GRB 150818A
GCN Circular 18244
Subject
GRB 150818A: TSHAO and SAO RAS optical observations
Date
2015-09-07T09:29:09Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), A. Moskvitin (SAO RAS), I. Reva (Fesenkov
Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical
Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of
larger GRB follow-up collaboration:
We are continuing observations the field of Swift GRB 150818A (D'Elia et
al., GCNC 18152) with Zeiss-1000 1-m telescope of Tien Shan
Astronomical Observatory and Zeiss-1000, 1-m telescope of SAO RAS. The
optical transient (Marshall et al. GCN 18155; McCauley et al. GCN 18161;
Mazaeva et al. GCN 18175; Sanchez-Ramirez et al. GCN 18177; Mazaeva et
al. GCN 18182, GCN 18189, GCN 18205; Schulze et al. GCN 18179) is
clearly visible on combined images in each epochs. The updated light
curve of Supernova (de Ugarte Postigo et al. GCN 18213; Mazaeva et al.
GCN 18205) + host galaxy (Sanchez-Ramirez et al., GCN 18177; de Ugarte
Postigo et al. GCN 18213) can be found in
http://grb.rssi.ru/GRB150818A/GRB150818A_R_lc.png
The evident maximum of SN brightness (in Rc-filter) was on ~ Sep. 1-2,
and the brightness of SN+host galaxy was R ~ 21.1 +/- 0.1 on Sep. 6 (UT)
18:00. We are grateful to V.P. Goranskiy for assistance in SAO RAS
observations.
GCN Circular 18213
Subject
GRB 150818A: Spectroscopic confirmation of the SN from GTC
Date
2015-08-31T17:49:21Z (11 years ago)
From
Antonio de Ugarte Postigo at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), Z. Cano (U. Iceland),
D. A. Perley (DARK/NBI), S. Schulze (PUC, MAS), D. Xu (NAOC/CAS),
R. Sanchez-Ramirez (IAA-CSIC), D. Malesani (DARK/NBI), G. Lombardi
(GRANTECAN, IAC, ULL), and A. Garcia (GRANTECAN), R. Scarpa
(GRANTECAN) report on behalf of a larger collaboration:
We observed the counterpart of GRB 150818A (D'Elia et al. GCN 18152;
Marshall et al. GCN 18155; McCauley et al. GCN 18161; Mazaeva et al.
GCN 18175; Sanchez-Ramirez et al. GCN 18177; Mazaeva et al. GCN
18182, GCN 18189, GCN 18205; Schulze et al. GCN 18179) with the
10.4 m GTC telescope (+OSIRIS) on the 29th August 2015 (11.4 days
after the burst). The observation consisted of 3x900 s spectroscopy using
the R1000B grism (3700-7800 AA coverage with a resolution of ~1000)
plus g-, r- and i-band imaging. We detect a point-like source at the location
of the afterglow superposed on top of an extended source.
The combined spectrum shows broad features typical of a broad-lined
Type Ic SN near maximum light, thus confirming the detection of a rising
supernova proposed by Mazaeva et al. (GCN 18205). The spectrum also
shows narrow emission features of [OII], [OIII] and H-beta at z=0.282
(Sanchez-Ramirez et al. GCN 18177).
GCN Circular 18205
Subject
GRB 150818A: possible SN rise in light curve of Mondy observations
Date
2015-08-27T16:54:50Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev
(ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up
collaboration:
We continue observations of the Swift GRB 150818A (D'Elia et al., GCN
18152) with AZT-33IK telescope of Sayan observatory (Mondy). We
imaged optical transient (Marshall et al., GCN 18155; McCauley et al.,
GCN 18161; Schulze et al., GCN 18164; Mazaeva et al., GCN 18175) in
R-filter on Aug., 21, 22, 23, and 26. The optical transient is clearly
visible in each epochs. Preliminary light curve of the optical transient
can be found in
http://grb.rssi.ru/GRB150818A/GRB150818A_R_lc.png
(Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al.,
GCN 18175).
One can suggest that steady re-brightening of the optical transient is
related to a Supernova associated with nearby GRB 150818A (z = 0.282,
Sanchez-Ramirez et al., GCN 18177). We encourage observation for
spectroscopic SN-confirmation.
GCN Circular 18198
Subject
Konus-Wind observation of GRB 150818A
Date
2015-08-24T09:58:14Z (11 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, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 150818A (Swift-BAT trigger #652603:
D'Elia, et al., GCN Circ. 18152; Palmer, et al., GCN Circ. 18157)
was detected by Konus-Wind in the waiting mode.
The burst light curve shows a single pulse
with a total duration of about 47 s.
As observed by Konus-Wind, the burst had a fluence of
5.3(-0.6,+0.7)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(BAT)-3.3 s, of 1.8(-0.3,+0.4)x10^-7 erg/cm2/s
(both in the 20 - 1000 keV energy range).
Modeling the K-W 3-channel time-integrated spectrum
(from T0(BAT)-6.2 s to T0(BAT)+40.9 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.4(-0.2,+0.6) and Ep = 100 (-18,+29) keV.
The K-W light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB150818A/
Assuming the redshift z=0.282 (Sanchez-Ramirez, et al., GCN 18177)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.0x10^51 erg,
the peak luminosity L_iso is ~3.6x10^49 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~128 keV.
All the quoted errors are at 1 sigma confidence level.
All the quoted values are preliminary.
GCN Circular 18189
Subject
GRB 150818A: continued Mondy optical observations
Date
2015-08-21T15:39:24Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev
(ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up
collaboration:
We continue observations of the of Swift GRB 150818A (D'Elia et al.,
GCNC 18152) with AZT-33IK telescope of Sayan observatory (Mondy). We
obtained several images in R-filter starting on Aug., 20 (UT)
16:54:32. The optical transient (Marshall et al., GCN 18155; McCauley
et al., GCN 18161; Schulze et al., GCN 18164; Mazaeva et al., GCN
18175) is clearly visible. Preliminary photometry of the optical
transient is following
Date UT start t-T0 Filter Exp. OT Err.
(mid, days) (s)
2015-08-20 16:54:32 2.23334 R 15*120 21.15 0.09
Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al.,
GCN 18175).
The continued shallow decay mentioned in Schulze et al. (GCN 18179)
indeed can be explained by underlying host galaxy (Sanchez-Ramirez et
al., GCN 18177).
GCN Circular 18182
Subject
GRB 150818A: Mondy optical observations
Date
2015-08-20T17:24:54Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev (ISTP),
A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We continue observations of the of Swift GRB 150818A (D'Elia et al., GCNC
18152) with AZT-33IK telescope of Sayan observatory (Mondy). We obtained
several images in R-filter starting on Aug., 19 (UT) 15:33:10. The
optical transient (Marshall et al., GCN 18155; McCauley et al., GCN 18161;
Schulze et al., GCN 18164; Mazaeva et al., GCN 18175) is clearly visible.
Preliminary photometry of the optical transient is following
Date UT start t-T0 Filter Exp. OT Err.
(mid, days) (s)
2015-08-19 15:33:10 1.18517 R 30*120 21.0 0.1
Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al., GCN
18175)
GCN Circular 18179
Subject
GRB 150818A: Continued NOT monitoring - afterglow confirmation
Date
2015-08-20T10:59:44Z (11 years ago)
From
Steve Schulze at U of Iceland <sts30@hi.is>
S. Schulze (PUC, MAS), J. P. U. Fynbo, D. Malesani (DARK/NBI), R. Tuma, S. Dinh, M. Homann, M. Munoz (NBI) and P. Jakobsson (U. Iceland) report on behalf a larger collaboration:
We observed the field of GRB 150818A (D'Elia et al., GCN 18152) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained a 300-s image in R band. Observations started at 21:03 UT on August 19 (i.e. 1.39 days after the burst).
We clearly detect the source reported in Marshall et al. (GCN 18155), McCauley et al. (GCN 18161), Schulze et al. (GCN 18164) and Mazaeva et al. (GCN 18175). We measure R=21.18 +/- 0.05 calibrated against several USNO stars. The optical transient faded by 0.3 mag compared to Schulze et al. (GCN 18164) in agreement with Mazaeva et al. (GCN 18175) who also found evidence for a shallow decay. Sanchez-Ramirez (GCN 18177) hinted that the host is possibly detected in GTC image. A significant host contribution would explain the shallow decay.
[GCN OPS NOTE(20aug15): Per author's request, the 18177 id_num for the S-R reference was added.]
GCN Circular 18177
Subject
GRB 150818A: 10.4m GTC spectroscopy and host galaxy
Date
2015-08-19T22:15:53Z (11 years ago)
From
Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>
R. Sanchez-Ramirez (UPV/EHU, IAA-CSIC), J. Gorosabel (+, UPV/EHU,
IAA-CSIC), D. Perez-Ramirez (+, Univ. de Jaen), S. Jeong (IAA-CSIC, SKKU),
A. J. Castro-Tirado (IAA-CSIC, ISA-UMA), F. J. Aceituno, R. Cunniffe, P.
Ferrero, Y. Hu, S. R. Oates, J. C. Tello, B.-B. Zhang (IAA-CSIC), M.
Jelinek (ASU-CAS), S. Guziy (Nikolaev Univ.), V. Sokolov (SAO-RAS), J.M.
Castro Ceron (ESAC), J. Cepa (IAC), A. Garcia (GRANTECAN) and R. Scarpa
(IAC, GRANTECAN), report:
Following the detection of GRB 150818A by Swift/BAT (D Elia et al. 2015,
GCNC 18152), we have obtained an optical spectrum (2 x 900s) with the
10.4m GTC telescope (+OSIRIS) in La Palma (Spain), starting on Aug 18,
22:05 UT (i.e. 10.5 hr postburst), covering the 3700-7800 A wavelength
range. The slit included the position of the proposed optical afterglow
(Marshall and D Elia, GCNC 18155; Schulze et al., GCNC 18164; Mazaeva et
al. GCNC 18175).
At the position of the optical afterglow, we see no obvious absorption
features with the continuum extending from 3700 to 7800 A. However we
clearly detect emission lines of [OII] 3727A, H-beta and [OIII]
4960A,5008A, all at a common redshift z = 0.282. Indeed a diffuse object
seems to be adjacent (within 1� to the west) to the optical afterglow in
the acquisition image (under 0�.7 seeing), which could be the host galaxy
at the above mentioned redshift.
Further spectroscopy and monitoring at all wavelengths is encouraged to
search for the emergence of the underlying supernova component in the next
weeks.
GCN Circular 18175
Subject
GRB 150818A: Mondy optical observations
Date
2015-08-19T16:25:12Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev
(ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up
collaboration:
We observed the field of Swift GRB 150818A (D'Elia et al., GCNC 18152)
with AZT-33IK telescope of Sayan observatory (Mondy) starting on Aug.,
18 (UT) 15:07:42. We obtained several images in R-filter of 120 s
exposure. The source previously mentioned (McCauley et al., GCN 18161;
Schulze et al., GCN 18164) is clearly visible. Coordinates of the
source are (J2000) 15:21:25.56 +68:20:32.0 with uncertainty of 0.3
arcsec in both coordinates. Preliminary photometry of the source is
following
Date UT start t-T0 Filter Exp. OT Err.
(mid, days) (s)
2015-08-18 15:07:42 0.16843 R 31*120 20.25 0.08
Photometry is based on USNO-B1.0 stars:
USNO-B.1_id R2
1583-0162302 16.65
1583-0162268 17.48
1583-0162214 16.71
1583-0162248 19.43
We can suggest the source as shallow fading afterglow because the source
is significantly faded between our observations (R=20.25+/-0.08 at 4 hrs
after burst trigger) and NOT observations at 9.62 hrs (Schulze et al.,
GCN 18164).
GCN Circular 18174
Subject
GRB 150818A: MITSuME Ishigakijima upper limits
Date
2015-08-19T14:55:43Z (11 years ago)
From
Daisuke Kuroda at OAO/NAOJ <dikuroda@oao.nao.ac.jp>
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 150818A (D'Elia et al., GCNC 18152)
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 2015-08-18 13:09:10 UT (~1.5h after the burst).
We could not detect the previously reported afterglow
(Marshall and D'Elia, GCNC 18155; McCauley et al., GCNC 18161;
Schulze et al., GCNC 18164) in all the three bands.
Three sigma upper limits of the OT are listed below.
We used GSC2.3 catalog for flux calibration.
#T0+[day] MID-UT T-EXP[sec] g' Rc Ic
-----------------------------------------------------
0.11943 14:28:30 6180.0 >19.4 >19.7 >19.5
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
GCN Circular 18171
Subject
GRB 150818A: MITSuME Akeno optical upper limits
Date
2015-08-19T12:38:55Z (11 years ago)
From
Taketoshi Yoshii at Tokyo Tech <yoshii.t.ac@m.titech.ac.jp>
T.Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi, Y. Yano,
S. Kurita, Y.Ono, S.Harita,Y.Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 150818A (V. D'Elia et al. GCN Circular #18152) with the
optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2015-08-18 11:54:53 UT (~18 min after the burst).
We did not find any new point source within XRT circle in all three bands.
We obtained following limits for the magnitudes.
T0+[sec] MID-UT T-EXP[sec] g' Rc Ic
---------------------------------------------------------------------------------------
1101 11:59:46 540 >19.4 >19.4 > 18.5
---------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration
GCN Circular 18166
Subject
GRB 150818A: Swift-XRT update, correction to GCN 18162
Date
2015-08-19T07:17:42Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U, Leicester) reports on behalf of the Swift-XRT team:
Due to a computer error, the light curve decay index was missing in GCN
18162.
At the present time, we have analysed 7.6 ks of XRT data for GRB 150818A
(D'Elia et al. GCN Circ. 18152), from 74 s to 44.1 ks after the BAT trigger.
The XRT light curve can be modelled as a broken power-law, with an
initial decay index of 2.36 (+0.08, -0.06), a break at T0 + 3600
(+/-500) s, and a subsequent shallow decay of 0.66 (+0.16, -0.15).
If the decay continues at alpha=0.66, the predicted count-rate at T0+24
hrs is 8.9e-3 ct/sec, which corresponds to an observed (unabsorbed)
0.3-10 keV flux of 2.97e-13 (3.56e-13) erg/cm^2/s.
This circular is an official product of the Swift-XRT team.
GCN Circular 18164
Subject
GRB150818A: NOT imaging
Date
2015-08-19T01:04:40Z (11 years ago)
From
Steve Schulze at U of Iceland <sts30@hi.is>
S. Schulze (PUC, MAS), J. P. U. Fynbo (DARK, NBI), T. Kruehler (MPE), D. Malesani, (DARK/NBI), I. V. Rasmussen, J. L. Marcher, L. L. Thomson (NBI), A. Djupvik (NOT), B. Milvang-Jensen (DARK/NBI) and P. Jakobsson (U Iceland) report on behalf a larger collaboration:
We observed the field of GRB 150818A (D'Elia et al., GCN 18152) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained a 180 s and a 3x300 s image in R band. Observations started at 21:34 UT on August 18 (i.e. 9.62 hr after the burst).
We clearly detect the source reported in Marshall et al. (GCN 18155) and McCauley et al. (GCN 18161). We measure R=20.86 +/- 0.08 mag calibrated against several USNO stars. This value is not corrected for foreground extinction.
Given the lack of evidence for variability (McCauley et al., GCN 18161), the association of this object with GRB 150818A remains unclear.
GCN Circular 18162
Subject
GRB 150818A: Swift-XRT refined Analysis
Date
2015-08-18T23:54:04Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), A. D'ai
(INAF-IASFPA), A. Maselli (INAF-IASFPA), L.M. McCauley (PSU), J.A.
Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U. Leicester)
and V. D'Elia report on behalf of the Swift-XRT team:
We have analysed 6.4 ks of XRT data for GRB 150818A (D'Elia et al. GCN
Circ. 18152), from 74 s to 21.7 ks after the BAT trigger. The data
comprise 34 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 Beardmore
et al. (GCN Circ. 18159).
The late-time light curve (from T0+3.5 ks) can be modelled with a
power-law decay with a decay index of alpha=.
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.59 (+0.11, -0.10). The
best-fitting absorption column is 2.33 (+0.28, -0.27) x 10^21 cm^-2,
in excess of the Galactic value of 2.5 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.96 (+0.30, -0.27)
and a best-fitting absorption column of 7.6 (+7.6, -5.1) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.3 x 10^-11 (3.9 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 7.6 (+7.6, -5.1) x 10^20 cm^-2
Galactic foreground: 2.5 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.96 (+0.30, -0.27)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00652603.
This circular is an official product of the Swift-XRT team.
GCN Circular 18161
Subject
GRB 150818A: Swift/UVOT Detection
Date
2015-08-18T20:39:33Z (11 years ago)
From
Marissa McCaule at PSU <marissamc@swift.psu.edu>
L. M. McCauley (PSU), L. M. Z. Hagen (PSU), and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150818A
94 s after the BAT trigger (D'Elia et al., GCN Circ. 18152).
A source consistent with the XRT position (Beardmore et al. GCN Circ. 18159)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 15:21:25.43 = 230.35594 (deg.)
Dec (J2000) = +68:20:33.0 = 68.34251 (deg.)
with an estimated uncertainty of 0.66 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits 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_fc 94 121 27 19.39+-0.25
white 3414 4790 344 19.92+-0.17
white 10222 10826 590 19.68+-0.07
v 3572 5201 393 >19.36
b 4385 4585 196 >20.16
b 5821 10217 927 20.56+-0.33
u 4180 4379 196 >19.66
u 5616 5816 196 19.63+-0.25
uvw1 3976 4175 195 18.78+-0.20
uvw1 5411 5611 196 18.95+-0.20
uvm2 3776 3976 192 18.81+-0.23
uvm2 5206 5406 196 18.89+-0.24
uvw2 4796 4996 196 18.90+-0.19
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 18159
Subject
GRB 150818A: Enhanced Swift-XRT position
Date
2015-08-18T18:09:34Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 2975 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 150818A, 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 = 230.35595, +68.34204 which is equivalent
to:
RA (J2000): 15h 21m 25.43s
Dec (J2000): +68d 20' 31.4"
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 18157
Subject
GRB 150818A: Swift-BAT refined analysis
Date
2015-08-18T17:25:59Z (11 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
V. D'Elia (ASDC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 150818A (trigger #652603)
(D'Elia, et al., GCN Circ. 18152). The BAT ground-calculated position is
RA, Dec = 230.340, 68.342 deg, which is
RA(J2000) = 15h 21m 21.7s
Dec(J2000) = +68d 20' 31.5"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 36%.
The mask-weighted light curves shows two overlapping peaks starting at ~T-25 sec,
peaking at ~T+1 sec, and ending at ~T+180 sec.
T90 (15-350 keV) is 123.3 +- 31.3 sec (estimated error including systematics).
The time-averaged spectrum from T-11.18 to T+165.12 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.96 +- 0.09. The fluence in the 15-150 keV band is 4.1 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.88 sec in the 15-150 keV band
is 2.4 +- 0.3 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/652603/BA/
GCN Circular 18155
Subject
GRB 150818A: Swift/UVOT candidate afterglow
Date
2015-08-18T14:59:35Z (11 years ago)
From
Frank Marshall at GSFC <femarsha@khamseen.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:
UVOT took a finding chart exposure of 28 seconds with the White filter
starting 94 seconds after the BAT trigger on GRB 150818A.
There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 15:21:25.48 = 230.35616
DEC(J2000) = 68:20:34.0 = 68.34278
with a 90%-confidence error radius of about 1.0 arc sec. This position is 10
arcseconds from the center of the XRT error circle (D'Elia et al. GCN Circ. 18152).
The estimated magnitude is 19.5 with a 1-sigma error of about 0.2.
No correction has been made for extinction.
GCN Circular 18154
Subject
GRB 150818A: Planned XMM-Newton observation
Date
2015-08-18T13:44:25Z (11 years ago)
From
Norbert Schartel at XMM-Newton/ESA <too@xmm.esac.esa.int>
XMM-Newton will observe GRB 150818A at location
(RA=15h 21m 26.9s, DEC=68d 20' 40.5", J2000),
starting at 18:15:45 UT, on August 18, 2015,
for an exposure of 22400 seconds.
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GCN Circular 18152
Subject
GRB 150818A: Swift detection of a burst
Date
2015-08-18T11:53:55Z (11 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
V. D'Elia (ASDC), A. A. Breeveld (UCL-MSSL),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
L. Izzo (URoma/ICRA), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB/PSU) report on
behalf of the Swift Team:
At 11:36:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150818A (trigger=652603). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 230.446, +68.342 which is
RA(J2000) = 15h 21m 47s
Dec(J2000) = +68d 20' 32"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single-peaked
structure with a duration of about 50 sec. The peak count rate
was ~1990 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 11:37:57.3 UT, 84.5 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 230.3621, 68.3446 which is equivalent to:
RA(J2000) = +15h 21m 26.90s
Dec(J2000) = +68d 20' 40.6"
with an uncertainty of 6.1 arcseconds (radius, 90% containment). This
location is 111 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.
UVOT took a finding chart exposure of 28 seconds with the White
filter starting 94 seconds after the BAT trigger. No credible
afterglow candidate has been found in the initial data products. The
2.7'x2.7' sub-image processing failed because of no aspect solution
is available. Results from the list of sources generated on-board
are not available at this time.
Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it).
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.)