XRF 030824

A. Klotz, F. Malacrino, J.L. Atteia, M. Boer
(CESR-LAT/OMP Toulouse) communicate:

Additonal observations of the field of XRF 030824 (HETE 2821) have been
obtained with MEGAPRIME at the Canada-France-Hawaii Telescope.

Two 800 sec exposures with i' filter, starting on Oct 3, 08:07 UT, and

Two 300 sec exposures with r' filter, starting on Oct 4, 06:57 UT

These data are being analyzed, in comparison with the data acquired
with MEGAPRIME on Sept 21st (i' filter, Klotz et al., GCN 2406
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 ) and with
the images of the Large Format Camera recorded on August 25 and 26th
(R filter, Fox et al., GCN 2364
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  & 2369)

A first result of these observations is to discard the two 
sources mentioned in GCN 2406
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  as being possibly associated
with XRF 030824. 
These objects where selected as being significantly
brighter in the September images than in the August images 
(as expected for a SN associated with XRF 030824).
The new observations show that they are in fact very red objects, 
very faint in R but clearly visible in all i' images, and not variable. 

The whole set of observations is being re-analyzed to search for
or to constrain a possible supernova associated with XRF 030824.

Y. Urata, T. Soyano, T. Tamagawa on behalf of the Kiso GRB team,
J. Jugaku (NAOJ), T. Kawamoto (Hokkaido University) report:

"We have observed XRF030824 field (M. Galassi et al. GCN 2402
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 ) using
the 105cm Schmidt telescope (Kiso Observatory, Institute of Astronomy,
the University of Tokyo) and 2kx2k CCD camera with 2 degree objective
prism from 76 to 153 min after the burst (from 16 min after HETE-2
alert).

 We have checked two candidates reported by Klotz et al (GCN 2406
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 )
comparing with Palomar images (Fox and Hunt GCN 2364
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  and 2369
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 ). We
could not find these two candidates brighter than R~17 limited
magnitude.

 We have also observed this field again at the end of September using
the same instruments. Further analysis is in progress.

 These images can be found at
http://cosmic.riken.go.jp/urata/XRF030824.gif 
(left image: Kiso 2D spectrum image, right image: Palomar image).  

 We thank to Dr. D. Fox for suppling Palomar images."

This message may be cited.

A. Klotz, F. Malacrino, J.L. Atteia, M. Boer (CESR-LAT/OMP Toulouse), D. Fox, 
M.P. Hunt (Caltech), and C. Veillet (CFHT) communicate:

We observed the error box of XRF 030824 (HETE 2821) with MEGAPRIME at the 
Canada-France-Hawaii Telescope, and i' filter, on September 21, 7h56 UT (two 
300 sec exposures). This XRF has a relatively low "pseudo-z" (see Atteia, 
2003, A&A, 407, L1), and we were looking for the possible rise of an 
associated type Ib,c supernova. 

Comparison with frames acquired at the 200-inch Hale Telescope and Large-
Format Camera on Mt. Palomar (Fox and Hunt GCNC # 2364 and 2369) reveals two 
new objects at the following J2000.0 coordinates: 

Object 1: 0h05m12.30s, +20d06'29.4" +-0.2", i'=22.7+-0.2; no host galaxy 
detected.

Object 2: 00h05m06.82s +20d05m00.4s +-0.4", i'=22.6+-0.4; offset from apparent 
host anonymous galaxy 0.56"W and 0.55"N, host magnitude i' = 21.5+-0.2 .

While the objects are visible on both CFHT i' frames, they are not visible on 
Palomar images. No catalogued asteroid is associated with any object on the 
frames. Given the wide area scanned, these objects may be supernovae not 
associated with the GRB, or TNOs, or one of them can be associated with XRF 
030824.

Images and first analysis of the frames are available at the following URL: 
http://www.cesr.fr/~klotz/grb030824/cand.htm

New observations are underway at CFHT.

This message is citable

M. Galassi, C. Graziani, Y. Shirasaki, G. Ricker, J-L. Atteia, N.
Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team;

T. Donaghy, E. Fenimore, M. Matsuoka, T. Sakamoto, M. Suzuki, T.
Tamagawa, K. Torii, A. Yoshida, Y. Nakagawa, R. Satoh, Y. Urata, T.
Yamazaki and Y. Yamamoto, on behalf of the HETE WXM Team;

A. Dullighan, N. Butler, G. Crew, J. Doty, G. Prigozhin, R. Vanderspek,
J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R.
Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE
Optical-SXC Teams;

M. Boer, J-F Olive, J-P Dezalay, C. Barraud and K. Hurley on behalf of
the HETE FREGATE Team;

report:

At 16:47:35.10 UTC (60455.10 s UT) on 24 August 2003, the HETE FREGATE
and WXM instruments detected event H2821, an X-Ray Flash.

The burst triggered FREGATE in the 6-80 keV energy band.  The WXM
flight localization was correct, but was not sent to the GCN because
the low fluence of the burst and its location at the edge of the WXM
FOV did not meet the criteria for automatic propagation.  Ground
analysis of the WXM data provided a localization that was reported in a
GCN Notice at 17:47:22 UT, 60 minutes after the burst.  Further ground
analysis of the WXM data provided a refined localization that was
reported in a GCN Notice at 19:13:33 UT.  The refined WXM ground
localization SNR was 6. The refined WXM localization can be expressed
as a 90% confidence circle, whose radius is 11.2 arcminutes and whose
center is at:

WXM-Ground:  R.A. = +00h 05m 02s, Dec. = +19d 55' 37" (J2000).

The SXC had not yet turned on because the burst occurred just before
orbit dusk.

The T90 duration for the burst was > 16 seconds in the WXM 2-25 keV
energy band.  The peak flux of the burst in 1 second is 5.4 x 10-8 erg
cm-2 s-1 in the 7-30 kev energy band and 2.1 x 10-8 erg cm-2 s-1 in the
30-400 keV energy band.  The fluence of the burst is 8.9 x 10-7 erg cm-2
and 5.8 x 10-7 erg cm-2 in the same energy bands, respectively.  Thus
S(2-30 keV)/S(30-400 keV) = 1.5, making this burst an X-ray flash.

A light curve and skymap for XRF030824 is provided at the following URL:

http://space.mit.edu/HETE/Bursts/GRB030824

A. Oksanen on behalf of the Nyrola Observatory GRB Team
and the AAVSO International High Energy Network reports:

Total of five 24 x 16 arcmin fields covering most of the HETE WXM error
circle of XRF030824 (HETE 2821) was imaged with the 0.4m SCT at the
Nyrola Observatory starting at August 24, 2003 20:40 UT, 4.0 hours after 
the inital burst under varying sky conditions (some clouds and haze).
 
Total of 22 240s Rc-exposures were combined and compared to
the Digitized Sky Survey (DSS2R). 

No new objects were found to the image limits of R = 17.5 - 19.0. 

Field        mid UT    exposure   limiting R mag
------------------------------------------------ 
XRF030824     20:50    5 x 240s       19.0
XRF030824NE   21:15    3 x 240s       18.5
XRF030824NW   21:35    5 x 240s       17.5 (clouds)
XRF030824SE   22:01    5 x 240s       19.0
XRF030824SW   22:24    4 x 240s       19.0
------------------------------------------------ 

The final combined images are available on the web with an image
showing the error circle and the sky coverage of each field:
http://nyrola.jklsirius.fi/grb/xrf030824/

The AAVSO International High Energy network is grateful for a 
generous grant from the Curry Foundation and to NASA for the 
financial support for the High Energy Workshops for Amateur 
Astronomers.

D.B. Fox and M.P. Hunt (Caltech), with P.A. Price (IfA/Hawaii) report
on behalf of the Caltech-NRAO GRB Collaboration:

"We have reobserved the HETE-2 WXM localization region for XRF030824
with the 200-inch Hale Telescope and Large-Format Camera on
Mt. Palomar.  Our dithered 4x300s images cover 95% of the
22.4'-diameter error circle at a mean epoch of August 26.42 UT, 1.72
days after the event.  PSF-matched image subtraction of our
first-epoch image (mean epoch Aug 25.25; Fox & Hunt, GCN 2364
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 ) does
not reveal any bright, stationary, variable objects within the part of
the WXM localization region covered by our images.  The limiting
magnitude of the individual images is approximately R~24.5.  Within
this region we set a lower limit of R>22.5 on the magnitude of any
strongly variable optical counterpart to XRF030824 at either epoch.
This is a conservative lower limit, which we consider appropriate
given the size of the region.

Separately, we note the presence of a slow-moving (15" per hour,
PA=-73 deg) object within the error circle in our Aug 25.25 image,
near RA 00:05:36.69, Dec +19:59:56.9 (J2000), with an approximate
R-band magnitude of 19.9.  

The nearest star to the location of the object reported by Moran et
al. (GCN 2363
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 ) is constant in brightness in our two images.  We find
no variable objects in the near vicinity; however, the location is
only 15" from the borders of our imaged region.

Observers interested in making their own investigation of these data,
or comparing with other datasets, should contact Fox by email to
arrange for data transfer."

M.A. Ibrahimov, I.M. Asfandiyarov, B.B. Kahharov (UBAI), A.Pozanenko
(IKI),V.Rumyantsev  (CrAO),  G.Beskin (SAO) report:

We have observed the WXM error box of XRF030824 (HETE trigger 2821) with
1.5m telescope of Maidanak High-altitude Observatory (UBAI) on August 24.
The 5x300s images taken between 21:19 and 21:51 UT (4.53hrs after the burst)
cover 40% around the center of WXM error circle.  The OT candidate (Moran et
al. GCN 2363
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 ) is out of our coverage. Visual comparison with DSS2 reveals no
new sources to the limiting magnitude R~19.5.

D.B. Fox and M.P. Hunt (Caltech) report on behalf of the Caltech-NRAO
GRB Collaboration:  

"We have observed the HETE-2 WXM localization region for XRF030824
with the 200-inch Hale Telescope and Large-Format Camera on
Mt. Palomar.  Our dithered 4x300s images cover 95% of the
22.4'-diameter error circle at a mean epoch of August 25.25 UT, 0.55
days after the event.  Visual comparison with the Digitized Sky Survey
(POSS-II) reveals no new, bright sources within the localization
region to the limiting magnitude of the GSC catalog, R~18.8.

"The nearest star to the location of the candidate of Moran et
al. (GCN 2363
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 ) has R~20.1 in our image."