GRB 150424A
GCN Circular 17743
Subject
GRB 150424A: Swift detection of a short burst
Date
2015-04-24T07:58:55Z (10 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. P. Beardmore (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL) and T. N. Ukwatta (LANL) report on behalf of the
Swift Team:
At 07:42:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150424A (trigger=638946). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 152.312, -26.647 which is
RA(J2000) = 10h 09m 15s
Dec(J2000) = -26d 38' 47"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single
structure with a duration of about 0.5 sec. The peak count rate
was ~55000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 07:44:24.7 UT, 87.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
152.3061, -26.6310 which is equivalent to:
RA(J2000) = 10h 09m 13.46s
Dec(J2000) = -26d 37' 51.6"
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This
location is 60 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 http://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 (6.03 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.8
(+3.00/-2.59) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 2.87e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 99 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
0.06.
Burst Advocate for this burst is A. P. Beardmore (apb AT star.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.)
GCN Circular 17745
Subject
GRB 150424A: Keck detection of optical afterglow
Date
2015-04-24T10:19:56Z (10 years ago)
From
Daniel Perley at Caltech <dperley@astro.caltech.edu>
D. A. Perley (Caltech) and N. J. McConnell (IfA) report:
We observed the field of short-duration GRB 150424A (Beardmore et al.,
GCN 17743) with the Low Resolution Imaging Spectrometer (LRIS) on the
Keck I 10m telescope. Three 120-second imaging exposures in g- and
R-bands were acquired between 09:15 and 09:26 UT (approximately 1.6
hours after the GRB trigger), at low elevation through moderate cloud cover.
In both filters we detect a bright (R~20 mag) source, not visible in
DSS, at the following location inside the XRT error circle:
RA = 10:09:13.381
dec = -26:37:51.50
(+/- 0.5" or less)
We suggest this as the optical afterglow of GRB 150424A.
We also note the presence of a large galaxy (resolved in DSS) 5 arcsec
to the southwest.
GCN Circular 17749
Subject
GRB 150424A: Enhanced Swift-XRT position
Date
2015-04-24T14:17:39Z (10 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 3164 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 150424A, 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 = 152.30569, -26.63092 which is equivalent
to:
RA (J2000): 10h 09m 13.37s
Dec (J2000): -26d 37' 51.3"
with an uncertainty of 1.7 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 17751
Subject
GRB 150424A: Swift/UVOT Observations
Date
2015-04-24T15:03:18Z (10 years ago)
From
Frank Marshall at GSFC <femarsha@khamseen.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC) and A. P. Beardmore (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150424A
99 s after the BAT trigger (Beardmore et al., GCN Circ. 17743).
A source consistent with the position
of the suggested optical afterglow
(Perley and McConnell, GCN Circ. 17745)
is detected in the initial UVOT exposures.
The source remains nearly constant in 6 exposures with the
white filter starting 99 s after the trigger and ending
6786 s after the trigger. The magnitude is approximately that
reported by Perley and McConnell. This may be a detection
of the host galaxy.
The preliminary UVOT position is:
RA (J2000) = 10:09:13.38 = 152.30577 (deg.)
Dec (J2000) = -26:37:51.1 = -26.63086 (deg.)
with an estimated uncertainty of 0.6 arcsec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limit using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 99 6786 609 20.38 +/- 0.07
v 641 5881 432 >19.8
b 567 6701 432 20.71 +/- 0.21
u 311 5061 462 20.13 +/- 0.20
w1 690 6291 413 20.00 +/- 0.24
m2 4452 6086 393 19.91 +/- 0.29
w2 616 5677 216 20.03 +/- 0.31
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.06 in the direction of the burst
(Schlegel et al. 1998).
[GCN OPS NOTE(24apr15): Per author's request the missing minus sign
on the hh:mm:ss format of the value was added; the decimal-deg value was correct.]
GCN Circular 17752
Subject
Konus-Wind observation of GRB 150424A
Date
2015-04-24T16:56:48Z (10 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:
The short-duration, intense GRB 150424A
(Swift/BAT detection: Beardmore et al., GCN Circ. 17743).
triggered Konus-Wind at T0=27781.073 s UT (07:43:01.073).
The burst light curve shows a multipeak structure
with a total duration of ~0.4 s.
The emission is seen up to 4 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150424_T27781/
As observed by Konus-Wind, the burst
had a fluence of 1.81(-0.11,+0.11)x10^-5 erg/cm2,
and a 2-ms peak flux, measured from T0+0.212 s,
of 1.85(-0.48,+0.48)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.37(-0.09,+0.10)
and Ep = 919(-76,+82) keV (chi2 = 66/57 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.8
(chi2 = 66/56 dof)
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 17756
Subject
GRB 150424A: NOT optical observations
Date
2015-04-24T23:08:53Z (10 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
D. Malesani (DARK/NBI), D. Xu (NAOC/CAS), D. J. Watson (DARK/NBI), and
P. Blay (IAC/NOT), report on behalf of a larger collaboration:
We observed the optical counterpart (Perley, GCN 17745; Marshall &
Beardmore, GCN 17751) of the short GRB 150424A (Beardmore et al., GCN
Circ. 17743), using the Nordic Optical Telescope equipped with the
AlFOSC camera. The first 300-s R-band exposure was taken starting at
20:57 UT (13.2 hr after the GRB)
We clearly detect the counterpart with a magnitude R = 20.67 +- 0.06
(assuming R = 16.27 for the USNO star at RA = 10:09:11.09, Dec =
-26:36:58.4).
This magnitude is just slightly fainter than the value reported by
Perley (GCN 17745) 1.6 hr after the trigger, indicating a very slow
decay - consistent with the UVOT report. The brightness of the afterglow
is unprecedented for a short GRB this late after the GRB. Such a
behaviour is unusual and we encourage further observations.
GCN Circular 17757
Subject
GRB 150424A: GROND detects strong fading
Date
2015-04-24T23:55:22Z (10 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann (TLS Tautenburg), M. Tanga, and J. Greiner (both MPE Garching)
report on behalf of the GROND team:
We observed the field of the extremely bright short GRB 150424A (Swift
trigger 638946; Beardmore et al., GCN #17743) 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 23:09 UT on 2015-04-24, 15.4 hrs after the GRB
trigger. They were performed at an average seeing of 1".2 and at an
average airmass of 1.1.
We detect the optical afterglow (Perley & McConnell, GCN # 17745; Malesani
et al., GCN # 17756).
Based on 7.7 min of total exposure time in g'r'i'z' and 8.0 min in JHK,
centered 15.54 hrs after the GRB, we estimate the following preliminary
magnitudes (all in AB system):
g' = 22.0 +/- 0.2 mag,
r' = 21.6 +/- 0.1 mag,
i' = 21.4 +/- 0.1 mag,
z' = 21.1 +/- 0.1 mag,
J = 20.4 +/- 0.5 mag, and
H > 19.9 mag.
Compared to the NOT detection about two hours earlier, the afterglow has
faded by 0.7 magnitudes, indicating the transition to a very rapid decay.
Given magnitudes are calibrated against GROND zero points (g'r'i'z') as
well as 2MASS field stars and are not corrected for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V)=0.06 mag in
the direction of the burst (Schlegel et al. 1998).
GCN Circular 17758
Subject
GRB 150424A: 10.4m GTC spectroscopy
Date
2015-04-25T01:34:57Z (10 years ago)
From
Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>
A. J. Castro-Tirado (IAA-CSIC, ISA-UMA), R. Sanchez-Ramirez (UPV/EHU,
IAA-CSIC), G. Lombardi (IAC, ULL, GRANTECAN) and M. A. Rivero (GRANTECAN),
on behalf of a larger collaboration, report:
Following the detection of the short-duration GRB 150424A by Swift/BAT
(Beardmore et al. 2015, GCNC 17743) and Konus-Wind (Golenetskii et al.
GCNC 17752), we have obtained an optical spectrum (2 x 900s) with the
10.4m GTC telescope (+OSIRIS) in La Palma (Spain), starting on Apr 24,
21:30 UT (i.e. 13.8 hr postburst), covering the 3700-10000 wavelength
range. The slit included the position of the proposed optical afterglow
(Perley and McConnell, GCNC 17745; Marshall and Beardmore, GCNC 17751;
Malesani et al., GCNC 17756; Kann et al. GCNC 17757) as well as the
extended galaxy 5 arcsec to the southwest (Perley and McConnell GCNC
17745).
At the position of the optical afterglow, we see no obvious absorption
features with the continuum extending to 3700 A (implying an upper limit
of z < 3 to the redshift of the GRB). At the position of the nearby
galaxy, we detect [O II] and H-alpha in emission at a redshift z = 0.30.
At this redshift, 5 arcsec corresponds to 22.5 kpc. A more detailed data
reduction is ongoing.
We acknowledge D. Perley for providing the corresponding ID-chart.
GCN Circular 17759
Subject
GRB 150424A: spectral lag, extended-time emission
Date
2015-04-25T01:52:26Z (10 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <james.r.cummings@nasa.gov>
J. P. Norris (BSU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
and N. Gehrels (GSFC) report:
We report spectral lag and extended emission measurements for the intense,
short GRB 150424A (trigger=638946; GCN Circ. 17743, 17745 & 17756) based
on Swift-BAT data.
Using a 4-ms binned light curve, the lag for the 25-50 keV to 100-350 keV bands
is estimated as 0.6 (+0.6/-1.0) ms; and -2.4 (+1.3/-0.7) ms for the 15-25 keV
to 50-100 keV bands.
A Bayesian Block analysis of the mask-tagged data reveals one significant
block of duration ~ 106 seconds at a level of 0.006 counts/det/s, following
the intense, initial pulse complex. This extended emission component is
three orders of magnitude lower than the peak intensity of the burst,
~ 5.3 counts/pixel/s.
GCN Circular 17760
Subject
GRB 150424A: Swift-XRT refined Analysis
Date
2015-04-25T07:59:05Z (10 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N.
Burrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), P.A.
Evans (U. Leicester), A. Amaral-Rogers (U. Leicester) and A.P.
Beardmore report on behalf of the Swift-XRT team:
We have analysed 5.1 ks of XRT data for GRB 150424A (Beardmore et al.
GCN Circ. 17743), from 77 s to 29.7 ks after the BAT trigger. The data
comprise 206 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 enhanced XRT position for this burst was given by Goad et al.
(GCN Circ. 17749).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.22 (+0.13, -0.29). At T+168 s the decay
steepens to an alpha of 2.75 (+0.14, -0.19) before breaking again at
T+676 s to a final decay with index alpha=0.64 (+0.08, -0.10).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.60 (+/-0.07). The
best-fitting absorption column is 9.4 (+2.7, -2.5) x 10^20 cm^-2, in
excess of the Galactic value of 6.0 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.00 (+0.19, -0.18)
and a best-fitting absorption column of 1.1 (+0.6, -0.5) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.3 x 10^-11 (4.2 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.1 (+0.6, -0.5) x 10^21 cm^-2
Galactic foreground: 6.0 x 10^20 cm^-2
Excess significance: 1.8 sigma
Photon index: 2.00 (+0.19, -0.18)
If the light curve continues to decay with a power-law decay index of
0.64, the count rate at T+24 hours will be 0.022 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.4 x
10^-13 (9.2 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/00638946.
This circular is an official product of the Swift-XRT team.
GCN Circular 17761
Subject
GRB 150424A: Swift-BAT refined analysis
Date
2015-04-25T15:46:23Z (10 years ago)
From
Tilan Ukwatta at LANL <tilan.ukwatta@gmail.com>
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/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 150424A (trigger #638946) (Beardmore, et al., GCN Circ. 17743).
The BAT ground-calculated position is RA, Dec = 152.305, -26.646 deg
which is
RA(J2000) = 10h 09m 13.2s
Dec(J2000) = -26d 38' 45.7"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 69%.
BAT light curve shows a bright multi-peaked episode starting
around T-0.05 sec, and ending around T+0.5 sec. Very weak
extended emission can be seen up to about T+100 sec as mentioned
in Norris, et al., GCN Circ. 17759. T90 (15-350 keV) is
91 +- 22 sec (estimated error including systematics).
The time-averaged spectrum from T-0.06 to T+106.32 sec is best fit by a
simple power-law model. The power law index of the time-averaged
spectrum is 1.23 +- 0.15. The fluence in the 15-150 keV band is
1.5 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from
T-0.06 sec in the 15-150 keV band is 12.0 +- 0.4 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/638946/BA/
GCN Circular 17762
Subject
GRB 150424A: RATIR Observations
Date
2015-04-25T17:26:07Z (10 years ago)
Edited On
2024-11-07T19:50:29Z (7 months ago)
From
Nat Butler at Az State U <natbutler@asu.edu>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús
González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and
Harvey Moseley (GSFC) report:
We observed the field of the short-duration GRB 150424A (Beardmore, et al.,
GCN 17743) with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astronómico Nacional on Sierra San Pedro Mártir from 2015/04 25.14 to 2015/04
25.28 UTC (19.54 to 23.05 hours after the BAT trigger), obtaining a total
of 2.4 hours exposure in the r, i, and z bands.
The optical afterglow (Perley, GCN 17745; Marshall & Beardmore, GCN 17751;
Malesani, et al., GCN 17756; Kann, et al., GCN 17757) is well-detected. In
comparison with 2MASS and the USNO-B1 catalog, we obtain the following
detections and upper limit (3-sigma):
r 21.92 +/- 0.11
i 21.65 +/- 0.09
z > 20.17
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. Compared to the earlier NOT and
GROND observations, the source appears to be continuing its strong fade
(Kann, et al. GCN 17757).
We thank the staff of the Observatorio Astronómico Nacional in San Pedro
Mártir.
GCN Circular 17804
Subject
GRB 150424A: 9.8 GHz VLA detection
Date
2015-05-07T17:03:52Z (10 years ago)
From
Wen-fai Fong at U of Arizona <wfong@email.arizona.edu>
W. Fong (Univ. of Arizona) reports:
"We observed the position of the short-duration GRB 150424A (Beardmore et
al., GCN 17743) with the Karl G. Jansky Very Large Array (VLA) beginning on
2015 Apr 25.073 UT (18.02 hr post-burst) at a mean frequency of 9.8 GHz. In
1 hour of observations, we detect a faint radio source at the position:
RA(J2000) = 10:09:13.37
Dec(J2000) = -26:37:51.49
with an uncertainty of 0.5" in each coordinate. This position is coincident
with the position of the X-ray afterglow (Goad et al., GCN 17749) as well
as the position of the optical afterglow (Perley and McConnell., GCN 17745;
Malesani et al., GCN 17756; Kann et al., GCN 17757; Butler et al., GCN
17762).
We measure a 9.8 GHz flux density of ~31 microJy. To assess the nature of
this radio source, we obtained two additional sets of VLA observations
starting at 4.67 and 7.88 days after the burst. The source is no longer
detected in each of these observations, as well as a deep, combined image,
to 3-sigma limits of 29 microJy and 20 microJy, respectively.
Due to the fading of the radio source, as well as the positional
coincidence with the X-ray and optical afterglows, we consider this source
to be the radio afterglow of GRB 150424A.
We thank the VLA staff for quickly executing these observations."
GCN Circular 18100
Subject
GRB 150424A: HST imaging
Date
2015-07-31T21:13:57Z (10 years ago)
From
Nial Tanvir at U.Leicester <nrt3@star.le.ac.uk>
N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick), A. S. Fruchter (STScI), J. Hjorth, D. Watson (DARK), D. Perley (Caltech), J. Greiner (MPE), A. de Ugarte Postigo, C. Thoene (IAA-CSIC), R. A. Hounsell (Illinois), S. Rosswog (U. Stockholm) report:
We observed the optical/nIR counterpart of short-GRB 150424A (Perley et al. GCN 17745) with HST at three epochs, roughly 6.7, 9.3 and 13.9 days post-trigger. On each occasion we obtained imaging with the WFC3/UVIS F606W and the WFC3/IR F125W and F160W filters.
The optical transient is visible at all epochs, fading from J(AB)=25.3 to J(AB)=26.9 over the course of the observations. There is a suggestion of a colour change, from r-H(AB)~1.1 to r-H(AB)~2 between the first and last epoch, although the errors are large (and in particular suffer a rather uncertain background correction - see below).
Significantly, the OT is superimposed on a faint source that is extended over about 1 arcsec. We propose that this extended source is most likely the host galaxy of the burst, rather than the bright nearby spiral whose redshift (z=0.3) was reported by Castro-Tirado et al. (GCN 17758). Our current best estimates of the magnitude of this source are r(AB)=26.8, J(AB)=26.1 and H(AB)=25.7, although we note that much of the flux in the r-band is due to a single blue knot of emission, whereas the nIR is more diffuse. Given the luminosity, size and colour of the proposed host, it is likely to be at z>0.7, where the 4000A break would help explain the red r-J colour of most of this galaxy.
If the burst was at z=0.3 (e.g. if the faint extended source is a satellite of the spiral, or just a background galaxy aligned by chance), then we place limits on any kilonova/macronova emission of M_J(AB)>~-14.7 at 7 days post-burst in the rest frame. A more likely redshift of z~1, for example, would mean that our reddest filter only corresponds to the rest-frame I-band, here providing a limit of M_I(AB)>~-17.0 at 7 days in the rest-frame (i.e. ~1 mag fainter than typical for a collapsar-produced supernova at the same time).
Further analysis is in progress.