GRB 060306
GCN Circular 4848
Subject
GRB 060306: Swift detection of a bright burst
Date
2006-03-06T01:24:47Z (19 years ago)
From
Scott Barthelmy at NASA/GSFC <Scott@lheamail.gsfc.nasa.gov>
L. Angelini (GSFC), S. Barthelmy (GSFC), D. Burrows (PSU),
M. Chester (PSU), J. Cummings (GSFC/ORAU), N. Gehrels (GSFC),
M. Goad (U Leicester), H. Krimm (GSFC/USRA), F. Marshall (GSFC),
D. Palmer (LANL)
on behalf of the Swift team:
At 00:49:10 UT, Swift-BAT triggered and located GRB 060306 (trigger=200638).
The spacecraft slewed immediately. The BAT on-board calculated location is
RA,Dec 41.099d,-2.153d {02h 44m 24s,-02d 09' 10"} (J2000), with an uncertainty
of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows
a multi-peak structure with a total duration of 30 sec. The peak count rate
was ~8000 counts/sec (15-350 keV), at ~1 seconds after the trigger.
The XRT began observing the field at 00:50:38 UT (88 sec after the trigger).
The XRT found a bright, fading, uncataloged X-ray source at
RA(J2000) = 2h 44m 22.7s
Dec(J2000) = -2d 8' 54"
with an estimated uncertainty of 5.4" (90% radius). This position is
24 arcseconds from the BAT position. The initial flux is 1.2E-9 ergs/cm2/sec.
UVOT took a finding chart exposure of 200 seconds with the V filter starting
93 seconds after the BAT trigger. No 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 3-sigma upper limit is 18.4 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 18.0 mag.
No correction has been made for the expected extinction of about 0.1 magnitudes.
We are currently in the Malindi downlink gap, and so we will not receive
the complete data set for another 6 hours.
GCN Circular 4849
Subject
GRB 060306: PROMPT Observations
Date
2006-03-06T02:23:56Z (19 years ago)
From
Melissa Nysewander at UNC,Chapel Hill <mnysewan@physics.unc.edu>
M. Nysewander, A. Foster, A. LaCluyze, D. Reichart, J. A. Crain, K.
Ivarsen, J. Haislip, J. Kirschbrown, C. MacLeod, and A. Trotter report on
behalf of the UNC team of the FUN GRB Collaboration:
Skynet observed the localization of GRB 060306 (Angelini et al., GCN 4848)
with one of the 16-inch PROMPT telescopes at CTIO beginning 49 sec after
the burst (25 sec after notification).
No new source is found, to i' > 17.4 mag at 7.5 min after the burst and r'
> 16.8 mag at 9.3 min after the burst (3 sigma; calibrated to five
USNO-B1.0 and NOMAD stars, respectively, using the transformation equations
of Smith et al. 2002.)
PROMPT is currently being built and commissioned.
GCN Circular 4850
Subject
GRB 060306: Swift-XRT team refined analysis
Date
2006-03-06T12:30:14Z (19 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page, M.R. Goad (U. Leicester) and L. Angelini (GSFC) report on
behalf of the Swift-XRT team:
The XRT began observing the field of GRB 060306 88 seconds after the BAT
trigger. Analysing the first 5 orbits of data, the following refined
position was obtained:
RA(J2000) = 02h 44m 23.0s
Dec(J2000)= -02d 08' 52.8"
with an estimated uncertainty of 3.9 arcsec (90% containment). This is 4.7
arcsec from the XRT position given in GCN 4848 (Angelini et al.), and
21.3 arcsec from the BAT position reported in the same circular.
The light-curve shows a steep initial decay, with alpha ~3.4, breaking to
a slope of ~0.6 at ~210 seconds after the trigger time.
The WT spectrum (96-173 seconds after the trigger) can be fitted with a
power-law of Gamma = 2.1 +/- 0.3, with NH ~4 x 10^21 cm^-2 (in addition to
the estimated Galactic value of 3.6 x 10^20 cm^-2). There is no evidence
for spectral evolution across the break in the light-curve. The observed
(unabsorbed) flux over 0.3-10 keV for the WT spectrum is 2.24 x 10^-10
(3.90 x 10^-10) erg cm^-2 s^-1.
Assuming the current decay of alpha ~0.6 continues, the estimated count
rate at 24 hours is 0.02 ct s^-1, corresponding to an observed
(unabsorbed) flux of 1.3 x 10^-12 (2.9 x 10^-12) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 4851
Subject
GRB 060306: Swift-BAT refined analysis
Date
2006-03-06T17:15:50Z (19 years ago)
From
Hans Krimm at NASA-GSFC <krimm@milkyway.gsfc.nasa.gov>
D. Hullinger (BYU-Idaho), L. Angelini (GSFC), L. Barbier (GSFC),
S. Barthelmy (GSFC), J. Cummings (GSFC/ORAU), E. Fenimore (LANL),
N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU),
G. Sato (ISAS), J. Tueller (GSFC),
on behalf of the Swift-BAT team:
Using the data set from T-300 to T+300 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 060306 (trigger
#200638) (Angelini, et al., GCN 4848). The BAT ground-calculated
position is (RA,Dec) = 41.096, -2.155 deg {2h 44m 23.0s, -2d 9' 19.3"} (J2000)
+- 1.0 arcmin, (radius, sys+stat, 90% containment). The partial
coding was 50%.
The light curve is a series of FRED-like peaks at T-1, T+1, T+27, T+43,
and T+60, with similar decay constants of ~2 sec. The dominant peak is
at T+1. The small peak at T+60 is soft compared to the others, which all
have similar spectra. T90 (15-350 keV) is 61 +- 2 sec (estimated error
including systematics).
The time-averaged spectrum from T-1.4 to T+66.9 is well fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.85 +- 0.10. The fluence in the 15-150 keV band is
2.2 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured
from T+0.20 sec in the 15-150 keV band is 6.1 +- 0.3 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.
GCN Circular 4852
Subject
Swift/UVOT observations of GRB060306
Date
2006-03-06T18:47:46Z (19 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL-UCL), L. Angelini (GSFC) on the behalf of the
Swift/UVOT team:
The Swift/UVOT began observing the field of GRB 060306 at 00:50:32 UT on
March 6, 2006, 79 sec after the trigger (Angelini et al. GCN 4848). No
source is detected at the refined XRT position (Page et al. GCN 4850) down
to the following 3 sigma upper limits:
Filter T-range (sec since trigger) Exp (sec) 3sigma U.L. (mag)
V 79-34440 2918 20.1
B 460-29558 2708 20.7
U 405-28651 2701 20.1
UW1 351-36040 2173 20.6
UM2 297-12199 2800 20.9
UW2 569-7040 2040 21.0
White 513-562 50 19.3
Quoted magnitudes have not been corrected for extinction, E(B-V)=0.036
GCN Circular 4854
Subject
GRB 060306: MAGNUM observations
Date
2006-03-06T23:02:26Z (19 years ago)
From
Paul Price at IfA,UH <price@ifa.hawaii.edu>
P.A. Price (IfA, Hawaii), T. Minezaki (IoA, Tokyo), L.L. Cowie, Y.
Kakazu (IfA, Hawaii) and Y. Yoshii (IoA, Tokyo) report:
We observed the XRT position (GCN 4850) of GRB 060306 (GCN 4848) with
the robotic MAGNUM telescope + MIP dual-beam camera beginning at Mar
6.235 UTC (4.8 hours after the GRB). Images in the R, I and J bands
show a source present within the XRT error circle, with R ~ 20.7 mag
(based on USNO-A2.0 star at 02:44:19.08 -02:08:53.6 with R = 15.2 mag).
However, this source is also present in the Digitised Sky Survey red
plate at a similar flux level. The position of the source from the DSS
plate is:
02:44:22.98 -02:08:51.1 J2000
Due to the limited time baseline, we cannot make a meaningful test for
variability, and hence it is not yet clear whether or not this source is
related to the GRB. If related, it would likely indicate that the GRB
is at a relatively low redshift. No other sources are identified within
the XRT error circle to R ~ 22 mag.
Images of the field are shown at
http://www.ifa.hawaii.edu/~price/magnum_grb060306.jpg
Observers with CCD images of the source at a different epoch are invited
to contact PAP to perform image subtraction.
This message may be cited.
GCN Circular 4857
Subject
GRB 060306: SOAR Ks Observations
Date
2006-03-10T20:39:30Z (19 years ago)
From
Melissa Nysewander at UNC,Chapel Hill <mnysewan@physics.unc.edu>
M. Nysewander, D. Reichart, A. Oliveira, P. Ugarte, and A. Alvarez report
on behalf of the UNC team of the FUN GRB collaboration:
We observed the localization of GRB 060306 (Angelini et al., GCN 4848) with
the SOAR infrared imager, OSIRIS, beginning at 00:31:56 UT on March 7th,
1.0 days after the burst. We detect no new source down to a 3-sigma
limiting magnitude of Ks = 18.2 based on six stars from the 2MASS
catalogue.
If one assumes minimal extinction in the Ks band and uses the extrapolated
to 24 hours, unabsorbed X-ray flux of Page et al. (GCN 4850), this suggests
a NIR to X-ray spectral index that is shallower than -0.7.
The source in the XRT error circle which is also in the DSS-Red plate (as
noted by Price et al., GCN 4854) is at Ks = 17.3 +/- 0.2 mag.
SOAR is currently being commissioned.
GCN Circular 4861
Subject
GRB060306: APO Ks-band Imaging Observations
Date
2006-03-12T04:41:38Z (19 years ago)
From
Hsiao-Wen Chen at U Chicago <hchen@oddjob.uchicago.edu>
H.-W. Chen (U Chicago), X. Fan (U Arizona), F. Hearty (Colorado), M. Bayliss
(Chicago), D. Q. Lamb (U Chicago), R. McMillan (APO), B. Ketzeback (APO), J.
Barentine (APO), J. Dembicky (APO), and D. York (U Chicago) report:
"We obtained a 3x300 sec dithered exposures in Ks of the field of
GRB060306 (Angelini et al., GCN 4848), using the NIC-FPS near-infrared camera
on the 3.5 m telescope at the Apache Point Observatory. The
observations started at 20060306.10 UT (~ 2 hrs after the initial
Swift trigger) through variable clouds and under a mean seeing
condition of 1 arcsec. Calibrating the final stacked image to 2MASS
stars in the field gives a 5 sigma depth of Ks=20.4 over a 1 arcsec diameter
aperture. Within the XRT error circle (Page et al., GCN 4850), we locate a
single source at
RA(J2000) = 02:44:23.0
Dec(J2000) = -02:08:51.2,
which is also present in the DSS red plate (see also Price et al.,
GCN 4854, and Nysewander et al., GCN 4857). Based on the 2MASS photometry,
we estimate the source brightness to be Ks=18.3 +/- 0.1 mag. Comarison with
the Ks image taken a day later by Nysewander et al. (GCN4857) shows no
variability of this source.
The stacked image is available at
http://lambda.uchicago.edu/public/grb/grb060306/grb060306K.fits.
NIC-FPS is currently in its commissioning phase."
GCN Circular 5079
Subject
GRB 060306: Further Analysis of SOAR and APO NIR Observations
Date
2006-05-06T03:53:15Z (19 years ago)
From
Don Lamb at U.Chicago <lamb@oddjob.uchicago.edu>
GRB 060306: Further Analysis of SOAR and APO NIR Observations
D. Q. Lamb (Chicago), M. Nysewander (UNC), F. Hearty (Colorado), H.-W.
Chen (Chicago), and D. E. Reichart (UNC) report on behalf of the FUN GRB
Collaboration:
We have further analyzed the Ks-band images taken with the ARC 3.5-meter
telescope using NIC-FPS, beginning 1.6 hours after the burst, and the
Ks-band images taken with the SOAR 4.1-meter telescope using OSIRIS,
beginning 24 hours after the burst.
From the ARC image, we measure a limiting magnitude of Ks = 19.5 (3
sigma) and a magnitude of Ks = 17.78 � 0.13 mag for the source that is
in the XRT error circle and in the DSS (Price et al., GCN 4854), using
six 2MASS objects (five of "A" quality and one of "C" quality;
Skrutskie et al. 2006, AJ, 131, 1163) in the NIC-FPS image for
calibration and an aperture radius of 1.6 arcsec, as dictated by a
curve of growth analysis of the source. The magnitude of Ks = 18.3 �
0.1 originally reported by Chen et al. (GCN 4861) corresponded to an
aperture radius of 1.0 arcsec, and is therefore fainter.
From the SOAR image, we measure a limiting magnitude of Ks = 18.4 (3
sigma) and a magnitude of Ks = 17.53 � 0.20 for the source, using the
four 2MASS objects (one of "A" quality and three of "C" quality) in
the OSIRIS image for calibration and an aperture radius of 1.6 arcsec,
as dictated by a curve of growth analysis of the source. This result
is consistent with that reported by Nysewander et al. (GCN 4857).
The two results are consistent with a constant brightness source, and
PSF-matched image subtraction provides no indication that the source
brightened between the two epochs.
The source appears to be marginally extended in the ARC image, and may
be the host galaxy (Price et al., GCN 4854). Spectroscopy of the source
is therefore encouraged. However, even if the source is the host
galaxy, or a chance-coincidence foreground star (~1% probability),
PSF-matched image subtraction of the Ks-band images does not detect the
afterglow at 1.6 hours after the burst to the limiting magnitude [Ks =
18.4 (3 sigma)] of the SOAR image.
If one assumes minimal extinction in the Ks-band and extrapolates the
unabsorbed X-ray flux (Page et al., GCN 4850) to 1.6 hours after the
burst, the resulting Ks-band to X-ray spectral index is shallower than
-0.48 (3 sigma), using the limiting magnitude of the SOAR image (which
is appropriate if the location of the burst is coincident with the
faint source in the XRT error circle), and shallower than -0.36 (3
sigma), using the limiting magnitude of the ARC image (which is
appropriate if the location of the burst is not coincident with the
faint source in the XRT error circle). This suggests one or more of
the following possibilities:
1. The redshift of the burst is greater than z ~ 17, which is highly
unlikely.
2. The cooling break is blueward of the Ks-band at 1.6 hours after the
burst. Given that the X-ray temporal index is ~-0.6 (Page et al., GCN
4850), the Ks-band to X-ray spectral index would be ~-0.7 (e.g., Sari,
Piran, and Narayan 1998, ApJ, 497, L17) if the cooling break were
instead redward of the Ks band.
3. The afterglow is highly extinguished. Given that the source-frame
N_H ~ 4 x 1021 cm^-2 (1+z)2.6 (Page et al., GCN 4850; Morrison and
McCammon 1983, ApJ, 270, 119), a redshift of only z ~ 1 is needed in
order to produce 3 - 4 mag of extinction in the observer-frame Ks-band,
provided that dust destruction by the burst and/or its afterglow is
minimal. Furthermore, a redshift of z ~ 1 yields source-frame values of
N_H that are consistent with giant molecular cloud environments.
Finally, we point out that the properties of the afterglow of this
burst are reminiscent of those of GRB 051022 (Doty et al., GCN 4145;
Butler et al., GCNs 4165 and 4170).