- GCN Circular #19552
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/LAT GRB 160623A.
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020666
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/LAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
- GCN Circular #19553
G. Vianello (Stanford), F. Dirirsa (UJ), N. Omodei (Stanford), J. L.
Racusin (NASA/GSFC), M. Axelsson (KTH Stockholm), D.Kocevski
(NASA/GSFC)
report on behalf of the Fermi-LAT team:
At 05:00:34.23 UT on June, 23, 2016 Fermi-GBM triggered on GRB 160623A
(trigger 488350837 / 160623209). This burst is also visible in the
Swift/BAT raw count rate light curve, during a slew with no event
capture (D. Palmer/Swift private communication).
As the source came into the field of view of Fermi-LAT 400 s later,
high-energy emission was detected at a position compatible with GRB
160623A.
The best LAT on-ground location is found to be
RA, Dec = 315.24, 42.27 deg (J2000)
with an error radius of 0.1 deg (90 % containment, statistical error only).
The source is very bright in the LAT, with a fading high-energy
emission detected up to approximately 12 ks after the trigger time. We
detect more than 15 photons above 1 GeV.
We note that the LAT position is close to the Galactic plane,
corresponding to (L,B) = (84.17, -2.69) deg. Given the large
uncertainty in the GBM localization, we cannot exclude at this stage
the possibility that the LAT transient is a Galactic transient
unrelated to the GBM GRB. However, as seen by the LAT, the transient
has spectral and temporal properties typical of a long GRB.
A Swift ToO has been requested for this burst.
The Fermi-LAT point of contact for this burst is Feraol Dirirsa
(fdirirsa@uj.ac.za)
The Fermi-LAT is a pair conversion telescope designed to cover the
energy band from 20 MeV to greater than 300 GeV. It is the product of
an international collaboration between NASA and DOE in the U.S. and
many scientific institutions across France, Italy, Japan and Sweden.
- GCN Circular #19554
D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:
The very bright, long-duration GRB 160623A
(Fermi-LAT detection: Vianello et al., GCN 19553)
triggered Konus-Wind at T0=17977.594 s UT (04:59:37.594).
The light curve shows a broad pulse in the interval
from ~T0-25 s to ~T0+30 s, followed by a weaker emission
lasting until ~T0+200 s.
The emission is seen up to ~15 MeV.
As observed by Konus-Wind, the burst had a fluence
of 6.6(-0.1,+0.1)x10^-4 erg/cm2, and a 64-ms peak flux,
measured from T0+9.920 s, of 1.27(-0.03,+0.03)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum (measured from T0 to T0+38.912 s)
is best fit in the 50 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.05 (-0.03,+0.03),
the high energy photon index beta = -2.67 (-0.10,+0.08),
the peak energy Ep = 562 (-23,+23) keV,
chi2 = 107/88 dof.
The spectrum near the peak count rate (measured from T0+7.936
to T0+11.776 s) is best fit in the 50 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.88 (-0.05,+0.05),
the high energy photon index beta = -2.95 (-0.14,+0.11),
the peak energy Ep = 648 (-32,+33) keV,
chi2 = 104/88 dof.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160623_T11977/
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
- GCN Circular #19555
B. Mailyan (UAH), K. Toelge (MPE) and O. Roberts (UCD)
report on behalf of the Fermi GBM Team:
"At 05:00:34.23 UT on 23 June 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160623A (trigger 488350838 / 160623209 ),
which was also detected by the LAT (G. Vianello et al. 2016, GCN 19553)
and Konus-Wind (D. Frederiks et al. 2016, GCN 19554).
The GBM on-ground location is consistent with the LAT position.
The angle from the Fermi LAT boresight at the GBM trigger time is 83
degrees.
The GRB was occulted by the Earth for a large part of its duration, and
the GBM trigger occurred ~50 s after the start of the GRB based on
the Konus-Wind lightcurve.
The GBM light curve consists of a single peak with a duration of about 50 s.
The time-averaged spectrum from T0-4.9 s to T0+32.8 s is
best fit by a power law function. The power law index is -1.60 +/- 0.04.
The event fluence (10-1000 keV) in this time interval is
(5.598 +/- 0.369)E-06 erg/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
- GCN Circular #19558
B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai
(INAF-IASFPA), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), J.A.
Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 160623A (Vianello et al. GCN Circ. 19553),
collecting 1.9 ks of Photon Counting (PC) mode data between T0+40.3 ks
and T0+45.4 ks.
Three uncatalogued X-ray sources are detected, of which one ("Source
1") is above the RASS limit, and is therefore likely the GRB afterglow.
The position of this source is RA, Dec=315.2967, +42.2205 which is
equivalent to:
RA (J2000): 21:01:11.22
Dec(J2000): +42:13:13.7
with an uncertainty of 3.5 arcsec (radius, 90% confidence). This
position is 2.5 arcmin from the Fermi/LAT position.
The light curve can be modelled with a power-law decay with a decay
index of alpha=2.3 (+0.5, -1.4).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.79 (+0.21, -0.20). The
best-fitting absorption column is 1.69 (+0.32, -0.29) x 10^22 cm^-2,
in excess of the Galactic value of 7.2 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 6.3 x 10^-11 (1.1 x 10^-10) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.69 (+0.32, -0.29) x 10^22 cm^-2
Galactic foreground: 7.2 x 10^21 cm^-2
Excess significance: 5.5 sigma
Photon index: 1.79 (+0.21, -0.20)
If the light curve continues to decay with a power-law decay index of
2.3, the count rate at T+24 hours will be 0.12 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.6 x
10^-12 (1.4 x 10^-11) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020666/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020666.
This circular is an official product of the Swift-XRT team.
- GCN/BACODINE POSITION NOTICE
TITLE: GCN/FERMI NOTICE
NOTICE_DATE: Thu 23 Jun 16 23:12:43 UT
NOTICE_TYPE: Fermi-LAT Offline Position
TRIGGER_NUM: 488350838
GRB_RA: 315.240d {+21h 00m 58s} (J2000),
315.393d {+21h 01m 34s} (current),
314.777d {+20h 59m 07s} (1950)
GRB_DEC: +42.220d {+42d 13' 12"} (J2000),
+42.285d {+42d 17' 06"} (current),
+42.023d {+42d 01' 23"} (1950)
GRB_ERROR: 6.00 [arcmin radius, 90% containment, statistical only]
GRB_DATE: 17562 TJD; 175 DOY; 16/06/23
GRB_TIME: 18034.22 SOD {05:00:34.22} UT
TRIGGER_ID: 0x20000000
MISC: 0x40000000
SUN_POSTN: 93.15d {+06h 12m 37s} +23.40d {+23d 24' 18"}
SUN_DIST: 103.61 [deg] Sun_angle= 9.2 [hr] (West of Sun)
MOON_POSTN: 316.51d {+21h 06m 02s} -13.89d {-13d 53' 24"}
MOON_DIST: 56.18 [deg]
MOON_ILLUM: 87 [%]
GAL_COORDS: 84.17, -2.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 338.12, 55.48 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: Fermi LAT Offline position.
COMMENTS: This Notice was ground-generated -- not flight-generated.
COMMENTS: It is the result of human-in-the-loop processing.
COMMENTS: This is a human generated position of a LAT ground detection.
COMMENTS: This source corresponds to GBM trigger.
- GCN Circular #19559
A. Tiengo (IUSS Pavia), G. Vianello (Stanford), P. Esposito (API/UVA),
R. Salvaterra (INAF/IASF Milano)
report on behalf of a larger collaboration:
GRB 160623A was detected by Fermi/LAT on 2016 June 23 (Vianello et al.
GCN Circ. 19553) and its X-ray afterglow was identified by Swift/XRT
(Maselli et al. GCN Circ. 19558).
The XRT observation started on 2016 June 23 at 16:11:43 UT (40.3 ks
after the Fermi trigger) and lasted until 17:37:24, collecting data in
PC mode for a net exposure time of approximately 1.9 ks.
This burst was exceptionally bright and located at low Galactic
latitude (b=-2.6). The total Galactic extinction towards the GRB is Av
= 4.1 according to Schlafly & Finkbeiner 2011, ApJ 737, 103, or 4.8
according to Schlegel et al. 1998, ApJ 500, 525.
A bright X-ray halo with radius of approximately 3.5 arcmin is
clearly visible around the GRB. This halo is possibly composed by
multiple rings produced by dust clouds in our Galaxy that scatter the
GRB X-ray emission.
The observation is too short to detect confidently the expansion of
the halo. From the size of the halo and the time of the GRB, we derive
a distance of about 800 pc for the closest dust structure responsible
for the scattering.
- GCN Circular #19561
A. Pozanenko (IKI), E. Mazaeva (IKI), P. Minaev (IKI), E. Klunko
(ISTP), A. Volnova (IKI), I. Korobtsev (ISTP), report on behalf of
larger GRB follow-up collaboration:
We observed the field of the bright hard GRB 160623A initially reported
by GBM and LAT (Vianello et al., GCN 19553; Mailyan et al., GCN 19555)
and also observed by Konus-Wind (Frederiks et al., GCN 19554) and
SPI-ACS/INTEGRAL with AZT-33IK telescope of Sayan observatory (Mondy)
starting on June, 23 (UT) 18:21:25. We obtained several images in
R-filter under good weather conditions and FWHM of about 1.6 arcsec. At
the edge of XRT error circle (Mingo et al., GCN 19558) we detect a
source which is not presented in USNO-B1.0 and not visible in POSS2
(any filter). Coordinates of the source are (J2000) 21:01:11.57
+42:13:15.8 with uncertainty of 0.7 arcsec. Preliminary photometry is
following
t-T0 Filter Exp. OT(?) Err
(mid, days) (s)
0.56330 R 20*60 19.94 0.07
0.57720 R 20*60 19.94 0.07
0.59112 R 20*60 20.32 0.13
Photometry is based on nearby USNO-B1.0 star
USNO-B.1_id R2
1322-0479855 15.22
Despite a hint of some decaying of the source it is unclear whether
source is an afterglow of GRB 160623A.
A finding chart can be found in
http://grb.rssi.ru/GRB160623A/GRB160623A_160623_Mondy.png
A light curve of SPI-ACS/INTEGRAL can be found in
http://grb.rssi.ru/GRB160623A/GRB160623A_spi-acs.png
- GCN Circular #19567
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC),
Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UNAM),
Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC),
John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:
We observed the field of GRB 160623A (Vianello, et al., GCN 19553) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional
on
Sierra San Pedro M=E1rtir from 2016/06 24.44 to 2016/06 24.47 UTC (29.48
to
30.31 hours after the BAT trigger), obtaining a total of 0.56 hours
exposure in the r and i bands and 0.23 hours exposure in the Z, Y, J, and
H
bands.
For a source on the edge of the Swift-XRT error circle (Mingo, et al., GCN
19558), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the
following detections:
r = 21.12 +/- 0.05
i = 19.77 +/- 0.02
Z = 18.73 +/- 0.02
Y = 18.41 +/- 0.02
J = 17.46 +/- 0.01
H = 16.93 +/- 0.01
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. Comparing our images to the finder
chart reported by Pozanenko, et al. (GCN 19561), we believe this to be the
same optical source. It has apparently faded by about 1 mag in r over the
~16 hours separating our observations.
The source is located at RA, Dec =3D 21:1:11.48, +42:13:14.6 (J2000,
+/-0.5"). Further observations are planned.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro
M=E1rtir.
- GCN Circular #19568
Alice Breeveld (UCL-MSSL) and A. Maselli (INAF-IASFPA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 160623A
40254 s after the LAT trigger (Vianello et al., GCN Circ. 19553).
No optical afterglow consistent with the XRT position (Mingo et al. GCN
Circ. 19558) or the Mondy and RATIR position (Pozanenko et al. GCN Circ.
19561; Butler et al. GCN Circ. 19567) 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 initial
exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
v 40657 51652 2859 >21.1
u 40254 51253 2008 >21.5
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 1.35 in the direction of the
burst (Schlegel et al. 1998).
- GCN Circular #19572
D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima),
K. Ohta (Kyoto) and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:
We observed the field of GRB 160623A (Vianello et al., GCNC 19553;
Tiengo et al., GCNC 19559) with the optical three color
(g', Rc and Ic) CCD camera attached to the Murikabushi 1m telescope
of Ishigakijima Astronomical Observatory.
The observation started on 2016-06-23 15:14:25 UT (~10.2 h after
the burst). We detected the previously reported afterglow
(Pozanenko et al., GCNC 19561; Butler et al., GCNC 19567) in
Rc and Ic bands.
Three sigma upper limit and photometric results of the OT are
listed below. We used GSC2.3 catalog for flux calibration.
#T0+[day] MID-UT T-EXP[sec] g' Rc Rc_err Ic Ic_err
------------------------------------------------------------------
0.42989 15:19:37 540.0 >20.4 18.63 0.06 17.19 0.06
0.45924 16:01:53 480.0 >20.4 18.86 0.09 17.63 0.11
------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
- GCN Circular #19574
E. Mazaeva (IKI), A. Kusakin (Fesenkov Astrophysical Institute), I. Reva
(Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI)
report on behalf of larger GRB follow-up collaboration:
We observed GRB 160623A (Vianello et al., GCN 19553; Mailyan et al.,
GCN 19555; Frederiks et al., GCN 19554) with Zeiss-1000 (East) 1-m
telescopes of Tien Shan Astronomical Observatory. We obtained several
images in R filter starting on June 24 (UT) 19:19:17. We detect optical
transient associated with GRB 160623A (Pozanenko et al., GCN 19561;
Butler et al., GCN 19567). Preliminary photometry of combined image
is following
Date UT start t-T0 Filter Exp. OT Err. UL
(mid, days) (s)
2016-06-24 19:19:17 1.62157 R 40*90 20.57 0.10 22.0
Photometry is based on nearby USNO-B1.0 star
USNO-B.1_id R2
1322-0479881 15.12
1322-0479687 15.57
1322-0479855 15.22
1322-0479927 17.43
1322-0479987 17.39
- GCN Circular #19584
Yuji Urata (NCU/ASIAA), Kuiyun Huang (NTNU), and Glen Petitpas (SMA/SAO)
report:
We observed the GRB 160623A afterglow (Mingo et al. GCN 19558, Butler
et al. 19567) with Submillimeter Array (SMA) on 2016/06/24 (1.1 day
after the Fermi-GBM trigger) and 2016/06/25 (2.2 day). The quick look
image at the 1st epoch shows the bright (~15 mJy) submm afterglow. The
source also shows a gradual fading at the 2nd epoch (corresponding
decay index of ~-0.4).
Further observation is ongoing.
We thank the staff of SMA.
- GCN Circular #19597
K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama,
Y. Yamada (AGU), S. Nakahira (JAXA), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa,
S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR),
M. L. Cherry (LSU), S. Ricciarini (U of Florence) P. S. Marrocchesi (U of Siena) ,
and the CALET collaboration:
The long-duration GRB 160623A (Mailyan et al., GCN Circ. 19555;
Vianello et al. GCN Circ. 19553; Mingo et al. GCN Circ. 19558;
Frederiks et al. GCN Circ. 19554) triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 04:59:34.27 on 23 June 2016. The burst signal
was seen by all CGBM instruments.
The light curve of the SGM shows a bright peak with several overlapping pulses.
The emission starts at T0, peaks at T0+12 sec and ends at T0+40 sec.
The T90 duration measured by the SGM data is 13.5 +- 0.6 sec (40-1000 keV).
The light curve is available at
http://cgbm.calet.jp/cgbm_trigger/flight/1150693129/
The CGBM data used in this analysis are provided by the Waseda CALET Operation Center
located at the Waseda University.
- GCN Circular #19609
K. P. Mooley, T. D. Staley, R. P. Fender (Oxford), G. E. Anderson
(Curtin), T. Cantwell (Manchester), C. Rumsey, D. Titterington, S. H.
Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge),
K. Grainge, A. Scaife (Manchester)
We observed the Fermi/LAT GRB 160623A (Vianello et al., GCN 19553) with
the AMI Large Array at 15 GHz on 2016 Jun 25.15 and Jun 27.15 (UT), 2.0
and 4.0 days post-burst, as part of the 4pisky program. We detect an
uncataloged variable radio source at the XRT location (Mingo et al., GCN
19558) at 5.0+/-0.1 mJy and 6.3+/-0.1 mJy (preliminary) respectively.
Monitoring of this source is underway. We thank the AMI staff for
scheduling these observations. The AMI-GRB database is a log of all GRB
follow up observations with the AMI, and is available at
http://4pisky.org/ami-grb/.
- GCN Circular #19614
A. Moskvitin (SAO RAS, Russia) report on behalf of the larger team.
We observed the field of GRB160623A (Vianello et al., GCNC #19553;
Mailyan et al., GCNC #19555) with the 1-meter telescope Zeiss-1000
of SAO RAS on June, 27.884 (4.676 days after the trigger).
A set of 8 x 300 sec. frames in Rc band were obtained.
The OT (coordinates reported by Pozanenko et al., GCNC #19561)
is clearly visible in the stacked image as the object
with the brightness R = 21.7 +/- 0.2. This estimation is based
on the USNO-B1 stars described by Mazaeva et al. (GCNC #19574).
The finding chart can be found at
ftp://ftp.sao.ru/pub/grb/GRB160623A/GRB160623A_z1000.jpg
- GCN Circular #19661
V. Bhalerao (IUCAA), V. Kumar (IUCAA), D. Bhattacharya (IUCAA), A. R. Rao
(TIFR), S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:
Analysis of Astrosat data showed the detection of very bright GRB 1600623A
(Fermi-LAT detection: Vianello et al., GCN 19553, Mailyan et al., GCN 19555;
Mingo et al. GCN 19558; Frederiks et al. GCN 19554)
The source was clearly detected in the 40-200 keV energy range. The light curve
shows a single peak at UT 04:59:45.0, 49.23 seconds before the fermi trigger At
05:00:34.23 (trigger 488350837 / 160623209). The peak count rate was 2940
counts/sec above the background (four quadrants summed together), with a total
of 20385 counts. The local mean background count rate of 193.2 is counts/sec.
Using cumulative rates, we measure a T90 of 14.2 sec.
CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=node/9 . CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and
PRL. The Indian Space Research Organisation funded, managed and facilitated the
project.
- GCN Circular #19708
D. Malesani (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC and DARK/NBI), M.
De Pasquale (UCL/MSSL), D. A. Kann (TLS Tautenburg), Z. Cano (Univ.
Iceland), D. A. Perley (DARK/NBI), L. Izzo (IAA-CSIC), C. C. Thoene
(IAA-CSIC),
N. Butler (ASU), A. M. Watson (UNAM), A. Kutyrev (GSFC), W. H. Lee
(UNAM), M. G. Richer (UNAM), O. Fox (STScI), J. X. Prochaska (UCSC), J.
S. Bloom (UCB), A. Cucchiara (GSFC/STScI), E. Troja (GSFC), O.
Littlejohns (ASU), E. Ramirez-Ruiz (UCSC), J. A. de Diego (UNAM), L.
Georgiev (UNAM), J. Gonzalez (UNAM), C. Roman-Zuniga (UNAM), N. Gehrels
(GSFC), H. Moseley (GSFC), J. Capone (UMD), V. Zach Golkhou (ASU), and
V. Toy (UMD), on behalf of the RATIR collaboration,
report:
We observed the field of GRB 160623A (Vianello et al., GCN 19553;
Frederiks et al., GCN 19554; Mailyan et al., GCN 19555) with the Nordic
Optical Telescope (NOT) equipped with the AlFOSC imager. Our
observations had a mid time 2016 July 8.09 UT (14.88 days after the GRB
trigger) and consisted of 6x300 s in the SDSS i filter.
Close to the position of the optical and X-ray afterglow (Mingo et al.,
GCN 19558; Pozanenko et al., GCN 19561; Butler et al., GCN 19567), we
detect a bright source at the following coordinates (J2000):
RA = 21:01:11.65
Dec = +42:13:15.0
We measure I = 20.6 +- 0.2 (Vega) against several nearby USNO stars
(error dominated by the calibration). To determine the relation of this
object with the GRB afterglow, we cross-registered our image with those
from RATIR (Butler et al., GCN 19567), yielding an RMS of 0.02". We find
that the NOT source is offset to the SE of the afterglow by 0.7". This
source could thus be the host galaxy or an unrelated, foreground star.
We also note some faint emission in the RATIR image at the NOT
coordinates, despite being blended with the brighter afterglow.
A picture showing the comparison of the two images is shown here:
http://www.astro.ku.dk/~malesani/GRB/160623A/GRB160623A_NOT_RATIR.png
A spectrum (3x1200 s exposure) was acquired using the Gran Telescopio
Canarias (GTC) equipped with OSIRIS, covering the wavelength range
5100-10,000 AA (grism R1000R), starting on 2016 July 10.163 UT (16.95
days after the GRB). The slit was centered at the coordinates of the NOT
object, but also partially overlapped with the afterglow location.
We detect continuum over the whole wavelength range and two emission
lines in the red part of the spectrum, which we interpret as Halpha and
[N II] at a common redshift z = 0.367. At the same redshift we also
detect weak [O III] 5008 (dimmed by the large foreground extinction).
This is most likely the redshift of GRB 160623A.
The source detected in the NOT image is possibly a foreground star (the
Galactic latitude is b = -2.7 deg). In the GTC acquisition image, the
object is pointlike with a seeing of 1.2". On the other hand, inspecting
the 2D spectrum, the spatial profile of the emission lines is different
from that of the continuum: the features are wider and elongated towards
the position of the afterglow. A compact host cannot however be excluded.
At z = 0.367, a SN as bright as SN 1998bw would only reach a peak
magnitude of I ~ 24.8 (Vega) given the large Galactic extinction (A_I =
2.2 mag; Schlafly & Finkbeiner 2011). From ground, such a SN would be
difficult to distinguish against the brighter foreground object.
We acknowledge excellent support from the observers at the NOT (in
particular Roi Alonso and Diego Hidalgo) and at the GTC.
- GCN Circular #19710
A. J. Castro-Tirado (IAA-CSIC), A. F. Valeev (SAO-RAS), S. Jeong (SKKU),
R. S=E1nchez-Ram=EDrez (IAA-CSIC), V. V. Sokolov (SAO-RAS), P. Ferrero
(IAA-CSIC), J. C. Tello (IAA-CSIC), Y. Hu (IAA-CSIC), B.-B. Zhang
(IAA-CSIC), A. Pozanenko (IKI-RAS), S. R. Oates (U. of Warwick), S.
Geier (GTC) and G. Lombardi (GTC), on behalf of a larger collaboration,
report:
Following the detection of GRB 160623A by Fermi (Vianello et al. GCNC
19553) and Konus-Wind (Frederiks et al. GCNC 19554), we observed the
optical afterglow of GRB 160623A (Pozanenko et al. GCNC 19561) with the
10.4m Gran Telescopio Canarias (GTC), gathering spectra at different
epochs: June 25 (1.9 days post-burst) and July 3/4, with both the R1000B
and R2500I grisms covering the range 3800-10000 A. At the position of
the afterglow, the reddest spectrum (2 x 1200s with R2500I) showed
H-alpha and [SII] in emission, from which we determine a redshift z =
0.367, confirming the value proposed by Malesani et al. (GCNC 19708).
The bluest range spectrum (1200s) also revealed a marginal detection of
H-beta (taking into account the high foreground Galactic extinction in
the line of sight). The faint continuum on the first epoch spectrum
extended down to 3800 A with no absorption lines being present.
Therefore we propose this is the redshift of the GRB 160623A host
galaxy.
We acknowledge excellent support from the GTC staff.
- GCN Circular #19848
A.J Nayana (NCRA-TIFR), Poonam Chandra (NCRA-TIFR), A. R. Rao (TIFR), Dipankar
Bhattacharya (IUCAA) and Varun Bhalerao (IUCAA) report:
We carried out Giant Metrewave Radio Telescope (GMRT) observations of GRB 160623A
(Vianello et al. GCN Circ. 19553) at 1460 MHz band on 2016 Aug 04.91 UT. We detect a
4.5-sigma source at the GRB position (Vianello et al. GCN Circ. 19553) with a flux
density of 207+/-78 uJy. This is most likely the radio afterglow of GRB 160623A. Map rms
is 50 uJy.
We thank GMRT staff for making these observations possible.
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