GRB 240727A
GCN Circular 37815
Subject
GRB 240727A: VIRT Optical Upper Limit
Date
2024-10-18T16:54:52Z (a year 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), D. Morris (NASA), T. Lombardi (Eckerd College), F. George (ERAU), K. Noonan (UVI), R. Querrard (UVI), D. Smith (UVI) report:
We observed the field of GRB240727A (Parsotan et al., GCN 36938) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2024-07-30 starting at 2:20:47 (Tmid+71.54 hrs). We performed a series of exposures in an R filter with a total exposure of 1600s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 1.56.
We do not detect any source within the enhanced XRT position (Beardmore et al. GCN 36950). This non-detection is consistent with detections reported by KAIT (Zheng et al., GCN 36939), TRT (Liu et al., GCN 36940), Skynet (Dubay et al., GCN 36941), NOT (An et al., GCN 36962) and SWIFT/UVOT (Kuin et al., GCN 36968) and upper limits reported by Bassano Bresciano (Quadri et al., GCN 36960), JinShan (An et al., GCN 36961), Nastro Verde (Ruocco et al., GCN 36964), MASTER (Lipunov et al., GCN 36969), and MarSEC (Lora et al., GCN 36971). We report the following 3-sigma upper limit:
T_mid ||Exposure ||Filter ||Limit
T+ 71.54 hrs ||1600s || R ||>20.44
The limit is estimated from comparison to nearby USNO B1 stars and is not corrected for Galactic extinction. The VIRT is still in the commissioning phase.
We acknowledge financial support from NASA MUREP MIRO award 80NSSC21M001, NASA EPSCoR award 80NNSC22M0063, NSF PAARE award 2319415, and NASA EPSCoR award 80NSSC24M0112. This message can be cited.
GCN Circular 36974
Subject
GRB 240727A: Swift-BAT refined analysis
Date
2024-07-29T19:11:10Z (a year ago)
From
Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>
Via
email
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)(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 240727A (trigger #1245074)
(Parsotan, et al., GCN Circ. 36938). The BAT ground-calculated position is
RA, Dec = 236.451, 8.612 deg which is
RA(J2000) = 15h 45m 48.2s
Dec(J2000) = +08d 36' 41.8"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The mask-weighted BAT light curve shows a complex structure with a duration of ~ 215 sec. T90 (15-350 keV) is 177.88 +- 35.46 sec (estimated error including systematics).
The time-averaged spectrum from T-6.79 to T+201.06 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.62 +- 0.18. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+3.12 sec in the 15-150 keV band is 0.4 +- 0.1 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/BATbursts/hand/1245074/bascript/top.html
GCN Circular 36971
Subject
GRB 240727A: observations of optical counterpart.
Date
2024-07-29T12:25:36Z (a year ago)
From
divulgazione@marsec.org
Via
Web form
Stefano Lora (MarSEC, Marana Space Explorer Center, Marana Di Crespadoro, VI, Italy)
Member of:
UAI/SSV - Unione Astrofili Italiani/Sezione Stelle Variabili, GRB section.
AAVSO (American Association Variable Stars Observers)
In collaboration with: Ivo Peretto and Giovanni Furlato (MarSEC, Marana Space Explorer Center, Marana di Crespadoro, VI, Italy)
Members of:
UAI/SSV - Unione Astrofili Italiani/Sezione Stelle Variabili, GRB section.
AAVSO (American Association Variable Stars Observers)
report:
We imaged the field of GRB 240727A detected by SWIFT(trigger=1245074)
with the telescope 14” RC Officina Stellare of MarSEC (Marana Space Explorer Center).
The observations with a series of 120 sec exposures started at 2024-07-27 19:40 UT, 952 min. after the GRB trigger, with a Ritchey-Chretien telescope D=360 mm f/ 8.
at the following position:
RA(J2000) = 15h 45m 44,98s
Dec(J2000) = +08d 37' 12,0",
Weather conditions were very good without Moon.
We co-added 73 exposures of 120 sec each.
Start T0+ End T0+ R lim.
952 min 1098 min 17,5
We did not found any optical counterpart in A.R. 15 45 44.98, DEC. +08 37 12.0 position and in the error box of the Swuift candidate.
ref.: GCN Circular 36938
Magnitudes were estimated with the APASS and
are not corrected for galactic dust extinction.
Reference:
https://www.marsec.org/
GCN Circular 36969
Subject
Fermi GRB 240727A: Global MASTER-Net observations report
Date
2024-07-29T03:15:38Z (a year ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich
(Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 240727A ( Fermi GBM team, GCN 36958) errorbox 1 days 9913 sec after notice time and 1 days 9945 sec after trigger time at 2024-07-29 02:37:31 UT, with upper limit up to 16.9 mag. The observations began at zenith distance = 79 deg. The sun altitude is -36.5 deg.
The galactic latitude b = -5 deg., longitude l = 248 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2543175
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
96376 | 2024-07-29 02:37:31 | MASTER-SAAO | (07h 08m 02.69s , -36d 44m 01.5s) | C | 60 | 16.4 |
96534 | 2024-07-29 02:40:10 | MASTER-SAAO | (07h 07m 41.05s , -34d 48m 14.6s) | C | 60 | 16.9 |
97030 | 2024-07-29 02:48:26 | MASTER-SAAO | (07h 06m 42.54s , -32d 56m 19.5s) | C | 60 | 16.2 |
97110 | 2024-07-29 02:49:45 | MASTER-SAAO | (07h 16m 18.00s , -32d 54m 03.9s) | C | 60 | 15.9 |
97190 | 2024-07-29 02:51:05 | MASTER-SAAO | (07h 16m 22.47s , -34d 47m 53.9s) | C | 60 | 15.8 |
97269 | 2024-07-29 02:52:25 | MASTER-SAAO | (07h 08m 03.99s , -36d 44m 12.2s) | C | 60 | 16.1 |
97349 | 2024-07-29 02:53:44 | MASTER-SAAO | (07h 19m 20.58s , -38d 35m 56.4s) | C | 60 | 15.9 |
97428 | 2024-07-29 02:55:03 | MASTER-SAAO | (07h 29m 35.38s , -38d 36m 57.4s) | C | 60 | 15.7 |
97507 | 2024-07-29 02:56:23 | MASTER-SAAO | (07h 18m 08.43s , -36d 41m 46.8s) | C | 60 | 15.9 |
97666 | 2024-07-29 02:59:01 | MASTER-SAAO | (07h 07m 36.44s , -34d 48m 22.6s) | C | 60 | 15.7 |
97745 | 2024-07-29 03:00:20 | MASTER-SAAO | (07h 27m 02.23s , -36d 43m 25.0s) | C | 60 | 15.0 |
97826 | 2024-07-29 03:01:42 | MASTER-SAAO | (07h 37m 08.56s , -36d 42m 39.8s) | C | 60 | 14.6 |
98064 | 2024-07-29 03:05:40 | MASTER-SAAO | (07h 06m 44.88s , -32d 55m 02.4s) | C | 60 | 15.5 |
98143 | 2024-07-29 03:06:59 | MASTER-SAAO | (07h 16m 11.65s , -32d 55m 09.9s) | C | 60 | 15.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 36968
Subject
GRB 240727A: Swift/UVOT detection
Date
2024-07-28T20:09:28Z (a year ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
Via
email
N. P. M. Kuin (UCL-MSSL) and T.M. Partosan (NASA/GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 240727A
126 s after the BAT trigger (Partosan et al., GCN Circ. 36938).
An optical afterglow consistent with the XRT position in GCN Circ
36956 (Gropp et al.) is detected in the initial UVOT exposures.
The initial UVOT position found is RA=236.4375000 Dec=8.6202807
RA(J2000) = 15h 45m 45.0s
Dec(J2000) = 08d 37' 12.9"
with uncertainty = +/- 0.5" (90% confidence)
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 126 276 147 18.29 +/- 0.06
u_FC 285 535 246 17.92 +/- 0.08
b 541 561 20 >19.0
white 565 585 20 18.60 +/- 0.17
b 714 734 20 18.9 +/- 0.3
u 689 709 20 18.5 +/- 0.4
v 615 635 20 >18.0
w1 664 684 20 >17.8
m2 4622 4823 197 >18.7
w2 590 610 20 >17.7
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.037 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 36965
Subject
GRB 240727A: Correction to time in GCN36960
Date
2024-07-28T14:30:48Z (a year ago)
From
Ulisse Quadri at Bassano Bresciano Observatory <osservatoriobassano@gmail.com>
Via
Web form
U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory)report:
The times given in GCN36960 are incorrect. The correct times are:
Start T0+ End T0+ Vlim
15.97 hour 17.06 hour 20
Magnitudes were estimated with the pan-STARRS catalog.
We apologize for the mistake.
GCN Circular 36964
Subject
GRB 240727A: Osservatorio Astronomico Nastro Verde upper limit
Date
2024-07-28T11:41:46Z (a year ago)
From
Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde@gmail.com>
Via
Web form
Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy
in a large collaboration with:
M.G. Dainotti (National Astronomical Observatory of Japan),
Y. Niino (Tokyo University, Institute of Astronomy),
K. Kalinowski (Aarhus University, Department of Physics and Astronomy),
B. De Simone (Universita' degli Studi Di Salerno)
report:
We image the field of GRB 240727A (Trigger 1245074 T. M. Parsotan (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL)
and B. Sbarufatti (INAF-OAB) GCN Circular 36938)
with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of:
AAVSO - American Association of Variable Star Observers.
UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili.
AstroCampania Associazione
The observations started at 19:40 UT of 2024/07/27, after about 15.35 hours after the GRB trigger, at the end of twilight, clear sky, with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME
I took 52 image of 60 sec each. All images are unfiltered, calibrated with masterdark and masterflat,stacked with Tycho Tracker software
We have not detected any clearly visible sources, up to 20th magnitude with clear skies.
Start T0+ End T0+ Rlim
19:26:25 UT 20:30:16 UT 19.5
We did not found any optical counterpart in the error box of the XRTcandidate.
Magnitudes were estimated with the Gaia DR2 cat. and
are not corrected for galactic dust extinction.
The message may be cited.
GCN Circular 36962
Subject
GRB 240727A: NOT optical observation
Date
2024-07-28T09:40:19Z (a year ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
J. An, S.Y. Fu, S.Q. Jiang, X. Liu, Z.P. Zhu, D. Xu (NAOC), S.G. Sorensen (NOT) report on behalf of a large collaboration:
We observed the field of GRB 240727A detected by Swift (Parsotan et al., GCN 36938) using the the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. We obtained 6x300 s Sloan r-band images at a median time of 21:45:11.8 UT on 2024-07-27.
The optical afterglow (Zheng & Filippenko, GCN 36939; Liu et al., GCN 36940; Dubay et al., GCN 36941) is clearly detected in our stacked r-band image with r = 23.4 +/- 0.1 mag, calibrated with nearby Pan-STARRS stars and not corrected for Galactic extinction.
GCN Circular 36961
Subject
GRB 240727A: JinShan optical upper limits
Date
2024-07-28T09:24:29Z (a year ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
J. An, S.Y. Fu, S.Q. Jiang, Z.P. Zhu, X. Liu, L.B. He, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of GRB 240727A detected by Swift (Parsotan et al., GCN 36938) using the 100C telescope of the JinShan project located at Altay, Xinjiang, China. A series of Sloan r- and i- band frames were obtained from 15:37:37 UT to 17:13:11 UT on 2024-07-27.
No source is detected at the optical afterglow position (Zheng & Filippenko, GCN 36939; Liu et al., GCN 36940; Dubay et al., GCN 36941), down to the 5-sigma upper limits of r ~ 23.0 and i ~ 21.8, calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.
We acknowledge the excellent support from S.W. Luo, M.M. Yang, Z.K. Feng, Q.C. Zhao and L.F. Huo for enabling these observations.
GCN Circular 36960
Subject
GRB 240727A Bassano Bresciano Observatory upper limit
Date
2024-07-28T08:09:05Z (a year ago)
From
Ulisse Quadri at Bassano Bresciano Observatory <osservatoriobassano@gmail.com>
Via
Web form
U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory),
Members of:
AAVSO - American Association of Variable Star Observers.
UAI/SSV - Unione Astrofili Italiani/SSV-GRB section.
GAC - Gruppo Astrofili Cremonesi.
In a large collaboration with:
M.G. Dainotti (National Astronomical Observatory of Japan),
Y. Niino (Tokyo University, Institute of Astronomy),
K. Kalinowski (Aarhus University, Department of Physics and Astronomy),
B. De Simone (Universita' degli Studi Di Salerno)
report:
We imaged the field of GRB 240727A detected by SWIFT(trigger 1245074)
with the robotic telescope of (IAU station 565) Bassano Bresciano
Observatory, Italy.
The observations started 19.78 hour after the GRB trigger, At the end of twilight
with our Newton telescope D=450 mm F/D=4.5.
Weather conditions were good.
We co-added 2 series of 30 exposures of 60 sec each.
Start T0+ End T0+ Vlim
19.78 hour 20.86 hour 20
We did not found any optical counterpart in the error box of the XRTcandidate.
Parsotan et al.(GCN 36938), WeiKanget al.(GCN 36939), X. Liu et al.(GCN 36940).
Magnitudes were estimated with the pan-STAR cat. and
are not corrected for galactic dust extinction.
Reference:
http://www.osservatoriobassano.org/GRB.asp
The message may be cited.
GCN Circular 36958
Subject
GRB 240727A: Fermi GBM Final Real-time Localization
Date
2024-07-28T00:02:26Z (a year ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 23:51:46 UT on 27 Jul 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240727A (trigger 743817111.069264 / 240727994).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 115.5, Dec = -33.0 (J2000 degrees, equivalent to J2000 07h 42m, -33d 00'), with a statistical uncertainty of 6.0 degrees.
The angle from the Fermi LAT boresight is 22.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240727994/quicklook/glg_skymap_all_bn240727994.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240727994/quicklook/glg_healpix_all_bn240727994.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240727994/quicklook/glg_lc_medres34_bn240727994.gif
GCN Circular 36956
Subject
GRB 240727A: Swift-XRT refined Analysis
Date
2024-07-27T20:27:35Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
J. D. Gropp (PSU), S. Dichiara (PSU), A.P. Beardmore (U. Leicester),
J.P. Osborne (U. Leicester), C. Salvaggio (INAF-OAB), M. Ferro
(INAF-OAB), R. Brivio (INAF-OAB), J.A. Kennea (PSU) and P.A. Evans
report on behalf of the Swift-XRT team:
We have analysed 6.6 ks of XRT data for GRB 240727A, from 109 s to 51.8
ks after the BAT trigger. The data comprise 377 s in Windowed Timing
(WT) mode (the first 8 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=0.89 (+0.26, -0.58), followed by a break at T+177 s to
an alpha of 1.80 (+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 1.98 (+/-0.06). The
best-fitting absorption column is 1.46 (+0.19, -0.18) x 10^21 cm^-2,
in excess of the Galactic value of 3.6 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.25 (+0.14, -0.12)
and a best-fitting absorption column consistent with the Galactic
value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 5.3 x 10^-11 (5.4 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.6 (+3.6, -0.0) x 10^20 cm^-2
Galactic foreground: 3.6 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.25 (+0.14, -0.12)
If the light curve continues to decay with a power-law decay index of
1.80, the count rate at T+24 hours will be 4.8 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x
10^-14 (2.6 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/01245074.
This circular is an official product of the Swift-XRT team.
GCN Circular 36950
Subject
GRB 240727A: Enhanced Swift-XRT position
Date
2024-07-27T19:08:09Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1103 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 240727A, 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 = 236.43735, +8.61996 which is equivalent
to:
RA (J2000): 15h 45m 44.96s
Dec (J2000): +08d 37' 11.9"
with an uncertainty of 2.8 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 36941
Subject
GRB240727A: Skynet Optical Afterglow Observations
Date
2024-07-27T05:40:13Z (a year ago)
From
maedubay@unc.edu
Via
Web form
Megan Dubay, Donovan Schlekat, Dylan Dutton, Ruide Fu, Daniel Reichart, Joshua Haislip, Vladimir Kouprianov report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill.
We observed the field of GRB 240727A with one of the PROMPT telescopes at the Cerro-Tololo Inter-American Observatory. We began observing the field at 03:52:11 UTC on July 27, 2024. The first detection occurred at 04:27:12 UTC on July 27, 2024, approximately 40 minutes after the trigger reported by Swift (Parsotan et al., GCN 36938).
We detect the optical afterglow, also reported by (Zheng and Filippenko, GCN 36939) and (Liu et al., GCN 36940).
The coordinates are:
R.A. (J2000): 15:45:45.02
Dec. (J2000): 08:37:12.95
We report the photometry below.
ExpLen | Filter | Mag | Mag Error | MJD
--------------------------------------------------
61.45 | R | 18.653 | 0.218 | 60518.1880
184.35 | R | 18.818 | 0.167 | 60518.1881
184.35 | V | 19.067 | 0.280 | 60518.1914
Our images have been calibrated using stars from the APASS catalog.
GCN Circular 36940
Subject
GRB 240727A: TRT optical afterglow detection
Date
2024-07-27T05:10:51Z (a year ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
X. Liu, S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), J. An, S.Y. Fu, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration:
We observed the field of GRB 240727A detected by Swift (Parsotan et al., GCN 36938), using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Cerro Tololo, Chile. Observations started at 04:04:58 UT on 2024-07-27 and 4 x 300 s frames were obtained in the R-band.
An uncatalogued and fading source is detected in each frame within the Swift/XRT error circle and localized at coordinates
R.A. (J2000) = 15:45:45.01
Dec. (J2000) = +8:37:12.61
with an uncertainty of ~ 0.5 arcsec, being positionally consistent with the KAIT measurement (Zheng & Filippenko, GCN 36939) . The source had R = 18.6 +/- 0.1 mag in the first frame and faded to R = 19.2 +/- 0.1 mag in the last frame, calibrated with PanSTARRS and not corrected for Galactic extinction.
We therefore conclude that the source is the optical afterglow of GRB 240727A.
GCN Circular 36939
Subject
GRB 240727A: KAIT Optical Afterglow Candidate
Date
2024-07-27T04:49:46Z (a year ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
legacy email
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 240727A (Parsotan et al.,
GCN 36938) starting on July 27, 04:22:16 UT. We detected an uncataloged
optical afterglow candidate not shown in DSS archive at position
of (error ~0.5"):
RA: 15:45:44.98 (J2000)
Dec: +08:37:13.15 (J2000)
This position is about 1.1 arcsec to the Swift/XRT localization
(Parsotan et al., GCN 36938). We measure the target is ~19.0 in our
clear band image at ~34 minutes after burst. We can not estimate the
variability at this time, further observations are encouraged.
GCN Circular 36938
Subject
GRB 240727A: Swift detection of a burst
Date
2024-07-27T04:06:04Z (a year ago)
From
David Palmer at LANL <palmer@lanl.gov>
Via
email
T. M. Parsotan (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL)
and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels
Swift Observatory Team:
Prior to 03:48 UTC, BAT triggered and located GRB 240727A
(Trigger 1245074) and slewed to the GRB location.
Due to a telemetry gap, no further BAT information
will be available until the next data downlink to the ground.
The XRT began observing the field at 03:48:12 UT. Using promptly downlinked data
we find a bright, uncatalogued X-ray source located at RA, Dec 236.43742, 8.62001
which is equivalent to:
RA(J2000) = 15h 45m 44.98s
Dec(J2000) = +08d 37' 12.0"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). 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 in excess of the Galactic value (3.64 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.7
(+3.19/-2.66) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 2.08e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of nominal 150.000 seconds with the White
filter starting at 03:48:20. Automatic processing FAILED due to its reliance
on BAT data for initial parameters.
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/)