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Archival searches for transient optical emission in the error box of the 1991 January 22 gamma-ray burst
We present here the results of a study carried out at the HarvardCollege Observatory Plate Collection. We examined 3995 plates coveringthe error box of the gamma-ray burst GRB 910122, over a time span of 90yr (from 1889 to 1979). The total exposure time is ~ 0.55 yr. Noconvincing evidence of optical transient emission was found within theGRB 910122 IPN error box. However, a possible OT was found outside theGRB 910122 error box. Optical ground based observations have revealed aV ~ 22.3 object consistent with the position of the new object. Thecolours of the object are typical of a K7/M0 star or a reddened galaxy,which could have caused the OT, but the fact that the object is far awayfrom the GRB error box makes both events unrelated.
| A Search for an X-Ray Counterpart to the Extremely Bright 1993 January 31 Gamma-Ray Burst
The classical gamma-ray burst of 1993 January 31 (GRB 930131) is thehighest peak flux burst ever recorded with CGRO/BATSE. It was alsoobserved by other satellites. Its position was determined to within anarrow annulus by the Third Interplanetary Network (IPN). We searchedfor an X-ray counterpart to this bright burst with ASCA on 1996 January9, and detected one X-ray source in the IPN annulus. Its positioncoincides with an X-ray source found with ROSAT, which had beenidentified with the normal F-type star HR 4657. The flux and spectrumobtained with ASCA are consistent with those for an F-type star, and weconfirm that the detected X-ray emission comes from HR 4657. Althoughthis source is in the IPN annulus, the high chance probability offinding an X-ray source in the annulus does not justify the associationof it with GRB 930131. We discuss whether or not this X-ray source isassociated with GRB 930131.
| Optical activity of HDE 249119.
We present results of further photographic and visual photometry of HDE249119 which has been found to be optically active 7 hrs after the gammaray burst GRB 790929 and is located inside of the error box of thissource. We have analysed 587 photographic and 29 visual observationsrepresenting ~1800hrs of monitoring time. The object has been found tobe optically stable except 5 brightenings with amplitudes of~0.5-0.6mag.
| On the Stellar Origin of Gamma-Ray Bursts
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| Optical counterparts to gamma ray burst sources - First decade
The results of the first decade of the searches for flashing opticalcounterparts to gamma-ray burst sources are summarized and discussed. Wediscuss the question of the existence of optical transients in generaland outline the progress achieved in optical searches for gamma-rayburst sources. It is shown tha the first decade of these searches hasnot led to any definitive conclusion: the existence of opticaltransients related to gamma-ray bursts still remains questionable.
| HDE 249119 and its possible relation to the 1979 SEP 29 gamma-ray burst
The error boxes of five gamma-ray bursts (GRBs) were examined foroptical activity on archival photographic plates taken several hoursbefore or after the GRB events. For the GRB 790929, a possiblebrightening 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 brighteningswere found at the same position on plates taken in 1986 and 1987. Theposition is consistent with the position of the star HDE 249119 which isnormally invisible on the plates. This star was also observed on moresensitive plates but no further brightenings were revealed. The realityof the three brightenings, which are all relatively faint (below 1 magabove the plate limit), is discussed. If they are real, it implies thatHDE 249119, believed to be a normal F5 V star, exhibits flares withamplitude of about 1.5 mag, assuming a duration of several hours. Theaverage interval between flares is 1-5 mo. If the 1979 brightening isrelated to the GRB, the ratio of the total gamma-ray to optical energycan be roughly estimated at about 1, and the total radiated energy wasof order 10 exp 36 - 10 exp 37 ergs. To confirm the peculiar nature ofHDE 249119, further observations of this star are needed.
| Vitesses radiales dans 4 champs de petite latitude galactique.
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