- GCN Circular #17789
V. D'Elia (ASDC), J. A. Kennea (PSU), T. Sakamoto (AGU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:
At 00:21:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150430A (trigger=639433). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 326.491, -27.928 which is
RA(J2000) = 21h 45m 57.8s
Dec(J2000) = -27d 55' 40.8''
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty).
The XRT began observing the field at 00:23:18.0 UT, 80 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 326.47958, -27.90212 which is equivalent to:
RA(J2000) = 21h 45m 55.1s
Dec(J2000) = -27d 54' 07.6''
with an uncertainty of 5 arcseconds (radius, 90% containment). This
location is 100 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 data is unavailable at this time.
Note, due to a telemetry drop-out no GCN Notices were sent for this
burst, and limited information is available at this time. We will send
further GCN Circulars as we know more.
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.)
- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 30 Apr 15 01:11:47 UT
NOTICE_TYPE: Swift-XRT Position
TRIGGER_NUM: 639433, Seg_Num: 0
GRB_RA: 326.4796d {+21h 45m 55.10s} (J2000),
326.7008d {+21h 46m 48.19s} (current),
325.7565d {+21h 43m 01.55s} (1950)
GRB_DEC: -27.9021d {-27d 54' 07.5"} (J2000),
-27.8309d {-27d 49' 51.1"} (current),
-28.1332d {-28d 07' 59.6"} (1950)
GRB_ERROR: 5.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN: 5.72e-09 [erg/cm2/sec]
GRB_SIGNIF: 12.00 [sigma]
IMG_START_DATE: 17142 TJD; 120 DOY; 15/04/30
IMG_START_TIME: 1398.00 SOD {00:23:18.00} UT, 76274.5 [sec] since BAT Trigger Time
TAM[0-3]: 327.61 237.19 261.35 242.66
AMPLIFIER: 2
WAVEFORM: 134
SUN_POSTN: 37.00d {+02h 28m 00s} +14.62d {+14d 37' 20"}
SUN_DIST: 80.18 [deg] Sun_angle= 4.7 [hr] (West of Sun)
MOON_POSTN: 173.56d {+11h 34m 14s} +1.12d {+01d 06' 55"}
MOON_DIST: 142.93 [deg]
MOON_ILLUM: 85 [%]
GAL_COORDS: 20.72,-49.11 [deg] galactic lon,lat of the burst
ECL_COORDS: 319.29,-13.60 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Coordinates.
COMMENTS: This Notice was ground-generated -- not flight-generated.
COMMENTS: TAM values are not valid.
COMMENTS: TDRSS outage caused missed GCN Notices
- GCN Circular #17790
S. R. Oates (IAA-CSIC/UCL-MSSL) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150430A
115 s after the BAT trigger (D'Elia et al., GCN Circ. 17789).
No optical afterglow consistent with the XRT position 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 115 265 147 >20.6
u_FC 273 523 246 >19.7
white 115 5422 344 >21.2
v 4196 5832 393 >19.8
b 5017 6487 231 >20.3
u 273 6447 639 >20.3
w1 4607 6242 393 >20.4
m2 4401 6037 393 >20.7
w2 3990 5627 393 >20.9
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).
- GCN Circular #17791
M. Fujita, H. Negoro (Nihon U.), M. Serino (RIKEN), S. Nakahira,
S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA)
T. Mihara, M. Sugizaki, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, T. Yoshii, Y. Tachibana, Y. Ono (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU),
H. Tsunemi, R. Imatani (Osaka U.),
M. Nakajima, F. Honda, T. Namba, T. Masumitsu, K. Tanaka (Nihon U.),
Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.),
Y. Tsuboi, S. Kanetou (Chuo U.),
M. Yamauchi, D. Itoh (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Morii (ISM)
report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 00:21:12 UT.
Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(326.501 deg, -28.137 deg) = (21 46 00, -28 08 12) (J2000)
(326.260 deg, -28.014 deg) = (21 45 02, -28 00 49) (J2000)
(326.513 deg, -27.682 deg) = (21 46 03, -27 40 55) (J2000)
(326.753 deg, -27.805 deg) = (21 47 00, -27 48 19) (J2000)
The position of GRB 150430A (D'Elia et al. GCN #17789) is inside
of the error box. The trigger time is 16 sec before the BAT trigger.
The data download was, however, delayed for about 8.8 hours
probably because of the data tracking problem.
The X-ray flux averaged over the scan was 512 +- 45 mCrab
(4-10keV, 1 sigma error). A simple power-law fit to the GSC 2-20 keV
spectrum gives a power-law index of 1.08 +/- 0.20.
There was no significant excess flux in the previous transit at 4/29 22:48 UT,
and in the next transit at 4/30 03:26 UT with an upper limit of 20 mCrab for each.
- GCN Circular #17792
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), A. D'a=EC (INAF-IASFPA), A. Maselli (INAF-IASFPA), A.
Melandri (INAF-OAB) and V. D'Elia report on behalf of the Swift-XRT
team:
We have analysed 10 ks of XRT data for GRB 150430A (D'Elia et al. GCN
Circ. 17789), from 84 s to 23.7 ks after the BAT trigger. The data
comprise 207 s in Windowed Timing (WT) mode (the first 8 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. Using 8645 s of PC mode data and 15 UVOT images, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec =3D 326.47988, -27.90181
which is equivalent to:
RA (J2000): 21h 45m 55.17s
Dec(J2000): -27d 54' 06.5"
with an uncertainty of 1.4 arcsec (radius, 90% confidence).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=3D3.97 (+/-0.17). At T+233 s the decay
flattens to an alpha of 0.73 (+0.07, -0.22) before breaking again at
T+4365 s to a final decay with index alpha=3D1.89 (+/-0.15).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.27 (+0.10, -0.09). The
best-fitting absorption column is 4.3 (+0.5, -0.4) 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 2.10 (+/-0.14) and a
best-fitting absorption column of 3.8 (+/-0.6) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.6 x 10^-11 (6.0 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.8 (+/-0.6) x 10^21 cm^-2
Galactic foreground: 2.5 x 10^20 cm^-2
Excess significance: 9.7 sigma
Photon index: 2.10 (+/-0.14)
If the light curve continues to decay with a power-law decay index of
1.89, the count rate at T+24 hours will be 1.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.2 x
10^-14 (8.4 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/00639433.
This circular is an official product of the Swift-XRT team.
- GCN Circular #17793
O.J. Roberts (UCD) and G. Younes (USRA at GWU) report
on behalf of the Fermi GBM Team:
"At 00:21:05.65 UT on the 30th of April 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 150430A
(trigger 452046068 / 150430015), which was also detected
by Swift (D'Elia et al. 2015, GCN 17789) and MAXI/GSC
(Negoro et al. 2015, GCN 17791). The GBM on-ground location
is consistent with the Swift position. The angle from the
Fermi LAT boresight is about 110 degrees.
The GBM light curve shows several bright pulses over a
duration (T90) of 116.7 s (50-300 keV). The time-averaged
spectrum from T0-4.1 s to T0+111.6 s is well fit by power
law function with an exponential high-energy cutoff. The
power law index is -0.95 +/- 0.15 and the cutoff energy,
parameterized as Epeak, is 346 +/- 57 keV.
The event fluence (10-1000 keV) in this time interval is
(2.1 +/- 0.1)E-05 erg/cm^2. The 1.024-sec peak photon
flux measured starting from T0+10.3 s in the 10-1000 keV
band is 9.7 +/- 0.5 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
- GCN Circular #17794
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 150430A
(Swift/BAT detection: D'Elia et al., GCN Circ. 17789;
MAXI/GSC detection: Fujita et al., GCN Circ. 17791;
Fermi/GBM detection: Roberts and Younes, GCN Circ. 17793)
triggered Konus-Wind at T0=1271.466 s UT (00:21:11.466).
The burst light curve shows three well separated emission episodes:
a weak episode at T-T0 ~ -320 s, the main episode at T-T0 ~ 0 s,
and a weak episode at T-T0 ~ 100 s.
The total burst duration is about 420 s.
There is a hint of soft precursor at T-T0 ~ -440 s.
The emission is seen up to ~5 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150430_T01271/
As observed by Konus-Wind, the burst
had a fluence of 2.95(-0.75,+1.14)x10^-5 erg/cm2,
and a 256-ms peak flux, measured from T0+1.248 s,
of 4.11(-1.02,+1.09)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the main episode
(measured from T0 to T0+114.944 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.79(-0.69,+1.48),
the high energy photon index beta = -2.21(-0.66,+0.33),
the peak energy 157(-70,+93) keV
(chi2 = 69/72 dof)
The spectrum near the maximum count rate
(measured from T0+0.000 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.47(-0.35,+0.45),
the high energy photon index beta = -2.11(-0.24,+0.16),
the peak energy 194(-38,+54) keV
(chi2 = 80/97 dof)
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
- GCN Circular #17795
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), N. Gehrels (GSFC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 150430A (trigger #639433)
(D'Elia, et al., GCN Circ. 17789). The BAT ground-calculated position is
RA, Dec = 326.481, -27.919 deg, which is
RA(J2000) = 21h 45m 55.5s
Dec(J2000) = -27d 55' 07.9"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 5%.
The mask-weighted light curve shows several peaks starting at ~T-10 sec,
the hightest peak at ~T+2 sec, the last peak at ~T+97 sec, and ending at ~T+110 sec.
T90 (15-350 keV) is 107.1 +- 6.7 sec (estimated error including systematics).
The time-averaged spectrum from T-11.64 to T+108.70 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.43 +- 0.12. The fluence in the 15-150 keV band is 6.9 +- 0.5 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.97 sec in the 15-150 keV band
is 5.0 +- 1.0 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/639433/BA/
- GCN Circular #17796
T. Schweyer (MPE Garching), D. A. Kann (TLS Tautenburg), and J. Greiner
(MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 150430A (Swift trigger 639433; D'Elia et al.,
GCN # 17789) 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 07:09 UT on 2015-04-30, 6.8 hrs after the GRB
trigger. They were performed at an average seeing of 0.9" and at an
average airmass of 1.6.
Inside the 1.4" enhanced XRT error circle (Burrows et al., GCN # 17792)
and in the nearby surroundings we detect no sources.
Based on 27 min of total exposure time in g'r'i'z' and 20 min in JHK
centered 7.56 hrs after the GRB, we estimate the following preliminary
upper limits (AB magnitudes):
g' > 24.3 mag,
r' > 24.3 mag,
i' > 23.8 mag,
z' > 23.5 mag,
J > 21.5 mag,
H > 20.8 mag, and
K > 19.5 mag.
Given magnitudes are calibrated against GROND zero points (g'r'i'z') as
well as 2MASS field stars (JHK) and are not corrected for the expected
Galactic foreground extinction corresponding to a reddening of
E_(B-V)=0.03 mag in the direction of the burst (Schlegel et al. 1998)
Previous IAU Circulars 