- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 14 Mar 15 04:55:16 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 634795, Seg_Num: 0
GRB_RA: 126.659d {+08h 26m 38s} (J2000),
126.991d {+08h 27m 58s} (current),
125.559d {+08h 22m 14s} (1950)
GRB_DEC: +63.833d {+63d 49' 60"} (J2000),
+63.782d {+63d 46' 57"} (current),
+63.997d {+63d 59' 50"} (1950)
GRB_ERROR: 3.00 [arcmin radius, statistical only]
GRB_INTEN: 25631 [cnts] Image_Peak=4145 [image_cnts]
TRIGGER_DUR: 1.024 [sec]
TRIGGER_INDEX: 148 E_range: 25-100 keV
BKG_INTEN: 21795 [cnts]
BKG_TIME: 17674.69 SOD {04:54:34.69} UT
BKG_DUR: 8 [sec]
GRB_DATE: 17095 TJD; 73 DOY; 15/03/14
GRB_TIME: 17692.86 SOD {04:54:52.86} UT
GRB_PHI: -64.91 [deg]
GRB_THETA: 35.05 [deg]
SOLN_STATUS: 0x20000003
RATE_SIGNIF: 255.99 [sigma]
IMAGE_SIGNIF: 25.72 [sigma]
MERIT_PARAMS: +1 +0 +0 +0 +2 +9 +0 +0 +34 +0
SUN_POSTN: 353.84d {+23h 35m 21s} -2.66d {-02d 39' 47"}
SUN_DIST: 110.09 [deg] Sun_angle= -8.9 [hr] (East of Sun)
MOON_POSTN: 268.90d {+17h 55m 36s} -18.22d {-18d 13' 20"}
MOON_DIST: 127.65 [deg]
MOON_ILLUM: 45 [%]
GAL_COORDS: 152.28, 34.59 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 111.12, 43.06 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT-BAT GRB Coordinates.
COMMENTS: This is a rate trigger.
COMMENTS: A point_source was found.
COMMENTS: This does not match any source in the on-board catalog.
COMMENTS: This does not match any source in the ground catalog.
COMMENTS: This is a GRB.
COMMENTS: This trigger occurred at longitude,latitude = 310.85,17.19 [deg].
COMMENTS:
COMMENTS: NOTE: This BAT event is temporally(2.0<100sec) coincident with the FERMI_GBM event (trignum=448001693).
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 14 Mar 15 04:56:55 UT
NOTICE_TYPE: Swift-XRT Position
TRIGGER_NUM: 634795, Seg_Num: 0
GRB_RA: 126.6756d {+08h 26m 42.14s} (J2000),
127.0080d {+08h 28m 01.91s} (current),
125.5758d {+08h 22m 18.18s} (1950)
GRB_DEC: +63.8321d {+63d 49' 55.5"} (J2000),
+63.7814d {+63d 46' 52.9"} (current),
+63.9962d {+63d 59' 46.4"} (1950)
GRB_ERROR: 4.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN: 5.85e-09 [erg/cm2/sec]
GRB_SIGNIF: 12.28 [sigma]
IMG_START_DATE: 17095 TJD; 73 DOY; 15/03/14
IMG_START_TIME: 17777.98 SOD {04:56:17.98} UT, 85.1 [sec] since BAT Trigger Time
TAM[0-3]: 327.65 237.21 261.53 243.82
AMPLIFIER: 2
WAVEFORM: 134
SUN_POSTN: 353.84d {+23h 35m 22s} -2.66d {-02d 39' 45"}
SUN_DIST: 110.10 [deg] Sun_angle= -8.9 [hr] (East of Sun)
MOON_POSTN: 268.92d {+17h 55m 40s} -18.22d {-18d 13' 20"}
MOON_DIST: 127.65 [deg]
MOON_ILLUM: 45 [%]
GAL_COORDS: 152.28, 34.59 [deg] galactic lon,lat of the burst
ECL_COORDS: 111.13, 43.06 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Coordinates.
COMMENTS: The XRT position is 0.45 arcmin from the BAT position.
COMMENTS: The object found at this position is either a very bright burst or a cosmic ray hit.
COMMENTS: Examine the XRT Image to differentiate (CRs are much more compact); see examples at:
COMMENTS: http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .
- GCN Circular #17573
L. M. Z. Hagen (PSU), S. D. Barthelmy (GSFC), J. A. Kennea (PSU),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf
of the Swift Team:
At 04:55:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150314A (trigger=634795). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 126.659d, +63.833d which is
RA(J2000) = 08h 26m 38s
Dec(J2000) = +63d 50' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single complex peak
structure with a duration of about 15 sec. The peak count rate
was ~45000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 04:56:17.9 UT, 85.1 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 126.6756, 63.8321 which is equivalent to:
RA(J2000) = +08h 26m 42.14s
Dec(J2000) = +63d 49' 55.6"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 26 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 not immediately available.
Burst Advocate for this burst is L. M. Z. Hagen (lea.zernow.hagen AT gmail.com).
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 Circular #17574
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 150314A (Hagen et al.,
GCN 17573) starting at 04:57:32 UT, 136 s after the burst. We
detect a fading source at position
RA= 08:26:40.96 (J2000)
DEC= 63:50:03.20 (J2000)
which faded from mag R~16.0 to R~17.5 in a time interval of about 10
minutes. We suggest this to be the optical afterglow of GRB 150314A.
However, we note that this position is about 11 arcsecond, a bit far
away from XRT position, indicating this might be unrelated source.
Observations are on going.
- GCN Circular #17575
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 2271 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 150314A, 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 = 126.67042, +63.83429 which is equivalent
to:
RA (J2000): 08h 26m 40.90s
Dec (J2000): +63d 50' 03.5"
with an uncertainty of 1.7 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 Circular #17576
M. Axelsson (KTH Royal Institute of Technology, Sweden), D. Kocevski (NASA/GSFC)
and J. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team:
At 04:54:50.9 UT on March 14, 2015, Fermi-LAT detected
high-energy emission from GRB 150314A, which was also detected by Fermi-GBM
(trigger 448001693/150314205) and Swift (Hagen et al., GCN 17573), and a possible
optical counterpart by KAIT (Zhang et al., GCN 17574).
The best LAT on-ground location is found to be
RA, Dec 125.40, 64.46 (J2000)
with an error radius of 0.85 deg (90% containment, statistical error only) and consistent
with the Swift/XRT location. This was ~40 deg from the LAT boresight at the time of the
trigger and triggered an autonomous repoint of the spacecraft.
The data from the Fermi-LAT show a significant increase in the event rate within 10 degrees
of the Swift/XRT location after the trigger. More than 14 photons above 100 MeV are observed
within 500 seconds. The highest-energy photon is a 670 MeV event which is
observed 78 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is
Magnus Axelsson (magnus.axelsson@astro.su.se).
The Fermi-LAT is a pair conversion telescope designed to cover
the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration between
NASA and DOE in the U.S. and many scientific institutions
across France, Italy, Japan and Sweden.
- GCN Circular #17577
A. Trotter, D. Reichart, A. LaCluyze, J. Haislip, V. Hoette, K. Cudworth, D. Harper, R. Kron, T. Linder, R. Russell, E. Struble, A. Aji, T. Berger, A. Dow, A. Foster, N. Frank, K. Ivarsen, M. Maples, J. Moore, M. Nysewander, C. Salemi, and J. A. Crain report:
Skynet observed the Swift BAT/XRT localization of GRB 150314A (Hagen et al., GCN 17573, Swift trigger=634795) with the 41" telescope at Yerkes Observatory in WI, USA, starting at 2015-03-14 04:58:22 (t=3.5m post-trigger) and continuing until t=41m post-trigger. Skynet took a total of 17 exposures ranging from 20s to 160s in the g', r' and i' bands. We detect a fading source in all three bands at the position reported by Zheng & Filippenko (GCN 17574).
A preliminary light curve is at:
http://www.skynet.unc.edu/grb/grb150314a.png
Magnitudes are in the AB System, calibrated to 4 APASS stars in the field. Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.035 (Schlafly & Finkbeiner 2011).
No further Skynet observations are scheduled.
- GCN Circular #17577
A. Trotter, D. Reichart, A. LaCluyze, J. Haislip, V. Hoette, K. Cudworth, D. Harper, R. Kron, T. Linder, R. Russell, E. Struble, A. Aji, T. Berger, A. Dow, A. Foster, N. Frank, K. Ivarsen, M. Maples, J. Moore, M. Nysewander, C. Salemi, and J. A. Crain report:
Skynet observed the Swift BAT/XRT localization of GRB 150314A (Hagen et al., GCN 17573, Swift trigger=634795) with the 41" telescope at Yerkes Observatory in WI, USA, starting at 2015-03-14 04:58:22 (t=3.5m post-trigger) and continuing until t=41m post-trigger. Skynet took a total of 17 exposures ranging from 20s to 160s in the g', r' and i' bands. We detect a fading source in all three bands at the position reported by Zheng & Filippenko (GCN 17574).
A preliminary light curve is at:
http://www.skynet.unc.edu/grb/grb150314a.png
Magnitudes are in the AB System, calibrated to 4 APASS stars in the field. Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.035 (Schlafly & Finkbeiner 2011).
No further Skynet observations are scheduled.
- GCN Circular #17578
T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi, Y. Yano,
S. Kurita, Y. Ono, T. Fujiwara, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 150314A (L. M. Z. Hagen et al., GCN Circular #17573) with the
optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm
telescope of Akeno Observatory, Yamanashi, Japan.
The observation started at 2015-03-14 05:21:32 UT (~5.4 h after the burst).
We could not find any new point source within the refined XRT-UVOT alignment error circle
(A.P. Beardmore et al., GCN Circular #17575) in all the three bands.
The obtained upper-limits are listed below.
T0+[sec] MID-UT T-EXP[sec] g' Rc Ic
-----------------------------------------------------------------------------
19292 11:19:44 6840 >21.6 >21.1 >20.1
-----------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.
- GCN Circular #17579
H.-F. Yu (MPE) reports on behalf of the Fermi GBM Team:
"At 04:54:50.85 UT on 14 Mar 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150314A (trigger 448001693 / 150314205),
which was also detected by the Swift (Hagen et al. 2015, GCN 17573)
and Fermi LAT (Axelsson et al. 2015, GCN 17576). The GBM on-ground
location is consistent with the Swift position. The trigger resulted
in an Autonomous Repoint Request (ARR) that was accepted and the
spacecraft slewed to the GBM in-flight location. The initial angle
from the Fermi LAT boresight is about 50 degrees.
The GBM light curve shows a bright single pulse with a duration (T90)
of about 10.7 s (50-300 keV). The time-averaged spectrum from
T0+0.002 s to T0+13.472 s is best fit by a Band function with
Epeak = 311 +/- 5 keV, alpha = -0.60 +/- 0.01, and beta = -2.32 +/- 0.04.
The event fluence (10-1000 keV) in this time interval is
(8.53 +/- 0.04)E-05 erg/cm^2. The 1.024-sec peak photon flux
measured starting from T0+2.144 s in the 10-1000 keV band
is 67.1 +/- 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 #17580
L. M. Z. Hagen (PSU) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150314A
95 s after the BAT trigger (Hagen et al., GCN Circ. 17573). We detect
a fading source consistent with the XRT position (Beardmore et al.
GCN Circ. 17575) and optical detections (Zheng & Filippenko GCN Circ.
17574, Trotter et al. GCN Circ. 17577) that is detected in all but the
bluest UVOT filters.
Preliminary detections and 3-sigma upper limits using the UVOT photometric
system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early
exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 97 244 144 17.22 +/- 0.03
white 587 781 38 19.13 +/- 0.18
white 5472 5671 196 >21.02
v 75 85 9 15.48 +/- 0.13
v 637 657 19 17.75 +/- 0.33
v 4445 6082 390 >19.77
b 562 756 38 19.28 +/- 0.35
b 5266 5466 196 >20.32
u 307 556 245 18.86 +/- 0.14
u 712 6528 253 >20.14
uvw1 687 6485 412 >20.31
uvm2 4650 6280 391 >20.16
uvw2 613 5877 412 >20.46
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).
- GCN Circular #17581
J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
N. Gehrels (GSFC), L. M. Z. Hagen (PSU), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
J. Tueller (GSFC), 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 downlink,
we report further analysis of BAT GRB 150314A (trigger #634795)
(Hagen, et al., GCN Circ. 17573). The BAT ground-calculated position is
RA, Dec = 126.661, 63.839 deg which is
RA(J2000) = 08h 26m 38.6s
Dec(J2000) = +63d 50' 21.0"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 34%.
The mask-weighted light curve shows a single bright FRED pulse that starts at
~ T-2 s, peaks at ~T0, and ends at ~T+13 s. There are some weak extended
emissions that last till ~ T+100 s. T90 (15-350 keV) is 14.79 +- 2.64 sec (estimated
error including systematics).
The time-averaged spectrum from T-2.17 to T+101.42 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.08 +- 0.03. The fluence in the 15-150 keV band is 2.2 +- 0.03 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band
is 38.5 +- 0.9 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/634795/BA/
- GCN Circular #17582
D. Xu (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), S. Geier
(GTC/IAC), K. E. Heintz, J. P. U. Fynbo, D. Malesani (DARK/NBI), P.
Jakobsson (U. Iceland) report on behalf of a larger collaboration:
We observed the field of GRB 150314A (Hagen et al., GCN 17573) using
the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC
camera. We obtained 3x300 s R-band images with a median time of
20:48:36 UT on 2015-03-14, i.e., 15.89 hr after the burst, and in a
seeing of ~0.9".
The optical afterglow (Zheng & Filippenko, GCN 17574; Trotter et al.,
GCN 17577) is clearly detected in our stacked image, with m(R)=22.7
+/- 0.3 mag, calibrated with USNO B1 catalog. The object is a bit
extended in the northwest-southeast direction, indicating that the
host galaxy might be emerging at the observational time.
- GCN Circular #17583
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), J.P.U. Fynbo (DARK/NBI),
C. Thoene (IAA-CSIC), N.R. Tanvir (U. Leicester), R. Sanchez-Ramirez
(UPV, IAA-CSIC), J. Gorosabel (UPV-EHU, IAA-CSIC), P. Pessev (ULL, IAC),
C. Alvarez Iglesias (ULL, IAC), M.A. Rivero (GRANTECAN) report on behalf
of a larger collaboration:
We obtained spectroscopy of the afterglow of GRB 150314A (Hagen et al.,
GCN 17573; Zheng & Filippenko, GCN 17574; Axelsson et al., GCN 17576;
Trotter et al., GCN 17577; Xu et al. GCN 17582) using OSIRIS at the 10.4 m
GTC telescope in La Palma (Spain). Observations consisted of 3 x 1200 s
exposure using the R1000B grism, covering the range between 3700 and
7875 A at a resolution of ~700 (1" slit). The mean observing time was 21:37 UT
(16.70 hr after the burst).
The spectrum shows a continuum with an average SNR ~ 7 (per resolution
element) on which several weak absorption features can be identified. Our
best match corresponds to lines of FeII, MgII, MgI as well as AlII, AlIII and CIV
at lower significance, all at a common redshift of 1.758, which we propose as
the redshift of the GRB.
At this redshift, the isotropic equivalent energy is Eiso = 6.74e53 erg
considering the fluence reported by Fermi/GBM (Yu et. al GCN 17579) in the
(10-1000) keV window.
- GCN Circular #17584
D. A. Perley (Caltech) and S. B. Cenko (NASA/GSFC) report:
The Palomar 60-inch robotic telescope began automatic follow-up of the
location of GRB 150314A (Hagen et al., GCN 17573) at 05:08:40 UT on
2015-03-14, 13.4 minutes after the GRB trigger. A sequence of
60-second r, i, and z exposures were acquired, lasting until 06:36 UT.
Another sequence of 180-second g, r, and i exposures was taken between
09:01 UT and 10:54 UT.
We detect the optical afterglow reported by Zheng and Filippenko (GCN
17574) in individual exposures from the early sequence as well as in a
stack of the later-time exposures. Calibrating to a nearby USNO star
(RA=126.701423, dec=63.829609, R2=15.33) gives the following photometry:
t_med = 834s : R = 18.59 +/- 0.05
t_med = 1179s : R = 18.96 +/- 0.05
t_med = 1437s : R = 19.06 +/- 0.07
t_med = 1693s : R = 19.41 +/- 0.07
t_med = 1977s : R = 19.59 +/- 0.08
t_med = 18365s : R = 21.73 +/- 0.13
The afterglow fades as approximately t^-0.9 throughout our observations.
- GCN Circular #17585
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 150314A (Hagen et al.,
GCN 17573) starting at 04:57:32 UT, 136 s after the burst.
Observations were performed with an automatic sequence in the
clear (roughly R), V, and I filters, and the exposure time was
20 s per image. The afterglow reported by Zheng and Filippenko
(GCN 17574) was detected in clear and I band, but not in V band.
Useful observations lasted for about 20 minutes before the weather
change to be coludy. Preliminary analysis shows that the afterglow
decays with a single power (with alpha = -1.12) from the
beginning of our observations until about a thousand seconds
after the burst. A preliminary light curve is posted at
http://astro.berkeley.edu/~zwk/grb/GRB150314A/GRB150314A_kait.png
- GCN Circular #17586
B. Sbarufatti (INAF-OAB/PSU), C. Pagani (U. Leicester), A.P. Beardmore
(U. Leicester), P.A. Evans (U. Leicester), V. D'Elia (ASDC), M. de
Pasquale (INAF-IASFPA), A. Maselli (INAF-IASFPA), D.N. Burrows (PSU),
J.A. Kennea (PSU) and L.M.Z. Hagen report on behalf of the Swift-XRT
team:
We have analysed 8.1 ks of XRT data for GRB 150314A (Hagen et al. GCN
Circ. 17573), from 78 s to 69.2 ks after the BAT trigger. The data
comprise 690 s in Windowed Timing (WT) mode (the first 6 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 Beardmore
et al. (GCN Circ. 17575).
The late-time light curve (from T0+4.2 ks) can be modelled with an
initial power-law decay with an index of alpha=0.57 (+0.13, -0.20),
followed by a break at T+11.6 ks to an alpha of 2.00 (+0.13, -0.12).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.760 (+/-0.026). The
best-fitting absorption column is 1.72 (+0.10, -0.09) x 10^21 cm^-2,
in excess of the Galactic value of 4.5 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.90 (+/-0.10) and a
best-fitting absorption column of 2.3 (+/-0.4) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.9 x 10^-11 (5.2 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.3 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 4.5 x 10^20 cm^-2
Excess significance: 8.4 sigma
Photon index: 1.90 (+/-0.10)
If the light curve continues to decay with a power-law decay index of
2.00, the count rate at T+24 hours will be 0.019 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.3 x
10^-13 (9.8 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00634795.
This circular is an official product of the Swift-XRT team.
- GCN Circular #17587
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, very intense GRB 150314A
(Swift-BAT trigger #634795: Hagen et al., GCN 17572; Cummings et al., GCN 17581;
Fermi-LAT detection: Axelsson et al., GCN 17576;
Fermi-GBM observation: Yu, GCN 17579)
triggered Konus-Wind at T0=17691.727 s UT (04:54:51.727).
The KW light curve shows a bright multi-peaked pulse
with a duration of ~14 s.
The emission is visible up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150314_T17691/
As observed by Konus-Wind, the burst had a fluence
of 9.1(-0.4,+0.4)x10^-5 erg/cm2, and a 64-ms peak flux,
measured from T0+1.344 s, of 2.2(-0.1,+0.1)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum (measured from T0 to T0+12.288 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.79 (-0.04,+0.04),
the high energy photon index beta = -2.91 (-0.28,+0.18),
the peak energy Ep = 350 (-17,+17) keV,
chi2 = 142/97 dof.
The spectrum near the peak count rate
(measured from T0+0.256 to T0+2.048 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.37 (-0.08,+0.09),
the high energy photon index beta = -2.81 (-0.27,+0.18),
the peak energy Ep = 348 (-27,+27) keV,
chi2 = 134/94 dof.
Assuming the redshift z=1.758 (de Ugarte Postigo et al., GCN 17583)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~6.9x10^53 erg,
the peak luminosity L_iso is ~4.6x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~965 keV.
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
- GCN Circular #17588
D. Xu (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D.
Malesani (DARK/NBI), D. Slumstrup (NOT), P. Jakobsson (U. Iceland)
report on behalf of a larger collaboration:
We continued to observe the field of GRB 150314A (Hagen et al., GCN
17573) using the 2.56m Nordic Optical Telescope (NOT) equipped with
the ALFOSC camera. We obtained 4x600 s R-band images with a median
time of 02:16:32 UT on 2015-03-16, i.e., 45.35 hr after the burst, and
in the seeing of 1.0"-1.5".
The optical afterglow (Zheng & Filippenko, GCN 17574; Trotter et al.,
GCN 17577) is still detected in our stacked image, with m(R) = 23.9
+/- 0.3 mag, calibrated with the same USNO B1 stars that were used in
our previous report (Xu et al., GCN 17582). Together with previous
observations (e.g., Perley & Cenko, GCN 17584; Zheng & Filippenko, GCN
17585), so far the object still nicely fits the decaying law of F(t) ~
t^-0.9.
- GCN Circular #17590
J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis,
of Los Alamos National Laboratory report:
The RAPTOR network of robotic optical telescopes made observations of Swift
trigger 634795 (Hagen, et al., GCN 17573). Our narrow-field instruments
located in Los Alamos, NM, USA, arrived on target at 04:55:20.83 UT, T+27.98
seconds after the BAT trigger time. Our initial 5s exposure shows the
counterpart (Zheng, et al., GCN 17574) at an unfiltered magnitude of
13.11 +- 0.02. The source fades steadily, reaching magnitude 15.87 +- 0.09
at T+180.38 s, in agreement with the KAIT lightcurve (Zheng, et al., GCN
17585). We derive a power-law decay slope of -1.50 using 04:54:52.86 as
the BAT T0. Our unfiltered magnitudes were calibrated to the USNO-B1 R-band
catalog.
The optical counterpart is not detected in any of our persistent wide-field
monitors during the gamma-ray emitting interval. Typical 3-sigma unfiltered
limiting magnitudes during this period were V~9.8 based on comparison to the
Tycho-2 V-band catalog.
- GCN Circular #17591
T. Laskar and E. Berger (Harvard) report on behalf of a larger
collaboration:
"We observed GRB 150314A (Hagen et al; GCN 17573) with the VLA beginning on
2015 March 16.1 UT (1.9 days after the burst). At a mean frequency of 5
GHz, we detect a radio source with a preliminary flux density of ~ 0.05 mJy
at
RA = 08:26:40.973 +/- 0.005
Dec = +63:50:03.29 +/- 0.08
consistent with the enhanced Swft/XRT position (Beardmore et al.; GCN
17575) and the optical position (Zheng et al.; GCN 17574). Follow-up
observations are planned."
- GCN Circular #17606
T. Laskar and E. Berger (Harvard) report:
"We observed GRB 150314A (Hagen et al; GCN 17573) with the VLA beginning on
2015 March 17.2 UT (3.0 days after the burst). No significant radio
emission is detected at the enhanced Swft/XRT position (Beardmore et al.;
GCN 17575) or the optical position (Zheng et al.; GCN 17574). We therefore
confirm the radio source reported in our previous observations (Laskar et
al.; GCN 17591) as the radio afterglow. No further follow-up observations
are planned."
- GCN Circular #17614
J. Mao, B. Lun and J.-M. Bai (YNAO) report:
We observed the field of GRB 150314A (Hagen et al., GCN 17573) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG) station of Yunnan Observatory. Observations began from UT 12:22:09.5 14th, March, 2015 (about 7.5 hours after the trigger). We did not detect any optical source at the XRT position down to a limit of R~21.0.
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