GRB 230205A
GCN Circular 33271
Subject
GRB 230205A: Swift detection of a burst
Date
2023-02-05T11:01:42Z (2 years ago)
From
Elena Ambrosi at INAF-IASF <elena.ambrosi@inaf.it>
E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA), A. Y. Lien (U Tampa),
A. Melandri (INAF-OAB), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB)
and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 10:29:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 230205A (trigger=1152764). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 202.072d, +46.684d which is
RA(J2000) = 13h 28m 17s
Dec(J2000) = +46d 41' 01"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). Due to a telemetry gap, the BAT light curve
before T+8s is not immediately available, and after that time shows
no obvious variability. The BAT rate trigger was on a 3 s timescale,
consistent with the lack of variation at later times.
The XRT began observing the field at 10:31:40.0 UT, 108.8 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 202.07147, 46.72613
which is equivalent to:
RA(J2000) = 13h 28m 17.15s
Dec(J2000) = +46d 43' 34.1"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 151 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
https://www.swift.ac.uk/sper. We cannot determine whether the source
is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.09 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.2
(+0.71/-0.56) x 10^22 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 100 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 none of
the XRT error circle. 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 0.036.
Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT 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/)
GCN Circular 33274
Subject
GRB 230205A: BOOTES-5/JGT early optical upper limit
Date
2023-02-05T17:16:06Z (2 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, I. Perez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar (UMA) and I. Carrasco (SMA), I. H. Park (SKKU) on behalf of a larger collaboration, report:
Following the detection of GRB 230205A by Swift (Ambrosi et al. GCNC 33271), the BOOTES-5/JGT 0.6m robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) observed the GRB location starting on Feb. 5, 10:30:47 UT (~ 56 s after trigger). In the co-added image (20 x 60 s exposures in the clear filter), no optical afterglow is detected within the enhanced Swift/XRT error region (Ambrosi et al. GCNC 33271) down to 20.4 mag, which is consistent with the limit reported by UVOT (Ambrosi et al. GCNC 33271).
We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for their excellent support.
GCN Circular 33275
Subject
GRB 230205A: Enhanced Swift-XRT position
Date
2023-02-05T17:46:40Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.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 2803 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 230205A, 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 = 202.07096, +46.72520 which is equivalent
to:
RA (J2000): 13h 28m 17.03s
Dec (J2000): +46d 43' 30.7"
with an uncertainty of 1.9 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 33277
Subject
GRB 230205A: Swift-XRT refined Analysis
Date
2023-02-05T21:29:13Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), T. Sbarrato
(INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), A.
Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J. D. Gropp (PSU), P.A.
Evans (U. Leicester) and E. Ambrosi report on behalf of the Swift-XRT
team:
We have analysed 7.9 ks of XRT data for GRB 230205A (Ambrosi et al. GCN
Circ. 33271), from 80 s to 30.1 ks after the BAT trigger. The data
comprise 10 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. The enhanced
XRT position for this burst was given by Goad et al. (GCN Circ. 33275).
The late-time light curve (from T0+5.1 ks) can be modelled with a
power-law decay with a decay index of alpha=0.85 (+0.29, -0.27).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.84 (+0.23, -0.22). The
best-fitting absorption column is 6.0 (+1.6, -1.4) x 10^21 cm^-2, in
excess of the Galactic value of 2.1 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 4.6 x 10^-11 (7.1 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 6.0 (+1.6, -1.4) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^20 cm^-2
Excess significance: 6.8 sigma
Photon index: 1.84 (+0.23, -0.22)
If the light curve continues to decay with a power-law decay index of
0.85, the count rate at T+24 hours will be 5.6 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x
10^-13 (4.0 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01152764.
This circular is an official product of the Swift-XRT team.
GCN Circular 33280
Subject
GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
Date
2023-02-06T04:14:03Z (2 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
T. Sakamoto (AGU), E. Ambrosi (INAF-IASFPA),
S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Parsotan (GSFC/UMBC), M. Stamatikos (OSU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 230205A (trigger #1152764)
(Ambrosi et al., GCN Circ. 33271). The BAT ground-calculated position is
RA, Dec = 202.057, 46.686 deg which is
RA(J2000) = 13h 28m 13.7s
Dec(J2000) = +46d 41' 08.1"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The mask-weighted light curve shows a short pulse that starts at ~T0,
peaks at ~T+2 s, and ends at ~T+3 s. In addition, there may be some
hint of extended emission that lasts till ~T+80 s. T90 (15-350 keV)
is 2.30 +- 0.36 sec (estimated error including systematics).
The time-averaged spectrum from T+0.32 to T+2.87 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.44 +- 0.29. The fluence in the 15-150 keV band is 1.6 +- 0.3 x 10^-7
erg/cm2.
The 1-sec peak photon flux measured from T+1.74 sec in the 15-150 keV band
is 0.9 +- 0.2 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/1152764/BA/
GCN Circular 33282
Subject
GRB 230205A: OHP/T193 optical observations
Date
2023-02-06T11:57:33Z (2 years ago)
From
Damien Turpin at NAOC (CAS) <dturpin-astro@hotmail.com>
D. Turpin (CEA Paris-Saclay), C. Adami (LAM), E. Le Floc'h,
D. Gotz, C. Plasse (CEA Paris-Saclay), B. Schneider (MIT),
�S. D. Vergani, A. Saccardi (GEPI, Observatoire de Paris),
S. Basa, M. Ferrari, A. Le Van Suu (LAM) report
on behalf of a larger collaboration:
We observed the field of the possible short GRB 230205A (Ambrosi et al.,
GCN 33271; Page et al., GCN 33277, Sakamoto et al., GCN 33280) using the
T193cm telescope equipped with MISTRAL at Observatoire de Haute-Provence
(France).
Six exposures were obtained in the R-band (5x20s + 1x60s + 1x120s +
2x180s) under poor weather conditions from 2023 06 Feb. 03:37:06 UT to
2023 06 Feb 04:07:34 UT.
In the combined last two frames (mid time ~17.57h after trigger),
we do not detect the source and obtain the following upper limit:
R > 20.95 mag (AB)
The photometric calibration was performed using nearby stars from
the PanSTARRS catalog.
No further observations using the MISTRAL instrument mounted on the
T193-OHP are planned.
We acknowledge the excellent support from Observatoire de Haute Provence,
in particular Stephane Favard, Jerome Schmitt.
GCN Circular 33283
Subject
GRB 230205A: SVOM/C-GFT optical upper limit
Date
2023-02-06T13:09:38Z (2 years ago)
From
Chao Wu at NAOC <wuchao.lamost@gmail.com>
Chao Wu (NAOC), Zhe Kang (CHO), Liping Xin (NAOC), Xuhui Han (NAOC),
Xiaomeng Lu (NAOC), Damien Turpin(CEA), Zhenwei Li (CHO)���Pinpin
Zhang (NAOC)���Ruosong Zhang (NAOC)���Yulei Qiu (NAOC)���You Lv (CHO)���Jing
Wang(GXU), Cordier Bertrand (CEA) and Jianyan Wei (NAOC) on behalf of
SVOM GRB team
We observed the burst GRB230205A (Ambrosi et al. GCN 33271) on
14:02:03 UT, Feb. 5th, 2023, about 3.5 hours after the Swift trigger
with C-GFT (Chinese Ground Follow-up Telescope in SVOM mission) in
System Test Mode (STM). C-GFT is located at Jilin (long.=126.33 deg,
lat.= 43.8243778 deg), Changchun Observatory, National Astronomical
Observatories, CAS. It has FOV of 1.5 deg X 1.5 deg with a 4k*4k CMOS
detector mounted on the primary focus of 1.2-meter-aperure telescope.
A series of g and r band images were obtained. The exposure time was
30 seconds for each frame.
No optical afterglow was detected within the enhanced XRT error box
(Goad et al., GCN 33275) down to a limit magnitude of 17.0 mag in each
r-band single frame (in STM). The photometry was calibrated with
nearby UCAC 4 catalogs. The upper limit is consistent with the limit
reports (Ambrosi et al. GCN 33271; Hu et al., GCN 33274).
More detailed analysis is continuing.
We thank the observation assistant Bowen Li at Jilin observatory for
their excellent support.
GCN Circular 33286
Subject
GRB 230205A: LCOGT Optical Upper Limits
Date
2023-02-06T16:21:38Z (2 years ago)
From
Robert Strausbaugh at University of Minnesota <rstrausb@umn.edu>
R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on
behalf of a larger collaboration:
We observed the GRB 230205A (Ambrosi et al., GCN 33271) field with the
LCOGT 1-meter Sinistro instrument at the McDonald Observatory, TX, USA
site, on February 6, from 11:51 to 12:23 UT (corresponding to 25.20 to
25.52 hours from the GRB trigger time) with the SDSS r and i filters.
We performed a series of 3x300s exposures in each band. We do not detect a
source in either band within the XRT enhanced error region (Goad et al.,
GCN 33275) consistent with other optical upper limits (Hu et al., GCN
33274; Turpin et al., GCN 33282; Wu et al., GCN 33283).
The following magnitudes and upper limits are calculated using the
PanSTARRS catalog as reference:
r > 21.2
i > 20.8
These magnitudes are not corrected for galactic extinction.
GCN Circular 33289
Subject
GRB 230205A: Swift/UVOT Upper Limits
Date
2023-02-06T20:44:18Z (2 years ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
M.H. Siegel (PSU) and E/ Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230205A
100 s after the BAT trigger (Ambrosi et al., GCN Circ. 33271).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 33275)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 100 250 147 >21.3
u_FC 258 508 246 >20.3
white 100 5198 526 >21.5
v 588 1581 117 >19.5
b 514 1680 117 >20.1
u 258 1481 343 >20.2
w1 638 657 19 >19.2
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.036 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 33302
Subject
GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
Date
2023-02-08T14:42:11Z (2 years ago)
From
Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>
L. Tomasella (INAF-OAPd), P. D���Avanzo, (INAF-OAB), E. Cappellaro (INAF-OAPd) on behalf of a larger collaboration report:
We observed the field of the possibly short GRB 230205A (Ambrosi et al, GCN Circ. 33271; Sakamoto et al., GCN Circ. 33280)
with the Schmidt telescope of the INAF - Padova Astronomical Observatory located in Asiago (Italy). Observations were carried
out in imaging mode with the r and i filters about 2.5 days after the burst T0.
No clear afterglow candidate is detected within the enhanced XRT position (Goad et al., GCN Circ. 33275) down to the following
magnitude limits: r > 21.2 mag, i > 21.0 mag (AB; 3sigma c.l.).
In our i-band image we detect a source at the SW edge of the XRT error circle at the following position (J2000):
RA = 13:28:16.87
Dec = +46:43:29.3
For this source we measure a magnitude of i = 21.1 +/- 0.3 (AB).
We note that this source is detected also in archival SDSS and Pan-STARRS images. In the SDSS the source is named as
SDSS J132816.81+464329.8 and is flagged as a galaxy with a photometric redshift of z = 0.484 +/- 0.090 and a magnitude
i = 21.19 +/- 0.11 mag (AB; consistent with our measurement).
This object is therefore a candidate host galaxy for GRB 230205A.
As a further note, we report that the position of the X-ray afterglow of GRB 230205A lies at about 3.5 arminutes (in projection)
to the galaxy NGC 5169 (whose luminosity distance is ~ 33 Mpc).
GCN Circular 33307
Subject
GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
Date
2023-02-09T16:31:10Z (2 years ago)
From
Kuiyun Huang at CYCU <kuiyun@gmail.com>
Y. Urata, K.Y. Huang on behalf of a larger collaboration
We processed pre-imaging data for the field of the possible short GRB
230205A (Ambrosi et al., GCN Circ. 33271; Sakamoto et al., GCN Circ. 33280)
obtained by SUBRU Hyper-Suprime-Cam with i-band filter on June 6, 2019.
No clear source is identified within the enhanced XRT position (Goad et
al., GCN Circ. 33275).
The host galaxy candidate suggested by Tomasella et al. (GCN Circ. 33302)
is clearly detected.
In addition to this source, there is a source with i = 22.1 +/- 0.1
at the NW edge of the XRT error circle at RA = 13:28:16.92 Dec =
+46:43:32.73.
The image is available at the following link.
https://lh3.googleusercontent.com/VfQ2VhB3PtkCkwrfTVEKX0M0ARJ4bMKJk5g8vnVejx2Onx5CO5HamxaU6h34PDI1m0_MYmf3s-QSkacCSJYbEIMLV57-NkLBpnrVQCxVrMatuUvc4uf0euvRk9m65tiY7A=w1280
GCN Circular 33309
Subject
GRB 230205A: 6 GHz VLA observations
Date
2023-02-09T22:07:28Z (2 years ago)
From
Genevieve Schroeder at Northwestern University <genevieveschroeder2023@u.northwestern.edu>
G. Schroeder, J. C. Rastinejad, W. Fong, C. D. Kilpatrick, A. E. Nugent
(Northwestern), E. Berger (Harvard), T. Laskar (Utah) report:
"We observed the position of the possibly short GRB 230205A (Ambrosi et al,
GCN 33271; Sakamoto et al., GCN 33280) with the Karl G. Jansky Very Large
Array (VLA) under program 23A-296 (PI: Schroeder) beginning on 2023
February 8.25 UT (2.81 days post-burst) at a mean frequency of 6 GHz.
We detect a radio source with a flux of ~40 microJy at the position:
RA(J2000) = 13:28:16.838
Dec(J2000) = +46:43:32.87
with an uncertainty of ~0.5" in each coordinate. This position is on the
outskirts of the XRT position (Goad et al. GCN 33275), on the NW edge. The
radio source position is consistent with the position of the optical source
reported by Urata et al. GCN 33307, although with a slight offset of
~0.85". If we assume this optical source is the host galaxy of GRB 230205A
and the radio source is afterglow, we find a probability of chance
coincidence of Pcc ~ 0.003 (Bloom et al. 2002). Alternatively, the detected
radio emission could originate from the host. In contrast, the radio source
is offset by ~3.6" from the center of the cataloged optical source (SDSS
J132816.81+464329.8) mentioned by Tomasella et al. GCN 33302. If we instead
assume that SDSS J132816.81+464329.8 is the host galaxy of GRB 230205A, we
find Pcc ~ 0.02.
Further observations are planned to determine the variability of the radio
source. We thank the VLA staff for quickly approving and executing these
observations."
GCN Circular 33334
Subject
GRB 230205A: Lowell Discovery Telescope Observations
Date
2023-02-17T00:43:14Z (2 years ago)
From
Brendan O'Connor at UMD <oconnorb@umd.edu>
B. O'Connor (UMD, GWU), E. Hammerstein (UMD), S.B. Cenko (UMD,
NASA-GSFC), E. Troja (UTV, ASU), S.Dichiara (PSU),
J. Durbak (UMD, NASA-GSFC), A. Kutyrev (UMD, NASA-GSFC),
S. Veilleux (UMD), I. Andreoni (UMD, NASA-GSFC), and
G. Srinivasaragavan (UMD):
We observed the field of GRB 230205A (Ambrosi et al. GCN 33271;
Sakamoto et al. GCN 33280) using the Large Monolithic Imager (LMI)
on the 4.3m Lowell Discovery Telescope (LDT) at Happy Jack, AZ.
We began observations on February 13, 2023 at 12:54:52 UT in
r-band and i-band for 600 s each. The target was at airmass
1.1 with seeing ~2".
We do not detect any source within the XRT enhanced position
(Goad et al. GCN 33275) to depth r>23.8 AB mag. The host
galaxy candidate (Tomasella et al. GCN 33302), hereafter S1,
is clearly detected in both filters. We likewise detect
the source (S2) reported by Urata et al. (GCN 33307).
We measure the following magnitudes for S1 and S2:
S1: r ~ 22.0 +/- 0.1 AB mag
S1: i ~ 21.20 +/- 0.05 AB mag
S2: r ~ 23.7 +/- 0.3 AB mag
S2: i ~ 22.7 +/- 0.2 AB mag
The magnitudes of S1 are consistent with the earlier report
of Tomasella et al. (GCN 33302) and the SDSS catalog. For S2,
we derive a slightly fainter i-band magnitude compared to
Urata et al. (GCN 33307). However, as their images were obtained
prior to the explosion, this is not an indication of fading.
Thus, both these sources are candidate host galaxies to
GRB 230205A (Schroeder et al. GCN 33309).
Magnitudes are calibrated against the SDSS catalog and are not
corrected for Galactic extinction.
We thank the staff of the Lowell Discovery Telescope for assistance
with these observations.
GCN Circular 33372
Subject
GRB 230205A: VLA radio afterglow confirmation
Date
2023-02-23T21:04:20Z (2 years ago)
From
Genevieve Schroeder at Northwestern University <genevieveschroeder2023@u.northwestern.edu>
G. Schroeder, (Northwestern), T. Laskar (Utah) report:
"We re-observed the position of the possibly short GRB 230205A (Ambrosi et
al., GCN 33271; Sakamoto et al., GCN 33280) with the Karl G. Jansky Very
Large Array (VLA) under program 23A-296 (PI: Schroeder) beginning on 2023
February 22.52 UT (17.08 days post-burst) at a mean frequency of 6 GHz.
The radio source detected in the previous VLA observation at 2.81 days
(Schroeder et al. GCN 33309) has brightened significantly at 6 GHz,
confirming this source as the radio afterglow of GRB 230205A. We report an
updated radio position of:
RA(J2000) = 13:28:16.837
Dec(J2000) = +46:43:33.13
With an uncertainty of ~0.1" in each coordinate.
Further observations are planned. We thank the VLA staff for quickly
approving and executing these observations."
GCN Circular 34640
Subject
GRB 230205A: LBT spectroscopy of two host galaxy candidates
Date
2023-09-08T08:40:01Z (2 years ago)
From
Elisabetta Maiorano at INAF <elisabetta.maiorano@inaf.it>
Via
Web form
E. Maiorano (INAF-OAS), V. D'Elia (SSDC & INAF-OAR), D. B. Malesani (Radboud Univ. and DAWN/NBI), A. Rossi, E. Palazzi (INAF-OAS), P. D’Avanzo (INAF-OAB), A. Melandri ( INAF-OAR), M. De Pasquale (Messina Univ.) on behalf of CIBO collaboration.
We report the results of the spectroscopic observations of two host galaxy candidates for the short GRB 230205A (Ambrosi et al., GCN 33271), first identified by Tomasella et al. (GCN 33302) and Urata et al. (GCN 33307) in deep Subaru archival imaging.
The optical spectra of the two candidate host galaxies were obtained with the Multi-Object Double Spectrographs (MODS) instrument mounted on the 2x8.4-m LBT telescope (Mt. Graham, AZ, USA) on 2023-03-04, 27 days after the burst trigger. The spectra cover the wavelength range 3200-10000 AA, with a total of exposure time of 1.5 hours.
We detect a faint and red continuum with few emission lines for the brightest galaxy that we tentatively identify as H-alpha, and H-beta at a common redshift of z=0.429 (consistent with the photometric redshift of z = 0.484 ± 0.090 provided by SDSS, see Tomasella et al., GCN 33302). The spectral trace of the fainter galaxy is too weak to allow a reliable identification of any emission line, thus not permitting its redshift estimate.
Multiband photometry was also collected between June and July (4-5 months after the GRB trigger) in the r, z and H bands, with both galaxies detected in all filters. These images also show an additional fainter host galaxy candidate at coordinates 13:28:16.56 +46:43:34.7, underlining the complexity of the field.
We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly D. Thompson, E. Marini, and D. Paris, in obtaining these observations.