| Summary table |
|---|
| Variable |
Value |
Source |
| T0 |
4:09:28 UTC |
GCN_circulars,Swift Det |
| ra |
227.5343° |
Swift |
| decl |
-19.6330° |
Swift |
| pos_error |
1.94e-04° |
Swift |
| T90 |
121.0 s |
Swift |
| T90_start |
4:09:28 UTC |
Swift |
| fluence |
1.40e-06 erg/cm² |
Swift |
| T100 |
121.0 s |
|
| GBM_located |
False |
|
| mjd |
57290.17324074074 |
GCN_circulars,Swift Det |
| IPN table |
|---|
| GRB_name |
GRB150925A |
| ra |
227.5208° |
| decl |
-19.6333° |
| pos_error |
5.00e-02° |
| Swift table |
|---|
| GRB_name |
GRB150925A |
| t_trigger |
4:09:28 UTC |
| ra |
227.5343° |
| decl |
-19.6330° |
| pos_error |
1.94e-04° |
| T90 |
121.0 s |
| fluence |
1.40e-06 erg/cm² |
| GCN 18365 table |
|---|
| GRB_name |
GRB150925A |
| GCN_number |
18365 |
| Detection_method |
Swift Det |
| t_trigger |
4:09:28 UTC |
| ra |
227.5200° |
| decl |
-19.6280° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18365
SUBJECT: GRB 150925A: Swift detection of a burst
DATE: 15/09/25 04:27:53 GMT
FROM: David Palmer at LANL
J. L. Racusin (NASA/GSFC), A. D'Ai (INAF-IASFPA),
A. Maselli (INAF-IASFPA), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:
At 04:09:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150925A (trigger=656604). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 227.520, -19.628 which is
RA(J2000) = 15h 10m 05s
Dec(J2000) = -19d 37' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). Only partial BAT lightcurve data is
currently available, and so no description of this image trigger
can be given.
The XRT began observing the field at 04:11:48.9 UT, 140.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
227.5340, -19.6325 which is equivalent to:
RA(J2000) = 15h 10m 08.16s
Dec(J2000) = -19d 37' 57.1"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 50 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 (1.01 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.7
(+4.53/-2.33) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 3.82e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 148 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
0.10.
Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov).
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 18366 table |
|---|
| GRB_name |
GRB150925A |
| GCN_number |
18366 |
| Detection_method |
Swift-XRT Det |
| ra |
227.5342° |
| decl |
-19.6330° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18366
SUBJECT: GRB 150925A: Enhanced Swift-XRT position
DATE: 15/09/25 12:48:22 GMT
FROM: Phil Evans at U of Leicester
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1379 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 150925A, 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 = 227.53421, -19.63298 which is equivalent
to:
RA (J2000): 15h 10m 8.21s
Dec (J2000): -19d 37' 58.7"
with an uncertainty of 1.5 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 18367 table |
|---|
| GRB_name |
GRB150925A |
| GCN_number |
18367 |
| Detection_method |
Swift-XRT Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18367
SUBJECT: GRB 150925A: Swift-XRT refined Analysis
DATE: 15/09/25 16:27:03 GMT
FROM: Phil Evans at U of Leicester
A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti
(INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), P.
D'Avanzo (INAF-OAB) and J.L. Racusin report on behalf of the Swift-XRT
team:
We have analysed 9.0 ks of XRT data for GRB 150925A (Racusin et al. GCN
Circ. 18365), from 129 s to 22.8 ks after the BAT trigger. The data
comprise 175 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 Osborne et
al. (GCN Circ. 18366).
The light curve can be modelled with an initial power-law decay with an
index of alpha=3.30 (+/-0.09), followed by a break at T+877 s to an
alpha of 1.20 (+0.19, -0.22).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.62 (+/-0.09). The
best-fitting absorption column is 2.7 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 1.0 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.89 (+0.25, -0.23)
and a best-fitting absorption column of 3.4 (+1.2, -1.0) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 4.1 x 10^-11 (5.8 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.4 (+1.2, -1.0) x 10^21 cm^-2
Galactic foreground: 1.0 x 10^21 cm^-2
Excess significance: 3.8 sigma
Photon index: 1.89 (+0.25, -0.23)
If the light curve continues to decay with a power-law decay index of
1.20, the count rate at T+24 hours will be 6.3 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x
10^-14 (3.7 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00656604.
This circular is an official product of the Swift-XRT team.
|
| GCN 18368 table |
|---|
| GRB_name |
GRB150925A |
| GCN_number |
18368 |
| Detection_method |
Swift-BAT Det |
| ra |
227.5380° |
| decl |
-19.6400° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18368
SUBJECT: GRB 150925A: Swift-BAT refined analysis
DATE: 15/09/25 16:46:23 GMT
FROM: Scott Barthelmy at NASA/GSFC
T. Sakamoto (AGU), S. D. Barthelmy (GSFC), 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), J. L. Racusin (NASA/GSFC),
M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 150925A (trigger #656604)
(Racusin, et al., GCN Circ. 18365). The BAT ground-calculated position is
RA, Dec = 227.538, -19.640 deg, which is
RA(J2000) = 15h 10m 09.0s
Dec(J2000) = -19d 38' 22.3"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 56%.
The mask-weighted light curve show several overlapping peaks starting at ~T-0,
peaking at ~T+25 sec, and ending at ~T+180 sec. T90 (15-350 keV) is
121 +- 27 sec (estimated error including systematics).
The time-averaged spectrum from T+3.51 to T+149.61 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.19 +- 0.20. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+30.68 sec in the 15-150 keV band
is 0.6 +- 0.2 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/656604/BA/
|
| GCN 18369 table |
|---|
| GRB_name |
GRB150925A |
| GCN_number |
18369 |
| Detection_method |
Swift-UVOT Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18369
SUBJECT: GRB 150925A: Swift/UVOT Upper Limits
DATE: 15/09/26 03:01:53 GMT
FROM: Mike Siegel at PSU/Swift MOC
M. H. Siegel (PSU) and J. L. Racusin (NASA/GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150925A
149 s after the BAT trigger (Racusin et al., GCN Circ. 18365).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 18366)
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 first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 149 298 147 >20.2
u_FC 307 557 246 >19.7
white 149 13178 1385 >21.2
v 637 7068 510 >19.7
b 563 18924 1676 >20.7
u 307 18430 2310 >20.2
w1 688 17516 1333 >20.8
m2 1589 22808 586 >21.1
w2 1019 6864 452 >19.8
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.10 in the direction of the burst
(Schlegel et al. 1998).
|