- GCN Circular #6024
K. Hurley and T. Cline, on behalf of the Mars Odyssey GRB team,
I. Mitrofanov, A. Kozyrev, M. Litvak, A. Sanin, V. Tret'yakov and A.
Parshukov, on behalf of the HEND-Odyssey GRB team,
W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on
behalf of the GRS-Odyssey GRB team,
K.Yamaoka, M.Ohno, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada,
T. Murakami, and K. Makishima on behalf of the Suzaku WAM team,
D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, C. Wigger, W.
Hajdas, and A. Zehnder, on behalf of the RHESSI GRB team,
A. von Kienlin, G. Lichti, and A. Rau, on behalf of the
INTEGRAL SPI-ACS GRB team, and
J. Cummings, H. Krimm, S. Barthelmy, and N. Gehrels, on behalf of
the Swift-BAT team, report:
Mars Odyssey (HEND and GRS), Suzaku (WAM), INTEGRAL (SPI-ACS),
and RHESSI observed this intense, ~60 s long event at 26445 s.
Using Odyssey, Suzaku, and INTEGRAL data, it was triangulated
to two annuli, whose preliminary coordinates are RA, Dec, Radius=
96.685, 23.883, 20.068 +/- 0.041, and 82.803, 82.086, 50.831 +/- 4.47
degrees.
Swift was slewing at the time of the burst. A marginal source (of
insufficient significance to trigger a regular GRB response) was
detected in a routine image made after the slew was completed. The
source coincides with the intersection of the Odyssey-INTEGRAL and
WAM-INTEGRAL annuli. Ground processing of the image improves the
significance of the detection. The BAT ground-derived position is
RA, Dec 117.850, +31.140 degrees
with a 2.5 arcmin radius error circle (estimated 90% confidence limit).
The detection implies that the burst was continuing in the BAT energy
range for > 4 minutes after T0.
A Swift ToO observation has been requested. Details of the energy
spectrum will be reported later.
- GCN Circular #6025
E. Bellm, M. Bandstra, S. Boggs, C. Wigger, W. Hajdas,
D. M. Smith, and K. Hurley on behalf of the RHESSI team report:
As observed by RHESSI, GRB070125 (Hurley et al., GCN 6024)
had a duration of ~70s starting at about T0=07:20:42 UT.
The preliminary fit to the time-integrated RHESSI spectrum from T0 -
T0+69s between 30 keV and 10 MeV is a cutoff power law with
alpha = -1.33 +0.11/-0.09
E0 = 1450. +710/-450. keV
Epeak = 980. +/-300. keV
(90% confidence levels).
The 30 keV-10 MeV fluence is 1.5 E-4 erg/cm^2.
The RHESSI data show two main periods of GRB emission. The first, from T0
- T0+13s, had a fluence of 4.6 E-5 erg/cm^2 and an Epeak of 950 +/-300
keV. A second, multi-peaked emission period occurred from T0+30s - T0+50s
and had a fluence of 7.2 E-5 erg/cm^2 and an Epeak of 675 +/-175 keV.
- GCN Circular #6026
Brenda Dingus reports for the Milagro Collaboration
GRB070125 occured at 9.5 degrees zenith for the Milagro TeV observatory. =
This burst is the brightest that has occured within the optimum field of =
view of Milagro. Very preliminary analysis doesn't show any significant =
excess. The interpretation of this observation depends on the redshift =
of the burst, because very high energy emission is absorbed for bursts =
at high redshifts due to pair production with the extragalactic =
background light.
We encourage observers to try to obtain a redshift for this GRB which =
would then result in the most stringent constraints on the ratio of very =
high energy emission to sub-MeV emission from GRBs.
- GCN Circular #6028
S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a
larger collaboration:
We have imaged the field of GRB070125 (Hurley et al., GCN 6024) with the
automated Palomar 60-inch telescope. Our images were taken in the Kron R
filter at approximately 2:36 UT 26 Jan. We identify a bright, stationary
source not present in the Digitized Sky Survey images at location
(J2000.0):
RA: 07:51:17.75 Dec: +31:09:04.2
with an uncertainty of ~ 0.5" in each coordinate. Comparison with nearby
objects in the USNO-B catalog indicates the source has an R-band magnitude
of ~ 18.6. While we cannot identify any variability in our initial
images, we consider it likely that this object is the optical afterglow
of GRB070126.
- GCN Circular #6029
A. C. Updike, D. H. Hartmann, G. L. Bryngelson, R. C. Goldthwaite, and J.
R. Puls (Clemson University) report on behalf of the Clemson GRB Follow-Up
Team:
We imaged the field of GRB 070125 (GCN 6024, Hurley et al.) beginning at
01:49:58 UT with the SARA 0.9m at Kitt Peak under decent weather
conditions. We have obtained 20 180-second exposures in the R band. In
stacked images, we can clearly see the afterglow candidate identified by
Cenko & Fox (GCN 6028). Observations are continuing.
The Clemson University GRB Response Site may be found at:
http://people.clemson.edu/~kgarime/burst/index.php
The SARA Homepage can be found at:
http://saraobservatory.org
This message may be cited.
- GCN Circular #6030
J. Racusin, L. Vetere (PSU) report on behalf of the Swift-XRT team:
The Swift-XRT began observing the field containing the IPN/BAT GRB 070125
(Hurley et al., GCN 6024) at 2007-01-25 20:18:48 UT, 46.7 ks after the
trigger. In four orbits of Photon Counting mode data totaling 5.4 ks we
detect an uncatalogued source at RA,Dec=117.82532,+31.1506 which is:
RA(J2000) = 7h 51m 18.08s
Dec(J2000) = +31d 09' 02.2"
with an uncertainty of 3.8 arcsec (90% containment). This is 85 arcseconds
from the initial position reported in GCN 6024, and 4.7 arcseconds from
the possible optical counterpart reported by Cenko et al. (GCN 6028).
The preliminary 0.3-10.0 keV lightcurve shows a fading behavior with a
decay index of 1.5 +/- 0.7. The XRT count rate is ~0.06 counts/s.
The PC spectrum is fit by an absorbed power-law with a photon index of 2.0
+/- 0.3. The absorption is at a level of 8.1e20 cm^-2, consistent with
Galactic absorption along the line of sight (4.8e20 cm^-2). The average
unabsorbed flux of the PC spectrum is 3.2e-12 ergs cm^-2 s^-1.
Assuming the X-ray emission continues to decline at the same rate, we
predict a 0.3-10.0 keV XRT count rate of 0.03 counts/s at T+24hr, and 0.01
counts/s at T+48hr, which corresponds to an observed flux of 1.5e-12 ergs
cm^-2 s^-1 and 5.3e-13 ergs cm^-2 s^-1, respectively.
Due to instrumental observing constraints, GRB070125 is not currently
being observed by Swift. Continued follow-up will likely occur over the
next few days.
This circular is an official product of the Swift-XRT team.
- GCN Circular #6031
Jason X. Prochaska (UCSC), Ryan Foley (UCB), Daniel Perley (UCB), and
Thea Steele (UCB) on behalf of GRAASP reports:
"We observed the afterglow of GRB 070125 with the Kast
dual spectrometer for 4800s total starting at UT 05:41
under variable conditions. Our low-resolution
spectrum covers 3400-8000A and reveals no significant absorption
or emission lines. We place these constraints on the
redshift (in order of descending confidence):
(1) The absence of a Lyman limit implies z<2.7.
(2) The absence of a damped Lya profile or obvious Lya forest
implies z<1.8.
(3) The absence of obvious MgII absorption implies z<0.4.
Further analysis is in progress."
This GCN may be cited.
- GCN Circular #6032
Jason X. Prochaska (UCSC), Gijs Roelofs (Nijmegen), Joshua Bloom (UCB)
and Danny Steeghs (CfA) report on behalf of GRAASP:
"We observed the afterglow of GRB 070125 with the LRIS
dual spectrometer for 600s total starting at UT 05:44
under variable conditions. Our high signal-to-noise
spectrum covers 3000-8000A and reveals no obvious absorption
or emission lines. We place these constraints -- which are tighter
than those presented in GCN 6031 -- on the redshift:
(1) The absence of a Lyman limit requires z<2.3.
(2) The absence of a damped Lya profile or obvious Lya forest
requires z<1.4
(3) The absence of MgII absorption suggests z<0.1.
Given that strong MgII absorption is a signature of nearly
every long duration GRB to date, we have confidence in the third
conclusion. On the other hand, the absence of obvious [OII] or Halpha
emission is surprising. If the GRB is at very low redshift, the
absence of
any source in the DSS imaging at this GRB position suggests a
significantly sub-L* host.
We strongly urge groundbased and spacebased follow-up programs
to plan an intensive campaign to search for and characterize any
associated supernova.
Further analysis is in progress."
- GCN Circular #6033
A. Pelangeon & J-L. Atteia (LATT-OMP) report:
We have used the spectral parameters of GRB 070125
provided by Bellm et al. (GCNC 6025) to compute the spectral
pseudo-redshift**
of this burst detected by the IPN Network and SWIFT-BAT (Hurley et al.,
GCNC 6024).
We find a pseudo-redshift pz= 1.6 ? 0.8
This pseudo-redshift relies on the assumption that GRB 070125
follows the Amati relation.
If we combine the constraints obtained from the pseudo-z computation
with the spectroscopic constraints given by Prochaska et al.
(GCNC 6031 & 6032), we suggest that the redshift of GRB 070125
is close to z=1.5.
** cf. http://www.ast.obs-mip.fr/grb/pz
- GCN Circular #6034
S. B. Cenko (Caltech) reports on behalf of a larger collaboration:
We have continued to monitor the proposed optical afterglow of GRB 070125
(GCN 6028) with the Palomar 60-inch telescope. We began a new series of
R-band observations at ~ 9:29 UT 26 Jan. Using 50 point sources from the
2MASS catalog, we have refined the astrometry of our imaging. The updated
position (J2000.0) for the optical candidate is:
RA: 07:51:17.767, Dec: +31:09:04.11
with an uncertainty of +/- 0.3" in each coordinate. The position of the
source is consistent between the two epochs, placing an upper limit on any
proper motion of <~ 0.06 arcsec / hr. Furthermore, from a preliminary
analysis of the photometry, we find evidence the source has faded by ~
0.13 mag between our two epochs. Observations and analysis are
continuing.
Given the unusual nature of the spectrum of this object (Prochaska et
al., GCNs 6031 & 6032), we urge further optical monitoring to confirm
this object is indeed the optical afterglow of GRB 070125.
- GCN Circular #6035
L.P. Xing, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng
Y. Urata and W.K. Zheng on behalf of EAFON report:
We have imaged the field of GRB 070125 with the TNT 0.8m telescope
at Xinglong Observatory started at 10:48 UT 26 Jan. Observation were
performed with R and V filters, the optical afterglow is detected
in all of these frames. Using the reference star derived form USNO
A-2.0 Ra=117.80128d Dec=31.17685d (J2000) R=15.2, we estimate the
afterglow had a mag R~18.73 +/- 0.15 at 10:53 UT. Observations are
continuing.
This message may be cited.
- GCN Circular #6036
F. E. Marshall (NASA/GSFC) and J. Racusin (PSU) report on behalf
of the Swift team:
Swift/UVOT observed the field of GRB 070125 (Hurley et al., GCN Circ. 6024)
starting 13 hours after the burst. A bright, fading source
at the position reported by Cenko (GCN Circ. 6034)
is detected with the V and B filters. Additional observations
are now being taken with the other UVOT filters.
The table below gives the measured magnitudes for the currently
available data. T_start and T_end are the start and stop
times of the summed exposures in seconds from the trigger.
No correction has been made for the expected
Galactic reddening of E(B-V) = 0.05.
Filter T_start T_end Exposure Mag Error
V 46685 53261 1736 18.54 0.06
V 58269 63986 1590 18.74 0.07
B 47550 54163 1674 18.92 0.03
B 59126 59947 798 19.03 0.06
- GCN Circular #6039
M. Uemura, A. Arai, and T. Uehara (Hiroshima Univ.),
report on behalf of the KANATA GRB team:
We took optical CCD images of the field of GRB070125 (GCN 6024)
during 16:11-16:32 UT 26 Jan. using the TRISPEC attached to the KANATA
1.5-m telescope at Higashi-Hiroshima Observatory, Japan.
We obtained 10 R-band images with a 123-s exposure time.
Using the same comparison star used in Xing et al. (GCN 6035; R=15.2),
our data reduction yielded the following result:
UT R mag err
Jan. 26.68209 19.09 0.05
- GCN Circular #6041
F. E. Marshall (NASA/GSFC), D. E. vanden Berk (PSU), and
J. Racusin (PSU) report on behalf of the Swift team:
The afterglow of GRB 070125 (Hurley et al., GCN Circ. 6024)
has now been detected in all 6 UVOT filters ranging from
V (central wavelength of 546 nm) to UWW2
(central wavelength of 193 nm).
The decay in the V filter is consistent
with a 1/t decay rate. Detection in the UVW2
filter requires a redshift of < 1.5, which
is consistent with earlier suggestions by
Prochaska et al. (GCN 6031 and 6032) and
Pelangeon and Atteia (GCN 6033).
The table below gives the measured magnitudes.
T_start and T_end are the start and stop
times of the summed exposures in seconds from the trigger.
No correction has been made for the expected
Galactic reddening of E(B-V) = 0.05.
Filter T_start T_end Exposure Mag Error
V 46685 53261 1736 18.54 0.06
V 58269 63986 1590 18.74 0.07
V 116966 117176 205 19.26 0.27
B 47550 54163 1674 18.92 0.03
B 59126 59947 798 19.03 0.06
UVW2 116119 116959 840 19.26 0.10
- GCN Circular #6042
A.J. van der Horst (University of Amsterdam) reports on behalf of a larger
collaboration:
"We observed the position of the GRB 070125 afterglow at 4.9 GHz with the
Westerbork Synthesis Radio Telescope at January 26 17.04 UT to 22.49 UT,
i.e. 1.40 - 1.63 days after the burst (GCN 6024).
We do not detect a radio source at the position of the optical counterpart
(GCN 6034). The three-sigma rms noise in het map around that position is
261 microJy per beam. The formal flux measurement for a point source at
the position of the optical counterpart is 44 +/- 87 microJy.
We would like to thank the WSRT staff for scheduling and obtaining these
observations."
- GCN Circular #6044
J. Haislip, D. Reichart, A. LaCluyze, K. Ivarsen, M. Nysewander, A. Foster,
and J.A. Crain report:
Skynet observed the localization of GRB 070125 (Hurley et al., GCN 6024)
with one of the 16-inch PROMPT telescopes at CTIO beginning 20.3 hours
after the burst in BVRI. The afterglow candidate identified by Cenko and
Fox (GCN 6028) is clearly visible in all filters.
We find the source to be R ~ 18.8 at a mean time of 21.8 hours after the
burst calibrated to 10 USNO B1.0 stars. Further observations are planned.
- GCN Circular #6047
G. Greco (Bologna University), F. Terra (Second University of
Roma "Tor Vergata"), C. Bartolini, A. Guarnieri, A. Piccioni
(Bologna University), G. Pizzichini (INAF/IASF Bologna),
D. Nanni (INAF/OAR and Second University of Rome "Tor Vergata"),
R. Gualandi (Bologna Observatory) and V. F. Polcaro (INAF/IASF Roma)
report:
On January 27-28 we observed the field of GRB 070125
(Hurley et al., GCN 6024) with the 152 cm Cassini Telescope
located in Loiano, equipped with BFOSC under clear sky
conditions (seeing approximately 2 arcsec).
The photometry is based on the SDSS stars and the
trasformation derived from Lupton (2005).
For the optical afterglow detected by Cenko and
Fox (GCN 6028) we find the following magnitudes:
..Mean..UT .......Filter........Exptime (s).......magnitude
Jan...27.950........Rc............1200............20.23 +/-0.10
Jan...27.966........Rc............1200............20.26 +/-0.11
Jan...27.983........Rc............1200............20.21 +/-0.11
Jan...28.087........Rc............1200............20.25 +/-0.11
Jan...28.102........Rc............1200............20.35 +/-0.12
One of our images is available in a public directory from where
it can be retrieved by sftp by using:
hostname: ermione.bo.astro.it
username: publicGRB
password: GRB_bo
directory: GRB070125
- GCN Circular #6048
D.T. Durig (Cordell-Lorenz Observatory, University of the South) and
B. Gary (Hereford Arizona Observatory) report on behalf of the AAVSO
International High Energy Network on optical observations of
GRB070125 (GCN #6024, Hurley et al.):
D.T. Durig reports the following unfiltered (CR) magnitudes:
2007 Jan 27, 04:02:58 UT: 19.4 +/- 0.2 (CR)
2007 Jan 27, 05:08:10 UT: 19.7 +/- 0.2 (CR)
2007 Jan 27, 06:13:17 UT: 19.9 +/- 0.2 (CR)
2007 Jan 27, 07:27:28 UT: 20.0 +/- 0.2 (CR)
B. Gary reports the following unfiltered magnitudes:
2007 Jan 27, 06:22:12 UT: 19.58 +/- 0.12 (clear)
2007 Jan 28, 05:36:00 UT: 20.20 +/- 0.24 (clear)
Details of these observations are available from the AAVSO at
ftp://ftp.aavso.org/grb,
and full details of these observations
are available at the following URLs:
Durig: http://www.aavso.org/pipermail/aavso-hen/2007-January/006934.html
Gary: http://www.aavso.org/pipermail/aavso-hen/2007-January/006937.html
-----------------------------
Observer: D. T. Durig, D. S. Hardage, N. M. Haymond, (CLW01)
Report: Afterglow is very faintly visible in single 120 sec images with
SNR 2.5 to 3.5. Very obvious in stacks of 10, 15 and 30 frames. Position
of 07 51 17.74 +31 09 04.1. Stacks of 30 frames gives SNR of 13 with
magnitude falling from 19.6 to 19.7 to 19.9 to 20.0 in each hour long
stack. We lost about 12 minutes in the last stack because we lost our
guide star, so intervals are slightly different. GIF image posted to
http://arthur.sewanee.edu/obsv/view.php
Observer: B. Gary
Report: One day later (2007.01.28, UT = 5.60) CV = 20.20 +/- 0.24. CV
for Jan 27 & 28 UT asssume B-V = +0.3. All SE errors are orthogonal sum
of stochastic and estimated systematic.
- GCN Circular #6049
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team report:
The long bright GRB 070125 (Hurley et al., GCN 6024),
triggered Konus-Wind at T0=26450.853 s UT (07:20:50.853).
The Konus-Wind light curve shows several multipeaked pulses
with a duration of ~70 s, followed by a weak tail
seen up to T-T0~200 s.
As observed by Konus-Wind the burst
had a fluence of 1.74(-0.15, +0.18)x10^-4 erg/cm2,
and the 64-ms peak flux measured from T0+41.472 s
2.25(-0.34, +0.36)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+75.008 s) is well fitted (in the 20 keV - 10 MeV range)
by GRBM (Band) model for which:
the low-energy photon index is alpha = -1.10(-0.09, +0.10),
the high energy photon index beta = -2.08(-0.15, +0.10),
the peak energy Ep = 367(-51, +65) keV (chi2 = 88/89 dof).
Fitting by a power law with exponential cutoff model
yields much worse chi2 = 118/90 dof.
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB070125_T26450/
- GCN Report 28.1
GCN_Report 28.1 has been posted:
http://gcn.gsfc.nasa.gov/reports/report_28_1.pdf
by J. Racusin
at PSU
titled: "Swift Observations of GRB 070125"
- GCN Circular #6050
M. Yoshida, K. Yanagisawa, (OAO, NAOJ) and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We detected the optical afterglow candidate of GRB 070125
reported by by Cenko and Fox (GCN 6028) with the 50cm MITSuME
Telescope at Okayama Astrophysical Observatory on January 26
UT. Photometric calibration was done using USNO-B1.0 catalog
magnitudes of eight stars around the target. The results are
following.
UT 26 January 2007 12:25 - 17:23 mid-UT 14:53
total exp time 123 min. (1 min. exp. x 123 frames)
------------------------------
g' 19.6 mag. +/- 0.2 mag.
Rc 18.8 mag. +/- 0.2 mag.
Ic 18.0 mag. +/- 0.3 mag.
------------------------------
Time variability in Rc
UT mid-UT exp.time Rc mag.
-----------------------------------------------
12:25 - 13:06 12:45 30 min. 18.9 +/- 0.3
13:07 - 14:35 13:51 37 min. 19.0 +/- 0.3
16:01 - 16:44 16:22 30 min. 18.7 +/- 0.2
16:44 - 17:23 17:03 26 min. 19.4 +/- 0.4
-------------------------------------------------
吉田道利
国立天文台 岡山天体物理観測所 所長
Michitoshi Yoshida, Dr.
Director of Okayama Astrophysical Observatory,
National Astronomical Observatory of Japan
Phone:+81-865-44-2155 FAX:+81-865-44-2360
yoshida@oao.nao.ac.jp
-------------------------------------------------
- GCN Circular #6051
D.T. Durig (Cordell-Lorenz Observatory, University of the South)
reports on behalf of the AAVSO International High Energy Network
on further optical observations of GRB070125 (GCN #6024, Hurley
et al.):
D.T. Durig reports the following unfiltered (CR) magnitude:
2007 Jan 29, 07:39:56 UT: 21.5 (CR)
Note that this is a marginal detection, with an estimated SNR
of 3.1.
Details of these observations are available from the AAVSO at
ftp://ftp.aavso.org/grb,
and full details of the observation
are available at the following URL:
http://www.aavso.org/pipermail/aavso-hen/2007-January/006947.html
-----------------------------
Observer: D. T. Durig (CLW01)
Report: I had to stack 148 images, but I finally got the SNR to 3.1. I
could clearly see it in stacks of 60, 90 and 120 but the SNR was only
between 2.5 and 2.8. I lost two images to wind, so only added the best
148 frames. Position 07 51 17.70 +31 09 04.3 GIF image posted to
http://arthur.sewanee.edu/obsv/view.php
- GCN Circular #6054
J. S. Bloom (UC Berkeley), D. Starr (UC Berkeley), and C. H. Blake =20
(CfA/Harvard) report on behalf of a larger collaboration:
For 11136 sec between 2007 Jan 28 02:54 UTC and 2007 Jan 28 09:37 we
observed the field of GRB 070125 (Hurley et al. 6024) with the
PAIRITEL 1.3m in Mt Hopkins, Arizona. Consistent with the afterglow
position reported in Cenko & Fox (GCN 6028) we detect a faint
(apparent point-like) source in J, H, and Ks band. The preliminary
magnitudes are:
J = 18.82 =B1 0.26
H = 18.33 =B1 0.25
Ks = 17.86 =B1 0.25
This source appears to be embedded in the Eastern edge of an apparent
galaxy, extending ~2.5" to the West from the OT; we associate this as
the host galaxy of GRB 070125. At the Western edge of the "host"
there is faint knot at position 07:51:17.49, +31:09:03.4 (J2000).
Few Swift GRB hosts are detected with similar integration times on
PAIRITEL and those that have been are uniformly low redshift. Given
this and the previous observational evidence for a low z (Prochaska
et al. 6031, 6032; Marshall et al. 6041), we continue to urge long-
term monitoring of GRB 070125 in search of any associated supernova.
A finder may be grabbed at:
http://lyra.berkeley.edu/~jbloom/grb070125.ps.gz
This message may be cited.
- GCN Circular #6059
A. Pelangeon & J-L. Atteia (LATT-OMP) report:
We provide an improved computation of the pseudo-redshift** of GRB 070125
(Hurley et al., GCNC 6024), based on the spectral parameters measured by
KONUS
(Golenetskii et al. GCNC 6049, and Val'Palshin, Ioffe Physico-Technical
Inst., private communication).
We find a pseudo-redshift pz= 1.3 =B1 0.3
This value is more precise than the value of pz= 1.6 =B1 0.8 (GCNC 6033
)
that we have obtained with the spectral parameters measured by RHESSI
(Bellm et al. GCNC 6025).
We provide this new estimate as a contribution to the on-going debate
on the distance of GRB 070125.
We thank V. Pal'shin for having kindly performed the spectral analysis
of KONUS data.
** cf. http://www.ast.obs-mip.fr/grb/pz
- GCN Circular #6061
Poonam Chandra (NRAO/UVA) and Dale A. Frail (NRAO) report on behalf of
the Caltech-NRAO-Carnegie GRB Collaboration:
"We report the radio detection of the GRB 070125 (GCN 6024) with the Very
Large Array in 8.46 GHz frequency band on 2007 January 30th at 5.65 UT.
Further radio 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 #6063
A.J. van der Horst (University of Amsterdam) reports on behalf of a larger
collaboration:
"We reobserved the position of the GRB 070125 afterglow at 4.9 GHz with the
Westerbork Synthesis Radio Telescope at January 30 16.78 UT to January 31
4.76 UT, i.e. 5.39 - 5.89 days after the burst (GCN 6024).
We detect a radio source with a flux of 102 +/- 26 microJy at the position
of the optical counterpart (GCN 6034).
We would like to thank the WSRT staff for scheduling and obtaining these
observations."
- GCN Circular #6064
F. Terra (Second University of Roma "Tor Vergata"), G. Greco,
C. Bartolini, A. Guarnieri, A. Piccioni (Bologna University),
G. Pizzichini (INAF/IASF Bologna), D. Nanni (INAF/OAR and Second
University of Rome "Tor Vergata"), R. Gualandi (Bologna Observatory)
and V. F. Polcaro (INAF/IASF Roma) report:
We continued to monitor the optical afterglow of GRB 070125
(GCN 6028) with the 152 cm Loiano telescope. Our obsevations were
done on 2007 Jan 28.927 and Jan 28.946, under not good weather
condition (seeing 3.2 arcsec), with 1200 sec exposure time each.
We identified the optical transient in the two co-added images
with 2-sigma level significance only. We find the following
magnitude: Rc= 20.8+/0.2 (1 sigma).
The photometry is based on the SDSS catalog and the trasformation
derived from Lupton (2005).
We note that in the SDSS object table there is a faint object at
position:
RA:07:51:17.50
DEC:31:09:04.2
It would be worth while to ascertain by deeper observations
if it is related to the possible host galaxy indicated
by Bloom et al. (GCN 6054).
- GCN Circular #6067
S. Sposetti (Gnosca, Switzerland) reports on behalf of the AAVSO
International High Energy Network on further optical observations of
GRB070125 (GCN #6024, Hurley et al.):
S. Sposetti reports the following unfiltered (CR) magnitudes:
2007 Jan 26, 18:51:50 UT: 18.8 (CR, S/N = 15)
2007 Jan 26, 19:35:02 UT: 19.1 (CR, S/N = 14)
2007 Jan 26, 20:19:41 UT: 19.4 (CR, S/N = 10)
2007 Jan 26, 21:01:26 UT: 19.4 (CR, S/N = 12)
2007 Jan 26, 22:39:22 UT: 18.9 (CR, S/N = 11)
2007 Jan 28, 18:15:50 UT: 20.9 (CR, S/N = 4)
2007 Jan 28, 19:39:22 UT: 20.9 (CR, S/N = 4)
Details of these observations are available from the AAVSO at
ftp://ftp.aavso.org/grb,
and full details of these observations
are available at the following URL:
http://www.aavso.org/pipermail/aavso-hen/2007-January/006960.html
The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.
-----------------------------
Observer: Stefano Sposetti
Report: CCD pictures begun january 26th at 18:30UT, about 21h later the
event announced in GCN 6024. A first set of 158 unfiltered images and a
second set of 64 unfiltered images under bad seeing conditions were
taken. In 5 stacked images a somewhat fading object located at the
position indicated in GCN 6028 and measured at:
RA: 07h 51m 17.77s
Dec:+31d 09m 04.4s
was measured (USNO A2.0 catalog).
At January 28th another set of 150 unfiltered images under better seeing
conditions were taken. The object was still there but fainter by about
2mag.
A stacked fit-image of the january 26th was posted. A composite
jpg-image showing this event was posted here:
http://aida.astroinfo.org/displayimage.php?pos=-2879
- GCN Circular #6071
D. B. Fox (PSU), E. Berger (Carnegie), P. A. Price (Hawaii) and
S. B. Cenko (Caltech) report on behalf of a larger collaboration:
"We observed the optical afterglow (Cenko & Fox, GCN 6028) of GRB
070125 (Hurley et al., GCN 6024) with the Gemini-North telescope +
Gemini Multi-Object Spectrograph in four 1800-s integrations with mean
epoch 06:16 UT on 26 Jan 2007 (approximately 23 hours post-burst).
Our spectral coverage is 6000-10,000 A for the first hour and
4000-8000 A for the second hour.
We confirm the absence of prominent absorption features noted in
contemporaneous optical spectra from the Lick 3m (Prochaska et al.,
GCN 6031) and Keck-I (Prochaska et al., GCN 6032) telescopes.
At the same time, we identify a single weak (EW < 1 A) absorption
doublet at observer-frame wavelengths 7122.9 A + 7140.9 A. Distinct
components of the doublet are well detected in separate spectra from
the first and second hour of observations, and the relative strength
of the two systems is consistent with their identification as the Mg
II (2796.4 A, 2803.5 A) doublet in absorption at redshift z=1.547.
We therefore conclude that GRB 070125 is at redshift z>1.547. As
noted by Prochaska et al. (GCN 6032), the absence of Lyman-alpha
forest absorption at short wavelengths simultaneously suggests that
the burst redshift is not much greater than this."
- GCN Circular #6073
P. Chandra (UVA/NRAO), D. Bock (OVRO), A. M. Soderberg (Caltech),
D. A. Frail (NRAO) and S. R. Kulkarni (Caltech) report on behalf
of a larger collaboration::
"We observed the field of view of GRB 070125 (GCN 6024) with Combined
Association for Research in Millimeter-Wave Astronomy (CARMA) telescope
in 3mm band (95 GHz) at the mean observation time of 2007 Feb 5, 0700 UT.
We detect the GRB at the P-60 optical afterglow position (GCN# 6028).
The flux density of the GRB is 2.2+/-0.7 mJy.
We acknowledge excellent support from the observing staff of CARMA."
- GCN Circular #6096
N. Mirabal, J. Halpern (Columbia U.), & J. R. Thorstensen (Dartmouth)
report on behalf of the MDM Observatory GRB follow-up team:
"We obtained several observations of the afterglow of GRB 070125
(Cenko & Fox, GCN 6028) between 2 and 12 days after the burst using the
MDM 2.4m and 1.3m telescopes. Results in the R-band are summarized as
follows:
---------------------------------------
Date(UT) t-t0(days) R(mag) +/-
---------------------------------------
Jan 27.270 1.964 19.71 0.02
Jan 28.299 2.993 20.44 0.03
Jan 29.346 4.040 21.07 0.07
Feb 6.307 12.001 >23.8
---------------------------------------
Calibration was performed with Landolt standard stars. In addition, we
compiled
data from the GCN circulars, and placed them on a common scale using their
stated
calibrators. MDM images and the compiled R-band light curve are shown at:
http://www.astro.columbia.edu/~jules/grb/070125/
The light curve shows an apparent plateau or rise at about 1 day. Between 1
and 4 days, it is well described by a power law of slope -1.6. Our upper
limit
at 12 days implies that a break occurred after 4 days, and that the slope
became steeper than -2.2. At redshift z=1.55 (Fox et al., GCN 6071) and
fluence 1.5x10^-4 erg cm^-2 (Bellm et al., GCN 6025), the assumed isotropic
energy is 9x10^53 erg. If we treat 4 days as a lower limit on the time
of any "jet break", then the jet opening angle is of order 6 degrees or
greater, and the beamed energy is 6x10^51 erg or greater.
This message may be cited."
- GCN Circular #6102
Poonam Chandra (NRAO/UVA), Ishwara Chandra (NCRA, Pune) and Neeraj Gupta
(NCRA, Pune) report:
"We used the Giant Meterwave Radio Telescope (GMRT) to observe the field
of view
toward GRB 070125 (GCN 6028) at a frequency of 610 MHz on 2007 January
30th.
We put the 2-sigma upper limit of 300 uJy on the GRB flux density.
We thank the staff of the GMRT who made these observations possible. The
GMRT is run
by the National Centre for Radio Astrophysics of the Tata Institute of
Fundamental Research."
- GCN Report 28.2
GCN_Report 28.2 has been posted:
http://gcn.gsfc.nasa.gov/reports/report_28_2.pdf
by J. Racusin
at PSU
titled: "Updated Swift Observations on IPN GRB 070125"
- GCN Circular #6165
P. Garnavich (Notre Dame), X. Fan, L. Jiang (U Ariz), X. Dai (Ohio State),
O. Kuhn (LBTO), N. Bouche, P. Buschkamp (MPE), P. Smith,
P. Milne, J. Bechtold (U Ariz), K. Z. Stanek, J. Prieto (Ohio State),
R. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State), J. Hill (LBTO/UAz),
A. Baruffolo, C. DeSantis, E. Diolaiti, A. DiPaola, J. Farinato,
A. Fontana, S. Gallozzi, F. Gasparo, E. Giallongo, A. Grazian,
F. Pasian, F. Pedichini, R. Ragazzoni, R. Smareglia, R. Speziali,
V. Testa, E. Vernet (LBC Team/INAF) reprt:
The Large Binocular Telescope (LBT) imaged the position of the GRB 070125
afterglow (Cenko & Fox, GCN 6028) with the LBC-blue CCD camera
(http//lbc.mporzio.astro.it) and 8.4-m SX mirror on 2007 February 21.1 (UT).
Ten dithered, 200 second exposures were obtained with the Sloan r filter
in 1.3" seeing. After combining the images a faint source is detected at
the position of the afterglow. Using SDSS stars in the field and
1.4" apertures, we estimate the brightness of the source
at r=26.3+/-0.3 mag. Since the source may be dominated by the host galaxy,
this observation represents a lower-limit on the magnitude of the
afterglow 26.8 days after the GRB.
The last reported detection of the GRB afterglow was R=21.07 at 4.04 days
(Mirabal, Halpern & Thorstensen, GCN 6096) and it was decaying with an
index of 1.6. Converting our observation to Johnson-Cousins R-band
(assuming beta=-1.0 so B-V=0.34) we find that after the light curve break
the power-law decay index was equal to, or greater than 2.5.
This confirms the sharp steepening in the light curve four days after the
GRB and the jet opening angle reported by Mirabal et al. (GCN 6096). We
expect that a supernova at z=1.5 and similar to SN 1998bw (Galama et al.
1998, Nature, 395, 670) would have r~28 mag at the time of our observation
so would not contribute significantly to the observed flux.
The LBT image is available at:
http://www.nd.edu/~pgarnavi/grb070125/LBT_070221.jpg
The X-ray light curve is generally consistent with the optical. Both show
a break at late time and a steep decay. The x-ray light curve actually has
a strong detection at an age of 10 days suggesting a steeper post-break
decay and possibly a wider opening angle than the optical limits.
It has been suggested that the existence of jet breaks in Swift x-ray
light curves are rare (e.g. Burrows & Racusin 2007, astro-ph/0702633),
but here is a good example occurring at a time later than expected. This
suggests the lack of Swift jet breaks is a selection effect and that many
occur beyond the Swift sensitivity limit.
The X-ray/optical light curve comparison is available at:
http://www.astronomy.ohio-state.edu/~xinyu/grb/070125.jpg
The LBT is an international collaboration between institutions in the
U.S.A., Italy and Germany. LBT Corporation partners are The Universities
of Arizona; Italy's Istituto Nazionale di Astrofisica; Germany's LBT
Beteiligungsgesellschaft representing the Max-Planck Society, the
Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State
University and The Research Corporation, which provides access to The
University of Notre Dame, University of Minnesota and University of
Virginia.
This message may be cited.
- GCN Report 28.3
GCN_Report 28.3 has been posted:
http://gcn.gsfc.nasa.gov/reports/report_28_3.pdf
by J.L. Racusin
at PSU
titled: "Final Swift Observations on IPN GRB 070125"
- GCN Circular #6181
D. N. Burrows and J. Racusin report on behalf of the Swift XRT team:
Garnavich et al. (GCN Circ. 6165) have suggested that the X-ray light
curve of GRB 070125 has a late break to a steep slope, in agreement
with the optical break reported by Mirabel, Halpern & Thorstensen
(GCN 6096) and confirmed by their observations.
We have re-examined the XRT light curve, which extends from ~44 ks to
~1.5 Ms post-burst, and reconfirm our original conclusions. Full
details, including a plot of the X-ray light curve showing several
possible fits of single and broken power laws, are given in GCN
Report 28.3 (http://gcn.gsfc.nasa.gov/reports/report_28_3.pdf). We find:
1) the X-ray light curve is best fit by a broken power law, but with
a break time at 1.35 +/- 0.35 days (90% confidence), not > 4 days as
required by the optical data (Mirabel, Halpern & Thorstensen, GCN
6096). However, this fit, with reduced chi**2=1.6 for 15 degrees of
freedom, is rather poor (P=0.065), due primarily to large residuals
between 100 and 200 ks.
2) a better fit can be obtained under the assumption that there is a
small X-ray flare at about 110 ks. If these data points are
excluded, the remaining X-ray data can be fit by a single power law
of slope 1.57 +/- 0.07 (90% confidence) with reduced chi**2 of 0.82
for 14 degrees of freedom. A broken power law fit to this data set
is slightly worse and has very poor constraints on the fit parameters.
We conclude that we cannot distinguish between a single power law fit
with a small flare at 110 ks, and a broken power law fit with
additional flaring (to account for the poor residuals). Therefore
the X-ray data do not show evidence for a jet break: they are
consistent with a jet break coincident with the optical break, but
are equally consistent with no break at all.
- GCN Circular #6186
S. B. Cenko, A. M. Soderberg (Caltech), D. A. Frail (NRAO), and D. B. Fox
(Penn State) report on behalf of a larger collaboration:
The Chandra X-ray Observatory + ACIS observed the field of GRB070125
(Hurley et al, GCN 6024) beginning 5 March 2007 21:28 UT for a 30 ks
exposure (mean epoch ~ 39.76 days after the burst). No source is detected
at the location of the optical afterglow (Cenko & Fox, GCN 6028).
Formally, using a circular aperture with 1" diameter, we detect 0.9 +/-
5.0 photons from 0.3-10 keV. Using spectral properties derived from early
XRT observations (Gamma=2.0, nH=8e20; Racusin and Vetere, GCN 6030),
we estimate an upper limit on the afterglow flux of < 2e-15 erg cm^-2
s^-1.
Had the X-ray flux seen by the Swift XRT (Burrows & Racusin, GCN 6181)
continued to decay as a single power-law with index ~ -1.5, we would
expect a flux ~ 5e-15 erg cm^-2 s^-1 at the Chandra epoch (~ 20 Chandra
ACIS-S photons), more than a factor of 2 above this upper limit. We
therefore conclude the X-ray decay has steepened since the last XRT
detection, confirming the jet break seen in the optical light curve
(Mirabal, Halpern, & Thorstensen, GCN 6096; Garnavich et al., GCN 6165).
A plot of the X-ray light curve can be found at:
http://www.srl.caltech.edu/~cenko/public/grb070125_xray.jpg
We would like to thank the entire Chandra X-ray Center staff for their
execution of this observation and the rapid processing of the data.
- 0710.4590 from 24 Oct 2007
Bellm: Observations of the Prompt Gamma-Ray Emission of GRB 070125
Abstract: The long, bright gamma-ray burst GRB 070125 was localized by the
Interplanetary Network. We present light curves of the prompt gamma-ray
emission as observed by Konus-WIND, RHESSI, Suzaku-WAM, and Swift-BAT. We
detail the results of joint spectral fits with Konus and RHESSI data. The burst
shows moderate hard-to-soft evolution in its multi-peaked emission over a
period of about one minute. The total burst fluence as observed by Konus is
$1.75 \times 10^{-4}$ erg/cm$^2$ (20 keV-10 MeV). Using the spectroscopic
redshift z = 1.547, we find that the burst is consistent with the Amati
$E_{peak,i}-E_{iso}$ and the Ghirlanda $E_{peak,i}-E_\gamma$ correlations.
- 0712.2828from 17 Dec 2007
Cenko: GRB070125: The First Long-Duration Gamma-Ray Burst in a Halo Environment
Abstract: We present the discovery and high signal-to-noise spectroscopic observations
of the optical afterglow of the long-duration gamma-ray burst GRB070125. Unlike
all previously observed long-duration afterglows in the redshift range 0.5 < z
< 2.0, we find no strong (rest-frame equivalent width W > 1.0 A) absorption
features in the wavelength range 4000 - 10000 A. The sole significant feature
is a weak doublet we identify as Mg II 2796 (W = 0.18 +/- 0.02 A), 2803 (W =
0.08 +/- 0.01) at z = 1.5477 +/- 0.0001. The low observed Mg II and inferred H
I column densities are typically observed in galactic halos, far away from the
bulk of massive star formation. Deep ground-based imaging reveals no host
directly underneath the afterglow to a limit of R > 25.4 mag. Either of the two
nearest blue galaxies could host GRB070125; the large offset (d >= 27 kpc)
would naturally explain the low column density. To remain consistent with the
large local (i.e. parsec scale) circum-burst density inferred from broadband
afterglow observations, we speculate GRB070125 may have occurred far away from
the disk of its host in a compact star-forming cluster. Such distant stellar
clusters, typically formed by dynamical galaxy interactions, have been observed
in the nearby universe, and should be more prevalent at z>1 where galaxy
mergers occur more frequently.
- 0802.2748from 20 Feb 2008
Chandra: A comprehensive study of GRB 070125, a most energetic gamma ray burst
Abstract: We present a comprehensive multiwavelength analysis of the bright, long
duration gamma-ray burst GRB 070125, comprised of observations in $\gamma$-ray,
X-ray, optical, millimeter and centimeter wavebands. Simultaneous fits to the
optical and X-ray light curves favor a break on day 3.78, which we interpret as
the jet break from a collimated outflow. Independent fits to optical and X-ray
bands give similar results in the optical bands but shift the jet break to
around day 10 in the X-ray light curve. We show that for the physical
parameters derived for GRB 070125, inverse Compton scattering effects are
important throughout the afterglow evolution. While inverse Compton scattering
does not affect radio and optical bands, it may be a promising candidate to
delay the jet break in the X-ray band. Radio light curves show rapid flux
variations, which are interpreted as due to interstellar scintillation, and are
used to derive an upper limit of $2.4 \times 10^{17}$ cm on the radius of the
fireball in the lateral expansion phase of the jet. Radio light curves and
spectra suggest a high synchrotron self absorption frequency indicative of the
afterglow shock wave moving in a dense medium. Our broadband modeling favors a
constant density profile for the circumburst medium over a wind-like profile
($R^{-2}$). However, keeping in mind the uncertainty of the parameters, it is
difficult to unambiguously distinguish between the two density profiles. Our
broadband fits suggest that \event is a burst with high radiative efficiency
($> 60 %$).
- 0805.1094 from 8 May 2008
Updike: The Rapidly Flaring Afterglow of the Very Bright and Energetic GRB 070125
Abstract: We report on multi-wavelength observations, ranging from the X-ray to radio
wave bands, of the IPN-localized gamma-ray burst GRB 070125. Spectroscopic
observations reveal the presence of absorption lines due to O I, Si II, and C
IV, implying a likely redshift of z = 1.547. The well-sampled light curves, in
particular from 0.5 to 4 days after the burst, suggest a jet break at 3.7 days,
corresponding to a jet opening angle of ~7.0 degrees, and implying an intrinsic
GRB energy in the 1 - 10,000 keV band of around E = (6.3 - 6.9)x 10^(51) erg
(based on the fluences measured by the gamma-ray detectors of the IPN network).
GRB 070125 is among the brightest afterglows observed to date. The spectral
energy distribution implies a host extinction of Av < 0.9 mag. Two
rebrightening episodes are observed, one with excellent time coverage, showing
an increase in flux of 56% in ~8000 seconds. The evolution of the afterglow
light curve is achromatic at all times. Late-time observations of the afterglow
do not show evidence for emission from an underlying host galaxy or supernova.
Any host galaxy would be subluminous, consistent with current GRB host-galaxy
samples. Evidence for strong Mg II absorption features is not found, which is
perhaps surprising in view of the relatively high redshift of this burst and
the high likelihood for such features along GRB-selected lines of sight.
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