiBjokJbUKs/edit?usp=sharing
  - including a timeline

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 a SURF student 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

This will be an update to Madsen et al. (2017) AJ 153, 2 https://iopscience.iop.org/article/10.3847/1538-3881/153/1/2

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

XRISM - (see IACHEC plenary presentation) Eric M.

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

Presentation: 20210513_IACHEC.pdf

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)