GRB 200826A
GCN Circular 28284
Subject
GRB 200826A: Fermi GBM Final Real-time Localization
Date
2020-08-26T04:40:17Z (5 years ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
The Fermi GBM team reports the detection of a likely SHORT GRB
At 04:29:52 UT on 26 Aug 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 200826A (trigger 620108997.570644 / 200826187).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 4.7, Dec = 35.3 (J2000 degrees, equivalent to J2000 00h 18m, 35d 17'), with a statistical uncertainty of 1.7 degrees.
The angle from the Fermi LAT boresight is 73.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200826187/quicklook/glg_skymap_all_bn200826187.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200826187/quicklook/glg_healpix_all_bn200826187.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200826187/quicklook/glg_lc_medres34_bn200826187.gif
GCN Circular 28285
Subject
Fermi GRB 200826A: Global MASTER-Net observations report
Date
2020-08-26T05:00:17Z (5 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin,
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov, D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova
(Irkutsk State University, API),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko
(Blagoveschensk Educational State University)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 200826A ( Fermi GBM team, GCN 28284) errorbox 18 sec after notice time and 46 sec after trigger time at 2020-08-26 04:30:38 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 76 deg. The sun altitude is -69.3 deg.
The galactic latitude b = -24 deg., longitude l = 116 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1427181
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
51 | 2020-08-26 04:30:38 | MASTER-OAFA | (00h 16m 30.99s , +38d 58m 23.2s) | C | 10 | 16.5 |
102 | 2020-08-26 04:31:24 | MASTER-OAFA | (00h 16m 59.22s , +35d 52m 18.4s) | C | 20 | 17.0 |
159 | 2020-08-26 04:32:16 | MASTER-OAFA | (00h 18m 21.45s , +36d 49m 55.4s) | C | 30 | 17.2 |
214 | 2020-08-26 04:33:06 | MASTER-OAFA | (00h 18m 17.46s , +36d 48m 57.2s) | C | 40 | 17.5 |
278 | 2020-08-26 04:34:05 | MASTER-OAFA | (00h 18m 22.91s , +36d 49m 03.8s) | C | 50 | 17.6 |
353 | 2020-08-26 04:35:15 | MASTER-OAFA | (00h 18m 20.27s , +36d 50m 58.1s) | C | 60 | 17.8 |
442 | 2020-08-26 04:36:34 | MASTER-OAFA | (00h 18m 20.68s , +36d 49m 32.1s) | C | 80 | 17.9 |
552 | 2020-08-26 04:38:14 | MASTER-OAFA | (00h 18m 23.06s , +36d 50m 57.8s) | C | 100 | 17.8 |
683 | 2020-08-26 04:40:15 | MASTER-OAFA | (00h 17m 00.73s , +35d 50m 57.2s) | C | 120 | 18.1 |
837 | 2020-08-26 04:42:34 | MASTER-OAFA | (00h 17m 02.07s , +35d 51m 59.4s) | C | 150 | 18.2 |
1022 | 2020-08-26 04:45:24 | MASTER-OAFA | (00h 17m 08.96s , +35d 51m 02.3s) | C | 180 | 18.3 |
1221 | 2020-08-26 04:48:43 | MASTER-OAFA | (00h 17m 02.21s , +35d 50m 06.3s) | C | 180 | 18.3 |
1421 | 2020-08-26 04:52:03 | MASTER-OAFA | (00h 17m 08.56s , +35d 50m 36.7s) | C | 180 | 18.3 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 28286
Subject
GRB 200826A: BALROG localization (Fermi Trigger 620108997 / GRB 200826187)
Date
2020-08-26T05:19:26Z (5 years ago)
From
Jochen Greiner at MPE,Garching <jcg@mpe.mpg.de>
F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
620108997 at 04:29:52 on 26 Aug. 2020 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 7.0+/-2.1 deg
Decl.(2000.0) = 36.1+/-2.4 deg
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB200826187/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB200826187/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB200826187/json
GCN Circular 28287
Subject
GRB 200826A: Fermi GBM observation
Date
2020-08-26T17:18:41Z (5 years ago)
From
Joe Mangan at UCD <joseph.mangan@ucdconnect.ie>
J.Mangan (UCD), R.Dunwoody (UCD) and C.Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 04:29:52.57 UT on 26 August 2020, the Fermi Gamma-Ray Burst Monitor
(GBM)
triggered and located GRB 200826A (trigger 620108997 / 200826187).
The on-ground calculated location, using the GBM trigger
data, was reported in GCN 28284.
The GBM light curve shows an exceptionally bright short GRB
with a duration (T90) of about 1.14 s (50-300 keV).
The time-averaged spectrum from T0-0.29 s to T0+1.76 s is
best fit by a Band function with Epeak = 89.8 +/- 3.7 keV,
alpha = -0.41 +/- 0.07, and beta = -2.4 +/- 0.1
The event fluence (10-1000 keV) in this time interval is
(4.8 +/- 0.1)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0 s in the 10-1000 keV band
is 39.06 +/- 0.42 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support
Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 28288
Subject
GRB 200826A: AstroSat CZTI detection
Date
2020-08-26T19:40:25Z (5 years ago)
From
Soumya Gupta at IUCAA/ASTROSAT <soumya@iucaa>
S. Gupta, V. Sharma, A. Vibhute and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (IUCAA/TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data showed the detection of a bright short GRB 200826A, which was also detected by Fermi GBM (GCN #28284), Global MASTER-Net (Lipunov V. et al., GCN #28285) and BALROG (Kunzweiler F. et al., GCN #28286).
The source was clearly detected in the 40-200 keV energy range. The light curve showed a single peak of emission peaking at 2020-08-26 04:29:51.529 UT. The measured peak count rate associated with the burst is 686 +/- 34 cts/s above the background in the combined data of four quadrants, with a total of 1383 +/- 10 cts. The local mean background count rate was 537 +/- 2 cts/s. Using cumulative rates, we measure a T90 of 1.95 +/- 0.01 s.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a single peak of emission peaking at 2020-08-26 04:29:51.000 UT. The measured peak count rate is 735 +/- 53 cts/s above the background in the combined Veto data of four quadrants, with a total of 1043 +/- 42 cts. The local mean background count rate was 1870 +/- 16 cts/s. We measure a T90 of 2.17 +/- 0.23 s from the cumulative Veto light curve.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.
GCN Circular 28289
Subject
GRB 200826A: AGILE detection
Date
2020-08-26T20:30:44Z (5 years ago)
From
Francesco Verrecchia at SSDC,INAF-OAR <francesco.verrecchia@ssdc.asi.it>
C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), A. Ursi (INAF/IAPS), M.
Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), F. Longo (Univ. Trieste
and INFN Trieste), N. Parmiggiani (INAF/OAS-Bologna), F. Lucarelli,�� (SSDC,
and INAF/OAR), A. Argan, M. Cardillo, C. Casentini, Y. Evangelista, G.
Piano
(INAF/IAPS), A. Bulgarelli, V. Fioretti, F. Fuschino (INAF/OAS-Bologna), M.
Marisaldi (INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois
(INAF/OA-Cagliari), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), report
on behalf of the AGILE Team:
The AGILE satellite detected the short burst GRB 200826A at T0=2020-08-26
04:29:52 (UTC), reported by Fermi-GBM (GCN #28284, trigger 620108997.570644
/ 200826187).
The event was detected by the scientific ratemeters of the Super-AGILE (SA;
18-60 keV) detector. The light curve shows a single peak profile,
lasting 0.5
s and releasing ~84 counts above an average background rate of about 40
counts/s. The short burst was observed at an off-axis angle of about 54
degrees. The Super-AGILE light curve can be found here:
https://tools.ssdc.asi.it/ImgView/Agile/SA-TOT_GRB200826A_lcr28
Additional analysis of AGILE data is in progress.
GCN Circular 28290
Subject
GRB 200826A: Tiled Swift observations
Date
2020-08-26T20:46:44Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the
Fermi/GBM GRB 200826A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00093
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/GBM event is high: 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.
GCN Circular 28291
Subject
IPN triangulation of GRB 200826A (short/bright)
Date
2020-08-26T21:28:52Z (5 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
K. Hurley, on behalf of the IPN,
I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Ridnaia,
and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:
The short-duration, bright GRB 200826A
(Fermi-GBM detection: The Fermi GBM Team, GCN Circ. 28284;
Mangan et al., GCN Circ. 28287;
BALROG localization: Kunzweiler et al., GCN Circ. 28286;
AstroSat-CZTI detection: Gupta et al., GCN Circ. 28288;
AGILE detection: Pittori et al., GCN Circ. 28289)
has been detected by Fermi (GBM trigger 620108997),
Konus-Wind, INTEGRAL (SPI-ACS), AstroSat (CZTI),
AGILE (SA), and Mars-Odyssey (HEND),
so far, at about 16193 s UT (04:29:53).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
6.817 (00h 27m 16s) +34.038 (+34d 02' 18")
Corners:
7.081 (00h 28m 19s) +34.000 (+34d 00' 00")
6.808 (00h 27m 14s) +34.222 (+34d 13' 21")
6.553 (00h 26m 13s) +34.075 (+34d 04' 31")
6.826 (00h 27m 18s) +33.854 (+33d 51' 14")
---------------------------------------------
The error box area is 288 sq. arcmin, and its maximum
dimension is 27 arcmin (the minimum one is 15 arcmin).
The Sun distance was 126 deg.
This box may be improved.
The IPN localization is consistent with, but reduces the area of, the Fermi
RoboBA and BALROG localizations (GCN Circ. 28284 and 28286).
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB200826_T16195/IPN
The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.
GCN Circular 28293
Subject
GRB200826A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 620108997)
Date
2020-08-26T22:32:02Z (5 years ago)
From
Tomas Ahumada at U. of Maryland <tahumada@astro.umd.edu>
Ana Sagues Carracedo (OKC), Harsh Kumar (IITB), Tomas Ahumada (UMD), Igor
Andreoni (Caltech), Shreya Anand (Caltech), Robert Stein (DESY), Michael
Coughlin (UMN), Leo Singer (NASA/GSFC) on behalf of the Zwicky Transient
Facility (ZTF) and Global Relay of Observatories Watching Transients Happen
(GROWTH) collaborations
We observed the localization region of the short GRB200826A (trigger
620108997) detected by the Gamma-Ray Burst Monitor (GBM) on the Fermi
satellite with the Palomar 48 inch telescope equipped with the 47 square
degree Zwicky Transient Facility (ZTF) camera.
We obtained a series of g- and r-band images covering 185.5 square degrees
beginning at 09:22:55 UT on 2020 Aug 26 (about 5 hours after the burst
trigger time). This corresponds to ~77.5% of the probability enclosed in
the GRB localization map (GCN 28284). Each exposure was 300s, reaching a
g-band median depth of 22.3 mag and r-band median depth of 22.1 mag. The
median limiting magnitude of the last 5 survey-mode nights (30 sec
exposures) was g ~ 20.6 mag and r ~ 20.0 mag, limiting our capability to
temporally constrain some of our faintest transients. The images were
processed in real-time through the ZTF reduction and image subtraction
pipelines at IPAC (Masci et al. 2019).
We queried the ZTF alert stream using Kowalski (Duev et al. 2019) and AMPEL
(Nordin et al. 2019). We required at least 2 detections separated by at
least 15 minutes to select against moving objects. Furthermore, we
cross-matched our candidates with the Minor Planet Center to flag known
asteroids, reject stellar sources (Tachibana and Miller 2018), and apply
machine learning algorithms (Duev et al. 2019, Mahabal et al. 2019). We
require no spatially coincident ZTF alert to be issued before the detection
time of the GBM trigger. The candidates within the 95% probability contour
of the GRB localization map that passed the automatic selection criteria
and human vetting are presented in the table below.
+----------------------------------------------------------------------------------------------------+
| ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag |
MagErr | g-r |MJD | Notes |
+----------------------------------------------------------------------------------------------------+
| ZTF20abwyple | AT2020sbi | 1.3824038 | 37.3638915 | r | 21.2 | 0.11 |
0.13 | 2459087.9109491 | (a) |
| ZTF20abwyueq | AT2020sbn | 9.2615748 | 39.6340049 | r | 21.8 | 0.13 |
0.08 | 2459087.9219444 | (a) |
| ZTF20abwyzdb | AT2020sbp | 9.2046817 | 43.6712369 | r | 21.7 | 0.17 |
0.4 | 2459087.9219444 | (b) |
| ZTF20abwytgj | AT2020sbc | 5.7051754 | 29.8539268 | r | 22.0 | 0.19 |
0.09 | 2459087.9181366 | (a) |
| ZTF20abwysgz | AT2020sbm | 8.2746333 | 30.7142518 | r | 20.2 | 0.05 |
0.1 | 2459087.9181366 | (a) |
| ZTF20abwywiz | AT2020sbv | 1.4094587 | 36.2573281 | r | 21.9 | 0.21 |
0.45 | 2459087.9145486 | (b) |
| ZTF20abwyrop | AT2020sbd | 359.33861 | 31.1190224 | r | 21.5 | 0.12 |
0.22 | 2459087.9145486 | (c) |
| ZTF20abwyxpj | AT2020sbs | 12.411974 | 31.7868639 | r | 21.8 | 0.16 |
0.35 | 2459087.9181366 | (c)(d) |
| ZTF20abwypor | AT2020sbk | 6.8956443 | 37.2409844 | r | 21.5 | 0.13 |
0.15 | 2459087.9109491 | (c) |
| ZTF20abwyvrl | AT2020sbj | 2.7749043 | 37.6768649 | r | 21.9 | 0.21 |
0.34 | 2459087.9109491 | (a) |
| ZTF20abwypqf | AT2020sbl | 5.1321015 | 39.4099175 | r | 21.8 | 0.21 |
0.0 | 2459087.9109491 | (a) |
| ZTF20abwyrzs | AT2020sbo | 359.79701 | 32.1773094 | r | 21.6 | 0.17 |
0.09 | 2459087.9145486 | (a)(d)(e) |
| ZTF20abwzabz | AT2020sbr | 12.580528 | 42.6494866 | r | 21.9 | 0.16 |
0.02 | 2459087.9219444 | (b)(e) |
| ZTF20abwysmm | AT2020sbt | 11.333202 | 33.4189371 | r | 21.5 | 0.14 |
0.0 | 2459087.9181366 | (d)(e) |
+----------------------------------------------------------------------------------------------------+
Notes:
(a) offset from a galaxy
(b) nuclear
(c) hostless
(d) PS1 detection at source position
(e) possible point-like source underneath
We checked for galaxies in the GLADE catalog (Dalya et al. 2018) around 100
arcsec of each candidate in the table above. We found crossmatches for
ZTF20abwysgz, which is 25.8 arcsec or 81.7 kpc away from a GLADE galaxy,
and ZTF20abwyrzs, 35.9 arcsec or 163.1 kpc offset. However, there are
several ZTF sources closer in the image to both candidates, which makes an
association between the ZTF candidates and GLADE galaxies improbable. In
fact, many candidates (including ZTF20abwysgz and ZTF20abwyrzs) appear to
be a few arcseconds offset from their possible host galaxies:
name | separation |
-------------+--------------
ZTF20abwyple | ~2.7 arcsec |
ZTF20abwypqf | ~1.1 arcsec |
ZTF20abwyple | ~2.6 arcsec |
ZTF20abwyueq | ~1.9 arcsec |
ZTF20abwytgj | ~2.0 arcsec |
ZTF20abwysgz | ~1.6 arcsec |
ZTF20abwyvrl | ~2.3 arcsec |
ZTF20abwypqf | ~5.3 arcsec |
ZTF20abwyrzs | ~5.0 arcsec |
Follow-up observations of these candidates is encouraged.
ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC,
USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY,
Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan;
IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia.
ZTF acknowledges the generous support of the NSF under AST MSIP Grant No
1440341.
GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.
Alert distribution service provided by DIRAC@UW (Patterson et al. 2019).
Alert database searches are done by AMPEL (Nordin et al. 2019) and Kowalski
(Duev et al. 2019).
GCN Circular 28294
Subject
Konus-Wind detection of GRB 200826A
Date
2020-08-27T13:29:13Z (5 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
A. Ridnaia, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:
The short-duration GRB 200826A
(Fermi-GBM detection: The Fermi GBM Team, GCN Circ. 28284;
Mangan et al., GCN Circ. 28287;
BALROG localization: Kunzweiler et al., GCN Circ. 28286;
AstroSat-CZTI detection: Gupta et al., GCN Circ. 28288;
AGILE detection: Pittori et al., GCN Circ. 28289;
IPN triangulation: Hurley et al., GCN Circ. 28291)
triggered Konus-Wind at T0=16195.106 s UT (04:29:55.106).
The burst light curve shows a multipeaked pulse
which starts at ~T0-0.1 s with a total duration of ~1.6 s.
The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB200826_T16195/
As observed by Konus-Wind, the burst
had a fluence of 3.30(-0.42,+0.47)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.560 s,
of 9.04(-2.49,+2.63)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = 1.27(-1.78,+4.03),
the high-energy photon index beta = -2.32(-0.25,+0.19),
the peak energy Ep = 67(-17,+31) keV
(chi2 = 50/59 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 28295
Subject
GRB200826A: Zwicky Transient Facility Identifies Optical Afterglow Candidate of a Fermi Short GRB (Trigger 620108997)
Date
2020-08-27T16:42:00Z (5 years ago)
From
Tomas Ahumada at U. of Maryland <tahumada@astro.umd.edu>
Tomas Ahumada (UMD), Shreya Anand (Caltech), Robert Stein (DESY), Harsh
Kumar (IITB), Ana Sagues Carracedo (OKC), Igor Andreoni (Caltech), Michael
Coughlin (UMN), Leo Singer (NASA/GSFC), Mansi Kasliwal (Caltech), Daniel
Perley (LJMU), Brad Cenko (NASA/GSFC), Varun Bhalerao (IITB), David Kaplan
(UWM) on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of
Observatories Watching Transients Happen (GROWTH) collaborations
We continued a second night of monitoring the localization region of the
short GRB200826A (Fermi trigger 620108997; GCN 28284, 28287) with the
Zwicky Transient Facility (first night summary in Sagues Carracedo et al.
GCN 28293). Each exposure was 600s, reaching a g-band median depth of 22.3
mag and r-band median depth of 22.3 mag. IPN also triangulated this GRB
(Hurley et al. GCN 28291). Our total coverage was >99% of the joint
Fermi-IPN localization.
We followed standard candidate vetting procedures. We identify the
following compelling candidate for the optical afterglow:
+-------------------------------------------------------------------------------------------------+
| ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag |
MagErr |MJD |
+---------------+-----------+-----------+-------------+--------+-------+--------+-----------------+
| ZTF20abwysqy | AT2020scz | 6.7855741 | +34.0273043 | g | 20.86 |
0.04 | 2459087.9181366 |
+---------------+-----------+-----------+-------------+--------+-------+--------+-----------------+
ZTF20abwysqy faded by >1.7 mag in 22.5 hours in the g-band. We ran forced
photometry and we obtained the following light curve:
+----------+--------+-------+--------+--------+
Time (Hrs) | Filter | Mag | MagErr | Limmag |
+----------+--------+-------+--------+--------+
| 5.07 | g | 20.86 | 0.048 | 22.50 |
| 5.53 | r | 20.70 | 0.050 | 22.28 |
| 6.67 | g | 20.96 | 0.168 | 21.24 |
| 27.5 | g | - | - | 22.53 |
| 29.1 | r | - | - | 21.31 |
| 30.9 | g | - | - | 21.21 |
+----------+--------+-------+--------+--------+
ZTF20abwysqy is spatially coincident with X-ray Source 3 reported by the
Neil Gehrels Swift Observatory (GCN 28290,
https://www.swift.ac.uk/xrt_products/TILED_GRB00093/) with a separation of
2" from the XRT position that has an uncertainty of 2.7". It also has a
faint underlying galaxy counterpart within 0.35" (Legacy Survey (LS) DR8
photometric redshift z = 0.714 +- 0.137 and LS DR8 r-mag = 22.55). We
strongly encourage multi-wavelength follow-up.
ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC,
USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY,
Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan;
IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia.
ZTF acknowledges the generous support of the NSF under AST MSIP Grant No
1440341.
GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.
Alert distribution service provided by DIRAC@UW (Patterson et al. 2019).
Alert database searches are done by AMPEL (Nordin et al. 2019) and Kowalski
(Duev et al. 2019).
--
Tom��s Ahumada (he/his)
Ph.D. Student
Department of Astronomy
University of Maryland, College Park
NASA <tomas.f.ahumdamena@nasa.gov> Goddard Space Flight Center, Code 661
B.Sc. Astronomy, Pontificia Universidad Cat��lica de Chile
GCN Circular 28300
Subject
GRB 200826A: Swift-XRT afterglow detection
Date
2020-08-28T15:55:28Z (5 years ago)
From
Boris Sbarufatti at PSU <bxs60@psu.edu>
A. D'Ai (INAF-IASFPA), B. Sbarufatti (PSU), S. R. Oates (U.
Birmingham), D.N. Burrows (PSU), J. D. Gropp (PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A.
Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and P.A. Evans (U.
Leicester) report on behalf of the Swift team:
Swift-XRT has performed follow-up observations of theFermi/GBM and IPN
detected burst GRB 200826A (Gupta et al. GCN Circ. 28288, Hurley et
al., GCN Circ. 28291) in a series of observations tiled on the sky. The
total exposure time is 7.4 ks, distributed over 4 tiles; the maximum
exposure at a single sky location was 5.2 ks. The data were collected
between T0+59.9 ks and T0+169.6 ks, and are entirely in Photon Counting
(PC) mode.
Seven uncatalogued X-ray sources are detected, of which one ("Source
3") is consistent with ZTF20abwysqy, reported by ZTF (Ahumada et al.
GCN Circ. 28293 and 28295).
Source 3 is fading with 3-sigma significance, and is therefore likely
the GRB afterglow. Using 1504 s of PC mode data and 1 UVOT image, we
find an enhanced XRT position (using the XRT-UVOT alignment and
matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
6.78466, +34.02670 which is equivalent to:
RA (J2000): 00h 27m 08.32s
Dec(J2000): +34d 01' 36.1"
with an uncertainty of 3.3 arcsec (radius, 90% confidence). This
position is 104 arcsec from the Fermi/GBM position.
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.3 (+0.7, -0.5).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.8 (+0.6, -0.5). The
best-fitting absorption column is 2.2 (+2.5, -1.6) x 10^21 cm^-2,
consistent with the Galactic value of 6.0 x 10^20 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.6 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.2 (+2.5, -1.6) x 10^21 cm^-2
Galactic foreground: 6.0 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.8 (+0.6, -0.5)
The results of the XRT-team automatic analysis of the likely afterglow
are at https://www.swift.ac.uk/xrt_products/TILED_GRB00093/Source3.php.
The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00093.
The Swift/UVOT began observations of the optical counterpart
ZTF20abwysqy, 140ks after the Fermi/GBM trigger (Fermi GBM Team, GCN
Circ. 28284). A source consistent with ZTF20abwysqy is detected in the
UVOT summed exposures. ZTF20abwysqy is consistent with XRT source 3,
however no earlier UVOT photometry is avaliable since XRT source 3 is
outside of the field of view for all earlier tiles. The UVOT detection
is possibly explained by the underlying galaxy emission.
The preliminary detection and 3-sigma upper limits using the UVOT
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373)
for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 140782 169578 5032 21.86 +/- 0.13
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.07 in the direction of
the burst (Schlegel et al. 1998).
This circular is an official product of the Swift-XRT and Swift-UVOT
teams.
GCN Circular 28301
Subject
GRB 200826A: further analysis of the Konus-Wind data and classification
Date
2020-08-28T18:29:11Z (5 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, D. Frederiks, A. Ridnaia, and A. Tsvetkova,
on behalf of the Konus-Wind team, report:
Following the X-ray afterglow detection (GCN 28300) and
the identification of possible optical transient (GCN 28295)
spatially coincident with the X-ray source,
we present a further analysis of the KW detection of
the short-duration, soft-spectrum, bright GRB 200826A
(GCNs 28284, 28287, 28288, 28289, 28294).
As observed by KW the burst duration is T50=0.286+/-0.029 s
(T90 = 0.772+/-0.188 s). The position of the GRB 200826A in
the hardness-duration diagram (logT50-logHR32) of 1610 KW bright GRBs
(Svinkin et al., JPhCS 1400, 2, 022010, 2019)
suggests that the burst comes from the long/soft GRB population.
The figure showing the hardness-duration diagram is available at
http://www.ioffe.ru/LEA/GRBs/GRB200826_T16195/GRB200826A_HRT50.png
The contours denote the 1 and 3 sigma confidence regions for
two-dimensional Gaussian distributions. The HR32 is the ratio of counts
in the 200-760 keV and 50-200 keV bands accumulated during burst
duration. The vertical dashed line at T50=0.7 s marks the boundary used
by Svinkin et al. 2019 to distinguish between short and long KW GRBs.
Assuming the redshift of an underlying galaxy z=0.714 (GCN 28295)
and a standard cosmology model with H_0 = 67.3 km/s/Mpc,
Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~4.7x10^51 erg,
the peak luminosity L_iso is ~1.6x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~115 keV.
With these values, GRB 200826A is within the 1 sigma prediction band of
both 'Amati' and 'Yonetoku' relations built for 138 Type II (long/soft)
GRBs with known z (Tsvetkova et al., ApJ 850 161, 2017).
Meanwile, in both Eiso-Ep,z and Liso-Ep,z planes,
the GRB 200826A position is inconsistent with
short-hard (Type I) GRB population,
see http://www.ioffe.ru/LEA/GRBs/GRB200826_T16195/GRB200826A.pdf
Thus, from the analysis of the KW detection, we conclude, that,
GRB 200826A may be classified as Type II (long/soft, core-collapse origin).
GCN Circular 28302
Subject
GRB 200826A: VLA Detection at 6 GHz
Date
2020-08-28T19:27:02Z (5 years ago)
From
Kate Alexander at Northwestern U <kate.alexander@northwestern.edu>
K. D. Alexander, W. Fong, K. Paterson, and J. Rastinejad (Northwestern)
report on behalf of a larger collaboration:
We observed the Fermi GRB 200826A (Fermi GBM Team GCN 28284; Mangan et al.
GCN 28287) at a mean frequency of 6 GHz with the Karl G. Jansky Very Large
Array (VLA; Program 19B-217) beginning 2020 August 28.47 UT (2.28 days
after the burst). We detect a radio source with a preliminary flux density
of ~40 microJy at:
RA (J2000) = 00:27:08.54
Dec (J2000) = +34:01:38.37
with an uncertainty of 0.3 arcsec in each coordinate. This position is
fully consistent with the position of the optical afterglow candidate
ZTF20abwysqy (Ahumada et al. GCN 28295) and the catalogued galaxy. The
position is also on the outskirts of the Swift/XRT afterglow position (D'Ai
et al. GCN 28300; 90% confidence). Follow-up observations are planned.
We thank the VLA staff for rapidly executing these observations.
GCN Circular 28306
Subject
GRB 200826A: Kitab optical observations
Date
2020-08-29T10:22:06Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Zhornichenko (KIAM), A. Pozanenko (IKI), N. Pankov
(HSE), E. Mazaeva (IKI), A. Volnova (IKI), Sh. Ehgamberdiev (UBAI)
report on behalf of IKI-GRB-FuN:
We observed the field of a Fermi short GRB 200826A (Fermi GBM team, GCN
28284; Kunzweileret al., GCN 28286; Manganal., GCN 28287) with
Kitab-ISON RC-36 telescope in Clear filter. In particular we cover a
whole region of IPN localization (Hurley et al., GCN 28291). The
optical afterglow ZTF20abwysqy/AT2020scz (Carracedo et al., GCN 28293;
Ahumada et al., GCN 28295) is not detected. Preliminary photometry of
the filed is following
Date, UT start, t-T0, Exp., Filter, OT, Err., UL
(mid, days)
2020-08-26 22:22:17 0.76626 3720 CR n/d n/d 20.2
2020-08-27 22:08:30 1.73515 5520 CR n/d n/d 20.4
The photometry is based on nearby USNO-B1.0 stars, R2 magnitudes
USNO-B1.0_id R2
1238-0009330 16.37
1239-0009591 16.56
GCN Circular 28312
Subject
GRB 200826A: Lowell Discovery Telescope observations of ZTF20abwysqy
Date
2020-08-29T19:16:00Z (5 years ago)
From
Simone Dichiara at UMCP/NASA/GSFC <dichiara@umd.edu>
S.Dichiara (UMD, NASA-GSFC), S.B. Cenko (NASA-GSFC), E. Troja
(UMD, NASA-GSFC), P. Gatkine (UMD), J.M. Durbak (UMD), A. Kutyrev (UMD,
NASA-GSFC), S. Veilleux (UMD), report on behalf of a larger
collaboration:
We observed at the position of the optical transient ZTF20abwysqy reported
by Ahumada el al. (GCN Circ. 28287) as a possible afterglow candidate for
GRB 200826A (Fermi GBM team, GCN 28284, Mangan et al., GCN Circ. 28287)
and coincident with the X-ray Source 3 reported by D'Ai et al. (GCN Circ.
28300). We use the Large Monolithic Imager (LMI) on the 4.3m Lowell
Discovery Telescope (LDT) at Happy Jack, AZ. Observations started on
August 29, 10:04:56 UT (3.23 days after the Fermi trigger) taking 8
exposures of 180 s each with SDSS r filter. Observations were taken at an
airmass of about 1 and seeing of 1.4".
We detect the underlying galaxy reported by Ahumada el al. (GCN Circ.
28287) with magnitude r=22.60 +/- 0.03 AB mag. We do not find any other
source at the reported position down to a 3-sigma field limit of r>24.5
AB mag.
Magnitudes are calibrated against the SDSS catalog and not corrected for
Galactic extinction.
We thank the staff of the Lowell Discovery Telescope for assistance with
these observations.
GCN Circular 28319
Subject
GRB 200826A
Date
2020-08-30T07:28:22Z (5 years ago)
From
Barry Rothberg at Large Binocular Telescope Obs <brothberg@lbto.org>
B. Rothberg (LBTO/George Mason University), O. Kuhn (LBTO), C. Veillet
(LBTO), S. Allanson (LBTO).
We observed the optical afterglow of GRB 200826A (Gupta et al. GCN Circ.
28288, Hurley et al., GCN Circ. 28291) using the Large Binocular Telescope
Observatory equipped with the Multi-Object Double Spectrographs (MODS).
Our spectra cover the wavelength range 0.38-1.0 microns. The observations
consist of 4 exposures of 900 seconds each in three of the four available
channels (MODS-1 Red, MODS-2 Blue, and MODS-2 Red). The observation mid
time was 09:39 UT 28 Aug 2020.
In two 60 second acquisition images taken simultaneously wiith the g-sloan
and r-sloan filters we measure a magnitude of g=22.96 +/- 0.07 and r=22.15
+/- 0.07 (both ABmags). The photometry was calibrated against the DR12
catalog magnitudes of nearby stars (Alam et al. 2015, ApJS 219,12A). The
acquisition images were taken at 08:52:34 and 08:54:35 UT 28 Aug 2020.
The spectroscopic observations were taken at a Position Angle = 17 degrees
in order to cover both GRB 200826A and a possible nearby galaxy 15" NE. The
observations used a 1" wide slit and the spectra were extracted for both
sources using a 1" wide aperture. We clearly detect a continuum from
0.38-0.9 microns. From the detection of multiple emission features, which
we interpret as [OII], [NeIII], H-gamma, H-beta, [OIII]/4959, [OIII]/5007,
we calculate a redshift of 0.7481 +/-0.0003.
The nearby galaxy, 15" NE, is determined to be unrelated to GRB 200826A.
From the detection of multiple emission features which we interpret as
[OII]/5007, [NII]/6548, H-alpha, [NII]/6583, [SII]/6716, and [SII]/6730, we
infer a redshift of 0.1730 +/- 0.0003.
Additional spectroscopic observations are planned.
We acknowledge and heartily thank the rest of the LBTO staff for excellent
support in readying the telescope for nighttime on-sky activities during
these chaotic times.
B. Rothberg also acknowledges the assistance of R.T. Gatto.
GCN Circular 28410
Subject
GRB 200826A: uGMRT radio upper limit at 1.25 GHz
Date
2020-09-11T17:23:21Z (5 years ago)
From
Sonalika Purkayastha at NCRA-TIFR <spurkayastha@ncra.tifr.res.in>
P. Chandra (NCRA-TIFR), S. Purkayastha (NCRA-TIFR), V. Bhalerao (IIT-B),
H. Kumar (IIT-B), M. Kasliwal (IPAC)
We observed the Fermi short GRB200826A (Fermi GBM Team GCN 28284; Mangan
et al. GCN 28287) with the Giant Metrewave Radio Telescope (uGMRT),
India, beginning 2020 September 9.53 UT (14.47 days after the burst) at
a central frequency of 1.25 GHz. We report non-detection of radio
afterglow from GRB200826A, with no evidence of radio emission above a
3-sigma upper limit of 48.6 microJy/beam. The final image has a
resolution of 4.13 arcsec by 1.65 arcsec at a position angle of 83.10
degrees. We thank the staff of the GMRT that made these observations
possible.
GCN Circular 28727
Subject
GRB200826A: GMOS-N detection of a supernova bump
Date
2020-10-21T18:40:54Z (5 years ago)
From
Tomas Ahumada at U. of Maryland <tahumada@astro.umd.edu>
Tomas Ahumada (UMD), Leo Singer (NASA GSFC), Harsh Kumar (IITB), and Simeon
Reusch (DESY) report on behalf of the ZTF and GROWTH collaborations:
We imaged position of ZTF20abwysqy/AT2020scz (Ahumada et al. GCN 28295),
the afterglow of GRB 200826A (GCN 28284) with the Gemini Multi-Object
Spectrograph (GMOS-N) mounted on the Gemini-North 8-meter telescope on
Mauna Kea, on 2020-09-23 and 2020-10-10.
Each epoch consisted of 14 r- and i- band 200s exposures. We reduced and
co-added the images from each epoch using DRAGONS, a Python-based data
reduction platform provided by the Gemini Observatory. We subtracted the
coadded images of the two epochs using HOTPANTS. A source is detected on
2020-09-23 at the position of the afterglow with i = 23.9 AB mag and r >
23.5 AB mag.
At host galaxy's redshift of z = 0.7481 (GCN 28319) and assuming Planck
2015 cosmological parameters, the absolute magnitude of the GMOS-N
detection is M_i = -19.5 AB mag. At this time, a kilonova would have an
absolute magnitude of M_i >~ -14.5 AB mag whereas a SN1998bw-like supernova
would have an absolute magnitude of M_i ~ -19 AB mag. Since the GMOS-N
detection is consistent with a supernova but not a kilonova, we conclude
that GRB 200826A was powered by a collapsar rather than a neutron star
merger.
We thank the Gemini Observatory Director for awarding this observing time
and the Gemini staff for help with planning and for executing the
observations.
--
Tomas Ahumada (he/him)
Ph.D. Student
Department of Astronomy
University of Maryland, College Park
NASA Goddard Space Flight Center, Code 661
B.Sc. Astronomy, Pontificia Universidad Cat��lica de Chile
GCN Circular 28949
Subject
GRB 200826A: TNG and LBT constraints on a supernova bump
Date
2020-11-24T10:54:35Z (5 years ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
A. Rossi (INAF-OAS), P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), A.
Melandri (INAF-OAB) and E.Palazzi (INAF-OAS) on behalf of the CIBO
collaboration, and B. Rothberg (LBTO/GMU), O. Kuhn, C. Veillet (LBTO)
report:
We searched for a supernova bump associated to ZTF20abwysqy/AT2020scz
(Ahumada et al. GCN 28295), the afterglow of GRB 200826A (Fermi, GCN
28284; Ridnaia et al., GCN 28294), which energetics are consistent with
being a long/soft event (Svinkin et al., GCN 28301).
We obtained two series of r-sdss images with the Italian 3.6m TNG
telescope equipped with DOLORES. The first set consists in a series of
13 x 240 s obtained on 2020-09-27 at a midtime 02:01 UT (~32 days after
the burst). A second set of 26x200 s of exposure time each have been
obtained on 2020-11-09.
Another two series of r-sdss images have been obtained with the MODS
double imager and spectrographs mounted on LBT. Both series consists of
13x180 sec r-band images with the MODS double imager and spectrographs
mounted on LBT and otained on 2020-09-28 and 2020-11-13.
Image subtraction between the two TNG observing epochs and between the
two LBT/MODS observing epochs using HOTPANTS (v5.1.11) does not reveal
the source found by Ahumada et al. (GCN 28727) and constrain the
presence of a SN bump beyond the conservative 5 sigma limit of r>25 in
both TNG and LBT first epochs. Assuming that the supernova responsible
for the bump detected by Ahumada et al. is similar to SN1998bw, at the
redshift of GRB 200826A z=0.748 (Rothberg et al., GCN 28319) its
brightness would be r~24.8, that includes the foreground Galactic
extinction on the line of sight of GRB 200826A (A_V=0.184; Schlafly &
Finkbeiner 2011). Our non detection then might indicate that the
supernova detected by Ahumada et al. was at least 10% faster and/or
fainter than SN1998bw.
At the position of the afterglow we clearly detect the host galaxy of
GRB 200826A, for which we report r=23.33+-0.09 in all observations,
calibrated against SDSS field stars.
We acknowledge the excellent support from the TNG staff, in particular
W. Boschin, and the LBTO and LBT-INAF staff, particularly A. Cardwell,
F. Cusano, S. Paiano and D. Paris, in obtaining these observations.
GCN Circular 29029
Subject
GRB 200826A: GMOS-N detected source magnitude (Correction)
Date
2020-12-11T23:06:21Z (4 years ago)
From
Tomas Ahumada at U. of Maryland <tahumada@astro.umd.edu>
Tomas Ahumada (UMD), Harsh Kumar (IITB), Christoffer Fremling (Caltech),
Leo Singer (NASA GSFC) report on behalf of the ZTF and GROWTH
collaborations:
Reanalysing the data used in Ahumada et al. GCN 28727, we provide a revised
magnitude of the source detected in the Gemini Multi-Object Spectrograph
(GMOS-N) i-band image of ZTF20abwysqy/AT2020scz (Ahumada et al. GCN 28295).
We imaged the region of GRB 200826A (GCN 28284) with GMOS-N, mounted on the
Gemini-North 8-meter telescope on Mauna Kea, on three nights: 2020-09-23
(2459115.9675 mjd), 2020-10-10 (2459133.8039 mjd) and 2020-11-08
(2459167.9342 mjd). Each epoch consisted of 14 r- and i- band 200s
exposures. We reduced and co-added the images from each epoch using
DRAGONS, a Python-based data reduction platform provided by the Gemini
Observatory. We subtracted the coadded images using HOTPANTS and PyZOGY
independently. We now present the revised magnitudes using a zero-point
calculated using 23 stars in the field from the SDSS catalog. We apologize
for any possible confusion caused by the erroneously reported photometry in
GCN 28727.
In the 2020-09-23 images, a source is detected at the position of the
afterglow with i = 25.49 +- 0.15 mag, but not in r-band up to r > 25.6 AB
mag. In the 2020-10-10 images, we do not detect a transient in either
filter up to a 5-sigma limit of i > 25.4 mag and r > 25.5 mag.
At the host galaxy's redshift of z = 0.7481 (GCN 28319) and assuming Planck
2015 cosmological parameters, the absolute magnitude of the GMOS-N
detection is M_i = -17.9 AB mag.
We thank the Gemini Observatory Director for awarding this observing time
and the Gemini staff for help with planning and executing the observations.
--
Tomas Ahumada (he/him)
Ph.D. Student
Department of Astronomy
University of Maryland, College Park
NASA <tomas.f.ahumdamena@nasa.gov> Goddard Space Flight Center, Code 661
B.Sc. Astronomy, Pontificia Universidad Cat��lica de Chile