GRB 060123
GCN Circular 4622
Subject
GRB 060123: Gemini spectroscopy of the putative host galaxy
Date
2006-01-30T22:49:55Z (21 years ago)
From
Edo Berger at Carnegie Obs <eberger@ociw.edu>
E. Berger (Carnegie Observatories), P. A. Price (IfA, Hawaii), and D. B.
Fox (Penn State) report on behalf of a larger collaboration:
"We obtained 2x1500 sec spectra of the putative host galaxy located inside
the XRT error circle of GRB 060123 (GCNs 4584,4595,4600) with GMOS on the
Gemini-N 8-m telescope starting on 2006 Jan 30.60 UT. The spectra cover
the range 6400-9100 A and reveal one strong and resolved emission line at
an observed wavelength of 7826.0A, and a possible weaker line at 7590.8A.
The latter line is located on the edge of the atmospheric A-band and and
its reality is therefore questionable. We find three possible
interpretations for the redshift:
[1] The broad line is the (barely resolved) [OII] 3727 doublet at z=1.099.
In this case there is no obvious interpretation for the second line.
[2] The broad line is H-alpha and the weak line line is [OI] 6364 at
z=0.193. In this case we may expect to detect the [NII] and [SII]
doublets, which we do not.
[3] The broad line is [OIII] 5007 and the weak line is H-beta at z=0.562.
In this case we expect to detect [OIII] 4959, which we do not.
Given that the weak line may not be real, and the lack of detection of
various other lines expected in scenarios [2] and [3], we favor the first
interpretation and a redshift z=1.099.
We note that spectra with bluer coverage may be able to confirm or rule
out options [2] and [3] through the detection (or lack thereof) of [OII],
[OIII], and H-beta at their corresponding redshifts."
GCN Circular 4621
Subject
GRB 060123: VLA Radio Observations
Date
2006-01-30T20:21:05Z (21 years ago)
From
Dale A. Frail at NRAO <dfrail@nrao.edu>
Dale A. Frail (NRAO) reports on behalf of a larger collaboration:
"We used the Very Large Array to observe the Swift burst GRB 060123
(GCN 4584; GCN 4608) at a frequency of 8.46 GHz on 2006 January 26.47
and January 30.52 UT. No radio emission was detected within the
refined 3-arcsec XRT error circle (GCN 4600) above a 4-sigma level at
either epoch, with sigma noise values of 26 uJy and 18 uJy, respectively.
No further observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
GCN Circular 4608
Subject
GRB 060123: Swift refined analysis of an unusual GRB
Date
2006-01-27T22:37:00Z (21 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
J. Cummings (GSFC/ORAU), V. Mangano (INAF-IASFPA),
L. Angelini (GSFC), L. Barbier (GSFC), S. Barthelmy (GSFC),
D.N. Burrows (PSU), M. Chester (PSU), E. Fenimore (LANL),
N. Gehrels (GSFC), D. Hullinger (UMD), J. Kennea (PSU),
H. Krimm (GSFC/USRA), V. La Parola (INAF-IASFPA),
A. Levan (U. Leicester), C. Markwardt (GSFC/UMD),
T. Mineo (INAF-IASFPA), J. Norris (GSFC), P. O'Brien (U. Leicester),
D. Palmer (LANL) A. Parsons (GSFC), E. Rol (U. Leicester),
P. Romano (INAF-OAB), T. Sakamoto (GSFC/ORAU), G. Sato (ISAS),
J. Tueller (GSFC),
on behalf of the Swift team:
Using Swift-BAT survey data from T-23 to T+877 sec and target of
opportunity (ToO) Swift-XRT observations, we report further
analysis of Swift-BAT GRB 060123 (Palmer, et al., GCN 4584).
T90 was 900 +- 100 seconds (estimated one-sigma error), with multiple
peaks but an overall gradual profile. Peak flux was
0.04 +- 0.01 photons/cm2/sec in the 15-150 keV band.
The prompt emission time-averaged spectrum is well fitted by a simple
power law model. The power law index is 1.9 +- 0.6. The fluence in
the 15-150 keV band was (3.0 +- 1.2) x 10^-7 erg/cm2.
A Swift ToO observation started at 19:14:14 on Jan 24th, 2006
(75.1 ks after the event). XRT detected a point source within the
BAT error box (Palmer et al, GCN 4584). Subsequent ToO observations
revealed that, after an initially flat phase, this source is steadily
decaying with a slope of -2.2 +/- 0.4. The initial flat phase
extended to ~1.1 x 10^5 sec. Further observations are ongoing.
The average XRT spectrum accumulated in the time interval from
75.1 ksec to 291 ksec after the event (20 ksec of net exposure) was
fitted, using Cash statistics, with an absorbed power law. The best
fit photon index is 2.1 +/- 0.2. The spectrum shows evidence of
absorption at the level of (2 +/- 1)e21 cm^-2, in excess of the
estimated Galactic value (1.6e20 cm^-2, Dickey & Lockman 1990). The
average unabsorbed 0.2-10 keV flux is 7.0e-13 ergs cm^-2 s^-1.
All the quoted errors are at the 90% confidence level except as
noted.
This was an unusual event. It was very long and very gradual, having
the longest duration and weakest peak flux of any BAT burst. The GRB
nature of the event would be uncertain on the basis of the BAT data
alone, but is highly probable given the fading XRT light curve. The
flat decay phase extends very late for a GRB. Followup observations
are strongly encouraged.
GCN Circular 4600
Subject
Refined XRT Position for GRB 060123
Date
2006-01-25T20:30:16Z (21 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
N. Butler and J. S. Bloom (UC Berkeley):
We determine a refined XRT positions for GRB060123 (Palmer et al.,
GCN 4584)
by matching the positions of X-ray sources to positions of SDSS
sources. A
similar procedure was employed in GCN 4500 to refine the XRT position
for
GRB060108. Using 4 X-ray sources detected in 4.5 ksec of PC mode data
and 6 SDSS sources, we determine a frame offset for the XRT of:
Frame Offset: RA -2.28 ; Dec 2.0 , 90% Conf. Error: 2.7"
Our refined XRT position for GRB060123 is then:
RA 11h 58m 47.66s ; DEC +45d 30' 50.55"
+/-
3.1" (90% Conf.)
This refined XRT position is coincident with the SDSS galaxy noted in
Bloom et al. (GCN 4595). Given this, we suggest that this
coincidence appears to disfavor the high-redshift hypothesis for the
burst (Palmer et al., GCN 4584)."
The X-ray/optical source offsets are shown at:
http://astro.berkeley.edu/~nat/060123/crosscor_sdss.jpg
The XRT overlap atop the SDSS and PAIRITEL images is:
http://astro.berkeley.edu/~jbloom/grb060123-nat.ps.gz
We thank Dave Burrows at PSU for his assistance.
GCN Circular 4595
Subject
GRB060123: Optical and IR Imaging
Date
2006-01-25T12:10:50Z (21 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
J. S. Bloom, F. Marchis (UCB), K Smalley, E. E. Falco, C. Blake
(CfA), N. Bulter, and R. Foley (UCB) report:
"With high winds and poor transmission on Mt. Hopkins we observed the
field of GRB 060123 (Palmer et al., GCN 4584) both with the PAIRITEL
1.3m and the 48" telescope equipped with Keplercam. At time 25.3 Jan
2006 UT we find no significantly new source in i, z, J, H, Ks within
the XRT error circle when compared with SDSS (Cool et al. GCN 4585).
Imaging in I and z' under better conditions at the Lick 3m + PFCam on
Mt. Hamilton began at 25.3 Jan 2006 UT: analysis is still in progress
but we confirm the conclusion of Cenko et al. (GCN 4594) that there
is no evidence for a new optical source to the SDSS limits. We do
note that there is a faint (z_AB = 19.87 mag) apparent galaxy (SDSS
J115847.6+453050.8) on the northern outskirts of the 90% containment
XRT error circle at J2000: 11:58:47.59, +45:30:50.8."
A SDSS-PAIRITEL-PFCam triptych may be found at:
http://astro.berkeley.edu/~jbloom/grb060123.ps
GCN Circular 4594
Subject
GRB 060123: P200 Observations
Date
2006-01-25T11:34:40Z (21 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko (Caltech), W. Reach, and D. Faied (JPL / IPAC) report on
behalf of the Caltech-NRAO-Carnegie Collaboration:
We have imaged the field of GRB060123 (Palmer et al., GCN 4584) with the
Large Format Camera mounted on the Palomar 200-inch Hale Telescope.
Observations consisted of 300 s frames in r' and i' beginning at
approximately 8:35 January 25 UT (~ 34.2 hours after the burst). In
single r' and i' exposures, we find no new sources in the XRT error circle
to a limiting magnitude of r',i' > 22.0. This limiting magnitude was
calculated with reference to the SDSS calibration stars provided by Cool
et al. (GCN 4585).
GCN Circular 4585
Subject
GRB060123: SDSS pre-burst observations
Date
2006-01-24T23:41:51Z (21 years ago)
From
Richard J. Cool at U.of AZ/Steward Obs <rcool@as.arizona.edu>
Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona), David
W. Hogg (NYU), Michael R. Blanton (NYU), David J. Schlegel (LBNL),
J. Brinkmann (APO), Donald P. Schneider (PSU), and Daniel E. Vanden
Berk (PSU) report:
The Sloan Digital Sky Survey (SDSS) imaged the field of burst
GRB060123 prior to the burst. As these data should be useful
as a pre-burst comparison and for calibrating photometry, we are
supplying the images and photometry measurements for this GRB field
to the community.
Data from the SDSS, including 5 FITS images, 3 JPGS, and
3 files of photometry and astrometry, are being placed at
http://mizar.as.arizona.edu/~grb/public/GRB060123
We supply FITS images in each of the 5 SDSS bands of a 8'x8' region
centered on the GRB position (ra=179.700 (11:58:47.9), dec=45.5126
(45:30:45.5); GCN 4584), as well as 3 gri color-composite JPGs (with
different stretches). The units in the FITS images are nanomaggies
per pixel. A pixel is 0.396 arcsec on a side. A nanomaggie is
a flux-density unit equal to 10^-9 of a magnitude 0 source or,
to the extent that SDSS is an AB system, 3.631e-6 Jy. The FITS
images have WCS astrometric information.
In the file GRB060123_sdss.calstar.dat, we report photometry
and astrometry of 182 bright stars (r<20.5) within 15' of the
burst location. The magnitudes presented in this file are asinh
magnitudes as are standard in the SDSS (Lupton 1999, AJ, 118,
1406). Beware that some of these stars are not well-detected in
the u-band; use the errors and object flags to monitor data quality.
In the files GRB060123_sdss.objects_flux.dat and
GRB060123_sdss.objects_magnitudes.dat, we report photometry of
428 objects detected within 6' of the GRB position. We have
removed saturated objects and objects with model magnitudes
fainter than 23.0 in the r-band. The fluxes listed in
GRB060123_sdss.objects_flux.dat are in nanomaggies while the
magnitudes listed in GRB060123_sdss.objects_magnitudes.dat are
asinh magnitudes.
All quantities reported are standard SDSS photometry, meaning that
they are very close to AB zeropoints and magnitudes are quoted
in asinh magnitudes. Photometric zeropoints are known to about
2% rms. None of the photometry is corrected for dust extinction.
The Schlegel, Finkbeiner, and Davis (1998) predictions for this
region are A_U=0.077 mag, A_g=0.057 mag, A_r = 0.041 mag, A_i=0.031
mag, and A_z=0.022 mag.
The file GRB060123_sdss.spectro.dat contains a list of the 1 objects
with SDSS spectroscopy within 6 arcminutes of the GRB position.
In addition to the redshift and 1-sigma error for each object,
this file also lists the object spectroscopic classification.
SDSS astrometry is generally better than 0.1 arcsecond per
coordinate. Users requiring high precision astrometry should take
note that the SDSS astrometric system can differ from other systems
such as those used in other notices; we have not checked the offsets
in this region.
More detailed information pertaining to our SDSS GRB releases
can be found in our initial data release paper (Cool et al. 2006,
astro-ph/0601218). See the SDSS DR4 documentation for more details:
http://www.sdss.org/dr4.
These data have been reduced using a slightly different pipeline
than that used for SDSS public data releases. We cannot guarantee
that the values here will exactly match those in the data release
in which these data are included. In particular, we expect the
photometric calibrations to differ by of order 0.01 mag.
This note may be cited, but please also cite the SDSS data
release paper, Adelman-McCarthy et al. (2006, ApJS, in press,
astro-ph/0507711), when using the data or referring to the technical
documentation.
GCN Circular 4584
Subject
GRB 060123: Swift detection of a very long, faint burst
Date
2006-01-24T23:09:07Z (21 years ago)
From
David Burrows at PSU/Swift <dxb15@psu.edu>
D. Palmer (LANL), J. Kennea (PSU), J. Cummings (GSFC), D. N. Burrows (PSU),
N. Gehrels (GSFC), F. Marshall (GSFC), C. Markwardt (GSFC/UMD), J. A.
Nousek (PSU), A. Parsons (GSFC) report on behalf of the Swift team:
At 22:22:40 UT, the Swift Burst Alert Telescope (BAT) located GRB
060123. The burst did not trigger GCN notices because the source was found
in a long-term (5 minute) image, for which triggers are not currently
enabled. The BAT ground-calculated location is RA,Dec 179.750, +45.513
{11h 59m 00s, +45d 30' 47"} (J2000) with an uncertainty of 3 arcmin
(radius, 90% containment, including systematic uncertainty). The BAT light
curve showed a multi-peaked structure with a duration of about 900 +- 100
sec. The peak count rate was ~160 counts/sec (15-50 keV, note the unusual
energy interval), at ~300 sec after the trigger. We note that this is a
very long duration burst, which suggests the possibility of a high-z event.
At 19:14:14 on Jan 24th, 2006 (75.1 ks after the event) Swift began a
target of opportunity observation of this source. Analysis of XRT data
reveals a faint, fading, uncataloged point source at the following coordinates:
RA(J2000): 11h 58m 47.9s
Dec(J2000): +45d 30' 45.5"
with an error circle of 6 arcseconds (90% containment). This position lies
128 arcseconds from the BAT position of this source. The fading X-ray
lightcurve of this object strongly suggests that this is a GRB afterglow.
UVOT took a 210 second exposure with the V filter starting at 19:14:14
UT. No source was detected with a 3-sigma upper limit of 20.0 mag. at the
XRT position.