GRB 260109C
GCN Circular 43362
Subject
GRB 260109C: LCO optical upper limits
Date
2026-01-09T21:27:52Z (a month ago)
Edited On
2026-01-09T22:41:01Z (a month ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
D. Turpin (CEA/Irfu) C. Wu, X.-H. Han, L.-P. Xin (NAOC), A. Saccardi, J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM mission team:
We observed the field of the possible GRB 260109C detected by Swift/BAT (Parsotan et al., GCN 43359) with the LCO 1m telescope at the Siding Spring Observatory (SSO) equipped with the Sinistro instrument.
Our observation started at 2026-01-09 13:16:04 about 29 minutes after the Swift/BAT trigger time. We obtained 2 epochs of 3x200s exposures in the PanSTARRS z filters. No any uncatalogued source was identified in our stacked frames in agreement with the non detection of the Kilonova-Catcher group in the Rc band (Freeberg et al., GCN 43360).
When stacking the our two series of observations, we measure the following upper limits (5 sigma) calibrated against the SkyMapper DR4 catalog, and not corrected for Galactic extinction:
z = 19.6 (AB) T_mid - T0 = 40 min
This project is funded by the SVOM collaboration. The transient detection and photometric calibration were performed with the STDPipe pipeline (Karpov et al., 2022).
GCN Circular 43361
Subject
GRB 260109C: Kilonova-Catcher optical upper limit
Date
2026-01-09T21:03:55Z (a month ago)
From
Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com>
Via
Web form
M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/IJCLab), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration:
We observed the field of GRB 260109C detected by Swift/BAT (Parsotan et al., GCN 43359) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iT30 itelescope located at the Siding Spring Observatory and operated by M. Freeberg. Our observations started at TGRB+34.5 min and were taken with Rc filter.
In our stacked frames, subtracted from the SkyMapper DR4 template image, we do not detect any optical counterpart in the Swift/BAT error radius.
We report our follow-up results in the table below:
+---------------+----------+-----------+----------------+-------------+
| Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument |
+===============+==========+===========+================+=============+
| 0.83 | 6 x 300s | Rc (Vega) | 20.8 (5 sigma) | iT30 |
+---------------+----------+-----------+----------------+-------------+
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Johnson-Cousins filters were calibrated using the GAIA DR3 Synphot 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 43359
Subject
Swift Trigger 1434591: possible GRB 260109C
Date
2026-01-09T13:17:07Z (a month ago)
From
P.A. Evans at U. Leicester <pae9@leicester.ac.uk>
Via
email
T. M. Parsotan (GSFC), P. A. Evans (U Leicester),
R. Gupta (NASA GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
A. Mei (INAF-OAB), K. L. Page (U Leicester), C. Salvaggio (INAF-OAB)
and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels
Swift Observatory Team:
At 12:47:15 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 260109C (trigger=1434591). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 123.728, -35.258 which is
RA(J2000) = 08h 14m 55s
Dec(J2000) = -35d 15' 27"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
structure with a duration of about 15 sec. The peak count rate
was ~4000 counts/sec (15-350 keV), at ~10 sec after the trigger.
The XRT began observing the field at 12:48:41.8 UT, 86.8 seconds after
the BAT trigger. No source was detected in 1.3 ks of promptly
downlinked data. We are waiting for the full dataset to detect and
localise the XRT counterpart.
UVOT took a finding chart exposure of 250 seconds with the U filter starting
146 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 25% of the
BAT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The
8'x8' region for the list of sources generated on-board covers 100% of the BAT
error circle. The limiting magnitude for the list of sources is expected to be
about 17.7. No correction has been made for extinction.
Burst Advocate for this burst is T. M. Parsotan (tyler.parsotan AT nasa.gov).
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/)