GRB 250327B
GCN Circular 40059
Subject
GRB 250327B: VIRT Optical Upper Limit
Date
2025-04-04T16:21:28Z (6 months ago)
From
Priya Gokuldass at ERAU <gokuldap@my.erau.edu>
Via
Web form
K. Smith (UVI), P. Gokuldass (ERAU), N. Orange (OrangeWave Innovative Science, LLC), B. Gendre (UVI), D. Morris (NASA), T. Lombardi (Eckerd College), F. George (ERAU), D. Smith (UVI), C. Watson (UVI) report:
We observed the field of GRB 250327B (Bouchet et al., GCN 39888) detected by SVOM/ECLAIRs with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2025-03-28 starting at 06:52:58.6 (T-mid ~ T0 + 10.5 hrs). We performed a series of exposures in an R filter with a total exposure of 2560s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 1.6.
We do not detect any source at the position reported by SAO/RAS (Moskvitin et al., GCN 39889). This non-detection is consistent with reported detections (Moskvitin et al., GCN 39889; Pankov et al., GCN 39906; Xin et al., GCN 39890; O’Neill et al., GCN 39891;Malesani et al., GCN 39893; Lian et al, GCN 39894; Shrestha et al., GCN 39896; Kumar et al., GCN 39904; Pérez-Fournon et al., GCN 39912; Ducoin et al., GCN 39897; Ducoin et. al., GCN 39930; Perley et al., GCN 39902; Dennefeld et al., GCN 39905; Tarasenkov et al., GCN 39913; Broens et. al., GCN 40006 and Siegel et. al., GCN 40009) and upper limits (Mo et. al., GCN 39914 and della Vecchia et. al., GCN 39969). We report the following 3-sigma upper limit:
T_mid ||Exposure ||Filter ||Limit
T+ 10.5 hrs || 2560 s || R || > 20.8
The limit is estimated from comparison to nearby USNO B1 stars and is not corrected for Galactic extinction.
We acknowledge financial support from NASA EPSCoR award 80NNSC22M0063, NSF PAARE award 2319415, and NASA EPSCoR award 80NSSC24M0112. This message can be cited.
GCN Circular 40009
Subject
GRB 250327B: Swift/UVOT Detection
Date
2025-04-02T13:32:05Z (6 months ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M.H. Siegel (PSU) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250327B 1753 s after the SVOM trigger sb25032706 (GCN Circ. 39888). A fading source consistent with the XRT position (Page et al., GCN Circ. 39895) and the optical counterpart (Moskvitin et al., GCN Circ. 39889; Xin et al., GCN Circ. 39890; O’Neill et al., GCN Circ. 39891; Lian et al., GCN Circ. 39894; Shrestha et al., GCN Circ. 39896; Ducoin et al., GCN Circ. 39897; Perley & Bochenek; GCN Circ. 39902; Kumar et al., GCN Circ. 39904; Dennefeld et al., GCN circ. 39905; Pankov et al., GCN circ. 39906) is detected in the initial UVOT exposures.
Preliminary detections and 3-sigma upper limits for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag(AB)
u 1753 2505 740 19.78+/-0.18
u 91894 113326 2601 >21.28
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.018 in the direction of the burst (Schlegel et al. 1998).
GCN Circular 40006
Subject
GRB 250327B: Kilonova-Catcher Observations
Date
2025-04-02T01:27:54Z (6 months ago)
From
Cristina Andrade at UMN <andra104@umn.edu>
Via
Web form
E. Broens, F. Dubois, M. Freeberg, A. Lekic, G. Parent, M. Serrau (KNC), C. Andrade (UMN), E. de Bruin (UMN), D. Turpin (CEA-Saclay/Irfu), S. Antier (OCA), M. Coughlin (UMN),S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS) on behalf of the GRANDMA/Kilonova-Catcher collaboration:
We observed the field of GRB 250327B (Bouchet et al., GCN 39888) detected by SVOM/ECLAIRs with the citizen science project, Kilonova-Catcher (KNC). These observations were performed by our members using the following telescopes: T-BRO, ODK16 f/6.8, Quatro F4, T180, a Newton telescope T200 and using the Telescope Live Network.
In our stacked frames, we detected an optical afterglow at the position reported by SAO/RAS (Moskvitin et al., GCN 39889, Pankov et al. GCN 39906), SVOM/VT (Xin et al., GCN 39890), GOTO (O’Neill et al. GCN 39891), the NOT (Malesani et al., GCN 39893), Mephisto (Lian et al, GCN 39894), the LCOGT (Shrestha et al. GCN 39896, Kumar et al. GCN 39904, Pérez-Fournon et al. GCN 39912), SVOM/COLIBRI (F-GFT) (Ducoin et al., GCN 39897, 39930), the Liverpool telescope (Perley et al., GCN 39902), the OHP/T193 telescope (Dennefeld et al. GCN 39905) and MASTER (Tarasenkov et al., GCN 39913).
We report some of our detections and upper limits (5 sigma) in the following table:
---------------------------------------------------------------------------------------------
| Tstart-TGRB (hr) | Exposure | Mag | UL (5σ) | Filter | Telescope |
---------------------------------------------------------------------------------------------
| 1.62 | 180s | 16.87 ± 0.06 | | Rc (Vega) | T-BRO |
| 1.67 | 180s | 17.48 ± 0.10 | | V (Vega) | T-BRO |
| 3.29 | 10x60s | 18.98 ± 0.09 | | V (Vega) | ODK16 f/6.8 |
| 3.52 | 180s | | 17.8 | V (Vega) | Quatro F4 |
| 3.56 | 2x300s | 19.78 ± 0.11 | | g’ (AB) | ODK16 f/6.8 |
| 3.58 | 180s | | 17.6 | R (Vega) | Quatro F4 |
| 3.81 | 3x300s | 18.93 ± 0.17 | | r’ (AB) | ODK16 f/6.8 |
| 4.24 |10x180s | 19.73 ± 0.21 | | V (Vega) | T-BRO |
| 6.49 |10x180s | | 20.6 | g’ (AB) | T180 |
| 6.51 |15x180s | 20.16 ± 0.36 | | Rc (Vega) | T-BRO |
| 6.74 |10x180s | 19.87 ± 0.24 | | r’ (AB) | T180 |
| 29.07 |100x40s | | 20.3 | r’ (AB) | Newton T200 |
| 76.42 | 59x80s | | 20.5 | V (Vega) | Telescope Live T200 |
---------------------------------------------------------------------------------------------
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022, 2025). Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog. Images obtained with sloan filters were calibrated using the PanSTARRS DR1 catalog.
We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023).
GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).
GCN Circular 39978
Subject
Konus-Wind detection of GRB 250327B
Date
2025-03-31T16:40:41Z (6 months ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long-duration GRB 250327B
(SVOM-ECLAIRs detection: Bouchet et al., GCN 39888)
was detected by Konus-Wind (KW) in the waiting mode
at T0 = T0(ECLAIRs) = 76287 s UT (21:11:27).
A Bayesian block analysis of the KW waiting mode data
in the 20-1200 keV band reveals a ~20 sigma count rate
increase in the interval from ~T0-12 s to ~T0+424 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250327B/
The total burst fluence is 2.31(-0.22,+0.26)x10^-5 erg/cm^2,
and the 2.944 s peak energy flux, measured from T0+85 s,
is 2.43(-0.52,+0.55)x10^-7 erg/cm^2.
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst,
measured from T0-12 s to T0+424 s,
can be described by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.11(-0.17,+0.21) and Ep = 212(-38,+48) keV.
The spectrum near the peak count rate, measured from T0+76 s to T0+91 s,
can be described by a CPL model with
alpha = -0.82(-0.31,+0.43) and Ep = 203(-49,+64) keV.
Assuming the redshift z=3.035 (Malesani et al., GCN 39893)
and a standard cosmology 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 4.78(-0.45,+0.54)x10^53 erg,
the peak luminosity L_iso is 2.03(-0.44,+0.46)x10^52 erg/s,
the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 856(-152,+195) keV and
the spectrum near the maximum count rate Ep,p,z is 818(-198,+257) keV.
With the obtained estimates, GRB 250327B is inside 68% prediction band for the 'Amati' and
90% prediction band for the 'Yonetoku' relations derived for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021),
see http://www.ioffe.ru/LEA/GRBs/GRB250327B/GRB250327B_rest_frame.pdf
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
GCN Circular 39933
Subject
GRB 250327B: ALMA detection
Date
2025-03-29T21:34:47Z (7 months ago)
From
Tanmoy Laskar at U of Utah <tanmoylaskar@gmail.com>
Via
Web form
T. Laskar (University of Utah), N. Franz, C. Christy, K. D. Alexander (University of Arizona), E. Berger (Harvard University), R. Chornock (UC Berkeley), W. Fong (Northwestern University), R. Margutti (UC Berkeley), P. Schady (University of Bath), and G. Schroeder (Cornell University), report on behalf of a larger collaboration:
“We observed GRB 250327B (Bouchet et al., GCN 39888) with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 97.5 GHz beginning on 2025 March 29 at 01:45 UT (28.5 hours after the burst).
Preliminary analysis reveals a mm source with flux density of ~ 0.5 mJy at position:
RA (J2000) = 11:47:06.72
Dec (J2000) = +29:50:24.71
with an uncertainty of 0.05" in each coordinate. This is consistent with the X-ray position (Bouchet et al., GCN 39888; Page et al. GCN 39895), optical position (Moskvitin et al., GCN 39889; Xin et al., GCN 39890), and radio position (Christy et al., GCN 39932).
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help with these observations."
GCN Circular 39932
Subject
GRB 250327B: VLA detection
Date
2025-03-29T21:32:49Z (7 months ago)
From
Tanmoy Laskar at U of Utah <tanmoylaskar@gmail.com>
Via
Web form
C. Christy, N. Franz (University of Arizona), T. Laskar (University of Utah), K. D. Alexander (University of Arizona), E. Berger (Harvard University), R. Chornock (UC Berkeley), W. Fong (Northwestern University), R. Margutti (UC Berkeley), P. Schady (University of Bath), and G. Schroeder (Cornell University), report on behalf of a larger collaboration:
“We observed GRB 250327B (Bouchet et al., GCN 39888) with the Karl G. Jansky Very Large Array (VLA) at multiple frequencies beginning on 2025 March 29 at 03:00 UT (29.8 hours after the burst).
In preliminary analysis, we detect a radio counterpart at 15.1 GHz with a flux density of ~0.2 mJy at the position:
RA (J2000) = 11:47:06.72 +/- 0.08”
Dec (J2000) = +29:50:24.89 +/- 0.05”
This is consistent with the X-ray position (Bouchet et al., GCN 39888; Page et al. GCN 39895) and optical position (Moskvitin et al., GCN 39889; Xin et al., GCN 39890). Further observations are planned.
We thank the VLA staff for scheduling and executing these observations.”
GCN Circular 39930
Subject
GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
Date
2025-03-29T19:02:34Z (7 months ago)
From
Alan Watson at UNAM <alan@astro.unam.mx>
Via
Web form
Jean-Grégoire Ducoin (CPPM), Noémie Globus (UNAM), Camila Angulo (UNAM), Sarah Antier (OCA), Ramandeep Gill (UNAM), Stéphane Basa (LAM), William H. Lee (UNAM), Dalya Akl (AUS), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Hui Yang (IRAP) report:
We observed the field of SVOM/ECLAIRs GRB 250327B (Bouchet et al. GCN Circ. 39888) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
We obtained 50 minutes of exposure in the i filter from 2025-03-29 03:49 and 11:32 (44.3 and 52.0 hours after the trigger). Our observations were not continuous, but rather were at the start and end of this interval with a long interruption for observations of other sources. We observed through thick clouds.
The data were coadded with the COLIBRI pipeline and analysed in STDWeb/STDPipe (Karpov 2021). The photometric calibration was performed using nearby stars from the Pan-STARRS DR1 catalog and the magnitude is not corrected for Galactic extinction.
At the position of the previously reported optical transient (Moskvitin et al., GCN Circ. 39889; Xin et al., GCN Circ. 39890; O’Neill et al., GCN Circ. 39891; Malesani et al., GCN Circ. 39893; Lian et al., GCN Circ. 39894; Page et al., GCN Circ. 39895; Shrestha et al., GCN Circ. 39896; Perley & Bochenek, GCN Circ. 39902; Kumar et al., GCN Circ. 39904; Dennefeld et al., GCN Circ. 39905; Pankov et al., GCN Circ. 39906; Pérez-Fournon et al., GCN Circ. 39912; Tarasenkov et al., GCN Circ. 39913; Mo et al., GCN Circ. 39914), we detect a source with
i = 22.23 +/- 0.15.
Compared to our previous observation at about 7.65 hours after the trigger, the temporal decay index is about -1.0.
We acknowledge the excellent support of the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and thank the COLIBRÍ and DDRAGO engineering teams.
GCN Circular 39914
Subject
GRB 250327B: J-band observations with WINTER
Date
2025-03-28T20:44:14Z (7 months ago)
From
Geoffrey Mo at MIT <gmo@mit.edu>
Via
Web form
Geoffrey Mo (MIT), Benjamin Schneider (LAM), Tomas Ahumada (Caltech), Danielle Frostig (CfA), Viraj Karambelkar (Caltech), Robert Stein (UMD), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:
We observed the field of GRB 250327B (Bouchet et al., GCN 39888) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024).
Observations began under poor weather conditions at 2025-03-28T10:04:53 UTC (12.9 hours after the GRB), consisting of 13 x 120 s exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565).
We do not detect a source at the optical and X-ray counterpart location (Moskvitin et al., GCN 39889; Xin et al., GCN 39890; O’Neill et al., GCN 39891; Malesani et al., GCN 39893; Lian et al., GCN 39894; Page et al., GCN 39895; Shrestha et al., GCN 39896; Duncoin et al., GCN 39897; Perley et al., GCN 39902; Kumar et al., GCN 39904; Dennefeld et al., GCN 39905; Pankov et al., GCN 39906; Pérez-Fournon et al., GCN 39912). We obtain the following 5-sigma upper limit: J ~ 17.5 mag (AB).
WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.
GCN Circular 39913
Subject
GRB 250327B: MASTER detection of OT rebrightening
Date
2025-03-28T20:43:27Z (7 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
A.Tarasenkov, V.Lipunov, A.Kuznetsov, G.Antipov, K..Zhirkov, P.Balanutsa, N.Tyurina, E.Gorbovskoy,
Ya.Kechin, A.Chasovnikov, V.Topolev, V.Senik, K.Labzina (Lomonosov MSU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
D.Buckley (SAAO),
A.Sosnovskij (Crao RAS),
O.Gress, N.Budnev, O.Ershova (ISU),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino,J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)
located in Argentina, started SVOM GRB 250327B (Bouchet et al. GCN 39888, Ttrigger=2025-03-27T21:11:27UT) at 2025-03-28 06:46:31UT with mlim=21m at 600s summary exposition.
There is optical source with m_OT=19.9 +-0.3m(by GAIA reference stars) at two single images and at summary one
at Moskvitin et al. (GCN 39889) position
(also observed by SVOM/VT (GCN 39890), GOTO (GCN 398901), NOT (39893), Mephisto (GCN 39894),
LCOGT (GCN 39896, GCN 39912, GCN 39904), COLIBRI (GCN 39897), LT (GCN 39902), OHP (GCN 39905), CrAO/SAORAS (GCN 39906)).
that means rebrightening 9.5h after trigger time
This message may by cited
GCN Circular 39912
Subject
GRB 250327B: LCO optical counterpart detection
Date
2025-03-28T18:04:55Z (7 months ago)
From
Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>
Via
Web form
I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, I. Correa-Plasencia, A.E. Hernández-Díaz (ULL), and A. López-Oramas (IAC and ULL)
We report Las Cumbres Observatory Global Telescope network (LCOGT) observations of GRB 250327B, detected by SVOM ECLAIRs and MXT (Bouchet et al., GCN circ. 39888) and VT (Xin et al., GCN circ. 39890) and Swift XRT (Page et al., GCN circ. 39895) at a redshift of z = 3.035 (Malesani et. al, GCN circ. 39893; Dennefeld et al., GCN circ. 39905).
We observed the field of GRB 250327B with the two LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Teide Observatory (Tenerife, Spain) in the SDSS r, g, and i filters, starting at 2025-03-27 23:55:43 UT, about 2.74 hours after the SVOM trigger. An uncatalogued source is clearly detected at the position of the optical counterpart reported by Moskvitin et al., GCN circ. 39889; Xin et al., GCN circ. 39890; O’Neill et al., GCN circ. 39891; Malesani et al., GCN circ. 39893; Lian et al., GCN circ. 39894; Shrestha et al., GCN circ. 39896; Ducoin et al., GCN circ. 39897; Perley and Bochenek, GCN circ. 39902; Kumar et al., GCN circ. 39904; Dennefeld et al., GCN circ. 39905; and Pankov et al., GCN circ. 39906).
We measure the following magnitudes, calibrated against Pan-STARRS DR2 stars and not corrected for Galactic extinction:
Date | UT start | mag | error | filter | exposure time (sec)
---------------------------------------------------------------------
2025-03-27 23:55:43 18.24 0.02 r 180
2025-03-28 00:31:11 20.07 0.06 g 180
2025-03-28 00:34:41 18.19 0.04 i 180
2025-03-28 02:12:57 18.79 0.06 i 180
2025-03-28 03:04:23 19.35 0.05 r 300
2025-03-28 03:09:13 21.25 0.14 g 180
This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF).
GCN Circular 39906
Subject
GRB 250327B: CrAO and SAO RAS Optical Observations
Date
2025-03-28T13:37:10Z (7 months ago)
Edited On
2025-03-28T14:14:32Z (7 months ago)
From
Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>
Via
email
N. Pankov (HSE, IKI), A. Moskvitin (SAO RAS), V. Rumyantsev (CrAO), O. I.
Spiridonova (SAO RAS), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:
We performed optical observations of the field of GRB 250327B (Bouchet et.
al, GCN 39888; Page et. al, GCN 39895) at the redshift of z = 3.035
(Malesani et. al, GCN 39893; Dennefeld et al., GCN 39905) with the
2.6-meter Shajn telescope (ZTSh) of the Crimean Astrophysical Observatory
(CrAO) and the 1-meter Zeiss-1000 telescope of the Special Astrophysical
Observatory of the RAS (SAO RAS). The observations started on (UT)
2025-03-27 22:24:22 at CrAO, i.e. about 0.05 days since GBM trigger. We
obtained the series of frames in the VRI filters with ZTSh and the series
of frames in the BVRI filters with Zeiss-1000. We clearly detect the bright
optical afterglow (Moskvitin et. al, GCN 39889; Xin et. al, GCN 39890;
O’Neill et. al, GCN 39891; Malesani et. al, GCN 39893; Lian et. al, GCN
39894; Shrestha et. al, GCN 39896; Ducoin et. al, GCN 39897; Perley &
Bochenek, GCN 39902) in the images from both telescopes. The preliminary
photometry of the afterglow in the end of each series is as follows:
Date UT start t-T0 Exp. Filter OT Err Telescope
(mid, days) (s)
2025-03-27 23:12:18 0.08410 30 I 16.45 0.07 ZTSh
2025-03-27 23:13:36 0.08500 30 R 17.15 0.08 ZTSh
2025-03-27 23:12:59 0.08457 30 V 17.80 0.10 ZTSh
2025-03-27 00:25:24 0.14229 4*300 Rc 18.22 0.05 Zeiss-1000
The photometry is based on nearby stars of USNO-B1.0 (R2 magnitudes; same
as in Moskvitin et. al, GCN 39889) and has not been corrected for the
Galactic extinction. Using the R-filter photometry between 0.01 and 0.1
days after trigger, we estimate a power law decay of the light curve to be
alpha = -1.87 +/- 0.03.
GCN Circular 39905
Subject
GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
Date
2025-03-28T12:49:52Z (7 months ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
M. Dennefeld (IAP/CNRS/Sorbonne U.), B. Schneider (LAM), C. Adami (LAM/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), A. Saccardi (CEA/Irfu), S. Vergani (CNRS, Obs. de Paris, LUX), S. Basa (Pytheas/OHP/LAM) report on behalf of the MISTRAL-GRB collaboration:
We observed the SVOM/ECLAIRs GRB 250327B (Bouchet et al., GCN 39888) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager in red setting.
We obtained 1x60 s in the r’, i’, z’ and Y bands starting at 22:44:30 UT on 2025-03-27 (T0+1.55 h after the trigger). The optical afterglow reported by Moskvitin et al. GCN 39889; Xin et al. GCN 39890; O’Neill et al. GCN 39891; Malesani et al. GCN 39893; Lian et al. GCN 39894; Shrestha et al. GCN 39896; Ducoin et al., GCN39897; Perley et al., GCN 39902; and Kumar et al., GCN 39904 is well detected at r = 17.25 +/- 0.05 mag (AB). The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction.
In addition, we obtained 3x15 min of spectroscopic observations covering from 6400 to 9950 AA starting at 2025-03-27 22:52:55 UT (T0+1.69 h). In the stacked spectrum, we clearly detect multiple absorption features, which we interpret as being due to Si II, Si II*, C IV, Fe II, Fe II*, Al II, Al III, Mg I, Ni II* at a common redshift of z = 3.038 +/- 0.005. The detection of fine-structure lines robustly associates this system to the high-energy transient. This value is also consistent with the value reported by Malesani et al. (GCN 39893).
We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Stéphane Favard.
GCN Circular 39904
Subject
GRB 250327B: further optical observations by LCOGT
Date
2025-03-28T12:22:25Z (7 months ago)
From
Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>
Via
Web form
Amit Kumar (RHUL/Warwick), Raya Dastidar (UNAB), Giuliano Pignata (UTA), Danny Steeghs, Thomas Killestein (Warwick), David O’Neill (Birmingham), Jonathan Andrés Pineda García (UNAB) and Mauricio Ramirez (UNAB) report on behalf of the wider collaboration:
We conducted optical follow-up observations of the optical counterpart to the SVOM/ECLAIRs-detected GRB 250327B (Bouchet et al., GCN 39888) using the LCOGT 0.4-m telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Teide Observatory, Tenerife, Spain, equipped with the SCICAM-QHY600 camera. Observations were carried out on 2025-03-28 between 02:18:54 UT and 03:34:29 UT, corresponding to approximately 5.1 to 6.4 hours post-burst.
Each epoch comprised a series of 6 × 300 sec exposures in the B-band. In the stacked image, we clearly detect the optical counterpart with a B-band magnitude of ~21.9 ± 0.2. The detected position is consistent with the location of the optical counterpart reported by Moskvitin et al. GCN 39889 (a.k.a. GOTO25bhx, AT 2025gcz), with supporting detections from Xin et al. (GCN 39890), O’Neill et al. (GCN 39891), Malesani et al. (GCN 39893), Lian et al. (GCN 39894), Shrestha et al. (GCN 39896), Ducoin et al. (GCN 39897), and Perley & Bochenek (GCN 39902).
The reported magnitude is calibrated against the USNO-B1 catalog and is not corrected for Galactic extinction in the direction of the event.
Further analysis and follow-up observations are ongoing. This circular may be cited.
GCN Circular 39902
Subject
GRB 250327b: Liverpool Telescope optical observations
Date
2025-03-28T09:30:33Z (7 months ago)
From
A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>
Via
Web form
D. A. Perley and A.Bochenek (LJMU) report:
We observed the field of GRB250327b (Bouchet et al., GCN 39888) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 1x100s exposures in the SDSS g, r, i, and z filters, starting at 2025-03-28 00:17:25 UT, approximately 3.1 hours after the trigger.
We report a detection in all our images at the position of the optical counterpart (Moskvitin et al., GCN 39889), given in the table below. Our results agree with previous optical observations (Moskvitin et al. GCN 39889; Xin et al. GCN 39890; O’Neill et al. GCN 39891; Malesani et al. GCN 39893; Lian et al. GCN 39894; Shrestha et al. GCN 39896; Ducoin et al., GCN39897).
MJD (mid) T_mid - T_0 Filter Mag. (AB)
60762.01268 3.11 hours r 18.47 ± 0.02
60762.01412 3.14 hours i 17.98 ± 0.04
60762.01556 3.18 hours g 19.87 ± 0.05
60762.01706 3.21 hours z 17.82 ± 0.06
The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction.
GCN Circular 39897
Subject
GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
Date
2025-03-28T06:11:29Z (7 months ago)
Edited On
2025-03-28T14:14:20Z (7 months ago)
From
J.-G. Ducoin at CPPM <ducoin@cppm.in2p3.fr>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of J.-G. Ducoin at CPPM <ducoin@cppm.in2p3.fr>
Via
Web form
Jean-Grégoire Ducoin (CPPM), Enrique Moreno Méndez (UNAM), Stéphane Basa (LAM), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of the SVOM/ECLAIRs GRB 250327B (Bouchet et al. GCN Circ. 39888) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
We observed from 2025-03-28 04:33 to 05:04 UTC (7.4 to 7.9 hours after the trigger) and obtained 11 minutes of exposure in the r filter at a mean observing time of T+7.6 hours. The data were coadded with custom software and analyzed with STDpipe (Karpov 2024) with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction.
We detect the afterglow (Moskvitin et al. GCN Circ. 39889, Xin et al. GCN Circ. 39890, O’Neill et al. GCN Circ. 39891, Malesani et al. GCN Circ. 39893, Lian et al. GCN Circ. 39894, Page et al. GCN Circ. 39895, Shrestha et al. GCN Circ. 39896) with a magnitude of
r = 20.01 +/- 0.02
Further observations are ongoing.
We acknowledge the excellent support from the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and thank the COLIBRÍ and DDRAGO engineering teams
GCN Circular 39896
Subject
GRB 250327B: Las Cumbres optical counterpart detection
Date
2025-03-28T04:43:23Z (7 months ago)
From
Manisha Shrestha at University of Arizona <mshrestha1@arizona.edu>
Via
Web form
M. Shrestha (Univ. of Arizona), D. Sand (Univ. of Arizona), K. D. Alexander (Univ. of Arizona), J. Andrews (Gemini), J. Pearson (Univ. of Arizona), N. Smith (Univ. of Arizona), K. Bostroem (Univ. of Arizona), C. Christy (Univ. of Arizona), N. Franz (Univ. of Arizona), D. A. Howell (LCO/UCSB), C. McCully (LCO/UCSB), M. Newsome (LCO/UCSB), J. Farah (LCO/UCSB) report on behalf of a wider Global Supernova Project collaboration:
We observed the field of GRB 250327B (SVOM team, GCN 39888) with the 1-m telescope, starting on 025-03-28T02:38:50.16 UT (60762.11 MJD, ~5.5 hours after the trigger) using the Sinistro instrument in g, r, i bands (exposure of 2×200 s). We clearly detect the optical counterpart as reported in previous circulars ( Moskvitin+ GCN 39889, Xin+ GCN 39890, O’Neill+ GCN 39891, Malesani+ GCN 39893, Lian+ GCN 39894). Preliminary photometric data are as follows:
g = 20.7 +-0.1 r = 19.4 +-0.1 i = 18.8 +- 0.1
These values were calculated with respect to ATLAS-REFCAT2 (Tonry et al. 2018, ApJ 867 105) catalog. They are not corrected for galactic extinction. This source is fading compared to the magnitude reported in Malesani+ GCN 39893.
GCN Circular 39895
Subject
GRB 250327B: Swift-XRT detection of the X-ray afterglow
Date
2025-03-28T03:39:17Z (7 months ago)
From
K.L. Page at U Leicester <klp5@leicester.ac.uk>
Via
email
K.L. Page, P.A. Evans (U. Leicester) and C.A. Gronwall (PSU) report on
behalf of the Swift-XRT Team
On 2025 March 27 at 21:35 UT, Swift began a Target-of-Opportunity
observation of the SVOM-discovered burst GRB 250327B (GCN Circ. 39888).
750 s of data were collected, starting 1.7 ks after the SVOM/ECLAIRs
trigger. A bright, fading X-ray source was found, at a position of RA, Dec
= 176.77890, 29.83953, which is equivalent to
RA (J2000) = 11h 47m 06.94s
Dec (J2000) = +29d 50' 22.3"
with an uncertainty of 3.5 arcseconds (radius, 90% confidence). This is
consistent with the optical afterglow (GCN Circs. 39889, 39890, 39891,
39894), with a measured redshift of 3.035 (GCN Circ. 39893).
The light curve can be modelled with a power-law decay with a decay index
of alpha=1.20 (+0.73, -0.66).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.47 (+/- 0.09) and the Galactic
column density of 1.76 x 10^20 cm^-2 (Willingale et al. 2013).
If the light curve continues to decay with a power-law decay index of
1.20, the count rate at T+24 hours will be 0.048 count s^-1
GCN Circular 39894
Subject
GRB 250327B: 1.6m Mephisto optical observations
Date
2025-03-28T01:40:32Z (7 months ago)
Edited On
2025-03-28T14:14:08Z (7 months ago)
From
Brajesh Kumar at SWIFAR, YNU <brajesh@ynu.edu.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Brajesh Kumar at SWIFAR, YNU <brajesh@ynu.edu.cn>
Via
Web form
Jianhui Lian, Brajesh Kumar, Xufeng Zhu, Fanchuan Kong, Yaosong Yu, Yuan Fang, Guowang Du, Xinlei Chen, Yu Pan, Xingzhu Zou, Helong Guo, Jinghua Zhang, Tao Wang, Chenxi Shang, Dan Zhu (all SWIFAR, YNU), Xinzhong Er (TAC, TJNU), Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team:
The field of SVOM GRB 250327B (Bouchet et al., GCN 39888) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgriz band observations were conducted starting from 2025-03-27 T21:14:19 UT (172 seconds after the SVOM/ECLAIRs trigger) to 2025-03-27 T21:21:16 UT. 1 exposure of 180s, 3 exposures of 50s and 2 exposures of 80s in the MEPHISTO uv, gr and iz bands, respectively, were obtained.
The optical afterglow candidate (Moskvitin et al., GCN 39889; Xin et al., GCN 39890; O’Neill et al., GCN 39891; Malesani et al., GCN 39893) is clearly detected in our each frame of v, g, r, i, z band with v-r, g-i color of 3.99 and 1.80 mag, respectively (Galactic extinction correction is not applied). The preliminary magnitudes of the first detections are below:
Start_Time(UT) |Band | Exp(s) | Mag(AB)
--------------------|-----|--------|-----------------
2025-03-27T21:14:19 | u | 180 | >21.22
2025-03-27T21:18:21 | v | 180 | 18.66 +/- 0.075
2025-03-27T21:14:19 | g | 50 | 16.53 +/- 0.013
2025-03-27T21:18:21 | r | 50 | 14.67 +/- 0.003
2025-03-27T21:14:19 | i | 80 | 14.73 +/- 0.004
2025-03-27T21:18:21 | z | 50 | 13.83 +/- 0.004
---------------------------------------------------------------------------------------
Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21.
---------------------------------------------------------------------------------------
GCN Circular 39893
Subject
GRB 250327B: NOT spectroscopic redshift z = 3.035
Date
2025-03-28T00:17:12Z (7 months ago)
Edited On
2025-03-28T01:21:28Z (7 months ago)
From
Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>
Via
Web form
D. B. Malesani (DAWN/NBI and Radboud), B. Schneider (LAM), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), J. T. Palmerio (CEA/Irfu), G. Corcoran (UCD), B. P. Gompertz (Birmingham), A. de Ugarte Postigo (LAM), T. Pursimo (NOT), report on behalf of a larger collaboration:
We observed the optical afterglow (Moskvitin et al., GCN 39889; Xin et al., GCN 39890; O'Neill et al., GCN 39891) of the SVOM GRB 250327B (Bouchet et al., GCN 39888) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC spectrograph. The covered wavelength range (grism #4) is 3200 - 9600 AA.
In an image of 2x180 s in the r-band, starting on 2025 Mar. 27 at 22:48:21 (1.7 hr after the trigger), we measure r = 17.13 +/- 0.04 (AB). The photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitude is not corrected for Galactic extinction.
Based on a preliminary reduction, the spectrum shows bright continuum all the way to the red, with a strong trough around 4900 AA and a break blueward of it, typical of DLA absorption and Lyman forest. From detection of multiple absorption features, which we interpret as due to, among others, Si II, C II, S IV, C IV, Fe II, Al II, we measure a redshift z = 3.035.
GCN Circular 39891
Subject
GRB 250327B: GOTO optical counterpart detection
Date
2025-03-27T23:19:12Z (7 months ago)
From
d.s.oneill@bham.ac.uk
Via
Web form
D. O’Neill, A. Kumar, B. Godson, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration:
We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the SVOM/ECLAIRS sb2503270 (Bouchet et al. 39888). The observations were conducted between 2025-03-27 21:14:55 (208 sec post-trigger) and 2025-03-27 22:24:37.72 (76.42 min post-trigger). Each observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings.
We detect the optical counterpart reported by SAO RAS and SVOM/VT (Moskvitin et al., GCN 39889; Xin et al., GCN 39890) as an initially rising source that reached a peak magnitude of L=15.098 ± 0.012 at 8.43 min after trigger, before decaying at a rate of approximately t^-0.8 to a magnitude of 17.011 ± 0.004 at t0+76.42 min post-trigger.
We find no evidence of the source prior to the GRB trigger time in previous GOTO observations, the ZTF observations provided by the Lasair broker (Smith et al. 2019), or the ATLAS forced photometry server (Shingles et al. 2021).
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
Observations are ongoing.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 39890
Subject
GRB 250327B: SVOM/VT optically bright counterpart
Date
2025-03-27T22:50:19Z (7 months ago)
From
Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>
Via
Web form
L.P. Xin, Y. L. Qiu, H. L. Li, C. Wu (NAOC),J. T. Palmerio(CEA/Irfu), Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, J. Y. Wei (NAOC), Laurent Bouchet, Hui Yang(IRAP) report on behalf of the SVOM team:
SVOM performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Bouchet et al., GCN 39888). SVOM/VT began observing the field automatically with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With VHF downlinked data, a very bright uncatalogued source was found in both channels, and brightening in the first and second sequences, compared to DESI catalog.
The coordinates are
R.A =11:47:06.70,
DEC.=+29:50:24.8
Error=0.5 arcseconds.
J2000
The magnitude is VT_B~15.8 mag(AB) and VT_R~14.2 mag(AB) in the first sequence with the mid time of 461 seconds after the burst.
The coordinates and the brightness are consistent with the candidate reported (Moskvitin et al., GCN 39889).
We proposed that this is the optical counterpart of the burst.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.
GCN Circular 39889
Subject
GRB 250327B: SAO RAS optical candidate
Date
2025-03-27T22:33:49Z (7 months ago)
From
Alexander Moskvitin at SAO RAS <mosk@sao.ru>
Via
Web form
A. S. Moskvitin, O. I. Spiridonova (SAO RAS), A. S. Pozanenko (IKI)
report on behalf of a larger collaboration.
We observed the field of the field of the SVOM GRB 250327B
(Bouchet et al., GCN 39888) with the SAO RAS 1-m telescope Zeiss-1000.
The observations started on 21:28:15 UT (~17 minutes after SVOM trigger)
We found a bright uncatalogued source with R = 14.1 +/- 0.1 (calibrated against R2 magnitudes of nearby USNO-B1 stars) and the coordinates
R.A. = 11:47:06.72
Dec. = +29:50:24.7 (+/- 0".5, Epoch = 2000.0)
The observations are ongoing.
GCN Circular 39888
Subject
GRB 250327B: SVOM detection of a burst
Date
2025-03-27T22:12:14Z (7 months ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Laurent Bouchet, Hui Yang, Olivier Godet, Marius Brunet (IRAP), Clara Plasse (CEA)
on behalf of the SVOM mission team.
SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250327B (SVOM burst-id sb25032706) starting at 2025-03-27T21:11:27 UTC (Tb).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 10 alerts. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 12.05 in the [8-120] keV energy band over a time window of 40.96 seconds starting at Tb. The light curve shows that the burst duration is about 300 s and the burst is still detected after the slew.
The localization of the best alert is R.A., Dec 176.7763, 29.8765 degrees (J2000) with a 90% C.L. radius of 6.70 arcminutes (including systematic error of 2 arcminutes added in quadrature).
SVOM slewed to the burst.
MXT began observing the field at 2025-03-27T21:14:41 UTC, 193 seconds after Tb.
Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec 176.788, 29.832 degrees:
RA (J2000) = 11h47m09.15s
DEC (J2000) = 29d49m55.57s
with a 90% C.L. radius of 25 arcseconds.
This MXT location is within the ECLAIRs error circle. This position may be improved as more data is received.
VT began observing the field after the slew. The analysis of the recorded images will be published in a future circular gathering information on the follow-up of the SVOM optical instruments.
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe.
The Burst Advocate (BA) on shift for this burst is Hui Yang: hui.yang@irap.omp.eu.
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.