- GCN Circular #17619
J. R. Cummings (CPI) on behalf of the Swift-BAT science team
At 09:28:38, Swift-BAT triggered (635929) on GRB 150323B. Imaging attempts
were prematurely terminated by a preplanned slew. A bright source
was detected in ground analysis at 260.447, +38.316, which is
RA (J2000) 17h 21m 47.3s
Dec (J2000) 38d 18' 59"
with an estimated 90% error radius of 1.5 arcmin.
The burst had multiple peaks with a T90 of about 60 seconds. We have
event data for only the first peak.
This is the same event as Fermi GBM 448795722. A Swift TOO has been
requested.
- GCN Circular #17620
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Swift/BAT GRB 150323B.
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020485
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 Swift/BAT 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 #17623
A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team:
"At 09:28:39.21 UT on 23 March 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150323B (trigger 448795722 / 150323395),
which was also detected by the Swift (Cummings et al. 2015, GCN 17619).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 69 degrees.
The GBM light curve consists of multiple peaks
with a duration (T90) of about 54 s (50-300 keV).
The time-averaged spectrum from T0-0.512 s to T0+60.929 s is
best fit by a Band function with Epeak = 99.14 (+4.50/-6.02) keV,
alpha = -0.89 (+0.07/-0.05), and beta = -2.04 (+0.03/-0.03).
The event fluence (10-1000 keV) in this time interval is
(2.19 +/- 0.03)E-05 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+1.152 s in the 10-1000 keV band
is 8.2 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
- GCN Circular #17634
P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), M. de Pasquale (INAF-IASFPA),
D.N. Burrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Swift/BAT-detected burst GRB 150323B (Cummings et al. GCN Circ. 17619),
collecting 4.6 ks of Photon Counting (PC) mode data between T0+40.4 ks
and T0+63.2 ks.
Two uncatalogued X-ray sources have been detected inside or close to
the Swift/BAT error region, however none of them is above the RASS
limit or shows definitive signs of fading. Therefore, at the present
time we cannot identify which, if any, is the afterglow. Details of
these sources are given below:
Source 1:
RA (J2000.0): 260.4534 = 17:21:48.83
Dec (J2000.0): +38.3179 = +38:19:04.6
Error: 4.3 arcsec (radius, 90% conf.)
Count-rate: 0.0103 +/- 0.0018 ct s^-1
Flux: (4.62 +/- 0.80)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Source 2:
RA (J2000.0): 260.4598 = 17:21:50.35
Dec (J2000.0): +38.2829 = +38:16:58.5
Error: 6.6 arcsec (radius, 90% conf.)
Count-rate: (2.3 +/- 1.0)e-3 ct s^-1
Flux: (9.2 +/- 4.1)e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020485.
This circular is an official product of the Swift-XRT team.
- GCN Circular #17638
L. P. Xin, X. F. Wang, J. Y. Wei, Y. L. Qiu, J. S. Deng,
J. Wang, X. H. Han and C. Wu on behalf of EAFON report:
We began to observe GRB 150323B (Cumming., GCN 17619; Kienlin., GCN 17623)
with Xinglong 0.8-m TNT telescope at 2015-03-23, 18:19:24(UT),
about 8.85 hour after the Swift trigger time.
No any new source was detected in our 10*300sec coadded image
within the errorbox of BAT (Cumming., GCN 17619),
and the errorbox of two uncatalogured X-ray sources (Avanzo et al., 17632)
down to the 3 sigma limit of 21.8 mag in R-band, calibrated by USNO B1.0 R2 mag,
at the mean time of 9.28 hours after the burst.
We noted that there was a source in USNO B1.0 catalog
( 17:21:50.446 +38:17:00.13 R2=20.5 mag ),
which was located in the errorbox of the Source 2 (Avanzo et al., 17632),
but the variation of its brightness was not decided.
The message may be cited.
- GCN Circular #17641
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 long-duration GRB 150323B
(Swift-BAT trigger #635929: Cummings, GCN 17619;
Fermi-GBM observation: von Kienlin, GCN 17623)
triggered Konus-Wind at T0=34121.196 s UT (09:28:41.196).
The burst light curve shows several bright peaks during first ~60 s
after the trigger.
In the instrument's soft energy channel, the flaring can be traced up to
~T0+150 s.
As observed by Konus-Wind, the burst
had a fluence of 2.0(-0.1,+0.2)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+22.656 s,
of 1.4(-0.6,+0.6)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst
(measured from T0 to T0+65.792 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.53(-0.10,+0.11),
and Ep = 109(-12,+15) keV (chi2 = 109/98 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.90 (chi2 = 109/97 dof).
The spectrum near the peak count rate
(measured from T0+16.640 to T0+24.832 s)
is best fit in the 20 keV - 1 MeV range
by the power law with exponential cutoff model
with alpha = -1.15(-0.25,+0.29),
and Ep = 215(-51,+108) keV (chi2 = 35/59 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -1.97 (chi2 = 35/58 dof).
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150323_T34121/
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
- GCN Circular #17643
J. Kelemen (kelemen at konkoly.hu) on behalf of the GRB OT observing program
at the Konkoly Observatory.
Starting on the night 24/03/2015 02:48 UT we observed the field GRB 150323B
(J. R. Cummings GCN 17619 ). We imaged the X-ray positions published by P.
D'Avanzo et al. GCN 17634.
On the coadded R band images (total exposure = 1500 sec) we found marginal
optical sources on the positions coincide with soure 1 and source 2.
Source 1 /GCN 17634/ our work R mag.(Based on USNO-B1.0 stars)
--------------------------------------------------------
RA: 17:21:48.83 RA: 17:21:48.62 20.8 +/-0.14
DEC: 38:19:04.6 DEC: 38:19:08.8
Source 2 /GCN 17634/ our work R mag.(Based on USNO-B1.0 stars)
--------------------------------------------------------
RA: 17:21:50.35 RA: 17:21:50.47 19.9 +/-0.14
DEC: 38:16:58.5 DEC: 38:16:59.7
Due to the bad weather variability was not confirmed.
- GCN Circular #17649
E. Mazaeva (IKI), S. Schmalz (AIP), N. Tungalag (Research Center of
Astronomy and Geophysics MAS), A. Volnova (IKI), I.Molotov (KIAM), A.
Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of GRB 150323B (Cummings et al., GCN 17619) with
ORI-40 telescope of Khureltogot observatory starting on Mar., 23 (UT)
16:06:11. We obtained 60 unfiltered images of 60 s exposure. Following
detection of XRT sources (D'Avanzo et al., GCN 17634) we do not detect
any source within XRT error circle of the source #1 up to a limiting
magnitude 21.2. In particular we do detect the optical source found by
Kelemen et al. (GCN 17643). At the position of XRT source #2 we found
optical source which coincides with USNO star mentioned by Xin et al.
(GCN 17638) and the star of SDSS DR9 catalog J172150.45+381700.1.
Photometry of the sources is following
Source# Date UT start t-T0 Filter Exp. mag. UL(3sigma)
(mid, days) (s)
1 2015-03-23 16:06:11 0.29859 none 60*60 n/d 21.2
2 2015-03-23 16:06:11 0.29859 none 60*60 20.7+/-0.25 21.2
The photometry is based on R magnitudes of nearby SDSS DR9 stars
SDSS9_id R(Lupton)
J172146.77+381659.6 15.65
J172126.47+382201.1 18.14
J172127.98+382239.0 15.39
- GCN Circular #17657
P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), M. de Pasquale (INAF-IASFPA),
D.N. Burrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:
Swift-XRT has conducted further observations of the field of the
Swift/BAT-detected burst GRB 150323B (Cummings et al. GCN Circ. 17619).
The observations now extend from T0+40.4 ks to T0+483.5 ks.
Of the sources reported by D'Avanzo et al. (GCN Circ. 17634), "Source
1" is fading with 3-sigma significance, and is therefore likely the GRB
afterglow. The position of this source is RA, Dec=260.4534, +38.3179
which is equivalent to:
RA (J2000): 17:21:48.83
Dec(J2000): +38:19:04.6
with an uncertainty of 4.3 arcsec (radius, 90% confidence). This
position is 18 arcsec from the Swift/BAT position. The source is
fading with alpha >0.3.
The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020485/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020485.
This circular is an official product of the Swift-XRT team.
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