J/MNRAS/488/2855ivo://CDS.VizieR/J/MNRAS/488/2855doi:10.26093/cds/vizier.74882855CDSPage M.J.Oates S.R.De Pasquale M.Breeveld A.A.Emery S.W.K.,Kuin N.P.M.Marshall F.E.Siegel M.H.Roming P.W.A.2024-08-20T20:12:06Z2023-02-03T14:33:23ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgamma-ray-astronomygamma-ray-burstsastrometryultraviolet-photometryvisible-astronomyWe examine the emission from optically bright gamma-ray burst (GRB) afterglows, as the Ultraviolet and Optical Telescope (UVOT) on the Neil Gehrels Swift Observatory first begins observing, following the slew to target the GRB, while the pointing of the Swift satellite is still settling. We verify the photometric quality of the UVOT settling data using bright stars in the field of view. In the majority of cases, we find no problems with the settling exposure photometry, but in one case, we excise the first second of the exposure to mitigate a spacecraft attitude reconstruction issue, and in a second case, we exclude the first second of the exposure in which the UVOT photocathode voltage appears to be ramping up. Of a sample of 23 afterglows which have peak V magnitudes <16, we find that all are detected in the settling exposures, when Swift arrives on target. For nine of the GRBs, the UVOT settling exposure took place before the conclusion of the prompt gamma-ray emission. Five of these GRBs have well-defined optical peaks after the settling exposures, with rises of >0.5mag in their optical light curves, and there is a marginal trend for these GRBs to have long T_90_. Such a trend is expected for thick-shell afterglows, but the temporal indices of the optical rises and the timing of the optical peaks appear to rule out thick shells.2019MNRAS.488.2855Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/488/2855CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/488/2855https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/488/2855http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/488/2855https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/488/2855https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/488/2855http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/488/2855GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/488/2855/tablea1 (Photometry of bright stars within the UVOT fields of view for the GRB afterglows used in the study)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/488/2855/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/488/2855/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/488/2855/tablea1?GETtext/xml+votable180.050000true278.132291726.22922220.0055555555555555566/3586 5625 11657 16282 17294 17316 17814 18777 18780 21360 27962 31281 32238-32239 33525 33735 34465 35633 40249 40433 44021 44857 47162 48458 49004 49006https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/488/2855?format=asciiGamma-rayUVOpticaldefaultJ/MNRAS/488/2855/tablea1Photometry of bright stars within the UVOT fields of view for the GRB afterglows used in the studySimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGRBGRB name (GRB YYMMDDA)meta.id;meta.maincharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainVsetmagV magnitude in the settling exposuremagphot.mag;em.opt.Vfloate_VsetmagError on Vsetmagmagstat.error;phot.magfloatVsubmagV magnitude in the subsequent settled exposuresmagphot.mag;em.opt.Vfloate_VsubmagError on Vsubmagmagstat.error;phot.magfloatDeltaVMagnitude difference Vsubmag-Vsetmag (1)magphot.mag;arith.difffloate_DeltaVError on DeltaVmagstat.errorfloat