GRB 200405B

K.L. Page (U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has performed a second follow-up observation of the
INTEGRAL/SPI-ACS and Swift-BAT GUANO detected possible short burst GRB
200405B (James DeLaunay et al. GCN Circ. 27497
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 ), collecting ~1.2 ks of
Photon Counting (PC) mode data between T0+550.8 ks and T0+584.0 ks. Of the
four uncatalogued X-ray sources reported in GCN 27500
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  (Sbarufatti et al.),
none shows any evidence of fading. We therefore conclude that Swift did
not detect the X-ray afterglow of this GRB.

This circular is an official product of the Swift-XRT team.

Dougal Dobie (USYD/CSIRO), Tara Murphy (USYD), James Leung (USYD/CSIRO),
Adam Stewart (USYD), Joshua Pritchard (USYD), David Kaplan (UWM)

GRB 200405B (GCN 27497
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 ) occurred in a field that has been observed 5 times
as part of the ASKAP Variables And Slow Transients (VAST; Murphy et al.
2013)
pilot survey between 2019-08-27 and 2020-01-25. We have searched for radio
emission from the BAT ground-calculated position and the 4 uncatalogued
X-ray sources detected by Swift (GCN 27500
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 ) and find no radio counterparts
to a detection limit of ~1.5 mJy at 888 MHz.

We also performed follow-up observations of all 5 positions with the ATCA
between 2020-04-09 05:00-10:30 UTC with 2x2 GHz bands centered on
5.5 and 9 GHz. No radio emission was detected coincident with any of the
sources, we list 3-sigma upper limits below

Source      5.5 GHz (uJy)    9 GHz (uJy)
BAT pos     81               54
Source 1    90               120
Source 2    84               96
Source 3    87               90
Source 4    90               114

We do detect a radio source at coordinates of 04:10:26.8, -51:31:55
(offset 7.2 arcsec from Source 4), coincident with WISEA
J041026.82-513155.2,
with a flux density of ~4 mJy at 5.5 GHz and ~7 mJy at 9 GHz. This source is
also detected in the VAST pilot survey with a flux density of ~10 mJy. We do
not consider this a candidate afterglow for the GRB.

Further observations with ATCA and as part of the VAST program are planned.

Thank you to CSIRO staff for supporting these observations during these
especially difficult times.

D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Ridnaia,
and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team, and

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
report:

The short-duration GRB 200405B (DeLaunay et al., GCN Circ. 27497
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 )
was detected by Swift (BAT), INTEGRAL (SPI-ACS), and Konus-Wind,
at about 14018 s UT (03:53:38).
The burst was found in ground analysis of Swift (BAT) data
with low partial coding.

We have triangulated it to INTEGRAL-Konus annulus centered at
RA(2000)=354.104 deg (23h 36m 25s) Dec(2000)=-6.682 deg (-6d 40' 55"),
whose radius is 71.411 +/- 18.656 deg (3 sigma) and
to a BAT-INTEGRAL annulus centered at
RA(2000)=59.460 deg (03h 57m 50s) Dec(2000)=-50.201 deg (-50d 12' 02"),
whose radius is 8.804(-8.804,+15.572) deg (3 sigma).
These annuli intersect to form a very large region
with an area of ~1600 sq. deg.

The Swift-BAT position reported in DeLaunay et al.
is consistent with the IPN localization.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB200405_T14018/IPN

The Swift (BAT) event data used for the IPN localization
came from the GUANO system (https://www.swift.psu.edu/guano/).

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift/BAT-GUANO GRB 200405B (DeLaunay et al., GCN 27497
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 ) with the LCO 1-m Sinistro instrument at the Siding Spring Observatory, Australia site, on April 6, from 08:49 to 09:29 UT (corresponding to 28.9 to 29.6 hours from the GRB trigger time) with the Bessel I and R filters.

We performed a series of 5x240s exposures in I and R. We do not detect any fading sources in the individual frames (or in stacked images).  We also do not detect any optical counterparts to the 4 potential Swift XRT candidates (Sbarufatti et al., GCN 27500
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 ).  Using the USNO-B.1 catalog as reference, we obtain the following 3-sigma upper limits:

R > 21.75

I > 20.86

These magnitudes are not corrected for galactic extinction.

R.S. is funded by NSF AST grant #1831682

B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), K.L. Page
(U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB),
T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the INTEGRAL/SPI-ACS
and Swift-BAT GUANO detected possible short burst GRB 200405B (James
DeLaunay et al. GCN Circ. 27497
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 ), collecting 5.0 ks of Photon Counting
(PC) mode data between T0+66.6 ks and T0+80.0 ks. 

Four uncatalogued X-ray sources have been detected, however none of
them is above the RASS limit or shows definitive signs of fading.
Therefore, at the present time we cannot identify which, if any, is the
afterglow. We note that Source 2 lies within the 4 arcmin BAT error
region reported in GCN Circ. 27497
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 . Details of these sources are given
below:

Source 1:
  RA (J2000.0):  62.6009  =  04:10:24.21
  Dec (J2000.0): -51.4435  =  -51:26:36.5
  Error: 5.5 arcsec (radius, 90% conf.)
  Count-rate: (1.87 [+0.90, -0.69])e-3 ct s^-1	 
  Distance: 530 arcsec from BAT position.
  Flux: (1.15 [+0.55, -0.43])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)


Source 2:
  RA (J2000.0):  62.8248  =  04:11:17.95
  Dec (J2000.0): -51.5687  =  -51:34:07.5
  Error: 6.5 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (3.31 [+1.13, -0.93])e-3 ct s^-1	 
  Distance: 152 arcsec from BAT position.
  Flux: (4.1 [+1.4, -1.1])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:
  RA (J2000.0):  62.5137  =  04:10:3.28
  Dec (J2000.0): -51.4509  =  -51:27:03.3
  Error: 4.6 arcsec (radius, 90% conf.)
  Count-rate: (1.96 [+0.97, -0.73])e-3 ct s^-1	 
  Distance: 684 arcsec from BAT position.

Source 4:
  RA (J2000.0):  62.6146  =  04:10:27.49
  Dec (J2000.0): -51.5329  =  -51:31:58.3
  Error: 4.3 arcsec (radius, 90% conf.)
  Count-rate: (3.74 [+1.18, -0.99])e-3 ct s^-1	 
  Distance: 391 arcsec from BAT position.
  Flux: (1.20 [+0.38, -0.32])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)


The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00020979.

This circular is an official product of the Swift-XRT team.

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the INTEGRAL GRB 200405B. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00020979

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the INTEGRAL event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), and Jamie Kennea
(PSU) report:

Swift/BAT did not trigger on GRB 200405B (T0: 2020-04-05 03:53:38 UTC).

The INTEGRAL/SPI-ACS Notice #8579, distributed at T0+35 seconds
triggered the Swift Mission Operations Center operated Gamma-ray
Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al.
2020, in prep).

Upon trigger by these notices, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 90 seconds of BAT event-mode data from
[-45,+45] seconds around the time of the burst.
All the requested event mode data was delivered to the ground.

In a ground analysis of the data, we detect the burst in the full
detector-summed rates (no localization information) with an SNR of ~9.
The detected duration is ~0.5 seconds.

With a maximum likelihood analysis (DeLaunay et al. 2020, in prep.) on
the event-mode data we detect a location for the burst with a square
root of the test statistic, sqrt(TS), of 12.4. The sqrt(TS) behaves
similarly to SNR.
Using the normal BAT imaging technique, we find an SNR of ~4 at the
same location.

The BAT ground-calculated position is
RA, Dec = 62.7894, -51.5326 deg which is
   RA(J2000)  = 4h 11m 9.5s
   Dec(J2000) =  -51d 31��� 57.4���
with an uncertainty of 4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 11.6%.

Due to the low partial coding, and the lack of any localization
information from SPI-ACS for a consistency check, we stress that while
this localization is significant, we cannot be certain of whether or
not the burst actually originated from outside the BAT coded field-of-view.

XRT and UVOT follow-up has been triggered and observations of this
region have already begun. Results of follow-up observations will be
reported in future circulars.

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/