GRB 180624A
GCN Circular 22867
Subject
GRB 180624A: NOT optical counterpart
Date
2018-06-27T19:06:20Z (7 years ago)
From
Jonatan Selsing at DARK/NBI <jselsing@dark-cosmology.dk>
Jonatan Selsing (DAWN/NBI), Kasper E. Heintz (Univ. Iceland and DAWN/NBI), Johan P. U.
Fynbo (DAWN/NBI), Daniele B. Malesani (DAWN/NBI and DARK/NBI), Jyri J. Lehtinen
(MPS), Teemu Willamo (Univ. of Helsinki), report on behalf of a larger
collaboration:
We observed the optical afterglow (Guidorzi, GCN #22839; Schady, GCN #22840;
Rossi et al., GCN #22845; Watson et al., GCN #22846; Guidorzi et al., GCN
#22858) of GRB 180624A (Gibson et al., GCN #22832) with the 2.5-m Nordic Optical
Telescope (NOT) equipped with StanCam.
Observations were carried out in the Bessel R filter, but calibrated against
Pan-STARRS r-band local photometry, using the transformations of Lupton (2005).
An optical afterglow is detected at a position consistent with previous reports.
At a mid time 11.0 hr after the BAT trigger, we measure for the counterpart R =
20.10 +- 0.04 (Vega). This measurement has not been corrected for Milky Way
extinction (A_V = 0.13). Due to the vicinity of the nearby galaxy noted by
Schady (GCN #22840), Guidorzi et al. (GCN #22858), and Rossi et al. (GCN 22845),
we cannot exclude some minor contamination from this object to the afterglow
photometry.
GCN Circular 22858
Subject
GRB 180624A: LCO Haleakala observations
Date
2018-06-26T15:32:43Z (7 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell
(U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara,
D. Morris (U. of Virgin Islands) on behalf of a large collaboration report:
The LCO 2-m unit at Haleakala Observatory (Hawaii) observed the optical
afterglow of Swift GRB 180624A (Gibson et al. GCN 22832) on June 25,
from 13:02 to 13:14 UT (0.97 days after the GRB trigger time) with the
SDSS r filter. The source is detected with a magnitude of 21.44 +- 0.10
(AB). Compared with previous reports (Guidorzi et al. GCN 22839; Schady
GCN 22840; Rossi et al. GCN 22845; Watson et al. GCN 22846) we confirm
that the source's decay has significantly steepened from ~0.6 to ~1.0
days, as first noted by Watson et al.
GCN Circular 22848
Subject
GRB 180624A: Swift-BAT refined analysis
Date
2018-06-26T02:19:59Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
J. R. Cummings (CPI), S. D. Barthelmy (GSFC),
S. L. Gibson (U Leicester), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180624A (trigger #844192)
(Gibson et al., GCN Circ. 22832). The BAT ground-calculated position is
RA, Dec = 318.096, -2.356 deg which is
RA(J2000) = 21h 12m 22.9s
Dec(J2000) = -02d 21' 21.0"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 47%.
The mask-weighted light curve shows a multi-peaked light curve that starts
at ~T-60 s and ends at ~T+540 s. The largest peak occurs at ~T+7 s. The
burst went out of the BAT FOV at ~T+720 s. T90 (15-350 keV) is 486.4 +- 38.5 sec
(estimated error including systematics).
The time-averaged spectrum from T-60.61 to T+541.80 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.91 +- 0.10. The fluence in the 15-150 keV band is 5.8 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+6.02 sec in the 15-150 keV band
is 1.4 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/844192/BA/
GCN Circular 22846
Subject
GRB 180624A: RATIR Optical Observations
Date
2018-06-25T22:16:14Z (7 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Eleonora Troja (GSFC), Nat Butler (ASU),
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer
(UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB),
Antonino Cucchiara (UVI), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:
We observed the field of GRB 180624A (Gibson et al., GCN Circ. 22832)
with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astron��mico Nacional on Sierra San Pedro M��rtir from 2018/06 25.26 to
2018/06 25.47 UTC (16.42 to 21.45 hours after the BAT trigger),
obtaining a total of 3.91 hours exposure in the r and i bands.
We detect a source in the enhanced Swift-XRT error circle (Goad et al.,
GCN Circ. 22835) with the following magnitudes:
r = 21.03 +/- 0.02
i = 20.45 +/- 0.01
These magnitudes are calibrated against the SDSS DR9 catalog, are in the
AB system, and are not corrected for Galactic extinction in the
direction of the GRB.
We note that the source has faded significantly from the earlier
observations of Guidorzi et al. (GCN Circ. 22839) of r = 19.9 +/- 0.1 at
0.54 hours and Schady (GCN Circ. 22840) of r = 20.2 +/- 0.1 at 15.07
hours. We also see the source fade by about 0.5 mag in each our bands
during the course of our observations.
We confirm the observation of Rossi et al. (GCN Circ. 22845) that the
source is a couple of arcsec to the SE of the SDSS galaxy
J211223.25-022015.9.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.
GCN Circular 22845
Subject
GRB 180624A: LBT/MODS redshift measurement
Date
2018-06-25T18:25:52Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
A. Rossi (INAF-OAS), A. Gargiulo (INAF/IASF Milano), D. B. Malesani
(DAWN/NBI and DARK/NBI), S. D. Vergani (GEPI/Obs. Paris), V. D'Elia
(ASDC), S. Campana (INAF-OAB), report on behalf of the CIBO collaboration:
We observed the field of GRB 180624A (Swift trigger 844192; Gibson et
al., GCN 22832) with the Multi-Object Double Spectrographs (MODS)
instrument mounted on the 2x8.4-m LBT telescope (Mt Graham, AZ, USA).
Images were obtained starting at 10:15 UT on 2018-06-25, 20.5 hr after
the GRB trigger.
Inspection of the 60 s acquisition image reveals a point source within
the Swift/XRT enhanced error circle (Evans et al., GCN 22835), at
coordinates:
RA(J2000) = 21:12:23.378
Dec(J2000)= -02:20:17.30
with an uncertainty of 0.2" in each coordinate, which is consistent with
the source reported by Guidorzi et al. (GCN 22839). The source has
magnitude r' = 20.6 +- 0.1 (AB), calibrated against r'-band SDSS field
stars, and it is not visible in Pan-STARRS images, thus clearly singling
it out as the afterglow.
Spectroscopy of the source was obtained for a total of 2x600 s, covering
the wavelength range 3200-10000 AA. A broad trough is well visible
centered around 4700 AA, which we identify as a DLA feature at z ~ 2.86.
Detection of several absorption features, which we interpret as due to,
among others, Si II, C IV, Al II, Al III, Fe II, allows to precisely
measure the redshift to be z = 2.855, which we consider to be the
redshift of GRB 180624A.
We also note the presence of a close-by and fainter galaxy, which is
also visible in the Pan-STARRS images, 2.5" NW of the afterglow, at
position:
RA(J2000) = 21:12:23.244
Dec(J2000)= -02:20:15.76
possibly consistent with the extended source reported by Schady (GCN
22840). Given the measured redshift, we do not consider this object as
related to the GRB, as it would have an unreasonable brightness and
large separation at z = 2.8.
No correction for the expected Galactic foreground extinction,
corresponding to a reddening of E_(B-V) = 0.05 mag in the direction of
the burst (Schlafly & Finkbeiner 2011), has been applied.
We acknowledge the excellent support from the LBT-INAF staff,
particularly Olga Kuhn and Steve Allanson in obtaining these observations.
GCN Circular 22840
Subject
GRB 180624A: GROND observations
Date
2018-06-25T08:09:51Z (7 years ago)
From
Patricia Schady at MPE/Swift <pschady@mpe.mpg.de>
Patricia Schady (MPE Garching) reports:
We observed the field of GRB 180624A (Swift trigger 844192; Gibson et al.,
GCN #22832) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla
Observatory (Chile).
Observations started at 04:42 UT on 2018-06-25, 14.9 hrs after the GRB
trigger. They were performed under poor seeing conditions and at an
average airmass of 1.5.
A source is visible within the 1.5" enhanced Swift-XRT error circle
reported by GOAD et al. (GCN #22835), and consistent with the position of
the optical afterglow candidate reported by Guidorzi et al. (GCN #22839).
The source appears extended and most of the flux in the JHK bands is to
the NW of the afterglow error circle.
Based on a total of 22 min exposure time in g'r'i'z', we estimate
preliminary AB magnitudes of
g' = 21.5 +/- 0.1 mag
r' = 20.2 +/- 0.1 mag
i' = 19.9 +/- 0.1 mag
z' = 19.6 +/- 0.1 mag
A fit to the GROND optical SED implies a photometric redshift of
z_phot=3.75+/-0.10.
Given magnitudes are calibrated against SDSS field stars and are not
corrected for the expected Galactic foreground extinction corresponding to
a reddening of E_(B-V)=0.04 in the direction of the burst (Schlafly &
Finkbeiner 2011).
We thank Markus Rabus for the excellent support from La Silla.
GCN Circular 22839
Subject
GRB 180624A: LCO Siding Springs afterglow candidate
Date
2018-06-25T06:43:03Z (7 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell
(U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara
(U. of Virgin Islands) on behalf of a large collaboration report:
One LCO 1-m unit at Siding Springs Observatory began observing Swift GRB
180624A (Gibson et al. GCN 22832) on June 24, 14:18 UT (28.5 min since
the GRB trigger time) with the SDSS r filter. Within the enhanced
Swift-XRT error circle (Goad et al. GCN 22835) we find an uncatalogued
object with a magnitude of r'=19.92 +- 0.10 (AB) at a mid time of 0.54
hours since the GRB trigger time at the following position:
RA(J2000) = 21:12:23.38
DEC(J2000)= -02:20:16.7
with an error radius of ~1".
GCN Circular 22838
Subject
GRB 180624A: MITSuME Okayama optical upper limits
Date
2018-06-25T04:46:32Z (7 years ago)
From
Ryosuke Itoh at Tokyo Institute of Tech. <itoh@hp.phys.titech.ac.jp>
R. Itoh, K. L. Murata, Y. Tachibana, K. Morita,
K. Shiraishi, M. Oeda, R. Adachi, K. Iida, S. Niwano, Y. Yatsu, and
N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 180624A (S. L. Gibson et al., GCN Circular #22832)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2018-06-24 13:51:38.54 UT (~118 sec after
the burst). We did not find any new point source within the
enhanced XRT error circle in all the three bands.
We obtained following limits for the magnitudes.
T0+[sec] MID-UT T-EXP[sec] g' Rc Ic
-------------------------------------------------------------------------------------------------------
~118 ~13:52:08 60 >15.5 >16.1 >16.2
~1537 ~14:15:47 2100 >17.2 >17.7 >17.6
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used UCAC-4 catalog for flux calibration.
GCN Circular 22837
Subject
GRB 180624A: Swift-XRT refined Analysis
Date
2018-06-25T00:10:26Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester),
V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), A.
Tohuvavohu (PSU) and S.L. Gibson report on behalf of the Swift-XRT
team:
We have analysed 10 ks of XRT data for GRB 180624A (Gibson et al. GCN
Circ. 22832), from 118 s to 23.6 ks after the BAT trigger. The data
comprise 538 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN Circ. 22835).
The late-time light curve (from T0+3.9 ks) can be modelled with a
power-law decay with a decay index of alpha=0.84 (+0.12, -0.11).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.472 (+/-0.025). The
best-fitting absorption column is 1.53 (+/-0.11) x 10^21 cm^-2, in
excess of the Galactic value of 4.6 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.08 (+0.19, -0.18)
and a best-fitting absorption column of 1.3 (+/-0.5) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.2 x 10^-11 (4.2 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.3 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 4.6 x 10^20 cm^-2
Excess significance: 3.0 sigma
Photon index: 2.08 (+0.19, -0.18)
If the light curve continues to decay with a power-law decay index of
0.84, the count rate at T+24 hours will be 0.013 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.2 x
10^-13 (5.5 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00844192.
This circular is an official product of the Swift-XRT team.
GCN Circular 22836
Subject
GRB 180624A: Swift/UVOT Upper Limits
Date
2018-06-24T22:33:42Z (7 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
N. P. M. Kuin (UCL-MSSL) and S. L. Gibson (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180624A
118 s after the BAT trigger (Gibson et al., GCN Circ. 22832). No optical
afterglow consistent with the XRT position (Gibson et al. GCN Circ.
22832) 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 118 268 147 >20.7
u_FC 276 526 246 >19.4
white 118 6151 541 >21.3
v 4927 6395 229 >20.0
b 4312 5947 393 >21.2
u 276 5742 639 >20.6
w1 3902 5537 393 >20.2
m2 5132 5332 197 >19.7
w2 4723 6357 393 >20.8
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 22835
Subject
GRB 180624A: Enhanced Swift-XRT position
Date
2018-06-24T21:20:42Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team.
Using 2472 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 180624A, 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 = 318.09749, -2.33826 which is equivalent
to:
RA (J2000): 21h 12m 23.40s
Dec (J2000): -02d 20' 17.7"
with an uncertainty of 1.5 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 22832
Subject
GRB 180624A: Swift detection of a burst
Date
2018-06-24T14:02:45Z (7 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
S. L. Gibson (U Leicester), S. D. Barthelmy (GSFC), A. Deich (PSU),
S. W. K Emery (UCL-MSSL), J.D. Gropp (PSU), K. L. Page (U Leicester),
T. Sakamoto (AGU) and M. H. Siegel (PSU) report on behalf of the Neil
Gehrels Swift Observatory Team:
At 13:49:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180624A (trigger=844192). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 318.071, -2.332, which is
RA(J2000) = 21h 12m 17s
Dec(J2000) = -02d 19' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). Due to missing downlinked realtime data
in the light curve, we cannot give the BAT light curve description.
The XRT began observing the field at 13:51:32.6 UT, 112.2 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 318.0951, -2.3397 which is equivalent to:
RA(J2000) = +21h 12m 22.82s
Dec(J2000) = -02d 20' 22.9"
with an uncertainty of 5.2 arcseconds (radius, 90% containment). This
location is 91 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.
The initial flux in the 2.5 s image was 1.93e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 118 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
0.05.
Burst Advocate for this burst is S. L. Gibson (slg44 AT le.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/too.html.)