GRB 090809
GCN Circular 9766
Subject
Title: GRB 090809: Further NOT optical observations
Date
2009-08-11T17:31:56Z (16 years ago)
From
Dong Xu at DARK,NBI <dong@astro.ku.dk>
D. Xu, G. Leloudas, J. P. U. Fynbo, D. Malesani (DARK/NBI), P. Jakobsson
(Univ. Iceland), and and G. Furesz (CfA/Harvard) report on behalf of a
larger collaboration:
We continued to observe the field of GRB 090809 (Markwardt et al., GCN
9754; Xu et al., GCN 9755; Landsman et al., GCN 9758) with the Nordic
Optical Telescope equipped with ALFOSC. We obtained 4x300 s i-band
frames staring on August 10th, 22:25:35 UT, 28.9 hr after the burst.
The optical afterglow is still detected in the stacked frame. The
magnitude is i=22.3+/-0.1 against several reference stars of the USNO B1
catalog in the field. The improved magnitude in our previous observation
is i=20.20+/-0.04, being consistent with the measurement in Wiersema et
al. (GCN 9762). Therefore, the optical afterglow is decaying with a
power-law slope of \alpha=1.0, similar to the general decaying of the
X-ray afterglow (Mao et al., GCN 9759).
We note that the rest-frame T90 (Barthelmy et al., GCN 9756) is less
than 2 s for this burst at z=2.737 (Malesani et al., GCN9761). But the
early energetic X-ray flares tend to make this burst more consistent
with the class of the conventional long bursts.
GCN Circular 9765
Subject
VLA radio upper limit on GRB 090809
Date
2009-08-11T14:53:03Z (16 years ago)
From
Poonam Chandra at U Virginia/NRAO <pc8s@virginia.edu>
Poonam Chandra (RMC) and Dale A. Frail (NRAO) report on behalf of a
larger collaboration:
"We used the Very Large Array to observe the field of view toward
GRB 090809 (GCN 9754) at a frequency of 8.46 GHz on 2009 Aug. 11.37
UT. The GRB radio afterglow is undetected. The peak flux at the NOT
optical afterglow position (GCN 9755) is 8+/-39 uJy.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
GCN Circular 9762
Subject
GRB 090809: WHT observations
Date
2009-08-10T17:50:15Z (16 years ago)
From
Klaas Wiersema at U of Leicester <kw113@star.le.ac.uk>
K. Wiersema (Leicester), D. Malesani (DARK/NBI), A. Levan, D. Steeghs, L. van
Spaandonk (Warwick) report on behalf of a larger collaboration:
We observed the field of GRB 090809 (Markwardt et al. GCN 9754) with the
William Herschel Telescope using the ACAM instrument. Observations
consisted of 4 x 300 second exposures with a sloan i filter, starting on
August 9, 23:41 UT (6.16 hrs after burst). We clearly detect the afterglow
(Markwardt et al. GCN 9754, Xu et al. GCN 9755) with i = 20.48 +/- 0.03
(calibrated using SDSS stars).
GCN Circular 9761
Subject
GRB 090809 X-shooter redshift
Date
2009-08-10T15:54:48Z (16 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
D. Malesani, J.P.U. Fynbo (DARK/NBI), L. Christensen (ESO),
A. de Ugarte Postigo (OAB-INAF), B. Milvang-Jensen (DARK/NBI),
S. Covino (OAB-INAF) report on behalf of a larger collaboration
We have observed the afterglow of GRB 090809 (Markwardt
et al. GCNC 9754) using the X-shooter spectrograph mounted
at the Kueyen telescope of ESO's VLT (Paranal Observatory,
Chile) during its science verification phase. The spectrum,
consisting of a combined exposure of 4x1800s, was started
at 03:40 UT on August 09 (10.15 hrs after the burst). It was
obtained with an initial seeing of 0.9" and an airmass of
1.2, when the afterglow had a magnitude of R~21. The
spectrum covers the complete range from 3000 to 25000
Angstroms. In a preliminary analysis we identify the
Lyman break, Lyman-alpha, SiII, OI, SiI*, SiIV, CIV, FeII, AlII,
AlIII and MgII at a common redshift of 2.737 +/- 0.002 (pending
final wavelength calibration), which we identify as the redshift
of the GRB.
We thank the Paranal staff for excellent support, in particular
Elena Mason and Claudia Cid.
GCN Circular 9759
Subject
GRB 090809: Swift-XRT refined analysis
Date
2009-08-10T08:01:42Z (16 years ago)
From
Jirong Mao at INAF-OAB <jirong.mao@brera.inaf.it>
J. Mao, R. Margutti, A. de Ugarte Postigo (INAF-OAB) and C. B. Markwardt
(CRESST/GSFC/UMD) report on behalf of the Swift-XRT team:
We have analysed 8.6 ks of XRT data for GRB 090809 (Markwardt et al. GCN
Circ. 9754), from 107 s to 23.3 ks after the BAT trigger. The data
comprise 59 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Evans et al. (GCN. Circ 9757).
The light curve shows a first flare evidence peaking around 189s, then,
it shows a second flare peaking around 4.6ks, these flares make an order
of magnitude increase in count-rate, after that, the light curve decays
continuously. In general, the underlying light curve can be modelled
with a power-law decay with a decay index of alpha=1.02+/-0.02.
A spectrum extracted from the WT mode data can be fitted with an
absorbed power-law with a photon spectral index of 1.75 (+/-0.09). The
best-fitting absorption column is 2.4 (+/-0.3) x 1021 cm^-2, in excess
of the Galactic value of 6.1 x 1020 cm^-2 (Kalberla et al. 2005). The PC
mode spectrum has a photon index of 1.84 (+0.14, -0.13) and a
best-fitting absorption column of 1.18 (+0.19, -0.18) x 1021 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 1.08 x 10^-11 (1.24
x 10^-11) erg cm^-2 count^-1.
If the light curve continues to decay with a power-law decay index of
1.0, the count rate at T+24 hours will be 0.007 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.9 x
10^-13 (3.4 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/00359530.
This circular is an official product of the Swift-XRT team.
GCN Circular 9758
Subject
GRB090809: Swift/UVOT observations
Date
2009-08-10T05:37:54Z (16 years ago)
From
Wayne Landsman at GSFC/SSAI <wayne.b.landsman@nasa.gov>
W.B. Landsman (NASA/GSFC) and C. Markwardt (CRESST/GSFC/UMD) report on
behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 090809
108s after the BAT trigger (Markwardt et al., GCN Circ. 9754), The
tentative UVOT detection reported by Markwardt et al. is confirmed
following the downlink of additional data. The UVOT position
determined from the white finding chart exposure is
RA (J2000) 21:54:43.19 = 328.679938 (deg)
Dec (J2000) -00:05:1.83 = -0.083842 (deg)
with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence,
statistical + systematic), consistent with the NOT afterglow position
(Xu et al., GCN Circ. 9755).
The initial magnitudes and upper limits are as follows:
Filter T_start(s) Tstop(s) Exp(s) Mag
white 108 194 84 19.53 +/- 0.14
white 3396 3545 147 21.03 +/- 0.33
v 3552 5181 393 19.87 +/- 0.30
b 4365 5976 367 >21.1 (3 sigma)
u 4162 5796 391 >20.8 (3 sigma)
uvw1 3962 5592 393 >20.7 (3 sigma)
uvm2 3757 5386 393 >20.5 (3 sigma)
uvw2 4776 10964 1082 >21.6 (3 sigma)
The values quoted above 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). The photometry is on the UVOT photometric
system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular 9757
Subject
GRB 090809: Enhanced Swift-XRT position
Date
2009-08-10T02:38:47Z (16 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 5518 s of XRT Photon Counting mode data and 13 UVOT
images for GRB 090809, 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 = 328.68012, -0.08366 which is equivalent
to:
RA (J2000): 21h 54m 43.23s
Dec (J2000): -00d 05' 01.2"
with an uncertainty of 1.4 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, arXiv:0812.3662).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 9756
Subject
GRB 090809: Swift-BAT refined analysis
Date
2009-08-10T02:07:52Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090809 (trigger #359530)
(Markwardt, et al., GCN Circ. 9754). The BAT ground-calculated position is
RA, Dec = 328.665, -0.083 deg which is
RA(J2000) = 21h 54m 39.5s
Dec(J2000) = -00d 04' 58.0"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.
The mask-weighted light curve shows a single, roughly triangularly shaped
peak starting at ~T-1 sec, peaking at ~T+3 sec, and ending at ~T+9 sec.
T90 (15-350 keV) is 5.4 +- 1.3 sec (estimated error including systematics).
The time-averaged spectrum from T-1.0 to T+6.4 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.34 +- 0.24. The fluence in the 15-150 keV band is 3.4 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+2.26 sec in the 15-150 keV band
is 1.1 +- 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/359530/BA/
GCN Circular 9755
Subject
GRB 090809: afterglow confirmation at the NOT
Date
2009-08-10T00:27:57Z (16 years ago)
From
Dong Xu at DARK,NBI <dong@astro.ku.dk>
D. Xu, G. Leloudas, D. Malesani, J.P.U. Fynbo (DARK/NBI), P. Jakobsson
(Univ. of Iceland), and G. Furesz (CfA/Harvard) report on a larger
collaboration:
We observed the field of GRB 090809 (Markwardt et al., GCN 9754) with
the Nordic Optical Telescope equipped with ALFOSC. We obtained 3x300 s
I-band frames, starting on August 9th, 21:49:10 UT, 4.29889 hr after the
burst; and 1x300 s R-band frame, starting 5.29861 hr after the burst.
We confirm the presence of the UVOT source (Markwardt et al., GCN 9754)
at coordinates:
RA(J2000) = 21:54:43.17
Dec(J2000) = -00:05:01.9
which are consistent with the UVOT position. We note that the source is
not visible in the archival SDSS frames of this field, thereby proving
that it is the optical afterglow of GRB 090809.
The afterglow is detected in each I-band and R-band frame. The
preliminary magnitudes are I~19.9 and R~20.3 respectively, against the
same reference star, 0899-0602834 in the USNO B1 catalog.
Further photometric observations are underway. We encourage
spectroscopic follow-up.
GCN Circular 9754
Subject
GRB 090809: Swift detection of a burst with a possible optical counterpart
Date
2009-08-09T17:51:30Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. B. Markwardt (CRESST/GSFC/UMD), S. D. Barthelmy (GSFC),
M. M. Chester (PSU), A. de Ugarte Postigo (INAF-OAB),
N. Gehrels (NASA/GSFC), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
N. P. M. Kuin (MSSL), W.B Landsman (GSFC), J. Mao (INAF-OAB),
R. Margutti (Univ Bicocca&OAB), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), P. Romano (INAF-IASFPA) and
M. H. Siegel (PSU) report on behalf of the Swift Team:
At 17:31:14 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090809 (trigger=359530). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 328.645, -0.083 which is
RA(J2000) = 21h 54m 35s
Dec(J2000) = -00d 04' 59"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a weak peak
with a duration of about 10 sec. The peak count rate
was ~900 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 17:32:58.5 UT, 104.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 328.67772, -0.08465 which is equivalent
to:
RA(J2000) = 21h 54m 42.65s
Dec(J2000) = -00d 05' 04.7"
with an uncertainty of 4.5 arcseconds (radius, 90% containment). This
location is 117 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 (6.08e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2.5
(+2.71/-2.28) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 86 seconds with the White
filter starting 107 seconds after the BAT trigger. A possible
afterglow candidate has been found in the list of sources generated
on-board, located at RA=328.68008 (21:54:43.22), dec=-0.08385
(-00:05:01.9), with an estimated White magnitude = 19.9 +/-0.4. The
2.7'x2.7' sub-image does not include the XRT position. No correction
has been made for the expected extinction corresponding to E(B-V) of
0.10.
Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt 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.)