| Summary table |
|---|
| Variable |
Value |
Source |
| T0 |
0:08:51 UTC |
GCN_circulars,Swift Det |
| ra |
185.6817° |
Swift |
| decl |
29.9732° |
Swift |
| pos_error |
3.11e-04° |
Swift |
| GBM_located |
False |
|
| mjd |
60662.00614583334 |
GCN_circulars,Swift Det |
| IPN table |
|---|
| GRB_name |
GRB241218A |
| ra |
185.6833° |
| decl |
29.9833° |
| pos_error |
5.00e-02° |
| Swift table |
|---|
| GRB_name |
GRB241218A |
| t_trigger |
0:08:51 UTC |
| ra |
185.6817° |
| decl |
29.9732° |
| pos_error |
3.11e-04° |
| GCN 38601 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38601 |
| Detection_method |
Swift Det |
| t_trigger |
0:08:51 UTC |
| ra |
185.6820° |
| decl |
29.9910° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38601
SUBJECT: GRB 241218A: Swift detection of a burst
DATE: 24/12/18 00:58:22 GMT
FROM: Boris Sbarufatti at INAF-OAB
M. A. Williams (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL),
B. Sbarufatti (INAF-OAB) and A. Tohuvavohu (Caltech) report on behalf
of the Neil Gehrels Swift Observatory Team:
At 00:08:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 241218A (trigger=1275005). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 185.682, +29.991 which is
RA(J2000) = 12h 22m 44s
Dec(J2000) = +29d 59' 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 25 sec. The peak count rate
was ~896 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 00:11:15.6 UT, 144.5 seconds after
the BAT trigger. The position determined from promptly downlinked data
differs significantly from the on-board position, suggesting that the
XRT may have centroided on a cosmic ray; the initial XRT position
notice should be treated with caution. Using promptly downlinked data
we find a fading, uncatalogued X-ray source with an enhanced position:
RA, Dec 185.68146, 29.97303 which is equivalent to:
RA(J2000) = 12h 22m 43.55s
Dec(J2000) = +29d 58' 22.9"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 64 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.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.23
x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 151 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
0.023.
Burst Advocate for this burst is M. A. Williams (mjw6837 AT psu.edu).
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 38604 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38604 |
| Detection_method |
Swift-XRT Det |
| ra |
185.6817° |
| decl |
29.9732° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38604
SUBJECT: GRB 241218A: Enhanced Swift-XRT position
DATE: 24/12/18 03:21:43 GMT
FROM: Phil Evans at U of Leicester
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1225 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 241218A, 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 = 185.68168, +29.97318 which is equivalent
to:
RA (J2000): 12h 22m 43.60s
Dec (J2000): +29d 58' 23.5"
with an uncertainty of 2.4 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 38605 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38605 |
| Detection_method |
Swift Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38605
SUBJECT: GRB 241218A: LCOGT Optical Upper Limit
DATE: 24/12/18 04:35:43 GMT
FROM: Robert Strausbaugh at Eastern Illinois University
R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration:
We observed the Swift GRB 241218A field (Williams et al., GCN 38601) with the LCOGT 1-meter Sinistro instrument at the Teide Tenerife site, on December 18, from 03:45 to 04:17 UT (corresponding to 3.62 to 4.15 hours after the GRB trigger time) with the sdss r and i filters.
We performed a series of 3x300s exposures in i-band and r-band. We do not detect a source within the Swift XRT enhanced error region (Beardmore et al., GCN 38604) in either band.
The following 5-sigma upper limits are calculated using the PanSTARRS catalog as reference:
r > 21.2
i > 20.9
These magnitudes are not corrected for galactic extinction.
|
| GCN 38614 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38614 |
| Detection_method |
Swift-XRT Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38614
SUBJECT: GRB 241218A: Swift-XRT refined Analysis
DATE: 24/12/18 11:32:21 GMT
FROM: Phil Evans at U of Leicester
V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), C. Salvaggio
(INAF-OAB), M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU),
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.1 ks of XRT data for GRB 241218A, from 131 s to 23.9
ks after the BAT trigger. The data comprise 19 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 a series of power-law decays. The
initial decay index is alpha=2.7 (+0.4, -0.3). At T+539 s the decay
flattens to an alpha of -1.5 (+0.0, -0.7) before breaking again at
T+972 s to a final decay with index alpha=1.52 (+0.19, -0.15).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.72 (+0.22, -0.12). The
best-fitting absorption column is consistent with the Galactic value
of 2.2 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 3.8 x 10^-11 (3.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.2 (+/-4.5) x 10^20 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.72 (+0.22, -0.12)
If the light curve continues to decay with a power-law decay index of
1.52, the count rate at T+24 hours will be 4.1 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x
10^-14 (1.6 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01275005.
This circular is an official product of the Swift-XRT team.
|
| GCN 38617 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38617 |
| Detection_method |
Optical |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38617
SUBJECT: GRB 241218a: Liverpool Telescope optical follow-up
DATE: 24/12/18 13:28:21 GMT
FROM: A. Bochenek at Liverpool John Moores University
A. Bochenek and D. A. Perley (LJMU) report:
We observed the Gamma-Ray Burst GRB 241218a (Williams et al., GCN 38601) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 3x200s exposures with the SDSS r’ and SDSS i’ filters starting at 2024-12-18 03:33:56 UT, approximately 3.4 hours after the trigger.
We do not detect any new sources at the Swift/XRT enhanced position (Beardmore et al., GCN 38604). The 3-sigma limiting magnitudes on the stacked images are r > 20.9 mag and i > 21.0 mag, calculated using the nearby PanSTARRS secondary standards as reference. The photometry was not corrected for extinction. |
| GCN 38620 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38620 |
| Detection_method |
Optical |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38620
SUBJECT: GRB 241218A: REM optical upper limit
DATE: 24/12/18 13:54:03 GMT
FROM: Riccardo Brivio at INAF-OAB
R. Brivio, M. Ferro, P. D’Avanzo (INAF-OAB), D. B. Malesani (DAWN/NBI and Radboud Univ.) S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of GRB 241218A detected by Swift (Williams et al., GCN 38601) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z bands, starting on 2024 December 18 at 08:05:53 UT (i.e. 8.0 hours after the Swift trigger), and lasting for about 1 hour.
From preliminary photometry we do not detect any optical counterpart at the XRT enhanced position (Beardmore et al., GCN 38604) down to the following 3sigma magnitude upper limits:
r > 19.2 (AB; calibrated against the Pan-STARRS catalogue)
at a mid-time of t - t0 = 8.4 hr after the trigger. |
| GCN 38629 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38629 |
| Detection_method |
Swift-BAT Det |
| ra |
185.6870° |
| decl |
29.9840° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38629
SUBJECT: GRB 241218A: Swift-BAT refined analysis
DATE: 24/12/18 22:02:20 GMT
FROM: Mike Moss at NASA GSFC
R. Gupta (GSFC), 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), D. Sadaula (GSFC/UMBC),
T. Sakamoto (AGU), M. A. Williams (PSU)
(i.e. the Swift-BAT team):
Using the data set from T-520 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 241218A (trigger #1275005)
(M. A. Williams, et al., GCN Circ. 38601). The BAT ground-calculated position is
RA, Dec = 185.687, 29.984 deg which is
RA(J2000) = 12h 22m 44.8s
Dec(J2000) = +29d 59' 04.2"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 52%.
The mask-weighted light curve shows a single pulse of emission lasting 40 seconds
with a possible second pulse at T+70 seconds.
The T90 (15-350 keV) is 23.31 +- 4.19 sec (estimated error including systematics).
The time-averaged spectrum from T-1.82 to T+26.16 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.31 +- 0.26. The fluence in the 15-150 keV band is 5.5 +- 1.0 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+16.64 sec in the 15-150 keV band
is 0.6 +- 0.2 ph/cm2/sec. 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/1275005
|
| GCN 38630 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38630 |
| Detection_method |
Optical |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38630
SUBJECT: GRB 241218A: NOT optical upper limits
DATE: 24/12/19 02:10:25 GMT
FROM: syfu@nao.cas.cn
S.Y. Fu (NAOC), D. B. Malesani (DAWN/NBI and Radboud Univ.), Z.P. Zhu, X. Liu, D. Xu (NAOC), L. Cotter (UCD), A. Amanda Djupvik (NOT) report on behalf of a large collaboration:
We observed the field of GRB 241218A detected by Swift (Williams et al., GCN 38601) using the StanCam instrument mounted on the Nordic Optical Telescope (NOT), 3 x 300 s in the Bessel R band and 5x200 s in the Sloan z band frames were obtained. Observations started at 04:37:19 UT on 2024-12-18, i.e., 4.5 hr after the trigger.
No new source is detected in the stacked frames within the enhanced Swift/XRT error circle (Beardmore et al. GCN 38604), with the limiting magnitudes of R > ~ 21.7 (Vega, converted from r-band, Lupton 2005) and z > ~ 21.0 (AB), calibrated with nearby Pan-STARRS stars and without Galactic extinction correction. |
| GCN 38634 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38634 |
| Detection_method |
Swift-UVOT Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38634
SUBJECT: GRB 241218A: Swift/UVOT Upper Limits
DATE: 24/12/19 14:17:44 GMT
FROM: Mike Siegel at PSU/Swift MOC
M. H. Siegel (PSU) and M. Williams (PSU) report on behalf of the
Swift/UVOTteam:
The Swift/UVOT began settled observations of the field of GRB 241218A
152 s after the BAT trigger (Williams et al., GCN Circ. 38601).
No optical afterglow consistent with the XRT position
(D'Elia et al., GCN Circ. 38614) 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 152 301 147 >20.7
u_FC 310 559 246 >19.8
white 152 1014 334 >21.0
v 640 1411 97 >18.5
b 565 1337 78 >18.7
u 310 1312 304 >19.8
w1 689 709 19 >21.1
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.024 in the direction of the burst
(Schlegel et al. 1998). |
| GCN 38639 table |
|---|
| GRB_name |
GRB241218A |
| GCN_number |
38639 |
| Detection_method |
Optical |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 38639
SUBJECT: GRB 241218A: Mondy AZT-33IK optical upper limit
DATE: 24/12/19 19:27:24 GMT
FROM: Nicolai Pankov at HSE, IKI RAS
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN:
We performed optical observations of the field of GRB 241218A (Williams et. al, GCN 38601; Beardmore et. al, GCN 38604; Strausbaugh et. al, GCN 38605; Maksut et. al, GCN 38611; D'Elia et. al, GCN 38614; Brivio et. al, GCN 38620; Gupta et. al, GCN 38629; Fu et. al, GCN 38630; Siegel et. al, GCN 38634) in the R filter with AZT-33IK of Sayan observatory (Mondy). The observations began on 2024-12-18 20:52 UT, i.e. ~0.88 days since Swift trigger. We do not detect an optical counterpart inside the XRT enhanced localization (Beardmore et. al, GCN 38604) in the stacked image of 58x60 sec. The preliminary photometry is given below:
Date UT start t-T0 Exp. Filter UL(3sigma)
(mid, days) (s)
2024-12-18 20:53:01 0.88415 58*60 R 20.8
The magnitudes were calibrated using nearby stars from USNO-B1.0 catalog (R2 magnitudes) and are not corrected for the Galactic extinction. The results are consistent with non-detections reported by other groups. |