GRB 241209A
GCN Circular 38608
Subject
GRB 241209A: ATCA radio follow-up observations
Date
2024-12-18T07:11:43Z (10 months ago)
From
Tao An at SHAO, CAS <antao@shao.ac.cn>
Via
Web form
Tao An, Yuanqi Liu (SHAO), Jinjun Geng (PMO), and Xuefeng Wu (PMO) report on behalf of the Einstein Probe radio follow-up team:
Following the detection of GRB 241209A by Fermi and Swift (Hamburg et al. 2024, GCN 38502; Evans et al. 2024, GCN 38523), we conducted radio follow-up observations using the Australia Telescope Compact Array (ATCA). We observed the VLT position [RA(J2000) = 10:21:35.14, Dec(J2000) = +06:19:44.5] during UTC 16:00:00-22:00:00 on December 14, 2024. No significant emission was detected at either 5.5 GHz or 9 GHz, yielding 3σ upper limits of 51 microJy and 36 microJy, respectively.
We thank the ATCA team for their rapid scheduling and support.
GCN Circular 38538
Subject
GRB 241209A: Chandra X-ray Detection
Date
2024-12-11T19:27:31Z (10 months ago)
From
Peter Blanchard at Harvard <peter.blanchard@cfa.harvard.edu>
Via
Web form
Peter K. Blanchard and Edo Berger (Harvard) report on behalf of a larger collaboration:
We observed the short GRB 241209A (GCNs 38474, 38476) with Chandra/ACIS (Program 25500091, PI: Berger) starting at UT 2024-12-10 13:47:26 with an exposure time of 19.8 ks (mid-time of 38.4 hr post-burst). We detect a source consistent with the enhanced Swift/XRT position (GCN 38486) at the following coordinates:
RA (J2000): 10:21:35.207
Dec (J2000): +06:19:42.73
with a one sigma uncertainty of 0.3” in RA and Dec.
The X-ray source is closer (~0.6” away) to the fainter galaxy of the two identified by de Ugarte Postigo et al. (GCN 38484), which has a redshift of z=1.490 (GCN 38487). The source is ~2” away from the infrared source identified by Schneider et al. (GCN 38506).
We thank the Chandra team for rapidly scheduling these observations.
GCN Circular 38535
Subject
GRB 241209A: Redshift of the likely host galaxy z = 0.784 from OSIRIS+/GTC
Date
2024-12-11T13:22:54Z (10 months ago)
From
Antonio de Ugarte Postigo at LAM/OCA, CNRS <deugarte@oca.eu>
Via
email
A. de Ugarte Postigo (OCA and LAM, CNRS), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. F. Agui Fernandez (CAHA), N. R. Tanvir (U. Leicester), C. C. Thoene (ASU-CAS, AbAO), N. A. Rakotondrainibe (LAM), L. Izzo (INAF-OACn & DARK/NBI), A. Martin-Carrillo (UCD), J. P. U. Fynbo (DAWN/NBI), S. Geier (GTC), G. L. Lombardi (GTC), N. Castro Rodriguez (GTC), A. Marante-Barreto (GTC), A. Cabrera Lavers (GTC) report:
The refined X-ray counterpart error region (Evans et al., GCN 38486) of the short GRB 241209A (Fermi collaboration, GCN 38474; Parson et al., GCN 38476; Cie et al., GCN 38478) includes two galaxies, which were identified in FORS2/VLT imaging (de Ugarte Postigo et al., GCN 38484). The fainter one, which was favoured by the initial X-ray localisation (Page et al., GCN 38479) has a redshift of z=1.490, as measured with X-shooter/VLT (Saccardi et al., GCN 38487). The inclusion of the brighter one within the refined X-ray error box, makes it a more likely candidate host for the GRB, because of a lower chance coincidence, as already mentioned by Saccardi et al. The candidate NIR counterpart reported by Schneider et al. (GCN 38506) also lies within the extension of the brighter galaxy. Should it be confirmed to fade, this would also favour this as the GRB host.
We obtained spectroscopy of this, brighter and more likely host galaxy candidate (located at RA = 10:21:35.09, Dec = +06:19:45.4) using OSIRIS+ mounted on the 10.4m GTC telescope, at the Roque de los Muchachos observatory, on the island of La Palma (Spain). The observation consisted of 3x900s using grism R1000R, which has a spectral coverage between 5100 and 10000Å at a resolving power of 670.
The spectrum shows continuum over the complete range and bright emission features that we identify as due to [OII], H-beta and [OIII] as well as CaII H and K absorptions at a common redshift of z = 0.784, which we identify as the redshift of the most likely host galaxy of GRB 241209A. We note that this is consistent with the Legacy Survey photometric redshift of 0.78+/- 0.08 (Zhou et al. 2021, MNRAS, 501, 3309).
GCN Circular 38523
Subject
GRB 241209A: Swift-XRT refined Analysis
Date
2024-12-10T13:03:21Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
We have analysed 4.9 ks of XRT data for GRB 241209A, from 91 s to 40.8
ks after the BAT trigger. The data comprise 42 s in Windowed Timing
(WT) mode (the first 9 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode.
The light curve can be modelled with an initial power-law decay with an
index of alpha=1.16 (+0.17, -0.16), followed by a break at T+485 s to
an alpha of 8.0 (+0.0, -1.2).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.8 (+/-0.3). The
best-fitting absorption column is 3.0 (+1.7, -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 3.7 x 10^-11 (5.0 x 10^-11) erg
cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
Total column: 3.0 (+1.7, -1.4) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^20 cm^-2
Excess significance: 3.4 sigma
Photon index: 1.8 (+/-0.3)
If the light curve continues to decay with a power-law decay index of
8.0, the count rate at T+24 hours will be 1.3 x 10^-18 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.0 x
10^-29 (6.8 x 10^-29) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01273071.
This circular is an official product of the Swift-XRT team.
GCN Circular 38517
Subject
GRB 241209A: EP-FXT follow-up observations
Date
2024-12-10T08:36:26Z (a year ago)
From
Yu-Han Yang at University of Rome Tor Vergata <yyang@roma2.infn.it>
Via
Web form
E. Troja (U Rome), Y. L. Wang (NAO, CAS), Y. Wang (PMO, CAS), H. L. Peng (NNU), W. D. Zhang (NAO,CAS), Y. -H. Yang (U Rome), R. L. Becerra (U Rome) report on behalf of the Einstein Probe team:
We performed a follow-up observation of the short GRB 241209A detected by Fermi/GBM (GCN 38474) and Swift/BAT (GCN 38476) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2024-12-09T18:20:45 (UTC), about ~ 12.75 hours after the trigger, for a total exposure time of 4093 seconds.
At the position of the XRT counterpart (GCN 38486), we detect no new source. Assuming a photon index of 1.5 and a Galactic absorption of NH = 2E20 cm^-2, we derive an upper limit of ~3E-14 erg/cm2/s (0.5-10 keV; 90% confidence level).
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.
GCN Circular 38509
Subject
GRB 241209A: BOOTES-7 and 2.2m CAHA early optical upper limits
Date
2024-12-10T00:49:36Z (a year ago)
From
Youdong HU at INAF-OAB <huyoudong072@hotmail.com>
Via
Web form
Y.-D. Hu (INAF-OAB), I. Perez-Garcia, A. J. Castro-Tirado, E. Fernandez-Garcia, S.-Y. Wu, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, G. Garcia-Segura, I. Olivares, A. Sota (IAA-CSIC), C. Perez del Pulgar, A. Castellon, S. Castillo (Univ. de Malaga), L. Hernandez-Garcia (Univ. de Valparaiso), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report:
Following the detection of the short-duration GRB 241209A by both Fermi/GBM (Fermi Team, GCN 38474) and Swift/BAT (Parsotan et al., GCN 38476), the 0.6m BOOTES-7 robotic telescope at San Pedro de Atacama (Chile) observed the GRB location starting on Dec 9, 05:39:06 UT (202 s after trigger) in different optical bands. No new optical source is detected on the co-added images (10x30s, clear-filter) at the position of the proposed near-IR counterpart candidate (Schneider et al. GCNC 38506; see also de Ugarte Postigo et al. CGCN 38484) down to 19.9 mag, consistent with other early-time reported limits (Kumar et al. GCNC 38481, Lipunov et al. GCNC 38483, Brivio et al., GCNC 38492, Pillas et al., GCNC 38500).
Additional observations were taken at the 2.2m CAHA telescope in Southern Spain (3x60s, starting on Dec 9, 06:03 UT, 28 min after trigger). Limiting magnitude for the resulting co-added image was 22.1 mag.
We thank the staff at Observatorio Astronomico de Calar Alto and San Pedro de Atacama celestial observations for their excellent support.
GCN Circular 38506
Subject
GRB 241209A: VLT/HAWK-I near-IR counterpart candidate
Date
2024-12-09T22:50:27Z (a year ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
B. Schneider (LAM), N. Habeeb (U. Leicester), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Martin-Carrillo (UCD), A. de Ugarte Postigo (OCA and LAM) and N. R. Tanvir (U. Leicester) report on behalf of the Stargate collaboration:
We observed the field of the short GRB 241209A (Parsotan et al., GCN 38476; Fermi GBM team, GCN 38474) with the ESO Very Large Telescope, equipped with the HAWK-I near-infrared camera. We obtained 12 min exposures in both the H and Ks bands, as well as an 11 min exposure in J band starting at 07:51:24 UT on 2024-12-09, i.e. 2.3 hr after the Swift trigger. The observations were obtained under excellent seeing (0.5" in the J band).
The two objects mentioned by de Ugarte Postigo et al. (GCN 38484; see also Saccardi et al., GCN 38487) are both detected in all filters.
Furthermore, in all three bands we detect a faint source overlapping the wings of the brighter galaxy mentioned by de Ugarte Postigo et al. (GCN 38484), approximately 1" SE of the galaxy nucleus. The coordinates of the source are:
RA(J2000) = 10:21:35.14 = 155.39642
DEC(J2000) = +06:19:44.5 = 6.32902
with an uncertainty of 0.5".
At the present time, we cannot state whether this source is transient or pre-existing, as we lack NIR comparison imaging of sufficient quality. Under a worse seeing, this source would be easily blended within the surrounding galaxy light. Further imaging is planned to assess fading.
A comparison of the VLT/FORS2 R-band image (seeing 1.0") reported by de Ugarte Postigo et al. (GCN 38484) with the Legacy survey r-band image reveals only a marginal (~3 sigma, or ~0.1 mag) flux excess at the location of the HAWK-I candidate. Thus, due to systematic errors arising from different PSF and filter shape, we cannot confirm the presence of this source in the FORS2 R-band image at the present time.
We acknowledge the excellent support provided by the Paranal staff, in particular Jonathan Smoker and Juan Carlos Olivares.
GCN Circular 38504
Subject
GRB 241209A: COLIBRÍ Optical Upper Limit
Date
2024-12-09T21:59:11Z (a year ago)
Edited On
2024-12-10T15:27:37Z (a year ago)
From
Damien Dornic <ddornic@km3net.de>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Sarah Antier at OCA <sarah.antier@oca.eu>
Via
Web form
J.-G. Ducoin (CPPM), Francesco Magnani (CPPM), Damien Dornic (CPPM), Alan M. Watson (UNAM), Margarita Pereyra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), S. Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Francis Fortin (IRAP), Dalya Akl (AUS) and Simona Lombardo (LAM), report:
We imaged the field of GRB 241209A detected by Swift/BAT and Fermi/GBM (GCN Circ. 38474, 38476, 38479) during the commissioning of the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
The observations started 171 minutes after the GRB trigger. We observed with the engineering test camera in a red filter that approximates SDSS r. The data were reduced using custom software and then analysed and calibrated against the PS1 catalog using the STDWeb service (Karpov et al. 2022).
In 7680 seconds of exposure, we estimate an upper limit of 23.07 mag (3-sigma). This limiting magnitude is consistent with other optical observations of GOTO (Kumar et al, GCN Circ. 38481), MASTER (Lipunov et al., GCN Circ. 38483), VLT (de Ugarte Postigo et al, GCN Circ. 38484