GRB 240218A
GCN Circular 35878
Subject
GRB 240218A: ALMA detection
Date
2024-03-05T21:41:49Z (2 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
Via
legacy email
T. Laskar, C. Peña (Utah), G. Schroeder (Northwestern), and K. D. Alexander
(Arizona) report on behalf of a larger collaboration:
"We observed GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755;
Svinkin et al., GCN 35758) with the Atacama Large Millimeter/Submillimeter
Array (ALMA) at 97.5 GHz beginning on 2024 March 02 02:46:33 UT (13.0 d
after the burst). ALMA observations of this burst were delayed due to
ALMA's annual February shutdown.
Preliminary analysis reveals a mm source with flux density of ~ 0.1 mJy at
97.5 GHz and position:
RA (J2000) = 10:47:11.5
Dec (J2000) = 1:16:36.0
with uncertainty ~ 0.3" in each coordinate, consistent with the X-ray
position (Evans et al. GCN 35748) and radio position (Schroeder et al., GCN
35794).
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help
with these observations."
GCN Circular 35877
Subject
GRB 240218A: Chandra Detection and Jet Break Confirmation
Date
2024-03-05T21:39:51Z (2 years ago)
From
corinna.pena@utah.edu
Via
Web form
C. Peña, T. Laskar (Utah), G. Schroeder (Northwestern), and K. D. Alexander (Arizona) report:
We observed GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755; Svinkin et al., GCN 35758) with Chandra/ACIS-S beginning on 2024 Mar 4 at 23:02:14 UT (16 days post-burst) for a total exposure of 20ks. In preliminary analysis, we detect a point source with a count rate of 5.5e-4 counts/s (0.3-8 keV; observer frame) at a position consistent with the VLA and XRT position (Schroeder et al., GCN 35794; Evans et al. GCN 35748). Using spectral parameters from the Swift/XRT PC-mode spectrum at a redshift z=6.782 (Saccardi et al., GCN 35756), we find a preliminary unabsorbed flux of ~ 1.2e-14 erg/(s cm^2) in the 0.3-8 keV band (observer frame).
This measurement confirms a potential break in the Swift/XRT observations at ~ 0.8 days after the trigger. The post-break decay rate of ~ -1.9 is consistent with a jet break. Further analysis is underway.
We thank Pat Slane, Douglas Swartz, and James Steiner for approving our DDT request. We thank Jen Lauer along with the rest of the CXC staff for arranging and executing the observations.
GCN Circular 35866
Subject
GRB240218A: ATCA observation of the radio counterpart
Date
2024-03-04T19:10:37Z (2 years ago)
From
Aishwarya L Thakur at INAF-IAPS, Rome <aishth@outlook.com>
Via
Web form
A.L. Thakur (INAF-IAPS), R. Ricci (INAF-IRA), G. Bruni, L. Piro, G. Gianfagna (INAF-IAPS), M. Wieringa (ATNF) report:
We observed the high-redshift GRB240218A (Page et al. GCN 35742, Veres and Meegan et al. GCN 35755, Svinkin et al. GCN 37558, D’Avanzo et al. GCN 35747, Saccardi et al. GCN 35756) with the Australian Telescope Compact Array under program C3546 (PI Thakur) on 4 March 2024 at a mean epoch of ~ 15 days post-burst. Observations were performed in the C-band for a total duration of ~6 hours.
Given the declination of the radio counterpart, the ATCA beam in the current array configuration is highly elongated on the North-South axis. We performed a check for potential confusing sources using a VLASS field at 3 GHz, centred on the position of the radio afterglow as detected by the VLA at RA=10:47:11.480 Dec=+01:16:35.29 (Schroeder et al., GCN 35794). No confusing sources are visible down to an rms of 130 uJy/beam.
In the preliminary 5.5 GHz ATCA image, we detect a source with a flux of ~ 0.2 mJy at a position consistent with the VLA detection.
Further monitoring of this counterpart is planned.
We thank CSIRO Space and Astronomy staff, particularly Jamie Stevens, for excellent support in planning and performing these observations. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (https://ror.org/05qajvd42), which is funded by the Australian Government for operation as a National Facility managed by CSIRO.
GCN Circular 35843
Subject
GRB 240218A: NOEMA upper limit
Date
2024-03-01T16:27:52Z (2 years ago)
From
Antonio de Ugarte Postigo at OCA <deugarte@oca.eu>
Via
email
A. de Ugarte Postigo (CNRS/OCA & LAM), T. Laskar (Utah), M. Bremer (IRAM),
C. C. Thoene (ASU-CAS), J. F. Agui Fernandez (CAHA), S. Antier (OCA), S. Basa (LAM), M. Michalowski (AOI-AMU), D. A. Perley (LJMU), S. Martin (ESO, ALMA),
K. D. Alexander (Arizona), E. Berger (Harvard), R. Chornock (Berkeley), W. Fong (Northwestern), R. Margutti (UC Berkeley), C. Peña (Utah), P. Schady (Bath), G. Schroeder (Northwestern),
report:
We observed the field of GRB 240218A (Page et al. 35742, Svinkin et al. GCN 35758) at a redshift of z = 6.782 (Saccardi et al. GCN 35756) with NOEMA at 74 and 90 GHz at a mean epoch 10.88 days after the burst.
Our observations show no detection of the afterglow (D’Avanzo et al. GCN 35747, Malesani et al. GCN 35749, Rossi et al. GCN 35762, Schroeder et al. GCN 35794) down to a 3-sigma limit of 65 microJy.
Based on observations carried out under project number W23DI with the IRAM NOEMA Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).
GCN Circular 35818
Subject
GRB 240218A: CMO SAI NIR upper limit
Date
2024-02-27T12:04:54Z (2 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Via
legacy email
A. Volnova (IKI), A. Pozanenko (IKI), B. Safonov (SAI MSU), A. Tatarnikov (SAI MSU), N. Pankov (HSE, IKI), S. Belkin (IKI, HSE) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755; Svinkin et al., GCN 35758) with the Astronomical Near-Infrared Camera-spectrograph (ANC) of the 2.5-meter telescope (SAI-2.5) of the Caucasian Mountain Observatory (CMO SAI) on Feb.23, 2024 starting on 22:16:46 UT, taking 47 frames of 1-minute exposure in the H-band under moderate conditions with seeing of 1.4". We do not detect the NIR counterpart (D'Avanzo et al., GCN 35747; Saccardi et al., 35756; Schroeder et al., GCN 35794; Rossi et al., GCN 35762; de Wet et al., GCN 35765) within the enhanced XRT error box (Evans et al., GCN 35748).
Preliminary photometry of the stacked image is following
Date UT start t-T0 Filter Exp. OT UL(3sigma)
(mid, days) (s)
2024-02-23 22:16:46 5.86743 H 47*59 n/d 20.8
The photometry is based on nearby 2MASS stars:
2MASS_ID RA Dec H errH
10471145+0118146 10:47:11.45808 +01:18:14.6268 15.422 0.098
10471594+0117439 10:47:15.94200 +01:17:43.9836 14.562 0.062
10471583+0116464 10:47:15.83136 +01:16:46.4844 14.243 0.045
GCN Circular 35794
Subject
GRB 240218A: VLA detection
Date
2024-02-26T01:13:49Z (2 years ago)
From
Genevieve Schroeder at Northwestern University <genevieveschroeder@u.northwestern.edu>
Via
Web form
G. Schroeder (Northwestern), C. Peña, T. Laskar (Utah), K. D. Alexander (Arizona) report:
"We observed GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755; Svinkin et al., GCN 35758) with the Karl G. Jansky Very Large Array (VLA) under program 24A-299 (PI: Laskar) beginning on 2024 Feb 23 at 09:38:35 UT (5.32 days post-burst) for 2.5 hours at multiple frequencies.
In preliminary analysis, we clearly detect a radio source at a mean frequency of 9.8 GHz with a flux density of ~280 microJy at the position:
RA(J2000) = 10:47:11.480
Dec(J2000) = +01:16:35.29
with an uncertainty of ~0.2" in each coordinate. This position is consistent with the X-ray position (Evans et al. GCN 35748) but offset (~2.7") from the preliminary NIR afterglow position reported by D'Avanzo et al. (GCN 35747). Further observations are planned.
We thank the VLA staff for scheduling and executing these observations."
GCN Circular 35765
Subject
GRB 240218A: MeerLICHT upper limits
Date
2024-02-20T20:32:37Z (2 years ago)
From
Simon de Wet at University of Cape Town <simdewet@gmail.com>
Via
Web form
S. de Wet (UCT), P.M. Vreeswijk (Radboud) and P.J. Groot (Radboud/UCT/SAAO) report on behalf of the MeerLICHT consortium:
The 0.6m wide-field MeerLICHT optical telescope located in Sutherland, South Africa, obtained a repeating series of 60s exposures in the q,u,g,r,i,z filters following the detection of GRB 240218A by Swift (Page et al., GCN 35742). Our observations began 96 seconds after the Swift trigger and continued for approximately 1 hour following the filter sequence quqgqrqiqz.
We do not detect an optical source at a position consistent with the high-redshift counterpart detected by REM and the VLT (D'Avanzo et al., GCN 35747; Malesani, GCN 35749; Saccardi et al., GCN 35756) in any individual exposure. Our earliest 3-sigma AB limiting magnitudes in each filter are:
u > 19.29 at 3.6 minutes post-trigger
g > 20.58 at 6.5 minutes post-trigger
q > 21.10 at 2.1 minutes post-trigger
r > 20.29 at 9.4 minutes post-trigger
i > 19.81 at 13.4 minutes post-trigger
z > 18.87 at 15.3 minutes post-trigger.
We additionally co-added all of the images in each filter and obtain the following 3-sigma AB limiting magnitudes at an average time of 36 minutes post-trigger:
u > 20.33
g > 21.61
q > 22.67
r > 21.21
i > 20.54
z > 19.54.
MeerLICHT is built and run by a consortium consisting of Radboud University, University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam.
GCN Circular 35762
Subject
GRB 240218A: LBT H-band detection
Date
2024-02-20T16:04:34Z (2 years ago)
From
Elisabetta Maiorano at INAF <elisabetta.maiorano@inaf.it>
Via
Web form
A. Rossi, E. Maiorano, G. Stratta (INAF-OAS), P. D'Avanzo (INAF-OAB) report on behalf of the CIBO collaboration:
We observed the field of the long GRB 240218A, detected by Swift-BAT (Page et al., GCN 35742), Fermi-GBM (Veres and Meegan, GCN 35755) and Konus-Wind (Svinkin et al., GCN 35758), and with spectroscopic redshift of z=6.782 (Saccardi et al., GCN 35756).
We obtained 40 min of J-, 1 hr of H- and 1.2 hr of Ks-band imaging with the LUCI cameras mounted on LBT (Mt. Graham, AZ, USA) on 2024-02-19 (mid-time 08:20:00 UT), 1.3 days after the burst trigger.
We clearly detect the NIR afterglow (D'Avanzo et al., GCN 35747, Malesani et al., GCN 35749) and measure a preliminary H-band magnitude of H ~ 20.2 AB, calibrated against 2MASS field stars, and not corrected for the foreground Galactic extinction.
We acknowledge the excellent support of A. Cardwell e J. Williams from the LBTO staff and E. Marini from LBT-INAF staff, in obtaining these observations.
GCN Circular 35761
Subject
GRB 240218A: Swift-BAT refined analysis
Date
2024-02-20T16:00:46Z (2 years ago)
From
Tyler Parsotan at NASA GSFC <tyler.parsotan@nasa.gov>
Via
email
S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), M. J. Moss (GSFC),
D. M. Palmer (LANL), T. Parsotan (GSFC),
T. Sakamoto (AGU), (i.e. the Swift-BAT team):
Using the data set from T-240 to T+200 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240218A (trigger #1215912)
(Page, et al., GCN Circ. 35742). The BAT ground-calculated position is
RA, Dec = 161.810, 1.295 deg which is
RA(J2000) = 10h 47m 14.4s
Dec(J2000) = +01d 17' 40.2"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 36%.
The mask weighted light curve shows two major pulses, one that is broad and the other
which is narrow.
T90 (15-350 keV) is 66.93 +- 11.28 sec (estimated error including systematics).
The time-averaged spectrum from T-38.93 to T+63.55 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 1.00 +- 0.32,
and Epeak of 103.1 +- 45.5 keV (chi squared 62.59 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 5.2 +- 0.3 x 10^-06 erg/cm2
and the 1-sec peak flux measured from T+21.62 sec in the 15-150 keV band is
3.0 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.51 +- 0.07 (chi squared 71.30 for 57 d.o.f.). All the quoted errors
are at the 90% confidence level.
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1215912/
GCN Circular 35758
Subject
Konus-Wind detection of GRB 240218A
Date
2024-02-20T02:33:53Z (2 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
legacy email
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 240218A
(Swift-BAT detection: Page et al., GCN 35742;
Fermi-GBM detection: Veres and Meegan, GCN 35755)
was detected by Konus-Wind (KW) in the waiting mode.
A Bayesian block analysis of the KW waiting mode data
in the 20-400 keV band reveals a >10 sigma count rate increase
in the interval from T0-12.646 s to T0+25.626 s,
where T0 = T0(BAT) = 02:00:00 UT.
The burst light curve shows a multi-peaked structure
with the brightest peak around ~T0(BAT)+20 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240218_T07200/
As observed by Konus-Wind, the burst had
a total fluence of 7.62(-2.22,+1.72)x10^-6 erg/cm^2 and
a 2.944-s peak energy flux, measured from T0+19.738 s,
of 5.29(-1.49,+2.21)x10^-7 erg/cm^2/s
(both in the 20 keV - 10 MeV energy range).
Modelling the 3-channel time-integrated spectrum of the burst
(measured from T0-12.646 s to T0+25.626 s)
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha > -0.56 and Ep = 180(-74,+77) keV.
Modelling the 3-channel spectrum near the peak count rate
(measured from T0+19.738 to T0+25.626 s) by the CPL model
yields alpha = -1.33(-0.29,+0.53) and Ep = 293(-120,+207) keV.
Assuming the redshift z=6.782 (Saccardi et al., GCN 35756)
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 burst isotropic energy release E_iso to 5.4(-1.6,+1.2)x10^53 erg,
the isotropic peak luminosity L_iso to 2.9(-0.8,+1.2)x10^53 erg/s,
the rest-frame peak energy of the time-integrated spectrum
Ep,i,z to 1401(-576,+599) keV, and the rest-frame peak energy at
the peak of the emission Ep,p,z to 2280(-934,+1611) keV.
With the obtained estimates, GRB 240218A is inside 68% prediction band
for both 'Amati' and '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/GRB240218_T07200/GRB240218A_rest_frame.pdf
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
GCN Circular 35757
Subject
GRB 240218A: Swift-XRT refined Analysis
Date
2024-02-19T23:02:31Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M. Ferro
(INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), J. D. Gropp
(PSU), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans report on
behalf of the Swift-XRT team:
We have analysed 5.7 ks of XRT data for GRB 240218A, from 137 s to
149.4 ks after the BAT trigger. The data comprise 118 s in Windowed
Timing (WT) mode (the first 10 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=2.12 (+0.11, -0.05), followed by a break at T+1538 s to
an alpha of 0.70 (+0.06, -0.05).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.39 (+/-0.04). The
best-fitting absorption column is 1.39 (+0.29, -0.27) x 10^23 cm^-2,
at a redshift of 6.782, in addition to the Galactic value of 4.2 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 4.8 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
Galactic foreground: 4.2 x 10^20 cm^-2
Intrinsic column: 1.39 (+0.29, -0.27) x 10^23 cm^-2 at z=6.782
Photon index: 1.39 (+/-0.04)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01215912.
This circular is an official product of the Swift-XRT team.
GCN Circular 35756
Subject
GRB 240218A: VLT/X-shooter redshift of z = 6.782
Date
2024-02-19T11:21:15Z (2 years ago)
From
Andrea Saccardi at Observatoire de Paris <andrea.saccardi@obspm.fr>
Via
Web form
A. Saccardi (GEPI/Obs. de Paris), D. B. Malesani (DAWN/NBI & Radboud Univ.), J. T. Palmerio (GEPI/Obs. de Paris & IAP), S. D. Vergani (GEPI/Obs. de Paris & IAP & INAF/OABr), E. Le Floc’h (CEA), L. Izzo (INAF/OACn & DARK/NBI), A. J. Levan (Radboud Univ. & Warwick Univ.), J. P. U. Fynbo (DAWN/NBI), P. D’Avanzo (INAF/OABr), A. Rossi (INAF/OAS), A. de Ugarte Postigo (OCA), report on behalf of the Stargate collaboration:
We observed the field of the Swift and Fermi GRB 240218A (Page et al., GCN 35742; D’Avanzo et al., GCN 35747; Malesani et al., GCN 35749; Veres et al., GCN 35755) using the ESO/VLT UT3 (Melipal) equipped with the X-shooter spectrograph.
Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 exposures of 1200 s each. The observation starting-time was 2024 Feb 19.179 UT (~26 hr after the trigger). We detect a clear continuum across the whole NIR arm. From the detection of multiple absorption features, which we interpret as due to SiII, FeII, AlII, CrII, ZnII, MgI, SiII*, FeII*, CIV and SiIV, we infer a redshift of z = 6.782.
We note that this is the highest GRB redshift measured accurately from metal absorption lines in a good S/N spectrum.
We encourage follow-up at all wavelengths.
We acknowledge the excellent support from the ESO staff in Paranal, in particular Jonathan Smoker, Rodrigo Romero and Pascale Hibon.
GCN Circular 35755
Subject
GRB 240218A: Fermi GBM Detection
Date
2024-02-19T01:21:14Z (2 years ago)
From
Peter Veres at University of Alabama in Huntsville <veresp@gmail.com>
Via
Web form
P. Veres and C. Meegan (both UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 02:00:21.72 UT on 18 February 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240218A (trigger 729914426/240218084),
which was also detected by Swift/BAT (Page et al. 2024, GCN 35742).
The Fermi GBM on-ground localization is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 93 degrees.
The GBM light curve consists of a single pulse followed by weaker emission with a duration (T90)
of about 38 s (50-300 keV). The time-averaged spectrum
from T0-2.6 to T0+30.2 s is best fit by
a Band function with Epeak = 100 +/- 20 keV,
alpha = -0.3 +/- 0.3, and beta = -1.9 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is
(5.2 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.5 s in the 10-1000 keV band is 3.1 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 35749
Subject
GRB 240218A: VLT/FORS2 z-band detection
Date
2024-02-18T15:18:26Z (2 years ago)
From
Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>
Via
Web form
We observed the near-infrared counterpart of GRB 240218A (Page et al., GCN 35742; D'Avanzo et al., GCN 35747) using the ESO VLT UT1 (Kueyen) equipped with the FORS2 imager. Observations were carried out in the Gunn z filter.
The GRB counterpart discovered by REM (D'Avanzo et al., GCN 35747) is well detected in the coaddition of our images (1080 s exposure time), at a mean epoch Feb 18.205 UT (2.925 hr after the GRB). Calibrated against nearby stars from the Pan-STARRS catalog, we preliminarily measure a magnitude z = 23.8 +- 0.15 (AB).
We acknowledge expert support from the VLT observing staff in Paranal, in particular Thomas Szeifert, Jonathan Smoker, Martina Baratella, and Juan Carlos Olivares.
GCN Circular 35748
Subject
GRB 240218A: Enhanced Swift-XRT position
Date
2024-02-18T12:09:38Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 75 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 240218A, 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 = 161.79682, +1.27634 which is equivalent
to:
RA (J2000): 10h 47m 11.24s
Dec (J2000): +01d 16' 34.8"
with an uncertainty of 4.2 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 35747
Subject
GRB 240218A: REM detection of a NIR afterglow candidate
Date
2024-02-18T11:08:05Z (2 years ago)
From
Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>
Via
legacy email
P. D’Avanzo, M. Ferro, R. Brivio, Y.-D. Hu, D. Fugazza, S. Covino (INAF-OAB) on behalf of the REM team, report:
We observed the field of GRB 240218A (Page et al., GCN 35742) with the REM 60cm robotic telescope located at the ESO Observatory of La Silla (Chile).
The observations were carried out in the g, r, i, z, H bands, starting on 2024 Feb 18 at 02:01:08 UT (i.e. 68 seconds after the burst T0) and lasted for about 3 hours.
An uncatalogued, fading source is detected in the initial H REM images. The source is not detected in the optical filters.
From preliminary astrometry we obtain the following position:
RA (J2000) = 10:47:11.50
Dec (J2000) = +01:16:38.0
(+/- 0.5”).
This position is located at the South-East edge of the 3.8” radius XRT error circle (https://www.swift.ac.uk/xrt_unenh_positions/01215912/ <https://www.swift.ac.uk/xrt_unenh_positions/01215912/>)
From preliminary analysis we derive:
H = 14.7 +/- 0.2 mag, at a mid time of t-t0 ~ 103 s after the GRB T0.
H = 15.8 +/ -0.2 mag, at a mid time of t-t0 ~ 511 s after the GRB T0.
Magnitudes are in the Vega system and calibrated against the 2MASS catalogue.
The optical magnitude limits reported by Malesani et al. (GCN Circ. 35743), although obtained about 1 hour after the REM detection, may imply a significant red color
for the afterglow (r - H > 4 mag, assuming the same decay from ~ 100 s to 3600 s after the GRB T0). In light of the low Galactic extinction along the GRB line of sight
and of the absence of evidence for intrinsic N(H) excess in the X-ray afterglow spectrum obtained by Swift/XRT (https://www.swift.ac.uk/xrt_spectra/01215912/ <https://www.swift.ac.uk/xrt_spectra/01215912/>),
we suggest that GRB 240218 can be a high-redshift event.
Further follow-up, especially in the NIR bands, is encouraged.
GCN Circular 35744
Subject
GRB 240218A : r-band upper limit from Observatoire de Haute-Provence
Date
2024-02-18T05:10:36Z (2 years ago)
From
Emeric Le Floc'h at CEA-Saclay <emeric.lefloch@cea.fr>
Via
Web form
C. Adami (LAM) and E. Le Floc'h (CEA-Saclay) report on behalf of the MISTRAL GRB collaboration:
We observed the field of GRB 240218A (Page et al., GCN 35742) using the MISTRAL spectro-imager mounted on the T193 telescope at Observatoire de Haute-Provence (France). We obtained a sequence of 5 images (5min, 10min, 3x15min) for an observation mid-time corresponding to 67min after the GRB) and a total observing time of 1h. Similar to the non detection reported earlier by Malesani et al. (GCN 35743), we did not detect any afterglow candidate consistent with the XRT position, down to the following upper limit :
r > 23 (AB)
The photometry was calibrated against the PanStarrs catalog within a circle of 2’ (radius) around the GRB position.
We acknowledge excellent support from Observatoire de Haute Provence, in particular Yoann Degot Longhi.
GCN Circular 35743
Subject
GRB240218A: VLT/X-shooter upper limits
Date
2024-02-18T03:49:19Z (2 years ago)
From
Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>
Via
Web form
D. B Malesani (DAWN/NBI and Radboud Univ.) and E. Le Floch (CEA) report on behalf of the Stargate collaboration:
We observed the field of GRB 240218A (Page et al., GCN 35742) using the ESO VLT UT3 with the X-shooter acquisition camera. A short sequence of imaging was secured in the r, g, and z bands. No afterglow is detected consistent with the position reported by XRT (https://www.swift.ac.uk/xrt_positions/), with the following upper limits:
r band: r > 23.0 (AB) on Feb 18.124 UT (1.00 hr after the GRB);
z band: z > 21.5 (AB) on Feb 18.127 UT (1.07 hr after the GRB).
We acknowledge excellent support from the VLT staff in Paranal, in particular Jonathan Smoker, Thomas Szeifert, and Rodrigo Romero.
GCN Circular 35742
Subject
GRB 240218A: Swift detection of a burst
Date
2024-02-18T02:17:56Z (2 years ago)
From
K.L. Page at U Leicester <klp5@leicester.ac.uk>
Via
email
K. L. Page (U Leicester), T. M. Parsotan (GSFC) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:
At 02:00:00 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240218A (trigger=1215912). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 161.781, +1.304 which is
RA(J2000) = 10h 47m 07s
Dec(J2000) = +01d 18' 14"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a broad single peak
structure after a period of noise with a duration of about 15 sec.
The peak count rate was ~1400 counts/sec (15-350 keV), at ~22 sec after the trigger.
The XRT began observing the field at 02:02:30.1 UT, 149.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 161.7953, 1.2782 which is equivalent to:
RA(J2000) = 10h 47m 10.87s
Dec(J2000) = +01d 16' 41.5"
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This
location is 106 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy.
UVOT took a finding chart exposure of 119 seconds with the White
filter starting 158 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 typical
3-sigma upper limit has been about 19.6 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 0.045.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk).
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/)