- GCN Circular #17404
J. R. Cummings (CPI.com) on behalf of the Swift science team
At 06:31:08, a GRB occurred during a preplanned Swift slew. This was the same
event as Fermi GBM trigger 444724270. A mosaic of images from BAT photon event
data revealed a bright source at RA, Dec 160.241, -64.043, which is:
RA (J2000) 10h 40m 57.8s
Dec (J2000) -64d 02' 34"
with an estimated 90% uncertainty radius of 1.5 arcmin.
The burst was a single symmetric cusp that lasted about 13 seconds.
A Swift TOO has been requested.
- GCN Circular #17406
M. Stamatikos (OSU), C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (CPI.com), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),
T. Sakamoto (AGU), J. Tueller (GSFC),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
We report further analysis of GRB 150204A. The best BAT position is the same
as reported earlier (Cummings, GCN # 17404), RA, Dec 160.241, -64.043, which is:
RA (J2000) 10h 40m 57.8s
Dec (J2000) -64d 02' 34"
with an estimated 90% uncertainty radius of 1.5 arcmin. The source was 77% coded
at the time of the burst.
The burst was a single symmetric cusp. T90 was 12 +- 2 seconds.
A simple powerlaw function is the best fit to the BAT spectrum. The photon index
is 1.62 +- 0.10. The fluence from 15 to 150 keV in 13 seconds was
(8.0 +- 0.4) x 10^-7 ergs/cm^2. The 1-second peak flux in this energy range was
1.85 +- 0.12 photons/cm^2. All uncertainties are 90% confidence.
A Swift TOO has been approved.
- GCN Circular #17407
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Swift/BAT GRB 150204A.
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020477
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 #17408
E. Burns (UAH) and H.-F. Yu (MPE)
report on behalf of the Fermi GBM Team:
"At 06:31:07.88 UT on 04 February 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150204A (trigger 444724270 / 150204272) which
was also found in ground analysis of Swift/BAT data
(Cummings et al. 2015, GCN 17404). The GBM on-ground location is
consistent with the Swift position. The angle from the Fermi LAT boresight
is 54 degrees.
The GBM light curve consists of one main peak
with a duration (T90) of about 10 s (50-300 keV).
The time-averaged spectrum from T0-6.144 s to T0+7.168 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.4 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 350 +/- 143 keV
The event fluence (10-1000 keV) in this time interval is
(2.2 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.064 s in the 10-1000 keV band
is 3.1 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
- GCN Circular #17409
A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), M.C. Stroh (PSU),
D.N. Burrows (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), C.
Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo
(INAF-OAB) 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 150204A (Cummings et al. GCN Circ. 17404),
collecting 4.4 ks of Photon Counting (PC) mode data between T0+51.2 ks
and T0+63.6 ks.
One uncatalogued X-ray source has been detected inside or close to the
Swift/BAT error region, it is below the RASS limit and shows no
definitive signs of fading. Therefore, at the present time we cannot
confirm this as the afterglow. Details of this source are given below:
Source 2:
RA (J2000.0): 160.2373 = 10:40:56.94
Dec (J2000.0): -64.0387 = -64:02:19.4
Error: 4.8 arcsec (radius, 90% conf.)
Count-rate: (8.9 +/- 1.8)e-3 ct s^-1
Flux: (3.69 +/- 0.75)e-13 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/00020477.
This circular is an official product of the Swift-XRT team.
- GCN Circular #17411
A. Breeveld (MSSL-UCL), D. Malesani (DARK/NBI) and B. Sbarufatti
(INAF-OAB/PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 150204A during follow-up
observations, 51182 s after the BAT trigger (Cummings et al. GCN Circ.
17404). No optical afterglow consistent with the possible XRT
counterpart (A. Melandri et al. GCN Circ. 17409) 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 57368 58276 885 >19.5
u 52088 52670 568 >19.5
w1 51182 63642 1495 >20.3
m2 58281 63016 1027 >20.1
w2 56461 57361 886 >19.9
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.824 in the direction of
the burst (Schlegel et al. 1998).
- GCN Circular #17412
S. Dichiara, C. Guidorzi (U. Ferrara), D. Kopac,
A. Gomboc (U. Ljubljana), C.G. Mundell (LJMU),
on behalf of a large collaboration report:
Two of the Las Cumbres Observatory 1-m telescopes in Sutherland
(South Africa) began observing simultaneously Swift and Fermi
GRB 150204A (Cummings et al. GCN 17404; Burns & Yu GCN 17408)
on February 04 at 19:47:41 UT, i.e. ~13.3 hours after the GRB,
with the r' and i' filters.
We re-observed with two 1-m telescopes in Siding Springs
(Australia) starting on February 05 at 13:58:33 (~31.4 hours)
with the same filters.
Within the XRT error circle (Melandri et al. GCN 17409)
we found no new source down to the following limit:
Mid time from Total Exp Filter Magnitude
trigger (hr) (s)
-------------------------------------------------
13.37 120x10 r' > 19.6
13.56 120x10 i' > 18.6
-------------------------------------------------
We found two uncatalogued sources close to the XRT error circle
at RA=10:40:55.98 Dec=-64:02:26.01 and RA=10:40:56.51 Dec=-64:02:13.8 (J2000)
with magnitudes r=19.68 +- 0.13 i=18.32 +- 0.13, r=19.47 +- 0.12
i=18.23 +- 0.12, respectively. However, image subtraction revealed
no significant variation between the two epochs.
The same conclusion holds for the entire BAT error circle
(Stamatikos et al. GCN 17406).
Magnitudes are calibrated against nearby USNO-B1 R2 and I
values.
- GCN Circular #17428
B. Sbarufatti (INAF-OAB/PSU) and D. Malesani (DARK/NBI) report on behalf of the Swift team
A second epoch of observations on the ground discovered GRB 150204A (Cummings, GCN 17404) was performed by Swift from T+378.9 ks to T+391.6 ks, with a 3.9 ks exposure.
The source reported by Melandri et al. (GCN 17409) has faded below detection, with a 3-sigma upper limit of 1.5E-3 counts/s (6.2e-14 erg cm^-2 s^-1). We therefore confirm that this is the X-ray afterglow of GRB 150204A.
This circular is an official product of the Swift-XRT team.
- GCN Circular #17430
D. A. Kann (TLS Tautenburg), K. Varela (MPE Garching), S. Schmidl (TLS
Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND
team:
We observed the field of GRB 150204A (Swift ground-analysis-detected GRB;
Cummings, GCN 17404) 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 01:34 UT on February 05, 2015, 19 hrs after the
GRB trigger. They were performed at an average seeing of 1".0 and at an
average airmass of 1.5. We obtained a second epoch of imaging the
following night, 47 hours after the trigger, with an average seeing of
1".2 and at an average airmass of 1.2.
We detect five faint sources in the 5".0 error circle of "Source 2"
reported by Melandri et al. (GCN 17409), confirmed to be the X-ray
afterglow by Sbarufatti et al. (GCN 17428). They are located at:
Source A:
RA (J2000) = 10:40:57.43
Dec. (J2000) = -64:02:20.3
Source B:
RA (J2000) = 10:40:57.18
Dec. (J2000) = -64:02:22.7
Source C:
RA (J2000) = 10:40:56.91
Dec. (J2000) = -64:02:23.1
Source D:
RA (J2000) = 10:40:56.73
Dec. (J2000) = -64:02:21.9
Source E:
RA (J2000) = 10:40:56.38
Dec. (J2000) = -64:02:19.2
with typical errors of 0".5 in each coordinate.
None of these source vary between 20 and 48 hours after the GRB, which we
also confirm via image subtraction; therefore they are likely not
associated with the GRB. The field is crowded, and especially in the NIR,
a part of the error circle is affected by scattered light from a nearby
bright star to the east.
Based on total exposures of 125 minutes in g'r'i'z' and 100 minutes in
JHK, at a midtime of 20.3 hrs after the burst, we measure the following 3
sigma upper limits (all AB magnitude system):
g' > 23.5 mag,
r' > 23.8 mag,
i' > 23.4 mag,
z' > 23.0 mag,
J > 21.1 mag,
H > 20.9 mag,
K > 19.8 mag.
The magnitudes are calibrated against an SDSS standard star field obtained
immediately after the second-epoch observations (g'r'i'z') and 2MASS field
stars (JHK) and are not corrected for the Galactic foreground extinction
corresponding to a reddening of E_(B-V)= 0.82 mag in the direction of the
burst (Schlegel et al. 1998).
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