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GCN Circular 3425

Subject

XRF 050509c optical afterglow

Date

2005-05-16T10:55:28Z (20 years ago)

Edited On

2024-11-18T10:04:21Z (a month ago)

From

Jens Hjorth at U.Copenhagen <jens@astro.ku.dk>

Edited By

Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>

J. Gorosabel (IAA-CSIC), B. L. Jensen (NBI), G. Galaz (Pont. Uni. de Chile),
R. Salinas (Uni. de Concepcion), J. Hjorth, J. P. U. Fynbo, H. Pedersen,
D. Watson, P. Jakobsson, J. M. Castro Cerón (NBI), report:

"We have carried out R-band observations of XRF 050509c (HETE trigger #3751; 
GCN 3402Loading...
 
 ) error box with the 1.54m Danish telescope (+DFOSC) on La Silla, 
as follows:

          ======================================
               Date UT     t-to   Texp  Seeing   
               May 2005    (hr)   (s)    (")     
          --------------------------------------
           10.1545-10.1703  5.1  2x600   1.2
           14.0490-14.0829 98.8  4x600   1.3
          ======================================

Both observations are centred in the SXC error box covering ~80% of it. 
Comparison of the two epoch images reveals, well centred in the SXC error 
box, a fading point-like object with coordinates:

     RA(J2000)   =  12:52:53.94 
     Dec(J2000)  = -44:50:04.1   (internal astrometric error of 1")

which we propose as the XRF 050509c optical afterglow.

Assuming R = 17.9 for the USNO star placed at (12:52:52.34, -44:49:23.1)
we estimate a decay from R~20.1 to R~24.0  between the two epochs. This
would imply a power-law decay index of -1.2 typical of GRB afterglows.

Finding charts can be found at:

http://www.dsri.dk/~jgu/grb050509c/FCs/grb050509c.1.54dk.epoch1.gif
http://www.dsri.dk/~jgu/grb050509c/FCs/grb050509c.1.54dk.epoch2.gif

Further observations are planned."