XRF 050522

Derek B. Fox (Caltech) reports on behalf of the Caltech-NRAO-Carnegie
GRB Collaboration:  

"Inspecting our near-infrared images of the Integral localization
region for XRF050522 (Gotz et al., GCN 3446
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 ) reveals no Ks-band
sources within the XRT localization region of Capalbi et al. (GCN
3463
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 ).  Our previously reported limit of Ks > 18.5 mag for the
afterglow at 2.6 hours after the burst (Fox, Erb & Reddy, GCN 3448
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 ;
Fox et al., GCN 3457
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 ) therefore applies to this candidate.

We note that there is a bright star and NOMAD catalog object located
7.75" (~2.6 sigma?) from the XRT candidate position, at RA
13:20:34.565, Dec +24:47:12.61 (J2000)."

M. Capalbi, M. Perri, P. Giommi (ASDC),
J. A. Kennea, D. N. Burrows, (PSU), F. Marshall,
N. Gehrels (NASA/GSFC) report on behalf of the Swift XRT team:

We have analyzed the Swift XRT data from the INTEGRAL XRF 050522
(Gotz et al., GCN 3446
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 ).  Analysis of 10077 seconds of Photon Counting mode 
data reveals a weak uncataloged X-ray source within the INTEGRAL error circle.
The probability that the source is a fluctuation of the background is about 
5.6E-5.

The source coordinates are:

RA(J2000) = 13 20 35.0
Dec(J2000) = +24 47 18

We estimate an uncertainty of 6 arcseconds radius (90% containment).
This source is located 12 arcseconds from the INTEGRAL position reported
in GCN 3446
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 .  The count rate in the 0.3-10 keV band is  1.6E-03+/-0.5E-03.
We cannot yet determine whether this X-ray source is fading.

We confirm that the X-ray source outside the INTEGRAL error circle
reported previously on the basis of a preliminary analysis (Kennea et al.,
GCN 3452
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 ) is not fading and is no longer considered an afterglow candidate.

Further XRT observations are planned.

P. B. Cameron (Caltech) reports on behalf of the
Caltech-NRAO-Carnegie GRB Collaboration:

"We observed the field of XRF050522 (GCN#3446
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 ) using the
Very Large Array at a frequency of 8.46 GHz on May 23.38 UT.
We do not detect a radio source within the 2.5 arcmin error
circle. We place a 3-sigma upper limit of 153 uJy."

A. Blustin (MSSL), F. Marshall (NASA/GSFC), K. McGowan,
S. Rosen, A. Breeveld (MSSL), N. Gehrels (NASA/GSFC) on
behalf of the Swift UVOT team

INTEGRAL detected XRF 050522 at 06:00:21 UT on 22nd May
2005 (GCN circ 3446
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 ). The Swift observatory executed a
ToO observation of the INTEGRAL position, and the UVOT
began taking data 32879 s after the burst.

No new source is detected in the UVOT field of view
within the INTEGRAL error circle in the B, U and UVW2
filters down to the following 5-sigma upper limits:

Filter  Limit  Exp (s)  T_start  T_stop

B       19.7     170     33786    34686
U       19.9     425     32879    33779
UVW2    20.2     241     34695    34936

Where T_start and T_stop are in seconds after the burst.

Derek B. Fox, S. Bradley Cenko, Kevin Bundy, Chris Conselice (Caltech) and
Paul Price (IfA) report on behalf of the Caltech-NRAO-Carnegie GRB
Collaboration:

We have again imaged the field of XRF 050522 (Gotz et al, GCN 3446
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 ) with
the Wide Field Infrared Camera (WIRC) mounted on the 200-inch Palomar
Hale Telescope.  Observations consisted of 15 images in the Ks band for a
total integration time of 30 minutes.  The mean epoch of our observations
is approximately 3:45 UT 23 May (~ 21.8 hours after the burst).

Digital subtraction reveals no significantly variable sources in the
Integral error circle.  The limiting magnitude of our observations,
estimated by comparison with several 2MASS sources in the field, is
approximately Ks ~ 18.5.

J. A. Kennea, D. N. Burrows (PSU), M. Perri (ASDC), J. Cummings (GSFC) and
N. Gehrels (NASA/GSFC) report on behalf of the Swift XRT team:

INTEGRAL detected XRF 050522 at 06:00:21 UT on 22th May 2005 (GCN Circ
3446
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 ). The Swift observatory executed an Target of Opportunity observation
of the INTEGRAL position and the XRT began taking data at 15:08:29 UT. In
a preliminary data analysis we detect a single uncataloged X-ray source
in the field, located at:

RA(J2000) = 13:20:19.4,
Dec(J2000) = +24:46:11

We estimate an uncertainty of 6 arcseconds radius (90% containment). This
position is 3.9 arcminutes from the INTEGRAL position reported in GCN
3446
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 , and lies outside of the 2.5 arcmin INTEGRAL error circle.
Preliminary analysis suggests that this source does not fade significantly
in observations across 2 orbits. We therefore tentatively suggest that
this source is not related to XRF 050522. Observations of this field with
Swift are continuing.

A. Henden (USRA/USNO) reports on behalf of the USNO GRB Team:

We have acquired BVRcIc all-sky photometry for an 11x11arcmin
field centered on the coordinates for the INTEGRAL burst
XRF050522 (Gotz, et al. GCN 3446
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 )
with the USNOFS 1.0-m telescope on one photometric night
but with bright moonlight.  Stars brighter than V=12.0
are saturated and should be used with care.  We have placed
the photometric data on our anonymous ftp site:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/xrf050522.dat
The astrometry in this file is based on linear plate solutions
with respect to UCAC2.  The external errors are less than 100mas.
The estimated external photometric error is about 0.02mag.

The first image was taken 16 minutes after the burst,
and show no new sources in the INTEGRAL error box down
to a plate limit of Rc=18.5.

Since no afterglow has been reported, we do not anticipate
any further observations at this time.  However,
as always, you should check the dates on the .dat file prior to
final publication to get the latest photometry.  There is
a README file on the ftp directory to give you information
about the procedures used to calibrate these fields.

XRF 050522 : Lulin observations

P.S. Chiang (NCKU), K.Y. Huang, W.H. Ip (NCU), Y. Urata(RIKEN),
Y. Qiu (BAO), Y.Q. Lou (THCA) on behalf of EAFON report:

" We have imaged the entire error region of XRF 050522 (Gotz et
al. GCN 3446
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 ) using 1.0-m telescope at Lulin Observatory, Taiwan.  The
R and VR band observations started at 12.03 UT (~ 6.02 hours after the
burst). The limiting magnitude of our R band co-added image is ~ 20.6
compared with USNO-B1.0 stars. No source was detected under the
limiting magnitude.

This message may be cited."

B. L. Gary (Hereford Arizona Observatory [G95]) and A. Price (AAVSO) report
on behalf of the AAVSO International High Energy Network on early optical
observations of XRF 050522 (GCN 3446
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 ; Gotz et al.):

No afterglow candidate is found in the field compared to DSS to a limiting
unfiltered magnitude of 18.7. Observation midpoint time was 06:38 UT (38
minutes after burst) on May 22, 2005. Details of the observation are below
along with a link to the FITS image.

The AAVSO thanks the Curry Foundation for their continued support of the 
AAVSO International High Energy Network.

 Observer: Bruce Gary (GBL)
 Site: Hereford Arizona Observatory (G95)
 Location: Sierra Vista, AZ; USA
 LatitudeLongitude: +31.45, -110.24
 Elevation: 1420 m
 Scope: Celestron CGE-1400, 0.35 m SCT
 ScopeFocalRatio: f/1.86, 661 mm (prime focus)
 CCDVendor: SBIG ST-8XE
 CCDDetector: KAF1602E
 CCDSize: 1530 x 1020
 CCDPixelScale: 2.80 "arc/pixel
 CCDFOV: 72 x 48 'arc
 Object: GRB050522
 ObsDate: 2005.05.22
 ObsMidPointTime: 06:38 UT
 TimePerFrame: 120 sec
 NumberOfFrames: 16
 Filters: Clear
 Processing: dark/flat/mediancombine
 Seeing: 3 "arc FHWM
 LimitingMag: 19.0 (SNR=3)
 Sky: Clear, calm
 afterglowmag: <18.7
 afterglowerr:
 compstars: All-sky
 Report: No new objects present when blinking with DSS image having similar 
limiting magnitude, for 20 'arc square FOV centered on GCN 3446
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  center 
coordinates; all stars brighter than 18.7 were accounted for in DSS. Image 
made 38 minutes after burst.
 comments:

A FITS image has been uploaded to 
ftp://ftp.aavso.org/grb/BruceGary_GRB050522_2453512.81830_.fits

Derek B. Fox, Dawn Erb, and Naveen Reddy (Caltech) report:

"We have observed the localization region of XRF050522 (Gotz et al.,
GCN 3446
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 ) with the Palomar Hale 5.0-m telescope and Wide-Field
Infrared Camera (WIRC), in a 30-minute series of exposures beginning
at 08:21 UT (mean epoch 02:36 after the burst).

We do not detect any bright new sources by comparison to 2MASS and
XDSS images of the region, and therefore estimate a limiting magnitude
for the afterglow of Ks > 17.2 mag at this time."

W. Li, University of California, Berkeley, on behalf of the 
KAIT GRB team, reports:

"The robotic 0.76-m KAIT at Lick Observatory observed
XRF 050522 detected with INTEGRAL (Gotz et al., GCN 3446
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 ).
A series of 23 images were automatically obtained from
06:01:40 UT (79s after the burst) to 07:35:25 UT (5704s
after the burst), and were observed with a combination of
using V and I filters, and without filters. The images
were affected by the proximity of the GRB position to the 
bright moon. We did not detect a new object in our images
when compared to the DSS II images. Our first 15s V-band
exposure started at 79s after the burst has a limiting
magnitude of about 16.2 when compared to the USNO-B1.0 
catalog, while a 20s unfiltered image started at 130s
after the burst has a limiting mag of about 18.7. "

This message may be cited.

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

A 15 s long GRB has been detected by IBAS in IBIS/ISGRI data in the 
15-40 keV band at 06:00:21 on May 22 2005. It is not detected above 40 
keV, which classifies it as an XRF.

Its refined coordinates (J2000) are:

RA:  200.1468 [degrees]
DEC: +24.7916 [degrees]

with an uncertainty of 2.5 arcmin (90% c.l. radius).

Its preliminary peak flux (20-200 keV, 1s integration time) is about 0.34 
ph (2.2E-08 erg)/cmsq/s. Its fluence (20-200 keV, 80 s integration time) 
is 1.7 ph (9E-08 erg)/cmsq.

A plot of the double peaked light curve will be posted at

http://ibas.mi.iasf.cnr.it/IBAS_Results.html

Note that this burst is located at high galactic latitude (b=+83 deg) and 
not affected by Galactic absorption. It is therefore a good target for 
optical follow-up searches.

This message can be cited.