GRB 050223

E. Berger (Carnegie) and Min-Su Shin (Princeton) report:

"We obtained spectroscopic observations of the host galaxy of GRB 050223
(GCN 5268
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 ) with the LDSS-3 spectrograph on the Magellan/Clay telescope on
2006 June 28 UT.  We find a single emission line at an observed
(vacuum-corrected) wavelength of 5933.8A, corresponding to [OII]3727 at a
redshift z=0.5915.  At this redshift, the observed brightness of the host,
R=21.6 mag (GCN 5268
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 ), corresponds to an absolute magnitude, M_B=-20.2 mag
or ~0.5L*.  We further detect an emission line at the same wavelength from
a galaxy about 1.3 mag fainter located 10" to the east of the host galaxy,
indicating that it is a companion to the host with a separation of about
65 kpc and a luminosity of about 0.15L*.

At the redshift of the host and with a fluence of 9.7e-7 erg/cm^2 (Page et
al. 2005, MNRAS, 363, L76), the isotropic-equivalent gamma-ray energy of
GRB 050223 is only 8.7e50 erg."

L.J. Pellizza (CEA Saclay, France & IAFE, Argentina), P.-A. Duc
(CEA Saclay, France), E. Le Floc'h (Steward Obs., USA), & I.F.
Mirabel (ESO), on behalf of the MISTICI collaboration.

We imaged the field of GRB 050223 (Mitani et al. 2005, GCN 3055
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 )
on May 10, 2005 and June 5, 2005. R (10 x 308 seconds) and Ks
(42 x 60 seconds) frames were obtained respectively with FORS1 and
ISAAC at VLT. In the combined R and Ks images we detect a single
galaxy within the revised XRT error circle (Moretti et al. 2006,
A&A, 448, L9), down to our limiting magnitudes R_lim ~ 26 and
Ks_lim ~ 21. Its position is RA(J2000) = 18:05:32.99, DEC(J2000) =
-62:28:18.8 (0.2 arcsec error), We measured R = 21.6 and Ks = 18.9
for this object (with an uncertainty of ~0.1 mag). Astrometry was
performed using USNO B1.0 stars, while photometry was calibrated
against 2MASS and USNO B1.0 (second epoch) magnitudes.

A. De Luca (IASF-Mi), S. Campana (OAB) on behalf of a larger
collaboration report:

We have analyzed the data from the XMM-Newton observation of
GRB050223, discovered by Swift on 2005, Feb 23, 03:09:06 UTC
(Giommi et al., GCN3054
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 ).

The XMM-Newton observation started on 2005, Feb. 23 at 13:04 UT
and ended on 2005, Feb 24 at 06:14:20, with a gap between
Feb. 23 16:54 UT and Feb. 23 18:56 UT  due to a ground station
outage. A first account of results, based on the analysis of
preliminary data, have been presented by the XMM-Newton SOC team
(http://xmm.vilspa.esa.es/external/xmm_news/items/grb050223/index.shtml).

Observation Data Files have been produced and released only for
the part of the observation starting from Feb. 23 18:55:57 UT
(after the gap) and lasting for 41 ks.

The whole observation is badly affected by low-energy particle
background, dramatically reducing the signal to noise, especially
in the data from the back-illuminated pn detector, which is
particularly sensitive to such background component.
This hampers a detailed study of the spectral and temporal
phenomenology of the faint source XMMU J180532.5-622821
(Gonzalez-Riestra et al., GCN 3060
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 ), the likely afterglow
of GRB050223.

As a first step, we improved the astrometry of the XMM-Newton/EPIC
images by matching X-ray sources in the field to bright stars in
the USNO-B1 catalogue.
The refined position (J2000) for the X-ray afterglow is

RA: 18h 05m 32.49s  Dec: -62d 28' 21.07"

The 1 sigma error radius is 1.5 arcsec (including the rms error on the
cross-correlation as well as systematic uncertainties in the optical
catalogue). The position is fully consistent with the XRT coordinates
(Giommi et al., GCN 3054
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 ) as well as with the preliminary XMM-Newton
position by Gonzalez-Riestra et al. (GCN 3060
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 ).

The EPIC light curve in the 0.5-2 keV range (where the signal-to-noise
is maximum) shows hints that the source is fading, following
a power law decay with index in the range 0.5-3 (90% confidence level).

We extracted time-averaged spectra from the three EPIC cameras and we
generated ad-hoc response and effective area files. A slightly absorbed
(NH<10^21 cm^-2, consistent with the Galactic column density in this
direction, 7x10^20  cm^-2) power law model with photon index
1.6(+0.6,-0.4) gives an acceptable description of the data in the 0.3-4
keV range, with a reduced chi2 of 1.5 (32 d.o.f). The quoted errors are
at 90% conf. level for a single interesting parameter.
The not optimal quality of the fit is most likely due to the heavy
background affecting the observation.
The observed flux (0.2-10 keV) is of ~3.7x10^-14 ergs cm^-2 s^-1;
the corresponding unabsorbed flux is ~4x10^-14 ergs cm^-2 s^-1.

This message may be cited.

A. Blustin (MSSL), G. Branduardi-Raymont (MSSL), A. Breeveld
(MSSL), C. Brocksopp (MSSL), M. Cropper (MSSL), C. James
(MSSL), N. Loaring (MSSL), K. Mason (MSSL), K. McGowan (MSSL),
M. de Pasquale (MSSL), M. Page (MSSL), T. Poole (MSSL),
G. Ramsay (MSSL), S. Rosen (MSSL), C. Saxton (MSSL), P. Schady
(MSSL), K. Wu (MSSL), S. Zane (MSSL), H. Ziaeepour (MSSL) on
behalf of the XMM-Newton Optical Monitor team


The XMM-Newton Optical Monitor began observations of GRB050223
at 14:23:15 on 2005-02-23, about 11 hours after the initial
Swift BAT trigger (Mitani et al, GCN 3055
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 ). We detect no
source at the position of the XMM-Newton pn source
(Gonzalez-Riestra et al, GCN 3060
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 ). The estimated limiting
magnitudes (5-sigma) in each of the OM filters are as follows:

Filter  Lim_Mag  Duration  T_start

B       21.22    4000      T+40449
UVW1    20.24    2500      T+60374
UVW1    20.49    4000      T+63181
UVM2    19.60    4000      T+67488
UVM2    19.56    4000      T+71795
UVW2    18.70    4000      T+76102
UVW2    18.67    4000      T+80409
UVW2    18.64    4000      T+84716

This message may be cited.

M. Nysewander, M. Bayliss, J. Haislip, P. Price (Hawaii), C. MacLeod, J.
Kirchbrown, D. Moschler, A. Foster, D. Reichart, O. Awam, A. Davis, M.
Greco, D. Kumar, T. Mack, A. Mann, B. Russ, C. Owen, and J. Phelps report
on behalf of the UNC team of the FUN GRB Collaboration:

We observed the 8 arcsecond position of the uncataloged x-ray source found
by the Swift XRT instrument (Giommi et al., GCN 3054
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 ) in the field of GRB
050223 with three telescopes of the PROMPT robotic telescope array located
at CTIO.  Manual observations first began in V 2.5 hours after the burst at
high airmass and no new sources were observed to the limiting magnitude of
a single exposure.  Observations continued in Rc and Ic and details are
given below.

PROMPT  filter   exposures        start       mean      2s limiting
  #                             time (hr)   time (hr)    magnitude
  1       Rc    20x90s, 120x60s   2.8         4.1          21.2
  3       V     130x90s           2.5         4.2          21.3
  5       Ic    60x90s            4.3         5.1          21.1
times are given in hours after the burst (03:09:06 UT).

Limiting magnitudes were calculated using 2 NOMAD stars for V, and 5
USNO-B1.0 stars for Ic and Rc.

An overview of PROMPT can be found at astro-ph/0502429.  The project is
still in the building/commissioning phase with only three telescopes
currently online.

P. Rodriguez from the XMM-Newton SOC
report:
 
Preliminary EPIC-pn images, light-curves and spectra from the XMM-Newton
observation of the field of GRB 050223 are available at the home-page of
the XMM-Newton Science Operations Centre:

http://xmm.vilspa.esa.es/external/xmm_news/items/grb050223/index.shtml

J. Gorosabel (IAA-CSIC, Granada),
S. Eguchi (Stelab, Nagoya Univ.),
A. de Ugarte Postigo (IAA-CSIC),
Ph. Yock (Univ. of Auckland) and
A.J. Castro-Tirado (IAA-CSIC), report:

"Following the detection by SWIFT of GRB
050223 (Mitani et al. GCN Circ. 3055
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 )
we imaged the error box with the 0.6 m
telescope at Mt. John Univ. Observatory.
We obtained a 300s image with the MOA
camera (+wide R-band filter) under poor
seeing conditions (4") starting on
23.55 Feb UT (i.e. 10.05 hr after the event).

A finding chart can be found at:

http://www.iaa.es/~deugarte/GRBs/050223/T1143-grb050223-red-2.gif

Comparison of the R-band image with
the DSS-2 revealed neither counterpart
within the 5" radius X-ray afterglow position
given by  XMM-Newton (Gonzalez-Riestra et 
al. GCN Circ. 3060
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 ) nor variable source to 
about R = 20.5 within the 4' radius SWIFT/BAT
error box."

This message can be cited.

R. Gonzalez-Riestra, M. Santos-Lleo, P. Rodriguez-Pascual and P. Munuera
report:

Quick-Look-Analysis of the XMM-Newton observation of the GRB050223
field based on a 5ks exposure in the EPIC pn camera that started at
13:57 UT, shows the
presence of a source within the SWIFT/XRT error circle (Giommi et al.,
GCN 3054
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 ).

XMMU J180532.5-622821 (J2000):
R.A. = 18h 05m 32.5s  Decl. = -62deg 28' 21''
with an estimated EPIC/pn count rate of 0.03 counts/sec;

At this stage of data reduction the position error is expected to be
less than 5''.

S. Mereghetti, D. Gotz (IASF, Milano), N. Mowlavi, S. Shaw, M. Beck
(ISDC, Versoix) and J. Borkowski (CAMK, Torun) on behalf of the IBAS
Localization Team report:


GRB 050223, discovered by Swift (Giommi et al. GCN 3054
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 , Mitani et al.
GCN 3055
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 ), has been also detected by the IBIS/ISGRI instrument on board
INTEGRAL.

The burst occurred during a 200 sec long time interval in which the
automatic distribution of IBAS Alerts was disabled due to the temporary
switch-off of one of the 8 modules of the IBIS/ISGRI detector.

The GRB coordinates (J2000) derived from an off-line analysis are:

RA:   271.4002 [degrees]
DEC:  -62.4739 [degrees]

with an uncertainty of 3 arcmin (90% c.l. radius).

The peak flux measured with IBIS/ISGRI is 0.6 ph/cmsq/s (20-200 keV, 1 s
integration time).

This message can be cited.

XMM-Newton will observe GRB 050223 at location 
(RA=18h 05m 32.6s, DEC=-62d 28' 20", J2000),
starting at 12:45:00 UT, on February 23, 2005,
for an exposure of 60000 seconds.

C. Gronwall (PSU), A. Blustin (MSSL), P. Brown (PSU), S. Rosen, K. 
McGowan, M. De Pasquale (MSSL), P. Boyd (GSFC/UMBC), S. Holland, M. Still 
(GSFC/USRA), W. Landsman (GSFC), S. Hunsberger (PSU), A. Breeveld (MSSL), 
P. Roming (PSU), K. Mason, P. Schady (MSSL), M. Ivanushkina (PSU), T. 
Poole, P. Smith, B. Hancock (MSSL), S. Koch (PSU), M. Carter, H. Huckle 
(MSSL),  P. Broos (PSU), T. Kennedy (MSSL), J. Racusin (PSU), E. Fenimore 
(LANL), B. Zhang (UNLV), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of 
the Swift UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of 
GRB050223 at 03:55:28 UT on 23 Feb 2005, about 46:22 UT after the initial 
Swift Bat trigger (Mitani et al, GCN 3055
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 ). The delay in observations was 
due to the Earth-limb constaint, which prevented an immediate slew. We 
detect no source in the intial 100s exposure at the Swift XRT position 
(Giommi et al, GCN 3054
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 ).

Title: GRB050223: ROTSE-III Optical Observations

Smith, D. A. (U. of Michigan) reports on behalf of the ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia responded to
Swift GRB 050223 (Trigger #106709).  An automatic response resulted in a series
of 97 images beginning 7.7 seconds after receipt of the GCN trigger under fair
conditions.  Some light clouds drifted through the field, but the images
calibrated successfully.  The first image began at 23 Feb 2005 03:10:07.74,
61.6 seconds after the burst.  We took 10 5-second, 10 20-second and 67 60-s
exposures.  The images are unfiltered and were calibrated relative to USNO
A2.0. At 18.8 degrees galactic latitude, the source is in a crowded field, and
our limits are adversely effected by source confusion.

Individual images have limiting magnitudes ranging from 16.4-17.1 (for longer
exposures).  Comparison to DSS (second epoch) reveals no new sources within the
3-sigma BAT error circle to a limiting magnitude of 18.0 for co-adds of 10
images taken up to 43 minutes after the burst.  In particular, no new source is
found at the location of the XRT source coordinates (Giommi et al., GCN
Circ. No. 3054).

T. Mitani (ISAS), L. Barbier, S. Barthelmy, J. Cannizzo, J. Cummings (GSFC), 
M. Chester (PSU), E. Fenimore, M. Galassi (LANL), N. Gehrels (GSFC), 
D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), 
F. Marshall (GSFC), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC), 
G. Sato (ISAS), M. Suzuki (Saitama), T. Takahashi (ISAS), F. Tamburelli (ASDC), M. Tashiro (Saitama), J. Tueller (GSFC)


At 03:09:06 UT, the Swift Burst Alert Telescope (BAT) triggered and
located on-board GRB050223.  Because of the Earth-limb constraint,
the spacecraft could not immediately slew to the burst location.
The location became unconstrained at T+35 min, and the spacecraft slewed.
The XRT and UVOT instruments then began their standard set of pre-programmed
observing sequences.

Using the time interval of the burst, the ground-calculated location
is RA, Dec 271.390, -62.481 (J2000) with an uncertainty of 4 arcmin
(radius, including a systematic uncertainty, 90% containment).
The burst was 36 degrees off the BAT boresight (70% encoding).

The burst lightcurve has several small, short peaks on top of a slow rise 
and fall with a T90 duration of ~23 sec (and T50 is 10 sec). The 
peak flux is 0.8 ph/cm2/sec for a 1-sec interval (15-350 keV).  Using 
a simple power law model, the fluence is 7.4 e-7 erg/cm^2 (15-350 keV).

P. Giommi, M. Capalbi, M. Perri, F. Tamburelli (ASDC), G. Cusumano, V. 
Mangano, V. La Parola (INAF-IASF/Palermo), D. N. Burrows, J. A. Kennea, J. 
A. Nousek (PSU), K. L. Page, M. R. Goad (U. Leicester), P. Romano, G. 
Tagliaferri, G. Chincarini (INAF-OAB), N. Gehrels (GSFC), B. Zhang (U. 
Nevada), report on behalf of the Swift XRT team:

The Swift BAT instrument detected GRB 050223 at 03:09:06 UT on 23 Feb 
2005.  The GRB was located within the Earth angle constraint of the Narrow 
Field Instruments and the observatory was not able to slew to it at that 
time.  Swift executed an automated slew to the BAT position at 03:44 UT 
while the observatory was in the SAA.  The XRT began taking data at about 
03:57 UT after exiting the SAA.  The XRT was in Manual state and made 
observations in PCmode.  We find an uncataloged X-ray source located at:

RA(J2000) = 18h 05m 32.6s,
Dec(J2000) = -62d 28' 19.7"

We estimate an uncertainty of about 8 arcseconds.  This position was 
generated using PSU processing software on 400 s of data.  Once data become 
available at the SDC a more accurate refined position will be determined.

This position is within 1.6 arcminutes of the BAT position.