J/A+A/652/A76ivo://CDS.VizieR/J/A+A/652/A76doi:10.26093/cds/vizier.36520076CDSHodgkin S.T.Harrison D.L.Breedt E.Wevers T.Rixon G.Delgado A.,Yoldas A.Kostrzewa-Rutkowska Z.Wyrzykowski L.van Leeuwen M.,Blagorodnova N.Campbell H.Eappachen D.Fraser M.Ihanec N.,Koposov S.E.KruszyNska K.Marton G.Rybicki K.A.Brown A.G.A.,Burgess P.W.Busso G.Cowell S.De Angeli F.Diener C.Evans D.W.,Gilmore G.Holland G.Jonker P.G.van Leeuwen F.Mignard F.,Osborne P.J.Portell J.Prusti T.Richards P.J.Riello M.,Seabroke G.M.Walton N.A.Abraham P.Altavilla G.Baker S.G.,Bastian U.O'Brien P.de Bruijne J.Butterley T.Carrasco J.M.,Castaneda J.Clark J.S.Clementini G.Copperwheat C.M.Cropper M.,Damljanovic G.Davidson M.Davis C.J.Dennefeld M.Dhillon V.S.,Dolding C.Dominik M.Esquej P.Eyer L.Fabricius C.Fridman M.,Froebrich D.Garralda N.Gomboc A.Gonzalez-Vidal J.J.Guerra R.,Hambly N.C.Hardy L.K.Holl B.Hourihane A.Japelj J.Kann D.A.,Kiss C.Knigge C.Kolb U.Komossa S.Kospal A.Kovacs G.Kun M.,Leto G.Lewis F.Littlefair S.P.Mahabal A.A.Mundell C.G.Nagy Z.,Padeletti D.Palaversa L.Pigulski A.Pretorius M.L.van Reeven W.,Ribeiro V.A.R.M.Roelens M.Rowell N.Schartel N.Scholz A.,Schwope A.Sipoecz B.M.Smartt S.J.Smith M.D.Serraller I.,Steeghs D.Sullivan M.Szabados L.Szegedi-Elek E.Tisserand P.,Tomasella L.van Velzen S.Whitelock P.A.Wilson R.W.Young D.R.2022-12-31T09:50:56Z2021-08-13T06:27:58ZCDS support team

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

cds-question@unistra.frvariable-starssupernovaeSince July 2014, the Gaia mission has been engaged in a high-spatial- resolution, time-resolved, precise, accurate astrometric, and photometric survey of the entire sky. We present the Gaia Science Alerts project, which has been in operation since 1 June 2016. We describe the system which has been developed to enable the discovery and publication of transient photometric events as seen by Gaia. We outline the data handling, timings, and performances, and we describe the transient detection algorithms and filtering procedures needed to manage the high false alarm rate. We identify two classes of events: (1) sources which are new to Gaia and (2) Gaia sources which have undergone a significant brightening or fading. Validation of the Gaia transit astrometry and photometry was performed, followed by testing of the source environment to minimise contamination from Solar System objects, bright stars, and fainter near-neighbours. We show that the Gaia Science Alerts project suffers from very low contamination, that is there are very few false- positives. We find that the external completeness for supernovae, C_E_=0.46, is dominated by the Gaia scanning law and the requirement of detections from both fields-of-view. Where we have two or more scans the internal completeness is C_I_=0.79 at 3 arcsec or larger from the centres of galaxies, but it drops closer in, especially within 1 arcsec. The per-transit photometry for Gaia transients is precise to 1 per cent at G=13, and 3 per cent at G=19. The per- transit astrometry is accurate to 55 milliarcseconds when compared to Gaia DR2. The Gaia Science Alerts project is one of the most homogeneous and productive transient surveys in operation, and it is the only survey which covers the whole sky at high spatial resolution (subarcsecond), including the Galactic plane and bulge.2021A&A...652A..76Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/652/A76CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/652/A76https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/652/A76http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/652/A76https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/652/A76https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/652/A76http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/652/A76GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/652/A76/svmclass (Results of binary classification for Gaia Science Alerts to distinguish between two classes of Galactic transient: young stellar objects (YSOs), and cataclysmic variables (CVs).)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/652/A76/svmclass?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/652/A76/svmclass?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/652/A76/svmclass?GETtext/xml+votable180.050000true253.49668-3.561260.0055555555555555566/121 491 569 809 817 839 969 1152 1306 1309 1360 1443 1761 1791 1833 1923 2045 2073 2116 2135 2173 2208 2373 2385 2425 2507 2538 2551 2607 2659 2716 2734 2748 2755 2778 2888 2891 2956 2973 3004 3013 3035 3038 3101 3245 3287 3549 3645 3670 3738 3759 3780 3881 3924 4061 4231 4437 4747 5229 5500 5688 6308 6379 6859 6883 6957 7033 7231 7404 7549 7595 7597 7617 7825 7845 7861 7935 7966 7981 8052 8109 8209 8280 8469 8589 8635 8690 8707 8947 9198 9201 9617 9701 9718 10041 10188 10198 10206 11213 11335 11592 11709 11723 11859 12039 12113 12133 12326 12349 12419 12436 12502 12731 12789 12832 12876 12889 12907 12933 12968 12996 13006 13019 13022 13049 13128 13174 13187 13240 13248 13285 13297 13323 13351 13380 13409 13457 13511 13533 13542 13564 13718 13818-13819 13825 13902 13917 13957 13989 13991 14029 14031 14094 14120 14143 14166 14170 14180 14214 14280 14298 14304 14316 14346 14353 14358 14370 14394 14415 14417 14420 14432 14442 14477 14480 14488 14511 14559 14563 14575-14576 14602 14606 14628 14631 14633 14635-14636 14644 14647 14662 14680 14689 14752 14770 14851 14945 14950 15019 15031 15035 15182 15362 15368 15409 15433 15542 15606 15664 15671 15677 15681 15687 15711 15815 15817 15826 16005 16036 16253 16522 16682 16688 16810 17010 17166 17477 17707 17734 17845 17882 18106 18303 18328 18343 18458 18516 18733 18746 18916 19002 19170 19217 19272 19651 19660 19705 19715 19859 19916 20327 20373 20421 20486 20522 20542 20547 20596 20639 20706 20750 20759 20764 20781 20833 20934 20937 20946 20967 21076 21081 21194 21200 21340 21354 21388 21397 21410 21412 21438 21499 21521 21581 21595 21602 21624 21646 21680 21686 21791 21804 21836 21911 21916 22097-22098 22145 22156 22170 22217 22220 22243 22409 22421 22489 22503 22511 22601 22605 22622 22644 22647 22780 22820 22840 22876 22900 22988 23008 23030 23042 23050 23296 23414 23529 23549 23637 23646 23685 23704 23747 23755 23769 23890 23918 24021 24152 24156 24265 24363 24487 24572 24612 24659 24687 24731 24788 24794 24938 24980 25175 25198 25223 25344 25427 25767 25832 25868 26429 26435 26503 26720 26898 26902 27003 27225 27636 27697 27966 28055 28087 28117 28143 28244 28785 28795 28800 28803 28806 28809-28810 28814 28838 28866 28889 28894 28900 28905 28922 28926 28930 29007 29054 29064 29113 29219 29295 29441 29513-29514 29534 29558 29739 29797 29883 29904 29935 29950 30075 30112 30125 30158 30315 30318-30319 30329 30334 30338 30340 30380 30383 30387 30400 30405 30428 30532 30539 30571 30591 30660-30661 30793 31105 31351 31357 31502 31566 31677 31738 31747 31827-31828 31939-31940 32031 32056 32159 32169 32206 32231 32312 32314 32316 32375 32473 32512 32515 32648 32705 32720 32768 32909 32972 33049 33096 33109 33148 33228 33391 33423 33628 33828 33950 34007 34061 34085 34106 34214 34252 34629-34630 34702 35046 35157 35332 35558-35559 35692 35805 35842 36126 36139 36197 36422 36588 36596 36721 36908 37178 37213 37293 37298 37318 37329 37331 37338 37341 37364 37368 37385 37415 37489 37526 37547 37556 37619 37622 37663 37702 37733-37734 37762 37784 37789 37820 37827 37837 37850-37851 37857 37860 37873 37875 37884 37897 37941-37942 37952 37977 37979 38019 38024 38045 38067 38123 38127 38245 38292 38451 38464 38495 38509 38525 38590 38601 38619 38644 38675 38757 38759 38807 38838 38849 38877 38938 39075 39223 39244 39249 39254 39257 39259 39270 39280-39281 39283 39352 39410 39510 39548 39618 39627 39645 39696 39728 39779 39796 39835 39854 39865 39877 39882 39894 39904 39909 39923 39942-39943 39963 39978 40002 40019 40068 40078 40089 40101 40103 40123 40225 40263 40340-40341 40347 40464 40479 40507 40577 40598 40645 40679 40698 40729 40833 40843 40864 40872 40971 40997 41034 41079 41115 41152 41166 41207 41218 41222 41270 41272 41321 41357 41359 41366 41378 41382 41384 41394 41413 41417 41465 41527 41581-41582 41603 41631 41643 41679 41684-41685 41688 41693 41697 41706 41737 41748 41758 41768 41822 41840 41858 41891 41905 41944 41963 41982 41988 42068 42113 42122 42144 42149 42157 42199 42201 42212 42226 42292 42300 42306 42311 42369 42380 42416-42417 42438 42451 42461-42462 42483 42528 42534 42551 42576 42632 42638 42646 42661 42725 42902 43016 43024 43040 43042-43043 43070 43153 43173 43297 43320 43399 43487 43519 43655 43759 43814 43856 43912 43923 44004 44038 44055 44089-44090 44092 44169 44333 44473 44555 44609 44761 44814 44986 45116 45207 45237 45253 45263 45312 45356 45415 45451 45493 45523 45554 45578-45579 45619 45661 45715 45719 45866 45928 45933 45955 45964 46009 46028 46045 46080 46112 46141 46192 46211 46268 46449 46451 46614 46918 46950 46999 47027 47121 47142 47170 47279-47280 47294 47345 47382 47442 47453 47467 47578 47641 47661 47675 47689 47693 47736 47802 47837 47905 47983 48002 48055 48094 48122 48138 48288 48290 48332 48440 48546 49001 49006 49076 490971.9867573869263685e-19 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/652/A76?format=asciidefaultJ/A+A/652/A76/svmclassResults of binary classification for Gaia Science Alerts to distinguish between two classes of Galactic transient: young stellar objects (YSOs), and cataclysmic variables (CVs).recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameAlert Name (GaiaNNaaa)meta.id;meta.maincharGaiaDR2DR2 source_idmeta.idRA_ICRS[0.29/359.65] Right ascension (ICRS) at Ep=2015.5degpos.eq.ra;meta.mainDE_ICRS[-89.26/85.48] Declination (ICRS) at Ep=2015.5degpos.eq.dec;meta.mainplx[0.0/9.09] Parallax (from DR2)maspos.parallax.trigfloate_plx[0.02/3.09] Parallax errormasstat.error;pos.parallaxfloatGmag[14.44/20.85] Gaia G-band mean magnitude (from DR2)magphot.mag;em.optdoubleBP-RP[0.02/3.53] Gaia BP-RP colour (from DR2)magphot.color;em.opt.B;em.opt.RdoubleSVMclass[YSO CV] Predicted class (1)meta.code.classcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RA.icrsRight ascension (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decnullableindexed