Abstract.
The error boxes of five gamma-ray bursts (GRB) were examined for optical
activity on archival photographic plates taken several hours before or after
the GRB events. For the GRB 790929, a possible brightening was found at the
edge of the error box (which is very large) on a plate taken 7.1--9.6 hours
after the GRB. Two further brightenings were found at the same position
on plates taken in 1986 and 1987. The position is consistent with the
position of the star HDE 249119 which is normally invisible on the plates.
This star was also observed on more sensitive plates but no further
brightenings were revealed.
The reality of the three brightenings, which are all relatively faint
(bellow 1 mag above the plate limit), is discussed. If they are real, it
implies that HDE 249119, believed to be a normal F5V star,
exhibits flares with amplitude of ~ 1.5 mag, assuming a duration
of several hours. The average interval between flares is 1--5 months.
If the 1979
brightening is related to the GRB, the ratio of the total gamma-ray
to optical energy can be roughly estimated as
E_gamma/E_opt ~1 and the total radiated energy was of
order 10^36--10^37 ergs. To confirm the peculiar nature
of HDE 249119, further observations of this star are needed.
Key words: gamma rays: bursts: optical transients -- stars: individual: HDE 249119 -- stars: variable
______________________________
back to the list of publications
next abstract
previous abstract