GRB 100823A
GCN Circular 11135
Subject
GRB 100823A: Swift detection of a burst
Date
2010-08-23T17:38:11Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
V. Mangano (INAF-IASFPA), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
M. M. Chester (PSU), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU),
E. A. Hoversten (PSU), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC),
P. T. O'Brien (U Leicester), T. Sakamoto (NASA/UMBC),
M. C. Stroh (PSU) and E. Troja (NASA/GSFC/ORAU) report on behalf of
the Swift Team:
At 17:25:35 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100823A (trigger=432420). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 20.703, +5.842, which is
RA(J2000) = 01h 22m 49s
Dec(J2000) = +05d 50' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single FRED-like peak
with a duration of about 25 sec. The peak count rate
was ~1000 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 17:26:44.6 UT, 68.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 20.70383, 5.83361
which is equivalent to:
RA(J2000) = 01h 22m 48.92s
Dec(J2000) = +05d 50' 01.0"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 30 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (3.73e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2.1
(+1.87/-1.66) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 5.93e-10 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White
filter starting 77 seconds after the BAT trigger. No credible
afterglow candidate has been found in the initial data products. The
2.7'x2.7' sub-image covers 100% of the XRT error circle. The 3-sigma
upper limit is 19.3 mag. The 8'x8' region for the list of sources
generated on-board covers 100% of the XRT error circle. The list of
sources is typically complete to about 18 mag. No correction has been
made for the expected extinction corresponding to E(B-V) of 0.04.
Burst Advocate for this burst is V. Mangano (vanessa AT ifc.inaf.it).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular 11136
Subject
GRB 100823A: Enhanced Swift-XRT position
Date
2010-08-23T20:20:57Z (15 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team.
Using 251 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 100823A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 20.70428, +5.83510 which is equivalent
to:
RA (J2000): 01h 22m 49.03s
Dec (J2000): +05d 50' 06.4"
with an uncertainty of 2.1 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 11137
Subject
GRB 100823A: Swift-BAT refined analysis
Date
2010-08-23T22:25:08Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD), T. Sakamoto (GSFC/UMBC),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 100823A (trigger #432420)
(Mangano, et al., GCN Circ. 11135). The BAT ground-calculated position is
RA, Dec = 20.706, 5.848 deg, which is
RA(J2000) = 01h 22m 49.4s
Dec(J2000) = +05d 50' 52.6"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.
The mask-weighted light curve shows a single FRED peak starting at ~T-2 sec,
peaking at ~T+1 sec, and ending at T+150 sec. T90 (15-350 keV) is
16.9 +- 3.5 sec (estimated error including systematics).
The time-averaged spectrum from T-1.2 to T+18.2 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.19 +- 0.18. The fluence in the 15-150 keV band is 4.1 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.14 sec in the 15-150 keV band
is 1.0 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/432420/BA/
GCN Circular 11138
Subject
GRB 100823A: WHT observations
Date
2010-08-24T04:28:24Z (15 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester), C. Copperwheat (U. Warwick)
report for a larger collaboration:
We observed the field of GRB 100823A (Mangano et al. GCN 11135) using the
William Herschel Telescope on La Palma with the ACAM instrument. Observations
were conducted in the z-band, and began at 00:37 UT, approximately 7.2 hours
after the burst.
Within the refined X-ray error circle (Goad et al. GCN 11136) we identify a
source, at
A:
RA(J2000): 01:22:48.97
DEC(J2000) 05:50:08.1
However, we note that a source is also present in the DSS2 images of the field
at this position.
Additionally we note the presence of a brighter source, not present in the DSS
images at
B:
RA(J2000): 01:22:48.79
DEC(J2000) 05:50:10.9
This source may be the afterglow of GRB 100823A (offset approximately ~6 arcseconds
from the XRT position), or alternatively could either be a red source, not visible in the
DSS2 red image, or a source with high proper motion.
Further observations will be required to assess the nature of any variability.
Images can be found at
http://www.star.le.ac.uk/~anl/100823A
GCN Circular 11139
Subject
GRB 100823A: Swift/UVOT Upper Limits
Date
2010-08-24T04:37:39Z (15 years ago)
From
Margaret Chester at PSU <chester@astro.psu.edu>
M.M. Chester (PSU) and V. Mangano (INAF-IASFPA) report on behalf of
the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 100823A
78 s after the BAT trigger (Mangano et al., GCN Circ. 11135). No
optical afterglow consistent with the enhanced Swift/XRT position
(Goad et al., GCN Circ. 11136) is detected in the initial UVOT
exposures. Preliminary 3-sigma upper limits using the UVOT
photometric system (Poole et al. 2008, MNRAS, 383, 627) for the
white and u finding chart (FC) and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 78 227 147 >20.1
u_FC 290 539 246 >19.4
white 78 17439 2181 >21.9
v 619 22361 1331 >20.5
b 545 16528 1278 >21.3
u 290 6512 639 >20.4
w1 669 6307 432 >20.2
m2 816 6102 413 >20.8
w2 767 18242 2082 >21.2
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 11141
Subject
GRB 100823A: TNG NIR observations
Date
2010-08-24T12:02:37Z (15 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D'Avanzo (INAF-OAB), A.J. Levan (U. Warwick), D. Malesani (DARK/NBI),
N.R. Tanvir (U. Leicester), E. Palazzi (INAF-IASFBo), A. Fiorenzano
(INAF-TNG), report:
We observed the field of GRB 100823A (Mangano et al. GCN 11135) using the
Italian 3.6m TNG telescope, located in the Canary Islands. A set of J-band
images were acquired on Aug 24.03490 UT (~7.4 hours after the burst; mid
exposure time) for a total exposure time of 16 minutes.
We detect the two objects reported by Levan et al. (GCN 11138) and Guziy
et al. (GCN 11140) with magnitudes J=21.0 for object "A" (the one within
the refined XRT error circle; Goad et al. GCN 11136) and J=19.4 for object
"B", calibrated against the 2MASS catalogue.
Although we have yet to photometrically calibrate the z-band image, from a
comparison of the TNG and WHT images (Levan et al. GCN 11138) we note that
object "B" has a z-J color significantly redder with respect to the
average color of field stars.
As suggested by Levan et al (GCN 11138) object "B" can thus be a red
source not visible in the DSS2 red image. In light of this, its location
outside the XRT refined error circle would make it likely unrelated to the
GRB.
GCN Circular 11142
Subject
GRB 100823A - second epoch WHT observations
Date
2010-08-24T12:16:50Z (15 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester), C. Copperwheat
(U. Warwick) report for a larger collaboration:
We obtained a second epoch of observations of GRB 100823A (Mangano
et al. GCN 11135) with the WHT, beginning at 05:38 UT, approximately
5 hours after our first epoch of observations (Levan et al. GCN
11138), and 12 hours after the GRB. In our images we detect both
sources A and B, both of which are constant within the photometric
errors.
Additionally, we have inspected archival images of the field obtained
with the UKIRT Wide Field Camera (WFCAM) in November 2008
in the YJHK bands. Object B is faintly detected in all bands, while
object A is below the detection limit of the shallow observations.
Given the location of object B well outside the refined XRT error
circle (Goad et al. GCN 11136) these results imply that it is not
related to GRB 100823A, confirming the conclusion of D'Avanzo
et al. (GCN 11141). We cannot rule out a faint contribution of
afterglow to object A, but it non-variability in our observations,
coupled with its detection in DSS2 suggest that it is not afterglow
dominated."
GCN Circular 11143
Subject
GRB 100823A: VLT/X-Shooter spectroscopy
Date
2010-08-24T13:33:09Z (15 years ago)
From
Nial Tanvir at U.Leicester <nrt3@star.le.ac.uk>
P. D'Avanzo (INAF/Brera), P. Jakobsson (Reykjavik), H. Flores (Paris
Obs.), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), N. R. Tanvir, K.
Wiersema (U. Leicester), A. J. Levan (U. Warwick), D. Malesani, J. P. U.
Fynbo, and B. Milvang-Jensen (DARK), report on behalf of a larger
collaboration:
We observed the location of GRB 100823A (Mangano et al. GCN 11135) with
the ESO VLT equipped with the X-shooter spectrograph on 2010 Aug 24,
beginning 08:17 UT (15.5 hr after the GRB). The slit was aligned so to
include both objects A and B first mentioned by Levan et al. (GCN 11138;
see also Guziy et al., GCN 11140; D'Avanzo et al., GCN 11141). We detect
both objects in the acquisition image, and confirm that object B is
fainter than the DSS limit.
In the spectra, we detect continuum from source A, and identify its
spectrum as being that of an M-dwarf based on evident TiO bands. Given
that object B is also likely unrelated to the GRB (D'Avanzo et al., GCN
11141; Levan et al., GCN 11142), we conclude that either the GRB event
is itself associated with a flare from this star, or that the GRB
afterglow is a fainter source not reported so far.
We acknowledge the support of the VLT staff, in particular Claudia Cid,
Stephane Brillant, Jonathan Smoker, and Christophe Martayan.
GCN Circular 11144
Subject
GRB 100823A: Swift XRT refined analysis
Date
2010-08-24T13:59:54Z (15 years ago)
From
Vanessa Mangano at INAF-IASFPA <vanessa@ifc.inaf.it>
V. Mangano (INAF IASF-PA) and B. Sbarufatti (INAF OAB/INAF IASF-PA)
report on behalf of the Swift-XRT team:
We have analyzed 8.7 ks of XRT data for GRB 100823A (Mangano et al. GCN
Circ. 11135), from 59 s to 22 ks after the BAT trigger. The data
comprise 68 s in Windowed Timing (WT) mode (the first 8 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The light curve can be modeled with a broken power-law decay with an
initial decay index of alpha1=2.9 (+/-0.2) , a break at T+163 (+/-11) s
and a final decay index of alpha2=1.19 (+/-0.03).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.6 (+0.8, -0.6). The
best-fitting absorption column is 2.8 (+1.2, -0.9) x 10^21 cm^-2,
in excess of the Galactic value of 3.7 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum (extracted from T+137.5 s to T+22.3 ks, 8.65 ks
exposure) has a photon index of 2.2 (+0.3, -0.2) and a best-fitting
absorption
column of 2.1 (+0.6, -0.5) x 10^21 cm^-2. The counts to observed
(unabsorbed)
0.3-10 keV flux conversion factor deduced from this spectrum is
4.0 x 10^-11 (6.6 x 10^-11) erg cm^-2 count^-1.
If the light curve continues to decay with a power-law decay index of
0.87, the count rate at T+48 hours will be 9.0 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of
3.6 x 10-14 (5.9 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00432420.
This circular is an official product of the Swift-XRT team.
GCN Circular 11145
Subject
GRB 100823A: Candidate IR afterglow
Date
2010-08-24T17:13:52Z (15 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), K. Wiersema, N. Tanvir (U. Leicester),
C. Copperwheat (U. Warwick) report on behalf of a larger collaboration:
We obtained infrared imaging of the location of GRB 100823A ( using
LIRIS on the 4.2m WHT, beginning at 01:34 UT, ~8 hours after the
burst. Observations were obtained in the JH and K bands, with a
total exposure time of 540 s in each band.
We detect sources A and B of Levan et al. (GCN), but also find a
new source within the XRT error circle of Goad et al. GCN 11135,
but see also,
http://www.swift.ac.uk/xrt_positions/00432420/image.php
with a position of,
C:
RA(J2000) 01:22:48.94
DEC(J2000) 05:50:05.9
The object has K=19.6 calibrated against 2MASS, and is faintly
visible in the H-band, but not in the J or z, suggestive of a red colour.
At the current time we cannot make statements as to the variability of
the source, but its red colour, akin to extinguished GRB afterglows,
coupled with a location within the XRT error circle leads us to
suggest that it is the afterglow of GRB 100823A.
GCN Circular 11146
Subject
GRB100823A : MOA optical observation
Date
2010-08-25T12:41:45Z (15 years ago)
From
Suzuki Daisuke at MOA-II <dsuke@stelab.nagoya-u.ac.jp>
D. Suzuki, K. Omori, N. Miyake, S. Kobara, H. Naito and T. Sako (STE Lab, Nagoya Univ.),
T. Saito (Tokyo Metropolitan College of Industrial Technology)
and K. Wada (Konan Univ.) on behalf of the MOA Collaboration report:
We searched for an optical afterglow of GRB 100823A (GCN 11135, Mangano et al.)
starting from 17:30:34 UT on 2010 Aug 23 (5 minutes after the burst)
with the MOA-II 1.8m telescope at Mt.John observatory in New Zealand.
In a single image of a 60sec exposure with a wideband Red filter (center
wavelength ~ 750nm and FWHM ~ 250nm), we found an object not found in the USNO-B1.0 catalog
within the error circle of the Swift XRT source position (GCN 11136 Goad et al.).
The position coincides with the source C (GCN 11145, Levan et al.) and
the magnitude is estimated to be I=17.1mag.
Additionally, we obtained a second epoch of observation of GRB 100823A
starting from 14:59:16 UT on 2010 Aug 24 (approximately 21.5 hours after the burst).
In a single image of a 300sec exposure with a wideband Red filter,
we detected source A (GCN 11138, Levan et al.) with magnitude I=21.3mag
,but we did not detect the source C in this epoch.
This photometry were done by using the DoPhot and calibrated against the
USNO-B1.0 catalog stars, and not corrected for the Galactic extinction.
GCN Circular 11148
Subject
GRB 100823A: Swift/UVOT Evidence for Fading Afterglow Emission
Date
2010-08-26T19:03:19Z (15 years ago)
From
Margaret Chester at PSU <chester@astro.psu.edu>
M. M. Chester (PSU), T.S. Koch (PSU), E. A. Hoversten (PSU), and
V. Mangano (INAF-IASFPA) report on behalf of the Swift/UVOT team:
Further examination of Swift/UVOT observations of GRB 100823A show
that a source detected in the white finding chart exposure, initially
thought to correspond to the DSS2 source mentioned in Levan et
al., GCN Circ. 11138, faded in subsequent exposures to an apparently
steady level. The source was marginally detected in the u finding
chart exposure. The position of the source in both the finding chart
and later images is consistent with the enhanced XRT position (Goad et
al., GCN Circ. 11136). We propose this result as further evidence that
Source C in Levan et al., GCN Circ. 11145, and referenced in Suzuki et
al., GCN Circ. 11146, is the afterglow of GRB 100823A.
Magnitudes for the white and u finding charts and white optimally co-
added exposures are given in the following table. All photometry was
performed using the UVOT photometric system (Poole et al. 2008, MNRAS,
383, 627). The values quoted are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.04 in the direction of
the burst (Schlegel et al. 1998).
Filter T_start(s) T_stop(s) Exp(s) Mag Error S/N
white_FC 78 227 147 20.7 +/-0.3 2.9
u_FC 290 539 246 20.4 +/-0.4 2.1
white 576 57266 3157 23.4 +/-0.8 2.3
white 61907 63386 1453 22.9 +/-0.7 2.4
white 67668 73670 2674 23.3 +/-0.8 2.1
white 73673 75876 2168 23.0 +/-0.7 2.5
The UVOT position determined from co-adding all of the later images
(after T=56215s) is:
RA (J2000) 01:22:49.03 = 20.70429 (deg)
Dec (J2000) +05:50:06.4 = +5.83511 (deg)
with an estimated uncertainty of 0.9 arcsec (radius, 90% confidence,
statistical + systematic).
GCN Circular 11151
Subject
GRB 100823A: MAXI/GSC detection
Date
2010-08-27T16:06:32Z (15 years ago)
From
Motoko Suzuki at RIKEN <motoko@crab.riken.jp>
M. Serino, T. Mihara, Y.E. Nakagawa, M. Sugizaki, T. Yamamoto,
T. Sootome, M. Matsuoka (RIKEN),
N. Kawai, M. Morii, K. Sugimori, R. Usui (Tokyo Tech),
K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA),
A. Yoshida, K. Yamaoka, S. Nakahira (AGU),
H. Tsunemi, M. Kimura (Osaka U.), H. Negoro, M. Nakajima
H. Ozawa, F. Suwa (Nihon U.), Y. Ueda, N. Isobe,
S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.), A. Uzawa,
T. Matsumura, K. Yamazaki (Chuo U.) report on behalf of the MAXI team:
The Gas Slit Camera (GSC) of MAXI detected a bright X-ray source at the
position consistent with GRB 100823A (Mangano et al, GCN 11135).
Assuming the XRT position (Goad et al., GCN 11136), the transit
of GSC over the source started at 17:25:25 UT on 23 August 2010,
10 seconds before the Swift/BAT trigger time.
A significant (8 sigma in 2-20 keV) rise of the count rate above the background
was observed at 17:25:33, and the burst was detected significantly for 25 seconds.
The peak X-ray flux (4-10 keV) was about 2.5 Crab, which was corrected for the collimator transmission efficiency assuming the source position by Swift XRT.
There are significant time structure within the transit light curve,
which would be simply triangular for a steady source.
From the preliminary spectral analysis, the time-averaged spectrum
from T+0 to T+25 sec is best fit by a power-law model with a photon index
of 2.0 +/- 0.2. The fluence in the 2-20 keV band is 5.1 +0.5 -0.9 x 10^-7 erg/cm2.
The sky image and the transit light curve is shown at the MAXI web site
http://maxi.riken.jp/ in the "News" section.
GCN Circular 11152
Subject
GRB 100823A: optical observations
Date
2010-08-27T20:23:43Z (15 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Pozanenko (IKI), A. Volnova (SAI MSU), B. Satovski (Astrotel), M.
Ibrahimov (MAO) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 100823A (Mangano et al. GCN 11135)
with AZT-22 telescope of Maidanak observatory. Several images in I-filter
were obtained starting on Aug. 23 (UT) 20:47:02.
We do not detect the object C (Levan et al. GCN 11145; Suzuki et al. GCN
11146) up to I=22.2m. We clearly detect both objects A and B (Levan et al.
GCN 11138). The photometry of stacked image is based on USNO-B1.0 star
0958-0013520 located at RA(J2000) = 01:22:45.50, DEC(J2000) = +05:49:03.0
and used as reference star in GCN 11140 (Guziy et al).
Object, t-T0, Filter, Exposure, OT, Upper
limit (3 sigma)
(mid, d) (s)
A 0.16605 I 19*180 21.06+/-0.09 22.2
B 0.16605 I 19*180 20.60+/-0.06 22.2
The photometry of the object A is compatible with photometry reported in
GCN 11146 (Suzuki et al).
Using photometry of the object C starting 5 minutes after burst (Suzuki et
al. GCN 11146) and upper limit I=22.2m at 0.16605 days one can estimate
power law decay index alpha > 1.25.
We thank Otabek Burhonov for performing the observations and for his
support.
GCN Circular 11154
Subject
GRB 100823A: optical upper limit
Date
2010-08-27T20:45:22Z (15 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
K. Antoniuk, V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of
larger GRB follow-up collaboration:
We observed the field of the Swift GRB 100823A (Mangano et al. GCN 11135)
with AZT-11 telescope of CrAO observatory. Several images in R-filter were
obtained on Aug. 23 between (UT) 22:05 - 22:53.
In enhanced XRT position (Goad et al. GCN 11136) we do not detect any source
up to R=20.7. The photometry of stacked image is based on USNO-B1.0 star
0958-0013520 located at RA(J2000) = 01:22:45.50, DEC(J2000) = +05:49:03.0
(assuming R=16.75):
t-T0, Filter, Exposure, OT, Upper limit (3 sigma)
(mid, d) (s)
0.2111 R 15*180 n/d 20.7