J/A+A/703/A101ivo://CDS.VizieR/J/A+A/703/A101CDSGuidorzi C.Maccary R.Maistrello M.Kobayashi S.Bulla M.Frontera F.2026-03-02T06:25:50Z2025-11-11T14:32:40ZCDS support team

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

cds-question@unistra.frgamma-ray-astronomygamma-ray-burstsx-ray-sourcesMost gamma-ray burst (GRB) X-ray afterglow light curves are characterised by a plateau, followed by a normal power-law decay, which is interpreted as afterglow emission, that is radiation emitted by the shocked interstellar medium that is swept up by the blast wave. Despite the numerous alternative interpretations, the origin of the plateau remains unclear. In the early years of the Neil Gehrels Swift Observatory, it was suggested that the plateau might be afterglow radiation, that started before the prompt gamma-ray emission, and its time profile would be an artefact of assuming the start time of the prompt gamma-ray emission as zero time (the so-called "prior activity model"). We aim to test the plausibility of the prior activity model by leveraging the current Swift sample of early X-ray afterglows of GRBs with measured redshifts, which is more than eight times larger than the one originally used (463 vs. 56). We modelled the GRB rest-frame X-ray afterglow luminosities assuming a simple power-law with the true reference time preceding the prompt gamma-ray emission trigger time by T0 and the X-ray luminosity L0 at the trigger time as free parameters. We tested each case applying both chi^2^ and runs tests. For 90% GRBs of our sample, the model provided a successful description. In ten cases the afterglow peak is identified and modelled appropriately. Using the 300 GRBs with accurate parameters' estimates, we confirm the anti-correlation between L0 and T 0 with 0.7dex scatter. In addition, selecting the subsample of 180 from the literature with reliable estimates of isotropic-equivalent released energy Egamma,iso, peak luminosity Lgamma,iso, and intrinsic peak energy Ep,i of the nuFnu spectrum of the prompt gamma-ray emission, we find a correlation between L0, T0, and Egamma,iso (0.4dex scatter) over nine decades in L0 and common to all kinds of GRBs. The afterglow likely begins in most cases before the start of the detected prompt gamma-ray emission by a lognormally-distributed rest-frame delay with a mean of 10^3^s and 0.8dex dispersion. As also suggested by the recent discoveries of Einstein Probe of X-ray emission starting long before the prompt gamma-rays, our results suggest that the occurrence of prior activity could be much more frequent than what has tacitly been assumed so far.2025A&A...703A.101Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/703/A101CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/703/A101https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/703/A101http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/703/A101https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/703/A101https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/703/A101http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/703/A101GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/703/A101/table3 (Time intervals that were excluded from the fit because of the presence of internal activity, for a restricted list of GRBs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/703/A101/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/703/A101/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/703/A101/table3?GETtext/xml+votable180.050000true212.0712083-3.77188890.005555555555555556Cone search capability for table J/A+A/703/A101/table4 (Best-fit parameters for the main group of GRBs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/703/A101/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/703/A101/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/703/A101/table4?GETtext/xml+votable180.050000true166.4124583-40.68413890.005555555555555556Cone search capability for table J/A+A/703/A101/table5 (Best-fit parameters for the AG-rise set)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/703/A101/table5?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/703/A101/table5?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/703/A101/table5?GETtext/xml+votable180.050000true210.667083332.17072220.0055555555555555566/186 207 314 393 500 503 576 614 646 699 744-745 825 866 895 908 923 944 1001 2044 2107 2315 2336 2357 2682 2735 2948-2949 3019 3089 3111 3447 3536 3586 3935 4271 4312 4323 4371 4449-4450 4809 4955 5051 5073 5135 5155 5184 5389 5431 5493 5625 5657 5726 5745 5790 5941 6278 6400 6413 6521 6523 6877 7044 7177 7182 7227 7518 7532 7589 7665 7750 8074 8182 8318 8345 8459 8569 8641 8669 8693 8761 8798 8932 8954-8955 9022 9321 9341 9370 9512 9627 9643 9682 9897 9989 10094 10279 10335 10400-10401 10405 10407 10424 10445 10447 10519 10602 10680 10704 10723 10762 10852 10912 11007 11058 11187 11220 11657 11673 11695 11708 11748-11749 11756 11822 11904-11905 12020 12134 12199 12597 12785 13084 13182 13252 13312 13476 13494 13694 13701 13779 13924 14162 14217 14892 14948 15054 15200 15326 15340 15530 15904 16057 16228 16282 16339 16392 16489 16546 16661 16845 16991 17071 17086 17316 17395 17411 17453 17531 17721 17733 17749 17814 17862 17980 18096 18494 18681 18728 18777 18843 18945 18978 19049 19082 19164 19168 19194 19293 19334 19389 19532 19544 19785 19865 19890 19911 20030 20191 20263 20348 20360 20372 20420 20460 20655 20676 20679 20710 20753 20774 21015 21082 21137 21284 21498 21595 21688 21766 21970 22129 22409 22422 22518 22559 22580 22619 22624 22793 22816 22916 23150 23306 24007 24097 24534 25174 25192 25293 25315 25336 25394 25761 25901 25946 26011 26036 26076 26409 26503 26585 26659 26671 27064 27085 27262 27287 27289 27320 27434 27437 27566 27572 27861 27906 27933 27962 27965 27983 28009 28032 28063 28071 28202 28224 28234 28364 28379 28442 28467 28496 28555 28930 29019 29052 29731 29816 30088 30170 30195 30947 31185 31281 31286 31385 31521 31583 31675 31700 31721 31856 31934 32091 32110 32239 32279 32310 32686 32713 32790 33004 33066 33146 33265 33278 33525 33617 33646 33679 33735 33751 33813 33826 33860 33925 34147 34168 34174 34271 34364 34435 34440 34465 34488 34552 34574 34590 34605 34699 34788 34832 34850 34878 34949 35045 35242 35285 35330 35367 35392-35393 35427 35448 35566 35569 35633 35702 35731 35844 36035 36066 36107 36142 36297 36307 36374 36460 36468 36527-36528 36800 37007 37383 37391 37459 38280 38301 38351 38399 38688 38869 38926 39008 39076 39461 39553 39559 39918 39993 40214 40249 40273 40433 40736 40943 41020 41064 42133 42545 42901 42914 43193 43316 43479 44021 44179 44212 44223 44264 44436 44447 44715 44857 45008 45180 45361 45409 45510 45561 45777 45828 45835-45836 45938 46002 46022 46150 46209 46212 46218 46395 46510 46594 46899 46989 47031 47148 47162 47244-47245 47251 47257 47436 47459 47491 47544 47588 47620 47966 47991 48054 48189 48219 48371 48447 48458 48481 49004https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/703/A101?format=asciiGamma-rayX-raydefaultJ/A+A/703/A101/table3Time intervals that were excluded from the fit because of the presence of internal activity, for a restricted list of GRBsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGRBGRB namemeta.id;meta.mainchartstartStart time of internal activity intervalstime.startinttstopStop time of internal activity intervalstime.endintSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPositions from Simbad and BAT (right ascension part)degpos.eq.ra;meta.main_DEPositions from Simbad and BAT (declination part)degpos.eq.dec;meta.mainJ/A+A/703/A101/table4Best-fit parameters for the main group of GRBsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSimbadSimbad column added by the CDSmeta.ref.urlcharGRBGRB namemeta.id;meta.maincharzRedshiftsrc.redshiftdoubletstartStart time of the interval used for fitstime.startdoubletstopStop time of the interval used for fitstime.enddoublelogL0Best-fit of afterglow luminosity (L0 in erg/s)log(1e-07W)phys.luminosity;em.X-rayfloate_logL0Error on logL0log(1e-07W)stat.errorfloatlogT0Best-fit of time measured since the true beginning of the eventlog(s)time;arith.difffloate_logT0Error on logT0log(s)stat.errorfloatalphaBest-fit power-law indexspect.indexfloate_alphaError on alphastat.error;pos.eq.rafloatPvalchi2p-value of chi^2^ teststat.fit.chi2doubleb_logL0Lower boundary of 90% confidence interval for logL0log(1e-07W)stat.fit.paramfloatB_logL0Upper boundary of 90% confidence interval for logL0log(1e-07W)stat.fit.paramfloatb_logT0Lboundary of 90% confidence interval for logT0log(s)stat.fit.paramfloatB_logT0Uboundary of 90% confidence interval for logT0log(s)stat.fit.paramfloatb_alphaLboundary of 90% confidence interval for alphastat.fit.paramfloatB_alphaUboundary of 90% confidence interval for alphastat.fit.paramfloatPvalRunsp-value of runs teststat.fit.goodnessdoubleNpNumber of pointsmeta.numberintCl[L S SEE] GRB Class (G1)meta.code.classcharT90T90 durationstime.durationdoublee_T90? Error on T90sstat.errordoublenullable_RAPositions from Simbad and BAT (right ascension part)degpos.eq.ra;meta.main_DEPositions from Simbad and BAT (declination part)degpos.eq.dec;meta.mainJ/A+A/703/A101/table5Best-fit parameters for the AG-rise sete_logT0Error on logT0log(s)stat.errorfloatlogTpBest-fit of time measured since the true zero timelog(s)time;arith.difffloatSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGRBGRB namemeta.id;meta.maincharzRedshiftsrc.redshiftfloattstartStart time of the interval used for fitstime.startfloattstopStop time of the interval used for fitstime.endfloatFSflag[0/1] Forward Shock (1), Reverse Shock (0)meta.codeintlogL0Best-fit of afterglow luminosity (L0 in erg/s)log(1e-07W)phys.luminosity;em.X-rayfloate_logL0Error on logL0log(1e-07W)stat.errorfloatlogT0Best-fit of time measured since the true beginning of the eventlog(s)time;arith.difffloatelogTpError on logTplog(s)stat.errorfloatpBest-fit p (e- energy distribution index)stat.fit.paramfloate_pError on pstat.errorfloatPvalChi2p-value of chi^2^ teststat.fit.chi2doubleb_logL0Lower boundary of 90% confidence interval for logL0log(1e-07W)stat.fit.paramfloatB_logL0Upper boundary of 90% confidence interval for logL0log(1e-07W)stat.fit.paramfloatb_logT0Lower boundary of 90% confidence interval for logT0log(s)stat.fit.paramfloatB_logT0Upper boundary of 90% confidence interval for logT0log(s)stat.fit.paramfloatb_logTpLower boundary of 90% confidence interval for logTplog(s)stat.fit.paramfloatB_logTpUpper boundary of 90% confidence interval for logTplog(s)stat.fit.paramfloatb_pLower boundary of 90% confidence interval for pstat.fit.paramfloatB_pUpper boundary of 90% confidence interval for pstat.fit.paramfloatPvalRunsp-value of runs teststat.fit.goodnessdoubleNpNumber of pointsmeta.numberintCl[L S] GRB Class (G1)meta.code.classcharT90T90 durationstime.durationfloate_T90Error on T90sstat.errorfloat_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main