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Discovery of the Optical Counterpart and Early Optical Observations of GRB 990712
We present the discovery observations of the optical counterpart of thegamma-ray burst GRB 990712 taken 4.16 hr after the outburst and discussits light curve observed in the V, R, and I bands during the first ~35days after the outburst. The observed light curves were fitted with apower-law decay for the optical transient (OT), plus an additionalcomponent that was treated in two different ways. First, the additionalcomponent was assumed to be an underlying galaxy of constant brightness.The resulting slope of the decay is0.97+0.05-0.02, and the magnitudes of theunderlying galaxy are V=22.3+/-0.05, R=21.75+/-0.05, and I=21.35+/-0.05.Second, the additional component was assumed to be a galaxy plus anunderlying supernova with a time-variable brightness identical to thatof GRB 980425, appropriately scaled to the redshift of GRB 990712. Theresulting slope of the decay is similar, but the goodness of fit isworse, which would imply that either this GRB is not associated with anunderlying supernova or the underlying supernova is much fainter thanthe supernova associated with GRB 980425. The galaxy in this case isfainter: V=22.7+/-0.05, R=22.25+/-0.05, and I=22.15+/-0.05, and the OTplus the underlying supernova at a given time is brighter. Measurementsof the brightnesses of the OT and the galaxy by late-time Hubble SpaceTelescope observation and ground-based observations can thus assess thepresence of an underlying supernova. Based on observations collected atSAAO, Sutherland; ESO, Paranal and La Silla (ESO Programs 63.O-0618 and63-O-0567) and AAT, Australia.
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| GRB 990712
IAUC 7225 available at Central Bureau for Astronomical Telegrams.
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Not Available
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Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1988MNRAS.231.1047M&db_key=AST
| Standard Stars for VRI Photometry with S25 Response Photocathodes
Not Available
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Datos observacionales y astrométricos
| Constelación: | Mosca |
| Ascensión Recta: | 11h45m18.65s |
| Declinación: | -74°52'26.3" |
| Magnitud Aparente: | 8.47 |
| Distancia: | 219.78 parsecs |
| Movimiento Propio en Ascensión Recta: | -27.8 |
| Movimiento Propio en Declinación: | -2.6 |
| B-T magnitude: | 8.786 |
| V-T magnitude: | 8.497 |
Catálogos y designaciones:
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