#  Limits on the hard X-ray emission from the periodic fast radio burst FRB
180916.J0158+65

Sibasish Laha Center for Space Science and Technology, University of Maryland
Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.  Astrophysics
Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
Center for Research and Exploration in Space Science and Technology,
NASA/GSFC, Greenbelt, Maryland 20771, USA  Zorawar Wadiasingh Department of
Astronomy, University of Maryland, College Park, Maryland 20742, USA
Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD
20771, USA.  Center for Research and Exploration in Space Science and
Technology, NASA/GSFC, Greenbelt, Maryland 20771, USA  Tyler Parsotan Center
for Space Science and Technology, University of Maryland Baltimore County,
1000 Hilltop Circle, Baltimore, MD 21250, USA.  Astrophysics Science Division,
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.  Center for
Research and Exploration in Space Science and Technology, NASA/GSFC,
Greenbelt, Maryland 20771, USA  Amy Lien University of Tampa, Department of
Chemistry, Biochemistry, and Physics, 401 W. Kennedy Blvd, Tampa, FL 33606,
USA  George Younes Astrophysics Science Division, NASA Goddard Space Flight
Center, Greenbelt, MD 20771, USA.  Bing Zhang Nevada Center for Astrophysics,
University of Nevada, Las Vegas, NV 89154, USA  Department of Physics and
Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 USA.  S.
Bradley Cenko Astrophysics Science Division, NASA Goddard Space Flight Center,
Greenbelt, MD 20771, USA.  Joint Space-Science Institute, University of
Maryland, College Park, MD 20742, USA  Eleonora Troja Astrophysics Science
Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
University of Rome Tor Vergata, Department of Physics, via della Ricerca
Scientifica 1, 00100, Rome, IT  Samantha Oates School of Physics and
Astronomy, University of Birmingham, Birmingham B15 2TT, UK  Institute for
Gravitational Wave Astronomy, University of Birmingham, Birmingham B15 2TT, UK
Matt Nicholl School of Physics and Astronomy, University of Birmingham,
Birmingham B15 2TT, UK  Institute for Gravitational Wave Astronomy, University
of Birmingham, Birmingham B15 2TT, UK  Eileen Meyer Department of Physics,
University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD
21250, USA.  Josefa González Becerra Instituto de Astrofísica de Canarias
(IAC), E-38200 La Laguna, Tenerife, Spain  Universidad de La Laguna (ULL),
Departamento de Astrofísica, E-38206 La Laguna, Tenerife, Spain  Ritesh Ghosh
Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, 411007,
India.  Noel Klingler Center for Space Science and Technology, University of
Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD
20771, USA.  Center for Research and Exploration in Space Science and
Technology, NASA/GSFC, Greenbelt, Maryland 20771, USA Sibasish Laha
sibasish.laha<EMAIL_ADDRESS>
###### Abstract

FRB 180916.J0158+65 is one of the nearest, periodically repeating, and
actively bursting fast radio burst (FRB) which has been localized to the
outskirts of a spiral galaxy. In this work we study the FRB with the hard
X-ray $14-195\rm\,\,{\rm keV}$ data from the Burst Alert Telescope (BAT) on
board The Neil Gehrels Swift observatory. BAT uses coded mask technology
giving a localization of $\lesssim 3$ arc-minute in the hard X-ray band, along
with an accurate background estimation. BAT has been observing the source
location in survey mode since February 2020. The survey mode observations
involves background subtracted spectra, integrated over a time span ranging
$300-2000$ seconds, at the source location (from Feb 2020-Jan 2022). We
analyzed all the $\sim 230$ survey mode observations from BAT and checked for
any signal in any of the observations. We did not detect any signal at
$>5\sigma$ confidence level in any of the observations. We could estimate a
$5\sigma$ upper limit on the $14-195\rm\,\,{\rm keV}$ flux, which ranged
between $4.5\times 10^{-10}-7.6\times 10^{-9}\rm\,erg\,cm^{-2}\,s^{-1}$. At
the source distance this relates to a $5\sigma$ upper limit on luminosity of
$5.08\times 10^{44}-8.5\times 10^{45}\rm\,erg\,s^{-1}$. With this estimate, we
could rule out any persistent X-ray emission, at the source location for these
snapshots of BAT observations.

Fast Radio Bursts

††journal: ApJ

##  1 Introduction

Fast radio bursts (FRBs) are bright, millisecond duration radio outbursts
whose origin is still not clearly understood. To date, most FRBs possess
dispersion measures (DM) larger than that of our own galaxy implying distances
consistent with an extra-galactic origin. In a few cases the host galaxies of
these FRBs have been localized. For e.g., FRB 121102 (Tendulkar et al., 2017),
where the authors have found that it’s located within a dwarf galaxy at a
redshift of $z\sim 0.192$ and there is a faint persistent radio source of
unknown origin at the FRB location (Chatterjee et al., 2017). Most FRBs have
not been found to repeat. But deeper sky surveys such as CHIME/FRB are
revealing an increasing number of repeater FRBs (Fonseca et al., 2020;
CHIME/FRB Collaboration et al., 2019b; Amiri et al., 2021). It has been
proposed that most FRBs that we observe are actually repeaters because their
all sky rates largely exceed the all sky rates of known cataclysmic events
(see e.g., Nicholl et al., 2017; Ravi, 2019; Zhang, 2020, and references
therein).

FRB 180916 is one of the most well known repeaters and also one of the most
nearby FRBs detected to date. In December 2019, the CHIME/FRB collaboration
reported the discovery of eight new repeating FRBs including FRB 180916, which
was localized to a star forming region of a nearby massive spiral galaxy at a
redshift of $z=0.0337\pm 0.0002$ (Marcote et al., 2020). The FRB 180916
exhibited $\sim 38$ radio bursts during September 2019- October 2020, showing
a clear periodicity of $16.35\pm 0.15$ days, the first for any FRB. All the
bursts arrived in a 5 day phase window and almost $50\%$ of the bursts arrived
in the 0.6 day phase window, and it’s the most active FRB in the published
CHIME/FRB sample (CHIME/FRB Collaboration et al., 2019a). The periodicity
suggests a mechanism which periodically modulates the observed emission
itself, or a periodic burst, or something else. Hence, this source is the
focus of intense multiwavelength campaigns.

High energy emission from magnetars has long been thought to be one of the
important mechanisms by which the FRBs may also be generated (see Margalit et
al., 2020, and references therein). The recent discovery of the connection
between FRB200428 and SGR 1935 (Mereghetti et al., 2020; Li et al., 2021;
Younes et al., 2020, 2021; Margalit et al., 2020; CHIME/FRB Collaboration et
al., 2020; Kirsten et al., 2021) confirmed this fact, that at least some of
the FRBs are produced by magnetar short bursts. The typical radio to X-ray
fluence measured was $\eta\equiv E_{\rm R}/E_{\rm X}\sim 10^{-5}$, implying
that the radio emission is weak and contributes little to the overall burst
energy budget. Moreover the radio fluence of FRB200428 was somewhat lower
compared to its extragalactic counterparts (the STARE2 burst energetics
however are strictly a lower limit since some of the burst appears to be out-
of-band). Variable high energy emission at different timescales (ms to years)
is one of the key features of magnetars, and may have a relation to the FRB
emission (Coti Zelati et al., 2018; Younes et al., 2020, 2015; Palmer et al.,
2005).

Here we discuss three most common types of emission phenomenology from
magnetars. Firstly, the flares associated with the short bursts which can be
bright ($L_{\rm X}\leq 10^{42}\rm\,erg\,s^{-1}{}$) and lasts a few 100s of ms.
These short bursts may happen in isolation, or during a burst storm when
hundreds of them are detected continuing for days. Secondly, magnetars can
exhibit giant flares, which consist of a very bright pulse ($L_{\rm X}\leq
10^{47}\rm\,erg\,s^{-1}{}$) at sub-ms level, followed by a softer pulsating
tail lasting for several minutes. These events have been detected in three
Galactic magnetars (e.g., SGR1806 Mazets et al., 1979; Hurley et al., 1999;
Palmer et al., 2005). Thirdly, on longer timescales, magnetars recurrently
enter outburst phases, when their persistent flux level increases by orders of
magnitude, accompanied by random spectral and temporal variability. These
phases often persist for a few months to years, after which they recover to
their pre-outburst levels. In this work we focus on detecting the second and
third kinds of emission from a putative extragalactic magnetar powering FRB
180916. Swift Burst Alert Telescope (BAT) survey observations, which cover the
energy range $14-195\rm\,\,{\rm keV}$ and having a time-integration of a few
100s of seconds, are constraining to models of young magnetars undergoing
giant flares.

Several works studying the X-rays to $\gamma$-rays have put upper limits on
the possible non-detection from the sky location of the FRB 180916. Verrecchia
et al. (2021) using AGILE in the energy range $0.4\rm\,\,{\rm
MeV}{}-30\rm\,\,{\rm GeV}{}$ could put an upper limit on the total hard X-ray
energy of $\sim 10^{46}\rm\,\,{\rm erg\,s^{-1}}{}$ comparable to that of SGR
1806-20. Although the extragalactic FRBs emit radio pulses of energies which
are significantly larger than that detected from SGR 1935, there are no
simultaneous or contemporaneous detections of $\rm\,\,{\rm keV},\,\rm\,\,{\rm
MeV},\,\rm\,\,{\rm GeV}$ photons to-date. Contemporaneous X-ray and radio
observations of the FRB 180916 were carried out by Scholz et al. (2020), with
CHIME and Chandra X-ray observatory. They detected no X-ray events in excess
of the background, and the non-detections imply a $5\sigma$ fluence limit of
$<5\times 10^{-10}\rm\,erg\,cm^{-2}{}$ in the $0.5-10\rm\,\,{\rm keV}$ energy
range during the prompt emission and $<1.3\times 10^{-9}\rm\,erg\,cm^{-2}{}$
any time during the observations. Given the cosmological distance of this FRB,
these relate to the total isotropic energies $<1.6\times 10^{45}$ erg and
$<4\times 10^{45}$ erg respectively. In the $10-100\rm\,\,{\rm keV}$ Fermi GBM
search for prompt emission (Scholz et al., 2020) led to a fluence upper limit
of $9\times 10^{-9}\rm\,erg\,cm^{-2}$. Tavani et al. (2020) searched for
contemporaneous $\gamma$-ray emission from FRB 180916 using AGILE and X-ray
emission using XRT telescope onboard The Neil Gehrels Swift observatory (Swift
from now on), during the bursting phases of the source in February and March
2020. They did not detect any hard X-ray or $\gamma$-ray photons, and could
provide a persistent flux upper limit of $5\times
10^{-14}\rm\,erg\,cm^{-2}\,s^{-1}$ which translates to an isotropic luminosity
of $L_{\rm X}\sim 1.5\times 10^{41}\rm\,erg\,s^{-1}$. Guidorzi et al. (2020)
using the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) could provide
a prompt emission upper limit in hard X-rays ($1-100\rm\,\,{\rm keV}$) of
$<10^{46}$ erg over a timescale of $\Delta t<0.1$s. They could rule out giant
flares similar to the ones that were observed in Galactic magnetars.

FRB sources like magnetars may emit the majority of their flux at photon
energies $>10\rm\,\,{\rm keV}$ (Margalit et al., 2020; Scholz et al., 2017;
Turolla et al., 2015; Woods & Thompson, 2006). To study the possible hard
X-ray emission in the $14-195\rm\,\,{\rm keV}$ energy band, we analyze all the
available Survey mode observations from BAT onboard Swift. BAT’s well-suited
energy range ($14-195\rm\,\,{\rm keV}$) coupled with hundreds of pointing on
the source over a period extending Feb 2020- Jan 2022, serves as a unique
opportunity for us to capture any hard X-ray emission from the FRB 180916
and/or put upper limits on the short term ($100$s of sec) or long term
($\sim$year) persistent X-ray emission from the source.

The paper is arranged as follows: Section 2 discusses the observations and
data analysis. Section 3 discusses the results, followed by conclusions in
Section 4.

##  2 Observation and data analysis

FRB 180916 has been observed by Swift BAT (Gehrels et al., 2004; Barthelmy et
al., 2005) $\sim 220$ times from Feb 2020 - Jan 2022 in the survey mode. We
checked in the CHIME FRB catalog (Amiri et al., 2021) for the time stamps of
the $\sim 90$ radio bursts detected to date from FRB 180916. Unfortunately,
none of the CHIME reported burst times were coincident with our BAT survey
observations. We also note that there are no time tagged event (TTE) data
avaiable in BAT archive where the FRB 180916 is in the field-of-view of BAT.
For out of the field-of-view sources, the response matrix of BAT is highly
uncertain and hence any measurement of flux is associated with large errors,
hence we did not use them in this work. Below we describe the methods used to
obtain the survey datasets, reprocess and analyze them. We have extensively
used bat-tools from HEASOFT.

The BAT “survey" mode data are also known as detector plane histograms or
DPHs. As opposed to event data, BAT survey data is accumulated in histograms
on-board the spacecraft, with typical integration times of 300 seconds or
more. An 80-channel binned spectrum is recorded for each of the active
detectors and saved in the DPH files. In this work we use all the available
BAT datasets and we explain below the steps we have taken to reprocess and
analyze them (See Table 5 for a full list of observations).

The BAT survey datasets were downloaded from HEASARC, and every survey
observation has one or more pointings and hence different integration time.
The task batsurvey performs basic analysis of BAT survey data and reduces a
set of “raw” observed DPHs. Most importantly, it performs data screening that
the BAT team has found vital for obtaining good quality results. It produces
sky images and source fluxes for each independent “snapshot," corresponding to
a single pointed visit by BAT. We chose a set of 8 independent energy bins,
and batsurvey recorded the images and fluxes in each of those bands
separately. batsurvey operates on a single BAT observation. For multiple
observations, we used batsurvey once for each observation. We provided the
source RA and Dec in the catalog which was used as an input to batsurvey.

The output from batsurvey gives us exposure-specific results. For example, one
of the important files produced for each pointing is the flux catalog. This
catalog contains sources listed in the input catalog (which in this case
includes FRB 180916) as well as sources detected by blind search. From this
file, we create the lightcurve for the source FRB 180916 using the command
“batsurvey-catmux". We then extract the Tstart, and $\Delta T$ from the
lightcurve and obtain the time integrated spectrum with eight energy channels.

In the first round, to generate the source spectrum we choose “CENT-RATE" as
the column for rate array, and use the background variance (BKG-VAR) for the
error on the rate. We note that the source spectrum is already background
subtracted due to coded mask technique, hence sometimes when the background
variance is larger than the “net source" counts, then the count rate may
become negative. Once the spectrum is obtained we obtain the response matrix
using the task “batdrmgen". We used the model cflux*powerlaw in XSPEC notation
to estimate the flux in the $14-195\rm\,\,{\rm keV}$ energy band. We froze the
powerlaw normalization to a value of $1e-03$ and kept the powerlaw slope
($\Gamma$) free, in order to calculate the flux using the model above. We did
not detect any excess emission above the background (at a $>5\sigma$
confidence) in any of the pointings of this source.

In the second round, we re-extracted the spectrum for every pointing, now
using the $5\times$ BKG-VAR as the rate array. Here we use a simple powerlaw
model with $\Gamma=1$ fixed, to estimate the flux in the $14-195\rm\,\,{\rm
keV}$ energy range. Note that this is the $5\sigma$ upper limit on the
background variance and hence the $5\sigma$ upper limit on the flux. In Table
1 we quote the $5\sigma$ upper limit on the $14-195\rm\,\,{\rm keV}$ flux
obtained for all the available BAT pointings. To carry out all the above steps
in a coherent way, we developed a user friendly pipeline in python, which will
be published in the near future.

##  3 Results and Discussion

We have carried out a hard X-ray counterpart search of the FRB 180916 using
“survey" mode observations of BAT onboard Swift. We have analyzed all
available observations as of 15th January 2022, using standard analysis
methods. We do not detect any source signal in excess of background with
$>5\sigma$ significance. The $5\sigma$ upper limit on the background flux
range from $4.5\times 10^{-10}-7.6\times 10^{-9}\rm\,erg\,cm^{-2}\,s^{-1}$ for
different pointings of BAT survey observations. At the source distance this
relates to a $5\sigma$ upper limit on luminosity of $5.08\times
10^{44}-8.5\times 10^{45}\rm\,erg\,s^{-1}$. Below we discuss our results in
context to previous estimates of X-ray limits on this source and also discuss
the possible progenitor scenarios. We note that the CHIME measured fluences
for this FRB vary considerably, and one representative value is $\sim 27$ Jy-
ms (for the burst ID:181222, in the CHIME catalog). Unfortunately, we did not
have any simultaneous CHIME and BAT (in-field-of-view) observation.

Observations with AGILE telescope (Tavani et al., 2021), working in the energy
range $400\rm\,\,{\rm keV}-100\rm\,\,{\rm MeV}$, could constrain the bursting
X-ray energy of FRB 180916 to $\sim 10^{46}$ erg, which is smaller than that
observed from giant flares from Galactic magnetars. Similar upper limits of
$\sim 10^{46}$ erg on the bursting energy of the FRB 180916 were obtained
using Insight-HMXT in the energy range $1-100\rm\,\,{\rm keV}$ (Guidorzi et
al., 2020). On the soft X-ray range $0.3-10\rm\,\,{\rm keV}$ strong limits on
persistent luminosity ($<2\times 10^{40}\rm\,erg\,s^{-1}$) and prompt emission
fluence ($<5\times 10^{-10}\rm\,erg\,cm^{-2}$) could be obtained during the
bursting phases of the FRB 180916 using observations from Chandra (Scholz et
al., 2020). Similarly, Tavani et al. (2020) could put a cumulative upper limit
on the X-ray flux using Swift XRT observations $F<5\times
10^{-14}\rm\,erg\,cm^{-2}\,s^{-1}$, obtained during the five day of active
period of the source. These clearly rule out magnetar giant flares and/or SGR
1935 type events.

The Swift-BAT flux upper limits in $14-195\rm\,\,{\rm keV}$, obtained in this
work, of a few $\times 10^{-9}\rm\,erg\,cm^{-2}\,s^{-1}$ correspond to
luminosity limit of about $\sim 10^{45}\rm\,erg\,s^{-1}$ at the source
location (that is at $149\,{\rm Mpc}$). We discuss the following three
progenitor scenarios:

  * •

Magnetar Giant Flares (MGF): Typical magnetar giant flares with luminosity
$\sim 10^{47}\rm\,erg\,s^{-1}$, lasting for $\sim 0.1$sec(Burns et al., 2021),
would lead to an average luminosity of $\sim 10^{43}\rm\,erg\,s^{-1}$, when
averaged over 1000 seconds of a typical BAT survey observation. This would
correponds to a flux of $\sim 4\times 10^{-12}\rm\,erg\,cm^{-2}\,s^{-1}$. This
flux level is well below the flux level that BAT is sensitive to, and hence we
cannot rule out an MGF event.

  * •

Pulsating tails of MGF: The pulsating tails have a typical luminosity of
$10^{42}\rm\,erg\,s^{-1}$, and their peak energy lies in the BAT energy range,
and they extend for several seconds (Burns et al., 2021; Younes et al., 2020).
The corresponding flux emitted by such pulsating tails would be $\sim
10^{-13}\rm\,erg\,cm^{-2}\,s^{-1}$ which is well below the flux level that BAT
is sensitive to.

  * •

For an SGR 1935 type event: For such an event happening at the location of FRB
180916 the expected $20-200\rm\,\,{\rm keV}$ flux is about a few$\times
10^{-14}\rm\,erg\,cm^{-2}\,s^{-1}$ (Mereghetti et al., 2020; Li et al., 2021).
This flux level is also well below the flux level that BAT is sensitive to,
and hence we cannot rule out an event like SGR 1935.

Our limits exclude any persistent emission or transient activity with the
source position down to $\sim 10^{45}$ erg s-1. The possible progenitor of FRB
180916 might be older than canonical magnetars, based on the offset reported
in Tendulkar et al. (2021). The authors suggest that the spatial offset and
hence the timescale (of travel from its presumed birth site) points more
towards high-mass X-ray binaries and gamma-ray binaries, rather than
magnetars. Given the unpredictable nature of FRBs and magnetars, such multi-
band long term monitoring snapshots are extremely useful. Future opportunities
with prompt downlink and analysis of Swift-BAT time-tagged-event (TTE) data of
FRBs (GUANO, Tohuvavohu et al., 2020; DeLaunay & Tohuvavohu, 2021),
contemporaneous with radio bursts will open up new avenues of hard X-ray
follow up of these hitherto unknown phenomenon.

##  4 Conclusions

We searched for high-energy transients in Swift BAT survey mode data
associated with FRB 180916 from February 2020 to January 2022. We did not
detect any significant emission in the $14-195\rm\,\,{\rm keV}$ energy band in
any of our observational snapshots when the FRB 180916 was in the field of
view of BAT. The upper limits on the flux estimated in these observations
exclude any persistent emission or transient activity with the source position
down to $\sim 10^{45}$ erg s-1, for all the snapshots. Our results confirm and
corroborate previous limits of high energy transients by Fermi-GBM, AGILE,
HXMT-Insight and XMM-Newton.

Table 1: List of Swift-BAT survey-mode observations of FRB 180916, and the
$5\sigma$ upper limit on the fluxes in the energy band $14-195\rm\,\,{\rm
keV}$.

Obs ID | Pointing ID | Start time (MET) | Start time (UTC) | exposure | flux upper-lim
---|---|---|---|---|---
| number |  | year:day:hr:min:sec | (sec) | $\rm\,erg\,cm^{-2}\,s^{-1}{}$
00013201002 | 20200341843 | 602448230.0 | 2020Feb03 at 18:43:25 | 240.0 | 3.35e-09
00013201005 | 20200371529 | 602695795.0 | 2020Feb06 at 15:29:30 | 1088.0 | 2.32e-09
00013201006 | 20200381645 | 602786919.0 | 2020Feb07 at 16:48:14 | 684.0 | 2.81e-09
| 20200381523 | 602781819.0 | 2020Feb07 at 15:23:14 | 1044.0 | 2.35e-09
00013201007 | 20200391516 | 602867799.0 | 2020Feb08 at 15:16:14 | 1044.0 | 2.39e-09
| 20200391702 | 602874130.0 | 2020Feb08 at 17:01:45 | 233.0 | 4.99e-09
00013201008 | 20200561709 | 604343363.0 | 2020Feb25 at 17:08:58 | 300.0 | 2.51e-09
| 20200561535 | 604337736.0 | 2020Feb25 at 15:35:11 | 179.0 | 1.62e-09
| 20200561400 | 604332006.0 | 2020Feb25 at 13:59:41 | 177.0 | 5.90e-09
00013201009 | 20200651430 | 605111453.0 | 2020Mar05 at 14:30:28 | 600.0 | 4.00e-09
00013201011 | 20200671419 | 605283823.0 | 2020Mar07 at 14:23:18 | 300.0 | 5.38e-09
00013201014 | 20200701357 | 605541476.0 | 2020Mar10 at 13:57:31 | 1567.0 | 2.39e-09
00013201019 | 20200871153 | 607002839.0 | 2020Mar27 at 11:53:34 | 1744.0 | 2.31e-09
00013201021 | 20201141454 | 609346533.0 | 2020Apr23 at 14:55:08 | 150.0 | 8.09e-09
| 20201141435 | 609345333.0 | 2020Apr23 at 14:35:08 | 900.0 | 3.60e-09
00013201023 | 20201161102 | 609505344.0 | 2020Apr25 at 11:01:59 | 1659.0 | 2.95e-09
00013201024 | 20201171055 | 609591323.0 | 2020Apr26 at 10:54:58 | 1660.0 | 2.96e-09
00013201025 | 20201181536 | 609694745.0 | 2020Apr27 at 15:38:40 | 1378.0 | 2.73e-09
00013201026 | 20201191526 | 609780416.0 | 2020Apr28 at 15:26:31 | 1687.0 | 2.50e-09
00013201027 | 20201201522 | 609866526.0 | 2020Apr29 at 15:21:41 | 1677.0 | 2.36e-09
00013201028 | 20201470743 | 612171836.0 | 2020May26 at 07:43:30 | 727.0 | 2.92e-09
| 20201470915 | 612177309.0 | 2020May26 at 09:14:43 | 654.0 | 3.13e-09
00013201029 | 20201480730 | 612257414.0 | 2020May27 at 07:29:48 | 1069.0 | 2.44e-09
| 20201480904 | 612263088.0 | 2020May27 at 09:04:22 | 855.0 | 2.91e-09
00013201030 | 20201490859 | 612349197.0 | 2020May28 at 08:59:31 | 666.0 | 3.11e-09
00013201031 | 20201500856 | 612435365.0 | 2020May29 at 08:55:39 | 478.0 | 3.61e-09
00013201032 | 20201510852 | 612521583.0 | 2020May30 at 08:52:37 | 240.0 | 5.105e-09
00013201034 | 20201630148 | 613532923.0 | 2020Jun11 at 01:48:17 | 560.0 | 3.52e-09
| 20201630943 | 613561411.0 | 2020Jun11 at 09:43:05 | 1112.0 | 3.087e-09
00013201035 | 20201641554 | 613670061.0 | 2020Jun12 at 15:53:55 | 1302.0 | 2.42e-09
00013201036 | 20201652211 | 613779079.0 | 2020Jun13 at 22:10:53 | 1484.0 | 2.237e-09
00013201037 | 20201661402 | 613836136.0 | 2020Jun14 at 14:01:50 | 1727.0 | 2.16e-09
00013201038 | 20201671357 | 613922236.0 | 2020Jun15 at 13:56:50 | 1607.0 | 2.183e-09
00013201039 | 20201681350 | 614008228.0 | 2020Jun16 at 13:50:02 | 1595.0 | 2.11e-09
| 20201682335 | 614043344.0 | 2020Jun16 at 23:35:18 | 439.0 | 3.88e-09
00013201040 | 20201692005 | 614117139.0 | 2020Jun17 at 20:05:13 | 1584.0 | 2.23e-09
00013201041 | 20201700231 | 614140312.0 | 2020Jun18 at 02:31:26 | 1691.0 | 2.25e-09
00013201043 | 20201800805 | 615024353.0 | 2020Jun28 at 08:05:27 | 600.0 | 3.32e-09
| 20201800604 | 615017085.0 | 2020Jun28 at 06:04:19 | 1098.0 | 2.77e-09
00013201044 | 20201810613 | 615103998.0 | 2020Jun29 at 06:12:52 | 1005.0 | 2.85e-09
| 20201810754 | 615110061.0 | 2020Jun29 at 07:53:55 | 762.0 | 3.03e-09
00013201045 | 20201820727 | 615194850.0 | 2020Jun30 at 07:27:04 | 333.0 | 4.60e-09
| 20201820606 | 615189999.0 | 2020Jun30 at 06:06:13 | 1200.0 | 2.49e-09
00013201046 | 20201830410 | 615269416.0 | 2020Jul01 at 04:09:50 | 467.0 | 4.18e-09
| 20201830603 | 615276238.0 | 2020Jul01 at 06:03:32 | 965.0 | 2.75e-09
00013201047 | 20201840559 | 615362370.0 | 2020Jul02 at 05:59:04 | 813.0 | 3.10-09
00013201048 | 20201850553 | 615448424.0 | 2020Jul03 at 05:53:18 | 799.0 | 2.98e-09
00013201049 | 20201860550 | 615534625.0 | 2020Jul04 at 05:49:59 | 578.0 | 8.3e-10

These datasets are all publicly available in the HEASARC archive as on 15th
January 2022.
The start times of the observations are given in two units. MET: Mission
elapsed time, and UTC: Universal Coordinated time.

Table 2: List of Swift-BAT survey-mode observations of FRB 180916. (Continued)  Obs ID | Pointing ID | Start time (MET) | Start time (UTC) | exposure | flux upper-lim
---|---|---|---|---|---
| number |  | year:day:hr:min:sec | (Sec) | $\rm\,erg\,cm^{-2}\,s^{-1}{}$
00013201051 | 20201960600 | 616399216.0 | 2020Jul14 at 05:59:50 | 1007.0 | 3.00e-09
| 20201960427 | 616393656.0 | 2020Jul14 at 04:27:10 | 687.0 | 3.42e-09
00013201052 | 20201970549 | 616484971.0 | 2020Jul15 at 05:49:05 | 1652.0 | 2.42e-09
00013201053 | 20201980551 | 616571487.0 | 2020Jul16 at 05:51:01 | 576.0 | 3.81e-09
| 20201980419 | 616565963.0 | 2020Jul16 at 04:18:57 | 460.0 | 4.17e-09
00013201054 | 20201990539 | 616657157.0 | 2020Jul17 at 05:38:51 | 826.0 | 3.196e-09
00013201055 | 20202000531 | 616743121.0 | 2020Jul18 at 05:31:35 | 842.0 | 3.33e-09
| 20202000356 | 616737379.0 | 2020Jul18 at 03:55:53 | 764.0 | 3.298e-09
00013201057 | 20202020347 | 616909656.0 | 2020Jul20 at 03:47:10 | 387.0 | 4.45e-09
| 20202020523 | 616915431.0 | 2020Jul20 at 05:23:25 | 432.0 | 4.26e-09
00013201058 | 20202130447 | 617863661.0 | 2020Jul31 at 04:47:15 | 802.0 | 3.74e-09
| 20202130311 | 617857887.0 | 2020Jul31 at 03:11:01 | 516.0 | 4.06e-09
00013201059 | 20202140437 | 617949461.0 | 2020Aug01 at 04:37:15 | 1282.0 | 3.12e-09
| 20202140303 | 617943818.0 | 2020Aug01 at 03:03:12 | 505.0 | 4.40e-09
00013201060 | 20202150430 | 618035428.0 | 2020Aug02 at 04:30:02 | 1200.0 | 3.23e-09
| 20202150255 | 618029745.0 | 2020Aug02 at 02:55:19 | 258.0 | 6.34e-09
00013201061 | 20202160425 | 618121550.0 | 2020Aug03 at 04:25:24 | 900.0 | 3.718e-09
00013201062 | 20202170416 | 618207380.0 | 2020Aug04 at 04:15:54 | 1200.0 | 3.0127e-09
00013201063 | 20202180409 | 618293397.0 | 2020Aug05 at 04:09:31 | 1200.0 | 2.9025e-09
00013201064 | 20202190402 | 618379338.0 | 2020Aug06 at 04:01:52 | 1200.0 | 2.627e-09
00013201065 | 20202290301 | 619239722.0 | 2020Aug16 at 03:01:36 | 1500.0 | 2.2564e-09
00013201066 | 20202300259 | 619325953.0 | 2020Aug17 at 02:58:47 | 300.0 | 1.94e-09
| 20202300313 | 619326853.0 | 2020Aug17 at 03:13:47 | 351.0 | 4.289e-09
00013201067 | 20202310253 | 619412011.0 | 2020Aug18 at 02:53:05 | 1173.0 | 2.4877e-09
00013201075 | 20202450243 | 620621040.0 | 2020Sep01 at 02:43:34 | 1023.0 | 2.7753e-09
| 20202450127 | 620616464.0 | 2020Sep01 at 01:27:18 | 799.0 | 3.1037e-09
00013201076 | 20202460233 | 620706802.0 | 2020Sep02 at 02:32:56 | 1481.0 | 2.439e-09
00013201077 | 20202470252 | 620794340.0 | 2020Sep03 at 02:51:54 | 223.0 | 5.8695e-09
| 20202470227 | 620792840.0 | 2020Sep03 at 02:26:54 | 600.0 | 3.7665e-09
00013201079 | 20202490225 | 620965519.0 | 2020Sep05 at 02:24:53 | 524.0 | 3.803e-09
| 20202490215 | 620964919.0 | 2020Sep05 at 02:14:53 | 600.0 | 3.612e-09
00013201080 | 20202500050 | 621046242.0 | 2020Sep06 at 00:50:16 | 862.0 | 1.07e-09
| 20202500210 | 621051011.0 | 2020Sep06 at 02:09:45 | 300.0 | 1.14e-09
00013201081 | 20202510044 | 621132260.0 | 2020Sep07 at 00:43:54 | 823.0 | 3.15e-09
| 20202510203 | 621137018.0 | 2020Sep07 at 02:03:12 | 865.0 | 2.9225e-09
00013201082 | 20202621247 | 622126051.0 | 2020Sep18 at 12:47:05 | 452.0 | 4.284e-09
00013201083 | 20202630129 | 622171746.0 | 2020Sep19 at 01:28:40 | 600.0 | 1.52e-09
00013201084 | 20202640120 | 622257621.0 | 2020Sep20 at 01:19:55 | 600.0 | 4.183e-09
00013201085 | 20202650112 | 622343567.0 | 2020Sep21 at 01:12:21 | 300.0 | 5.9935e-09
00013201086 | 20202660102 | 622429350.0 | 2020Sep22 at 01:02:04 | 1413.0 | 2.8653e-09
| 20202660240 | 622435259.0 | 2020Sep22 at 02:40:33 | 244.0 | 1.99e-09
00013201087 | 20202670055 | 622515337.0 | 2020Sep23 at 00:55:11 | 900.0 | 3.3738e-09
00013201088 | 20202680048 | 622601317.0 | 2020Sep24 at 00:48:11 | 900.0 | 1.09e-09
| 20202680104 | 622602517.0 | 2020Sep24 at 01:08:11 | 386.0 | 4.797e-09
00013201089 | 20202780123 | 623467428.0 | 2020Oct04 at 01:23:22 | 795.0 | 3.5332e-09
| 20202780256 | 623472974.0 | 2020Oct04 at 02:55:48 | 649.0 | 3.748e-09
00013201090 | 20202790108 | 623552892.0 | 2020Oct05 at 01:07:46 | 291.0 | 5.9376e-09
00013201092 | 20202802325 | 623719559.0 | 2020Oct06 at 23:25:33 | 1684.0 | 2.4675e-09
00013201093 | 20202812317 | 623805468.0 | 2020Oct07 at 23:17:22 | 1755.0 | 2.4223e-09
00013201094 | 20202830045 | 623897158.0 | 2020Oct09 at 00:45:32 | 300.0 | 5.422e-09
| 20202822329 | 623892555.0 | 2020Oct08 at 23:28:49 | 648.0 | 3.5875e-09

Table 3: List of Swift-BAT survey-mode observations of FRB 180916. (Continued) Obs ID | Pointing ID | Start time (MET) | Start time (UTC) | exposure | flux upper-lim
---|---|---|---|---|---
| number |  | year:day:hr:min:sec | (Sec) | $\rm\,erg\,cm^{-2}\,s^{-1}{}$
00013201095 | 20202850045 | 624069912.0 | 2020Oct11 at 00:44:46 | 531.0 | 3.962e-09
| 20202842306 | 624063983.0 | 2020Oct10 at 23:05:57 | 1300.0 | 2.7107e-09
00013201096 | 20202960710 | 625043405.0 | 2020Oct22 at 07:09:39 | 1438.0 | 2.7067e-09
| 20202960540 | 625038245.0 | 2020Oct22 at 05:43:39 | 959.0 | 3.256e-09
| 20202960534 | 625037645.0 | 2020Oct22 at 05:33:39 | 300.0 | 5.359e-09
00013201097 | 20202970710 | 625129843.0 | 2020Oct23 at 07:10:17 | 1639.0 | 2.735e-09
00013201098 | 20202980839 | 625221570.0 | 2020Oct24 at 08:39:04 | 1593.0 | 2.5897e-09
00013201099 | 20202991142 | 625318925.0 | 2020Oct25 at 11:41:39 | 1738.0 | 2.517e-09
00013201100 | 20203001929 | 625433370.0 | 2020Oct26 at 19:29:04 | 1653.0 | 2.126e-09
00013201101 | 20203011759 | 625514363.0 | 2020Oct27 at 17:58:57 | 600.0 | 3.018e-09
00013201102 | 20203131851 | 626554315.0 | 2020Nov08 at 18:51:29 | 300.0 | 4.32e-09
| 20203132200 | 626565653.0 | 2020Nov08 at 22:00:27 | 300.0 | 4.849e-09
| 20203131716 | 626548616.0 | 2020Nov08 at 17:16:30 | 247.0 | 4.689e-09
| 20203132031 | 626560256.0 | 2020Nov08 at 20:30:30 | 187.0 | 6.013e-09
00013201103 | 20203140731 | 626599904.0 | 2020Nov09 at 07:31:18 | 919.0 | 2.765e-09
00013201104 | 20203142018 | 626645888.0 | 2020Nov09 at 20:17:42 | 955.0 | 2.5645e-09
| 20203142149 | 626651392.0 | 2020Nov09 at 21:49:26 | 1151.0 | 7.94e-10
00013201111 | 20203440406 | 629179624.0 | 2020Dec09 at 04:06:37 | 1319.0 | 2.524e-09
00013201112 | 20203450531 | 629271120.0 | 2020Dec10 at 05:31:33 | 1683.0 | 2.3245e-09
00013201113 | 20203481134 | 629552099.0 | 2020Dec13 at 11:34:32 | 1444.0 | 2.415e-09
00013201114 | 20203490816 | 629626618.0 | 2020Dec14 at 08:16:31 | 1565.0 | 2.519e-09
00013201115 | 20203501119 | 629723996.0 | 2020Dec15 at 11:19:29 | 900.0 | 3.0374e-09
00013201116 | 20203651817 | 631045081.0 | 2020Dec30 at 18:17:34 | 782.0 | 3.335e-09
| 20203651956 | 631050977.0 | 2020Dec30 at 19:55:50 | 646.0 | 3.897e-09
00013201117 | 20203661959 | 631137568.0 | 2020Dec31 at 19:59:01 | 300.0 | 5.841e-09
| 20203661808 | 631130943.0 | 2020Dec31 at 18:08:36 | 1260.0 | 2.591e-09
00013201118 | 20210011139 | 631193954.0 | 2021Jan01 at 11:38:47 | 649.0 | 3.2846e-09
| 20210010827 | 631182432.0 | 2021Jan01 at 08:26:45 | 1311.0 | 2.5016e-09
00013201119 | 20210100240 | 631939239.0 | 2021Jan10 at 02:40:12 | 1764.0 | 2.389e-09
00013201120 | 20210110233 | 632025217.0 | 2021Jan11 at 02:33:10 | 1766.0 | 2.3602e-09
00013201121 | 20210122136 | 632180188.0 | 2021Jan12 at 21:36:01 | 1595.0 | 2.2733e-09
00013201122 | 20210131951 | 632260302.0 | 2021Jan13 at 19:51:15 | 1701.0 | 2.40e-09
| 20210132127 | 632266051.0 | 2021Jan13 at 21:27:04 | 1712.0 | 2.20e-09
00013201123 | 20210141634 | 632334864.0 | 2021Jan14 at 16:33:57 | 1719.0 | 2.4425e-09
00013201124 | 20210151938 | 632432312.0 | 2021Jan15 at 19:38:05 | 1711.0 | 2.3778e-09
00013201125 | 20210160213 | 632455971.0 | 2021Jan16 at 02:12:24 | 300.0 | 5.7285e-09
| 20210160157 | 632455071.0 | 2021Jan16 at 01:57:24 | 300.0 | 5.201e-09
00013201132 | 20210331559 | 633974372.0 | 2021Feb02 at 15:59:05 | 287.0 | 2.7897e-09
00013201134 | 20210621452 | 636475946.0 | 2021Mar03 at 14:51:59 | 637.0 | 3.995e-09
00013201136 | 20210641324 | 636643500.0 | 2021Mar05 at 13:24:33 | 483.0 | 1.94e-09
00013201139 | 20210771309 | 637765766.0 | 2021Mar18 at 13:08:59 | 300.0 | 5.444e-09
00013201142 | 20210801305 | 638024954.0 | 2021Mar21 at 13:08:47 | 409.0 | 4.538e-09
00013201143 | 20210811240 | 638109627.0 | 2021Mar22 at 12:40:00 | 1716.0 | 2.37e-09
00013201145 | 20211091202 | 640526551.0 | 2021Apr19 at 12:02:26 | 212.0 | 6.509e-09
00013201146 | 20211101131 | 640611085.0 | 2021Apr20 at 11:31:20 | 1658.0 | 2.618e-09
00013201147 | 20211111124 | 640697088.0 | 2021Apr21 at 11:24:43 | 1635.0 | 2.6705e-09
00013201148 | 20211121117 | 640783039.0 | 2021Apr22 at 11:17:14 | 1484.0 | 2.753e-09
| 20211121610 | 640800645.0 | 2021Apr22 at 16:10:40 | 678.0 | 3.474e-09
00013201149 | 20211130001 | 640828877.0 | 2021Apr23 at 00:01:12 | 300.0 | 4.806e-09
| 20211131110 | 640869039.0 | 2021Apr23 at 11:10:34 | 1644.0 | 2.5765e-09
| 20211130009 | 640829477.0 | 2021Apr23 at 00:11:12 | 166.0 | 6.636e-09
00013201150 | 20211141107 | 640955238.0 | 2021Apr24 at 11:07:13 | 1605.0 | 2.519e-09

Table 4: List of Swift-BAT survey-mode observations of FRB 180916. (Continued) Obs ID | Pointing ID | Start time (MET) | Start time (UTC) | exposure | flux upper-lim
---|---|---|---|---|---
| number |  | year:day:hr:min:sec | (Sec) | $\rm\,erg\,cm^{-2}\,s^{-1}{}$
00013201151 | 20211151100 | 641041209.0 | 2021Apr25 at 11:00:04 | 1614.0 | 2.559e-09
| 20211150436 | 641018178.0 | 2021Apr25 at 04:36:13 | 1005.0 | 2.917e-09
00013201153 | 20211290922 | 642244925.0 | 2021May09 at 09:22:00 | 600.0 | 3.751e-09
| 20211291055 | 642250528.0 | 2021May09 at 10:55:23 | 600.0 | 3.76e-09
00013201154 | 20211300908 | 642330541.0 | 2021May10 at 09:08:56 | 970.0 | 2.9134e-09
00013201155 | 20211311051 | 642423373.0 | 2021May11 at 10:56:08 | 350.0 | 4.7754e-09
00013201159 | 20211441041 | 643545682.0 | 2021May24 at 10:41:17 | 278.0 | 5.653e-09
| 20211440911 | 643540283.0 | 2021May24 at 09:11:18 | 460.0 | 4.28e-09
00013201160 | 20211450555 | 643614931.0 | 2021May25 at 05:55:26 | 582.0 | 3.3717e-09
00013201161 | 20211580807 | 644746078.0 | 2021Jun07 at 08:07:53 | 1385.0 | 2.673e-09
00013201162 | 20211590800 | 644832053.0 | 2021Jun08 at 08:00:48 | 1200.0 | 2.7623e-09
00013201163 | 20211600753 | 644918000.0 | 2021Jun09 at 07:53:15 | 1200.0 | 2.908e-09
00013201164 | 20211610746 | 645004014.0 | 2021Jun10 at 07:46:49 | 1200.0 | 2.9817e-09
00013201165 | 20211620740 | 645090007.0 | 2021Jun11 at 07:40:02 | 1200.0 | 2.8246e-09
00013201166 | 20211630732 | 645175978.0 | 2021Jun12 at 07:32:53 | 1200.0 | 2.779e-09
00013201167 | 20211640724 | 645261882.0 | 2021Jun13 at 07:24:37 | 1461.0 | 2.6162e-09
00013201169 | 20211730447 | 646030030.0 | 2021Jun22 at 04:47:05 | 1200.0 | 2.7585e-09
| 20211730510 | 646031530.0 | 2021Jun22 at 05:12:05 | 173.0 | 6.483e-09
00013201170 | 20211740745 | 646127135.0 | 2021Jun23 at 07:45:30 | 1708.0 | 2.1495e-09
00013201171 | 20211750620 | 646208442.0 | 2021Jun24 at 06:20:37 | 1041.0 | 2.642e-09
00013201172 | 20211761548 | 646328943.0 | 2021Jun25 at 15:48:58 | 360.0 | 4.869e-09
| 20211770908 | 646391293.0 | 2021Jun26 at 09:08:08 | 710.0 | 3.3605e-09
| 20211761856 | 646340223.0 | 2021Jun25 at 18:56:58 | 840.0 | 3.0734e-09
| 20211772334 | 646443271.0 | 2021Jun26 at 23:34:26 | 512.0 | 4.242e-09
| 20211760602 | 646293757.0 | 2021Jun25 at 06:02:32 | 1707.0 | 2.2164e-09
00013201173 | 20211780424 | 646460698.0 | 2021Jun27 at 04:24:53 | 545.0 | 3.6787e-09
| 20211780719 | 646471186.0 | 2021Jun27 at 07:19:41 | 737.0 | 3.207e-09
| 20211790904 | 646563890.0 | 2021Jun28 at 09:04:45 | 853.0 | 2.981e-09
00013201174 | 20211790535 | 646551329.0 | 2021Jun28 at 05:35:24 | 1114.0 | 2.835e-09
| 20211790711 | 646557091.0 | 2021Jun28 at 07:11:26 | 392.0 | 4.593e-09
00013201175 | 20211890605 | 647417112.0 | 2021Jul08 at 06:05:07 | 1431.0 | 4.57e-10
00013201176 | 20211900554 | 647502881.0 | 2021Jul09 at 05:54:36 | 1702.0 | 2.365e-09
00013201177 | 20211910729 | 647594963.0 | 2021Jul10 at 07:29:18 | 460.0 | 4.218e-09
| 20211910555 | 647589325.0 | 2021Jul10 at 05:55:20 | 1238.0 | 2.5826e-09
00013201178 | 20211920542 | 647674932.0 | 2021Jul11 at 05:42:07 | 951.0 | 3.031e-09
00013201180 | 20211940217 | 647835482.0 | 2021Jul13 at 02:17:57 | 781.0 | 3.2184e-09
| 20211940531 | 647847077.0 | 2021Jul13 at 05:31:12 | 706.0 | 3.4086e-09
00013201181 | 20211950659 | 647938771.0 | 2021Jul14 at 06:59:26 | 812.0 | 3.408e-09
| 20211950525 | 647933106.0 | 2021Jul14 at 05:25:01 | 597.0 | -8.812
00013201182 | 20212060447 | 648881252.0 | 2021Jul25 at 04:47:27 | 391.0 | 5.223e-09
| 20212060621 | 648886885.0 | 2021Jul25 at 06:21:20 | 459.0 | 5.304e-09
00013201183 | 20212070614 | 648972868.0 | 2021Jul26 at 06:14:23 | 600.0 | 4.791e-09
| 20212070439 | 648967168.0 | 2021Jul26 at 04:39:23 | 875.0 | 3.613e-09
00013201184 | 20212080431 | 649053124.0 | 2021Jul27 at 04:31:59 | 1139.0 | 3.385e-09
| 20212080607 | 649058880.0 | 2021Jul27 at 06:07:55 | 244.0 | 7.674e-09
00013201185 | 20212090419 | 649138798.0 | 2021Jul28 at 04:19:53 | 1500.0 | 2.9306e-09
00013201186 | 20212100413 | 649224800.0 | 2021Jul29 at 04:13:15 | 1723.0 | 2.727e-09
00013201187 | 20212110410 | 649311053.0 | 2021Jul30 at 04:10:48 | 1270.0 | 3.1487e-09
00013201188 | 20212121021 | 649419943.0 | 2021Jul31 at 10:25:38 | 600.0 | 4.162e-09
00013201189 | 20212560558 | 653205519.0 | 2021Sep13 at 05:58:34 | 264.0 | 6.923e-09
00013201191 | 20212600035 | 653531755.0 | 2021Sep17 at 00:35:50 | 300.0 | 6.383e-09
| 20212600050 | 653532655.0 | 2021Sep17 at 00:50:50 | 300.0 | 5.919e-09
00013201199 | 20212760010 | 654912618.0 | 2021Oct03 at 00:10:13 | 1665.0 | 2.19e-09
00013201200 | 20212770003 | 654998591.0 | 2021Oct04 at 00:03:06 | 300.0 | 4.91e-09

Table 5: List of Swift-BAT survey-mode observations of FRB 180916. (Continued) Obs ID | Pointing ID | Start time (MET) | Start time (UTC) | exposure | flux upper-lim
---|---|---|---|---|---
| number |  | year:day:hr:min:sec | (Sec) | $\rm\,erg\,cm^{-2}\,s^{-1}{}$
00013201201 | 20212771745 | 655062358.0 | 2021Oct04 at 17:45:53 | 1325.0 | 2.526e-09
00013201202 | 20212780131 | 655090278.0 | 2021Oct05 at 01:31:13 | 1665.0 | 2.1616e-09
00013201203 | 20212912230 | 656289186.0 | 2021Oct18 at 22:33:01 | 477.0 | 4.265e-09
| 20212912218 | 656288286.0 | 2021Oct18 at 22:18:01 | 600.0 | 1.54e-09
00013201204 | 20213072113 | 657666951.0 | 2021Nov03 at 21:15:46 | 192.0 | 6.118e-09
00013201205 | 20213082235 | 657758161.0 | 2021Nov04 at 22:35:56 | 300.0 | 5.638e-09
00013201207 | 20213102215 | 657929752.0 | 2021Nov06 at 22:15:47 | 1200.0 | 2.9644e-09
00013201210 | 20213232044 | 659047485.0 | 2021Nov19 at 20:44:40 | 900.0 | 3.343e-09
00013201211 | 20213242041 | 659133687.0 | 2021Nov20 at 20:41:22 | 1200.0 | 2.875e-09
00013201214 | 20213362039 | 660170354.0 | 2021Dec02 at 20:39:09 | 1369.0 | 2.3474e-09
00013201215 | 20213372031 | 660256279.0 | 2021Dec03 at 20:31:14 | 1304.0 | 2.289e-09
00013201216 | 20213382036 | 660342979.0 | 2021Dec04 at 20:36:14 | 1364.0 | 2.1998e-09
00013201217 | 20213392016 | 660428224.0 | 2021Dec05 at 20:16:59 | 1679.0 | 2.0684e-09
00013201218 | 20213402009 | 660514188.0 | 2021Dec06 at 20:09:43 | 1694.0 | 2.1318e-09
00013201219 | 20213412003 | 660600200.0 | 2021Dec07 at 20:03:15 | 1663.0 | 2.141e-09
00013201220 | 20213421955 | 660686158.0 | 2021Dec08 at 19:55:53 | 1685.0 | 2.207e-09
00013201221 | 20213591835 | 662150105.0 | 2021Dec25 at 18:35:00 | 1018.0 | 2.785e-09
00013201224 | 20220041732 | 663010338.0 | 2022Jan04 at 17:32:13 | 1005.0 | 3.1497e-09
| 20220041855 | 663015305.0 | 2022Jan04 at 18:55:00 | 898.0 | 3.3017e-09
00013201225 | 20220051722 | 663096183.0 | 2022Jan05 at 17:22:58 | 960.0 | 3.1152e-09
| 20220051847 | 663101271.0 | 2022Jan05 at 18:47:46 | 852.0 | 5.12e-09
00013201226 | 20220061700 | 663181256.0 | 2022Jan06 at 17:00:51 | 1147.0 | 3.1096e-09
| 20220061840 | 663187256.0 | 2022Jan06 at 18:40:51 | 547.0 | 4.237e-09
00013201227 | 20220071831 | 663273119.0 | 2022Jan07 at 18:31:54 | 1624.0 | 7.94e-10
00013201228 | 20220081823 | 663359039.0 | 2022Jan08 at 18:23:54 | 1684.0 | 2.4566e-09
00013201229 | 20220091815 | 663444962.0 | 2022Jan09 at 18:15:57 | 1681.0 | 2.415e-09
00013201230 | 20220101807 | 663530826.0 | 2022Jan10 at 18:07:01 | 1677.0 | 2.385e-09

The material is based upon work supported by NASA under award number
80GSFC21M0002. ET acknowledges support from NASA grant 80NSSC18K0429. MN is
supported by the European Research Council (ERC) under the European Union’s
Horizon 2020 research and innovation programme (grant agreement No. 948381)
and by a Fellowship from the Alan Turing Institute.

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Send correspondence to A.G. or M.S.
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# Status of the PSF Reconstruction Work Package for MICADO@ELT

Andrea Grazian  INAF Osservatorio Astronomico di Padova, Vicolo
dell’Osservatorio 5, I-35122, Padova, Italy  Matteo Simioni  INAF Osservatorio
Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122, Padova, Italy
Carmelo Arcidiacono  INAF Osservatorio Astronomico di Padova, Vicolo
dell’Osservatorio 5, I-35122, Padova, Italy  Jani Achren  Incident Angle Oy,
Capsiankatu 4 A 29, FI-20320 Turku, Finland  Yann Clenet  LESIA, Observatoire
de Paris, Section de Meudon 5, place Jules Janssen, F-92195 Meudon Cedex,
France  Yixian Cao  MPE - Max-Planck-Institut für extraterrestrische Physik
Giessenbachstrasse 1, D-85748 Garching bei Muenchen, Germany  Richard Davies
MPE - Max-Planck-Institut für extraterrestrische Physik Giessenbachstrasse 1,
D-85748 Garching bei Muenchen, Germany  Marco Gullieuszik  INAF Osservatorio
Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122, Padova, Italy
Tapio Helin  LUT University, P.O.Box 20, FI-53851, Lappeenranta, Finland
Daniel Jodlbauer  Industrial Mathematics Institute, Johannes Kepler University
Linz, Altenberger Strasse 69, 4040 Linz, Austria  RICAM - Johann Radon
Institute for Computational and Applied Mathematics, Altenberger Strasse 69,
4040 Linz, Austria  Hanindyo Kuncarayakti  Tuorla Observatory, Department of
Physics and Astronomy, FI-20014, University of Turku, Finland  Finnish Centre
for Astronomy with ESO (FINCA), Quantum, Vesilinnantie 5, University of Turku,
FI-20014 Turku, Finland  Miska Le Louarn  European Southern Observatory, Karl
Schwarzschild Strasse 2, D-85748 Garching bei Muenchen, Germany  Seppo Mattila
Tuorla Observatory, Department of Physics and Astronomy, FI-20014, University
of Turku, Finland  Fernando Pedichini  INAF - Osservatorio Astronomico di
Roma, Via Frascati 33, I-00078, Monte Porzio Catone, Italy  Roberto Piazzesi
INAF - Osservatorio Astronomico di Roma, Via Frascati 33, I-00078, Monte
Porzio Catone, Italy  Elisa Portaluri  INAF - Osservatorio Astronomico
d’Abruzzo, Via Mentore Maggini, I-64100 Teramo, Italy  INAF Osservatorio
Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122, Padova, Italy
Aleksi Salo  LUT University, P.O.Box 20, FI-53851, Lappeenranta, Finland  Gijs
Verdoes Kleijn  University of Groningen, PO Box 72, 9700 AB Groningen, the
Netherlands  Benedetta Vulcani  INAF Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5, I-35122, Padova, Italy  Roland Wagner  Industrial
Mathematics Institute, Johannes Kepler University Linz, Altenberger Strasse
69, 4040 Linz, Austria  RICAM - Johann Radon Institute for Computational and
Applied Mathematics, Altenberger Strasse 69, 4040 Linz, Austria  Steven
Williams  Tuorla Observatory, Department of Physics and Astronomy, FI-20014,
University of Turku, Finland  Finnish Centre for Astronomy with ESO (FINCA),
Quantum, Vesilinnantie 5, University of Turku, FI-20014 Turku, Finland  Anita
Zanella  INAF Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5,
I-35122, Padova, Italy  Werner W. Zeilinger  Department of Astrophysics,
University of Vienna, Tuerkenschanzstrasse 17, A-1180, Wien, Austria

###### Abstract

MICADO is a workhorse instrument for the ESO ELT, allowing first light
capability for diffraction limited imaging and long-slit spectroscopy at near-
infrared wavelengths. The PSF Reconstruction (PSF-R) Team of MICADO is
currently implementing, for the first time within all ESO telescopes, a
software service devoted to the blind reconstruction of the PSF. This tool
will work independently of the science data, using adaptive optics telemetry
data, both for Single Conjugate (SCAO) and Multi-Conjugate Adaptive Optics
(MCAO) allowed by the MORFEO module. The PSF-R service will support the state-
of-the-art post-processing scientific analysis of the MICADO imaging and
spectroscopic data. We provide here an update of the status of the PSF-R
service tool of MICADO, after successfully fulfilling the Final Design Review
phase, and discuss recent results obtained on simulated and real data gathered
on instruments similar to MICADO.

###### keywords:

PSF Reconstruction, MICADO, ELT, Telemetry data, WFS

##  1 INTRODUCTION

MICADO (Multi-Adaptive Optics Imaging Camera for Deep Observations) is the
first light instrument of the European Southern Observatory (ESO) Extremely
Large Telescope (ELT) and it will be a workhorse facility for Adaptive Optics
(AO) diffraction limited imaging and long-slit spectroscopy at near-infrared
wavelengths [1]. We provide here an update of the status of the point spread
function reconstruction (PSF-R) service tool of MICADO, after successfully
fulfilling the Final Design Review (FDR) phase, and discuss recent PSF-R
results obtained on simulated and real data gathered on instruments similar to
MICADO [2].

A first-generation ELT instrument, MICADO will take high resolution images of
the Universe at near-infrared wavelengths. This makes MICADO the ideal
instrument for identifying exoplanets, but also for resolving individual stars
in local galaxies (up to Virgo and Fornax), the star forming clumps in high-
redshift galaxies, including the dynamics of dense stellar systems, and
investigating the mysterious center of the Milky Way. The optimal scientific
exploitation of MICADO implies the detailed knowledge of the PSF of each
acquired science image or spectrum. The PSF-R service will support the state-
of-the-art post-processing scientific analysis of the MICADO imaging and
spectroscopic data, but it will not be available for coronographic
observations. Indeed, the knowledge of the reconstructed PSF is essential in
order to evaluate the quality of the observed astronomical data. Additional to
quality evaluation, the reconstructed PSF can be used for further improving
the reduction of images and spectra in the post processing phase.

The structure of this paper is the following: in Section 2 we describe the
methodology adopted for the PSF reconstruction of AO-assisted diffraction
limited instruments, e.g. MICADO. The first results obtained by the MICADO
PSF-R Team have been highlighted in Section 3. The size of telemetry data
required by the PSF-R Service every day is discussed in Section 4, while
conclusions are drawn in Section 5.

##  2 METHOD

Different methods are available to obtain the PSF of AO-assisted instruments:
pure PSF Reconstruction (PSF-R), Hybrid, Calibrated, Empirical, Adaptive
methods. All these methods have been described in detail in [3]. MICADO will
adopt as baseline the pure PSF Reconstruction method, relying only on
telemetry data, without accessing the focal plane data (i.e. the scientific
frames).

The motivations behind the choice of the Pure (or blind) PSF-R method rely on
different strategic points. For 35-40% of the extragalactic targets, a MICADO
science frame will be void of point sources suitable for standard PSF
characterization (e.g. with empirical or semi-empirical methods).
Extragalactic deep fields are selected for having as few stars as possible. In
general, it is unlikely to have interesting or well studied extragalactic
targets in fields with many stars per square arcmin. Extragalactic fields
usually have no bright stars suitable to build reliable empirical PSF model,
nor reliable empirical PSF at the position of each galaxy or rare objects
(e.g. high-z/lensed targets).

In case of crowded fields, it is difficult to recover the shape of the PSF,
especially on the wings, due to contamination from neighboring stars. For
these reasons, the Pure PSF-R approach is required when extended targets cover
most of the FoV.

The point spread function reconstruction (PSF-R) Application is a deliverable
of the MICADO project. The PSF-R Team of MICADO is currently implementing, for
the first time within all ESO telescopes, a software service devoted to the
pure (blind) reconstruction of the PSF. This tool will work independently of
the science data in the focal plane, only using adaptive optics telemetry data
of the MICADO camera and spectrograph, both for Single Conjugate (SCAO) and
Multi-Conjugate Adaptive Optics (MCAO) allowed by the MORFEO module, in post-
processing analysis.

The PSF-R application will provide the reconstructed PSFs through an archive
querying system, using the Wave Front Sensor telemetry data that MICADO will
generate and save synchronously to each associated science frame. The PSF-R
Application of MICADO is designed to work without accessing to the science
data themselves, differently from other PSF-R techniques that instead use the
science data themselves to optimize the parameters used during the
reconstruction phase [4, e.g.]. This allows the pure PSF-R tool to be the most
generally applicable, especially in the extra-galactic cases where empty
fields, devoid of bright stars, are routinely observed.

The PSF-R Team will build up the software tools and architecture needed to
develop and test the PSF-R Service for MICADO, when the instrument will be
mounted on the bench, at the Preliminary Acceptance in Europe (PAE) and later
on at the ELT site in Cerro Armazones for the Final Acceptance.

The pure PSF-R method has been described in detail in [5, 6, 2], and [7].

##  3 RESULTS

The pure PSF-R algorithms of MICADO have been tested using COMPASS [8]
simulated data with a bright star (15th magnitude), a Shack-Hartmann Wave
Front Sensor (SH WFS) and the ELT M4 geometry. Strehl ratio (SR), FWHM, and
encircled energy (EE) of the simulated star are recovered by the pure PSF-R
software at the 1-2% level (Fig. 1). Fig. 1 shows the radial profile of the
simulated (blue) and reconstructed (orange) PSF.

Figure 1:  The radial profile of the simulated (blue) and reconstructed
(orange) PSF. Accuracies of 1-2% have been reached in Strehl ratio, FWHM, and
EE.

Real data from the SOUL [9] Adaptive Optic module of the Large Binocular
Telescope (LBT) have been used in order to check that the SCAO Critical
Algorithms of the MICADO PSF-R Service can successfully process also real data
from other instruments. The first results show that the PSF-R algorithms are
able to recover the Strehl ratio (SR), FWHM and encircled energy profiles
within a few ($\sim 1-7\%$) percent level [2]. Based on this tests, we can
confirm that the MICADO PSF-R Application has reached at present a Technology
Readiness Level (TRL) corresponding to TRL=7. Further details on the PSF
reconstruction of LBT/SOUL+LUCI data can be found in this proceeding (Simioni
et al. 2022).

The Final design Review (FDR) of the PSF-R software tool for MICADO has been
successfully accomplished in July 2021. This review has been mainly focused on
the development plan, the data flow, the telemetry data rate, the end-to-end
workflow, and the development of the critical algorithms for PSF-R. No
critical item has been emerged during the FDR, indicating that the maturity
level reached by the MICADO PSF-R software is adequate for that milestone.

The scientific evaluation of the PSF-R tools is currently on-going for
extragalactic cases (e.g. galaxy morphology, clumps), as detailed in this
proceeding (Simioni et al. 2022). We have also developed tools and a pipeline
to evaluate how uncertainties on the reconstructed PSF translate into
uncertainties on scientific measurements (and viceversa). In the future, the
scientific evaluation of the PSF-R products will be expanded to other science
cases.

##  4 TELEMETRY DATA RATES

The pure PSF-R software of MICADO relies only on WFS telemetry data, saved at
the highest temporal frequency, in order to better reproduce the sudden
variation of the atmospheric conditions.

The telemetry data rate of MICADO WFS is 4.2 Terabyte per night, assuming 9
hours of observation, 100% of open shutter time, control, and interactive
matrices saved at a frequency of 0.2 Hz. The telemetry data rate is instead
2.1Tb per night, assuming 70% open shutter time plus control and interactive
matrices saved at 0.1 Hz. The expected data rate for telemetry is comparable
or even less than the scientific data rate. This amount of data rate is not a
problem considering the planned ESO/ELT infrastructure. Fig. 2 summarizes the
expected data rates in the SCAO case for the PSF-R Service of MICADO.
Preliminary calculations for the MCAO mode of MICADO indicate that the
expected data rate for MCAO is slightly lower than in SCAO mode.

Figure 2:  The expected data rates for the SCAO option of the PSF-R Service of
MICADO.

##  5 CONCLUSIONS

The present status of the PSF-R software tools of MICADO has been summarised
in this paper. In particular, a number of achievements have been reached by
the MICADO PSF-R team:

  * •

Accuracies of 1-7% have been reached both with simulated PSFs and with real
LBT SOUL+LUCI data, as described in [7].

  * •

A TRL=7 has been reached by the MICADO PSF-R Service tools.

  * •

There’s no issue for the ESO Raw Science Archive to transfer and store all the
WFS telemetry data produced by MICADO.

  * •

No critical issue has been emerged during the FDR review, indicating that the
maturity level of the PSF-R tools is adequate for that milestone.

  * •

No showstopper for PSF-R has been currently identified, and the PSF-R Service
is ready to meet the First Light of MICADO at ELT in 2027.

The PSF-R software is a data intensive tool, since it requires powerful
computers and lot of disk space for storage. In the future, the development of
smart and efficient algorithms is required in order to reduce the loading
factor on the science users of ELT.

Further details on the PSF-R service for MICADO can be found in this
proceeding (Arcidiacono et al. 2022; Simioni et al. 2022).

###### Acknowledgements.

This work has been partly supported by INAF through the Math, ASTronomy and
Research (MAST&R), a working group for mathematical methods for high-
resolution imaging. This proceeding is in memory of our PSF-R team member
Aleksi Salo, who sadly passed away on June 11th 2022. Aleksi was a friend and
a talented young doctoral student with many bright discoveries ahead. He will
be greatly missed by his family, friends, and colleagues. Farewell Aleksi, may
the stars shine upon you.

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