| Summary table |
|---|
| Variable |
Value |
Source |
| T0 |
1:34:16 UTC |
GCN_circulars,Swift Det |
| ra |
167.3734° |
Swift |
| decl |
-54.3264° |
Swift |
| pos_error |
2.46e-04° |
Swift |
| T90 |
21.9 s |
Swift |
| T90_start |
1:34:16 UTC |
Swift |
| fluence |
1.10e-06 erg/cm² |
Swift |
| T100 |
21.9 s |
|
| GBM_located |
False |
|
| mjd |
58008.065462962964 |
GCN_circulars,Swift Det |
| IPN table |
|---|
| GRB_name |
GRB170912A |
| ra |
167.3708° |
| decl |
-54.3667° |
| pos_error |
5.00e-02° |
| Swift table |
|---|
| GRB_name |
GRB170912A |
| t_trigger |
1:34:16 UTC |
| ra |
167.3734° |
| decl |
-54.3264° |
| pos_error |
2.46e-04° |
| T90 |
21.9 s |
| fluence |
1.10e-06 erg/cm² |
| GCN 21861 table |
|---|
| GRB_name |
GRB170912A |
| GCN_number |
21861 |
| Detection_method |
Swift Det |
| t_trigger |
1:34:16 UTC |
| ra |
167.3720° |
| decl |
-54.3600° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 21861
SUBJECT: GRB 170912A: Swift detection of a burst
DATE: 17/09/12 01:45:00 GMT
FROM: David Palmer at LANL
A. Tohuvavohu (PSU), D. N. Burrows (PSU), C. Gronwall (PSU),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), B. Sbarufatti (PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:
At 01:34:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170912A (trigger=772006). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 167.372, -54.360 which is
RA(J2000) = 11h 09m 29s
Dec(J2000) = -54d 21' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single-peak
structure with a duration of about 20 sec. The peak count rate
was ~1200 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 01:36:15.6 UT, 118.7 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 167.37341, -54.32690 which
is equivalent to:
RA(J2000) = 11h 09m 29.62s
Dec(J2000) = -54d 19' 36.8"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 119 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 consistent with the Galactic value of 3.14
x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 122 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 none of
the XRT error circle. 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 0.46.
Burst Advocate for this burst is A. Tohuvavohu (aaronb AT swift.psu.edu).
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 21862 table |
|---|
| GRB_name |
GRB170912A |
| GCN_number |
21862 |
| Detection_method |
Swift-XRT Other |
| ra |
167.3734° |
| decl |
-54.3262° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 21862
SUBJECT: GRB 170912A: Prompt enhanced Swift-XRT position
DATE: 17/09/12 02:14:56 GMT
FROM: Phil Evans at U of Leicester
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 170912A, we find an
enhanced XRT position of the afterglow: RA, Dec: 167.3734, -54.3262
which is equivalent to:
RA (J2000) = 11 09 29.61
Dec (J2000) = -54 19 34.4
with an uncertainty of 2.2 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/772006.
Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
|
| GCN 21863 table |
|---|
| GRB_name |
GRB170912A |
| GCN_number |
21863 |
| Detection_method |
Swift-XRT Det |
| ra |
167.3734° |
| decl |
-54.3264° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 21863
SUBJECT: GRB 170912A: Enhanced Swift-XRT position
DATE: 17/09/12 05:24:57 GMT
FROM: Phil Evans at U of Leicester
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team.
Using 426 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 170912A, 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 = 167.37343, -54.32638 which is equivalent
to:
RA (J2000): 11h 09m 29.62s
Dec (J2000): -54d 19' 35.0"
with an uncertainty of 2.1 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 21874 table |
|---|
| GRB_name |
GRB170912A |
| GCN_number |
21874 |
| Detection_method |
Swift-UVOT Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 21874
SUBJECT: GRB 170912A: Swift/UVOT Upper-Limits
DATE: 17/09/12 17:07:43 GMT
FROM: Sam LaPorte at PSU
GRB 170912A: Swift/UVOT Upper Limits
S. J. LaPorte (PSU) and Tohuvavohu (PSU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170912A
122 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 21861).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 21863)
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 122 272 147 >20.9
u_FC 335 585 246 >19.4
white 122 1362 373 >21.6
v 666 1412 97 >18.8
b 591 1338 78 >19.6
u 335 1313 304 >19.2
w1 715 1461 78 >18.7
m2 690 1436 78 >20.0
w2 641 1387 97 >19.7
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.46 in the direction of the burst
(Schlegel et al. 1998).
|
| GCN 21876 table |
|---|
| GRB_name |
GRB170912A |
| GCN_number |
21876 |
| Detection_method |
Swift-XRT Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 21876
SUBJECT: GRB 170912A: Swift-XRT refined Analysis
DATE: 17/09/12 21:32:08 GMT
FROM: Phil Evans at U of Leicester
J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), P.A. Evans (U.
Leicester), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), P.
D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), D.N.
Burrows (PSU) and A. Tohuvavohu report on behalf of the Swift-XRT team:
We have analysed 6.5 ks of XRT data for GRB 170912A (Tohuvavohu et al.
GCN Circ. 21861), from 104 s to 62.2 ks after the BAT trigger. The
data comprise 17 s in Windowed Timing (WT) mode (the first 8 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 Goad
et al. (GCN Circ. 21862).
The light curve can be modelled with a power-law decay with a decay
index of alpha=4.8 (+nan, -nan).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.85 (+0.54, -0.22). The
best-fitting absorption column is consistent with the Galactic value
of 3.1 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 3.9 x 10^-11 (5.4 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.1 (+/-2.3) x 10^21 cm^-2
Galactic foreground: 3.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.85 (+0.54, -0.22)
If the light curve continues to decay with a power-law decay index of
4.8, the count rate at T+24 hours will be 1.4 x 10^-13 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.4 x
10^-24 (7.4 x 10^-24) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00772006.
This circular is an official product of the Swift-XRT team.
|
| GCN 21877 table |
|---|
| GRB_name |
GRB170912A |
| GCN_number |
21877 |
| Detection_method |
Swift-BAT Det |
| ra |
167.3860° |
| decl |
-54.3430° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 21877
SUBJECT: GRB 170912A: Swift-BAT refined analysis
DATE: 17/09/12 21:42:52 GMT
FROM: Amy Lien at GSFC
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
A. Tohuvavohu (PSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 170912A (trigger #772006)
(Tohuvavohu et al., GCN Circ. 21861). The BAT ground-calculated position is
RA, Dec = 167.386, -54.343 deg which is
RA(J2000) = 11h 09m 32.6s
Dec(J2000) = -54d 20' 35.4"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 34%.
The mask-weighted light curve shows a single-peaked structure that starts
at ~T0, peaks at ~T+3, and ends at ~T+25 s. T90 (15-350 keV) is
21.9 +- 5.6 sec (estimated error including systematics).
The time-averaged spectrum from T-0.42 to T+25.64 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.04 +- 0.21. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+2.38 sec in the 15-150 keV band
is 2.0 +- 0.4 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/772006/BA/
|