GRB 070223

E.  Rol,  N. Tanvir (Leicester), N.  Mirabal  (Columbia), K.  Wiersema
(Amsterdam),  J.P.   Halpern   (Columbia),  A.   Levan  (Warwick),  R.
Chapman (Hertfordshire), A.  Melandri (Liverpool JMU) and D.  Pinfield
(Hertfordshire), report on behalf of a larger collaboration:

We  re-observed  the position  of  the  X-ray  afterglow of  GRB070223
(Vetere  et al,  GCN report  35.1) with  the LIRIS  instrument  on the
William  Herschel Telescope,  between  7.99 and  8.08  days after  the
burst. Our J  and K images do  not show any source inside  the XRT 90%
error  circle. As our  observations are  considerably deeper  than the
first epoch  LIRIS observations reported by Castro-Tirado  et al (GCNC
6168; private  communication), we conclude the source  reported is the
nIR afterglow of GRB070223.

We also  re-examined the optical  images taken with the  MDM telescope
(Mirabal et  al., GCNC 6162), and  find a faint optical  source at the
position of  the nIR afterglow. We  point out that this is a different
source than the one located at RA (J2000) = 10 13 48.19, Dec (J2000) =
43 07 54.7  (S1, GCNC 6162), which now also  falls outside the revised
XRT position (Vetere et al.).

We derive a position for the optical afterglow of (J2000):

   RA  =  10 13 48.39
   Dec = +43 08 00.7

which   fully   agrees   with   the   X-ray   position   (GCN   report
35.1).  Astrometry was done  relative to  the SDSS  (Cool et  al, GCNC
6128), and errors are about 0.3 arcsecond in each coordinate.

The latest MDM image is posted at
http://www.astro.columbia.edu/~mirabal/grb070223mdm.jpg

A.J. Castro-Tirado, A. de Ugarte Postigo, M. Jelinek, 
J. Gorosabel (IAA-CSIC), J. Licandro and D. Bramich 
(ING La Palma), report:

"We have observed the XRT position of GRB 070223 (Vetere et al. GCN
6130
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 ) with the 4.2m WHT (+LIRIS) telescope at the Spanish Observatorio
del Roque de los Muchachos in La Palma. The observations were carried
out in the JHK-bands starting on Feb 23.165-23.195 UT. We detect a faint 
object in all bands consistent with the one reported by Mirabal et al. 
(GCNC 6162) and also with the XRT position given by Vetere et al. 
Further imaging is required to confirm if this is the NIR afterglow 
to GRB 070223."

This message can be quoted.

N. Mirabal (Columbia U.), A. Melandri (Liverpool JMU), and
J. P. Halpern (Columbia U.) report

"We have further analyzed deep R-band images of Swift
GRB 070223 (Vetere et al., GCN 6125
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 ) obtained with the
2-m Liverpool Telescope (Melandri, GCN 6127
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 ) and the
MDM 1.3m telescope (Mirabal & Halpern, GCN 6126
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 ) on
Feb. 23.025 and Feb. 23.272, respectively. The
afterglow candidate reported by Melandri (GCN 6127
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 )
is not detected in our coadded frames. We therefore consider
it unlikely that this is the OT of GRB 070223.

In both sets of images, we find a faint object located at:

RA(J2000) = 10h 13m 48.19s
Dec(J2000) = +43d 07' 54.65 ''

with a preliminary magnitude of R~23.7, which is consistent with
the XRT position (Vetere, GCN 6130
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 ). We have not established
any optical variability at this time."

Poonam Chandra (NRAO/UVA) and Dale A. Frail (NRAO) report on behalf of 
the Caltech-NRAO-Carnegie GRB Collaboration:



"We used the Very Large Array to observe the field of view toward GRB
070223 (GCN 6125
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 ) at a frequency of 8.46 GHz on 2007 February 25 at
4.93 UT.  The GRB is undetected and the peak radio brightness at the 
Liverpool Telescope Possible Afterglow Candidate position (GCN 6127
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 ) 
is 41+/-56 uJy and at SWIFT-XRT position (GCN 6130
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 ) is 77+/-57 uJy.  



The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."

A. C. Gupta
National Astronomical Observatories/Yunnan Observatory 
CAS, P.O. Box 110, Kunming, Yunnan 650011, China

We observed the field of GRB 070223 (GCN 6125
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 ) with CCD detector
at our 1.02 meter telescope of the Yunnan observatory, Kunming, 
China. We started our observation on Feb. 23, 2006 at UT 13:21:20.
We took 5 image frames of 200 seconds exposure time of each in
the optical R passband. There is no detection of optical afterglow
candidate in our combined 5 images. The 5-sigma limiting magnitude
of our observations is R ~ 20.0 mag.

W. Landsman(NASA/GSFC), L. Angelini(GSFC/JHU) and J. Greiner(MPE) report 
on behalf of the Swift UVOT team:

The Swift/UVOT observed the field of GRB 070223 starting 102s after the 
BAT trigger (Vertere et al. 2007, GCN Circ. 6125
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 ) with the settling 
exposure.

We do not find any source, in any of the UVOT observations, inside of 
the refined XRT error circle (Vertere et al. 2007, GCN Circ. 6130
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 ).

We have the following 3-sigma upper limits for a source inside the XRT 
error circle in the first exposure with the White filter, and in the 
coadded frames with all filters:

Filter  T_Start    T_End   Exp (s)   3sigma U.L. mag

White   120         219      98         20.2

V       102         295      79         18.9
B      5893        6084     189         20.6
U      5688       16398     351         20.5
UVW1   3863       16234    1069         21.2
UVM2   3658        3858     197         20.1
White   120       11872    1002         21.4

No correction has been made for the small extinction corresponding to 
E(B-V) = 0.015
(Schlegel et al. 1998).

M. Uemura, A. Arai, and T. Uehara (Hiroshima Univ.), 
report on behalf of the KANATA GRB team:

  We took optical and IR images of the field of GRB070223 (GCN 6125
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 ) at 
12:31-12:52 UT 23 Feb. using TRISPEC attached to the KANATA 
1.5-m telescope at Higashi-Hiroshima Observatory, Japan.  
We obtained 10 sets of V, J, and Ks-band images with a 123, 120, and 96-s 
exposure time, respectively.  
The images were calibrated with neighbor stars in the USNO A2.0 and 2MASS 
catalog.

We cannot significantly detect the optical and IR afterglows.  
at the position of the X-ray afterglow reported in GCN 6130
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 . 
The limit magnitudes are below:   

UT                      Limit mag     Exp. Time
Feb. 23.52863            V  > 21.3    123 * 10
Feb. 23.52858            J  > 18.7    120 * 10
Feb. 23.52843            Ks > 16.3     96 * 10

G. Sato (GSFC/ISAS), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), L. Vetere (PSU)
on behalf of the Swift-BAT team:
 
Using the data set from T-240 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070223 (trigger #261664)
(Vetere, et al., GCN Circ. 6125
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 ).  The BAT ground-calculated position is
RA, Dec = 153.453, 43.132 deg which is 
   RA(J2000)  = 10h 13m 48.6s 
   Dec(J2000) = 43d 07' 55.4" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 82%.
 
The mask-weighted lightcurve starts at ~T-20 sec and then rises
to two main peaks at T+15 and T+35 sec with a long decaying profile
out to T+150 sec.  T90 (15-350 keV) is 89 +- 2 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-3.4 to T+98.5 is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.87 +- 0.12.  The fluence in the 15-150 keV band is 1.7 +- 0.1 x 10^-6
erg/cm2.  The 1-sec peak photon flux measured from T+34.35 sec
in the 15-150 keV band is 0.7 +- 0.1 ph/cm2/sec.  All the quoted errors
are at the 90% confidence level.

The initial series of GCN Notices were delayed by ~460 sec because
the trigger occurred during a Malindi telemetry downlink pass
when the TDRSS messages are buffered on-board until the transmitter
becomes available.

V. Lipunov, V.Kornilov, N.Shatskiy, E.Gorbovskoy, A.Belinski, D.Kuvshinov, 
N.Tyurina, P.Gritsyk
Sternberg Astronomical Institute, Moscow Union 'Optic'

A. Tlatov, I.Golubov
Kislovodsk Solar Station of the Pulkovo observatory

MASTER Very Wide Field Camera located at Kislovodsk Solar Station
(http://observ.pereplet.ru, D=70 mm, 420 square degrees, 11 Mpixel's CCD) 
has moved to the Swift-BAT trigger 261664 and it has taken a series of 5s 
exposures  starting 1 s after notice arrivel time at  01:23:11.719 UT 
under good weather  condition and yang moon.

We note that the GBR position (L. Vetere et al. GCN Circ No. 6125) was 
at 5 degrees outside of the our field of view.

We note that the VWF camera continuously takes frames during the night.


These unfiltered images are calibrated relative to USNO A2.0 (R).
There is no OT was found inside Swift error box.

T-Tgrb     Mean Time     Limit   Coadd?           Note

491s        493.5s       11.0     no       slightly moving

496s        498.5s       11.5     no

496s         521 s       12.5     10

496s         586 s       13.0     36



The message can be cited.

mailto: lipunov@sai.msu.ru

L. Vetere (PSU) reports on behalf of the Swift-XRT team:

We have analysed the first four orbits (up to 16.5 ks after the BAT trigger) of
Swift XRT data for  GRB 070223 (Vetere et al., GCN 6126
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 ). Using ~2.8 ks of
Photon Counting (PC) mode data we find the following refined position:

RA (J2000)  =  10h 13m 48.4s
Dec(J2000)  = +43d 07' 58.2"

with an error radius of 4.5 arcseconds (90% confidence). This is 4.4 arcsec away
from  XRT initial position and 4.1 arcsec from the possible optical candidate
reported by A. Melandri (GCN 6127
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 ).

The WT lightcurve shows a rapid decay with a slope of alpha~2.3 while the PC
light curve shows a possible flattening (~0.6) but we still need more data to
confirm it.

The WT mode spectrum can be fitted with a single power law of photon index of
1.7 +/- 0.1 and column density of (4.5 +/-0.1 )e21 cm**-2. We note the Galactic
column density in the direction of the source is 1.1e20 cm**-2.
The 0.3-10 keV observed flux was 6.5e-10 ergs cm**-2 s**-1, which corresponds to
an unabsorbed flux of 9.2e-10 ergs cm**-2 s**-1.

This circular is an official product of the Swift-XRT team.

Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona), David W. Hogg
(NYU), Michael R. Blanton (NYU), David J. Schlegel (LBNL), J.  
Brinkmann (APO),
Donald Q. Lamb (Chicago), Donald P. Schneider (PSU), and Daniel E.  
Vanden Berk
(PSU) report:

The Sloan Digital Sky Survey (SDSS) imaged the field of burst GRB070223
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/GRB070223

We supply FITS images in each of the 5 SDSS bands of a 8'x8' region  
centered
on the GRB position (ra=153.452 (10:13:48.5), dec=43.1210  
(43:07:15.6); GCN
6125
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 ), 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 GRB070223_sdss.calstar.dat, we report photometry and  
astrometry
of 308 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 GRB070223_sdss.objects_flux.dat and
GRB070223_sdss.objects_magnitudes.dat, we report photometry of 1529
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 GRB070223_sdss.objects_flux.dat are in nanomaggies
while the magnitudes listed in GRB070223_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=0.078 mag, A_g=0.057 mag,  
A_r =
0.042 mag, A_i=0.032 mag, and A_z=0.022 mag.

The file GRB070223_sdss.spectro.dat contains a list of the 2 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, PASP 118, 733).   
See the
SDSS DR4 documentation for more details: http://www.sdss.org/dr5.

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, 162, 38), when using the data or
referring to the technical documentation.

A. Melandri (Liverpool JMU) on behalf of the Liverpool GRB group
report


The 2-m Liverpool Telescope robotically followed up GRB070223
(Vetere et al., GCN 6125
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 , trigger=261664) beginning  ~18 minutes
after the GRB trigger time (UT:01:15:00).

We detect a very faint object inside the XRT position (Vetere et al.,
GCN 6125
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 ) not present in the USNO B1 catalog at this position

RA = 10:13:48.73
Dec = +43:08:00.54

with an uncertainty of 0.5 arcsec. In a coadded frames (with a total
integration time of 780 sec) the object has a magnitude R~23 +/- 0.3
(with respect the USNO B1) between 18 and 51 minutes after the burst.

At the moment it is not possible to state if the object is fading.

Further analysis and observations are ongoing.

N. Mirabal and J. P. Halpern (Columbia U.) report
on behalf of the MDM Observatory GRB follow-up team:

"We have observed the Swift location of GRB 070223 (Vetere et al.,
GCN 6125
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 ) with the MDM 1.3m telescope at a mean epoch
Feb. 23, 02:18 UT (~1 hr post-burst). Inside the XRT error circle,
we find no new optical sources to preliminary limiting
magnitudes R > 20.3, I > 20.0. Observations are ongoing.

This message may be cited."

L. Vetere (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
S. Campana (INAF-OAB), M. M. Chester (PSU), N. Gehrels (NASA/GSFC),
D. Grupe (PSU), J. A. Kennea (PSU), W. B. Landsman (NASA/GSFC),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
M. Stamatikos (NASA/ORAU) and E. Troja (INAF-IASFPA) report on behalf
of the Swift Team:

At 01:15:00 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070223 (trigger=261664).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 153.452, +43.121 which is 
   RA(J2000)  =  10h 13m 49s
   Dec(J2000) = +43d 07' 16"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several peaks
with a duration of about 50 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 01:16:50 UT, 110 seconds after the
BAT trigger. XRT found a bright, fading, uncatalogued X-ray source
located at RA, Dec 153.4533, +43.1336 which is
   RA(J2000)  =  10h 13m 48.7s
   Dec(J2000) =  43d 08' 00.9"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). 
This location is 45 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 3.0e-09 erg/cm2/s (0.2-10 keV). 

UVOT took a finding chart exposure of nominal 100 seconds with the
White (160-650 nm) filter starting 120 seconds after the BAT trigger,
and a finding chart in V starting 226 seconds after the trigger. No
afterglow candidate has been found in the initial data products. 
Image catalog data are not available at this time. The 2.7'x2.7'
immediately available image covers 100% of the XRT error circle. The
list of sources is typically complete to about 18 mag. No correction
has been made for the expected extinction corresponding to E(B-V) of
0.01.