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Gaia Early Data Release 3. Gaia photometric science alerts

Hodgkin, S. T. and Harrison, D. L. and Breedt, E. and Wevers, T. and Rixon, G. and Delgado, A. and Yoldas, A. and Kostrzewa-Rutkowska, Z. and Wyrzykowski, Ł. and van Leeuwen, M. and Blagorodnova, N. and Campbell, H. and Eappachen, D. and Fraser, M. and Ihanec, N. and Koposov, S. E. and Kruszyńska, K. and Marton, G. and Rybicki, K. A. and Brown, A. G. A. and Burgess, P. W. and Busso, G. and Cowell, S. and De Angeli, F. and Diener, C. and Evans, D. W. and Gilmore, G. and Holland, G. and Jonker, P. G. and van Leeuwen, F. and Mignard, F. and Osborne, P. J. and Portell, J. and Prusti, T. and Richards, P. J. and Riello, M. and Seabroke, G. M. and Walton, N. A. and Ábrahám, P. and Altavilla, G. and Baker, S. G. and Bastian, U. and O’Brien, P. and de Bruijne, J. and Butterley, T. and Carrasco, J. M. and Castañeda, J. and Clark, J. S. and Clementini, G. and Copperwheat, C. M. and Cropper, M. and Damljanovic, G. and Davidson, M. and Davis, C. J. and Dennefeld, M. and Dhillon, V. S. and Dolding, C. and Dominik, M. and Esquej, P. and Eyer, L. and Fabricius, C. and Fridman, M. and Froebrich, D. and Garralda, N. and Gomboc, A. and González-Vidal, J. J. and Guerra, R. and Hambly, N. C. and Hardy, L. K. and Holl, B. and Hourihane, A. and Japelj, J. and Kann, D. A. and Kiss, C. and Knigge, C. and Kolb, U. and Komossa, S. and Kóspál, Á. and Kovács, G. and Kun, M. and Leto, G. and Lewis, F. and Littlefair, S. P. and Mahabal, A. A. and Mundell, C. G. and Nagy, Z. and Padeletti, D. and Palaversa, L. and Pigulski, A. and Pretorius, M. L. and van Reeven, W. and Ribeiro, V. A. R. M. and Roelens, M. and Rowell, N. and Schartel, N. and Scholz, A. and Schwope, A. and Sipőcz, B. M. and Smartt, S. J. and Smith, M. D. and Serraller, I. and Steeghs, D. and Sullivan, M. and Szabados, L. and Szegedi-Elek, E. and Tisserand, P. and Tomasella, L. and van Velzen, S. and Whitelock, P. A. and Wilson, R. W. and Young, D. R. (2021) Gaia Early Data Release 3. Gaia photometric science alerts. Astronomy and Astrophysics, 652 . Art. No. A76. ISSN 0004-6361. doi:10.1051/0004-6361/202140735.

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Context. Since 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. Aims. 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. Methods. 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. Results. 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. Conclusions. The per-transit photometry for Gaia transients is precise to 1% at G = 13, and 3% at G = 19. The per-transit astrometry is accurate to 55 mas 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.

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Mahabal, A. A.0000-0003-2242-0244
Additional Information:© S. T. Hodgkin et al. 2021. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 5 March 2021; Accepted 20 May 2021; Published online 13 August 2021. We thank the anonymous referee for comments and suggestions that improved this article. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Further details of funding authorities and individuals contributing to the success of the mission is shown at We thank the United Kingdom Particle Physics and Astronomy Research Council (PPARC), the United Kingdom Science and Technology Facilities Council (STFC), and the United Kingdom Space Agency (UKSA) through the following grants to the University of Bristol, the University of Cambridge, the University of Edinburgh, the University of Leicester, the Mullard Space Sciences Laboratory of University College London, and the United Kingdom Rutherford Appleton Laboratory (RAL): PP/D006511/1, PP/D006546/1, PP/D006570/1, ST/I000852/1, ST/J005045/1, ST/K00056X/1, ST/K000209/1, ST/K000756/1, ST/L006561/1, ST/N000595/1, ST/S000623/1, ST/N000641/1, ST/N000978/1, ST/N001117/1, ST/S000089/1, ST/S000976/1, ST/S001123/1, ST/S001948/1, ST/S002103/1, and ST/V000969/1. This paper made use of the Whole Sky Database (WSDB) created by Sergey Koposov and maintained at the Institute of Astronomy, Cambridge with financial support from the Science and Technology Facilities Council (STFC) and the European Research Council (ERC). We thank the William Herschel and Isaac Newton Telescopes on the Roque de los Muchachos Observatory, La Palma, Spain, as well as the Optical Infrared Coordination Network for Astronomy (OPTICON) for their support of this project through telescope time, especially during the commissioning and verification phases. We thank the Copernico 1.82 m telescope (Mt. Ekar, Asiago Italy) operated by INAF Padova for supporting the project through telescope time (under the Large Programme Tomasella-SNe) during the verification phases. We acknowledge observations taken as part of the PESSTO project collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 199.D-0143. Authors at the ICCUB were supported by the Spanish Ministry of Science, Innovation and University (MICIU/FEDER, UE) through grant RTI2018-095076-B-C21, and the Institute of Cosmos Sciences University of Barcelona (ICCUB, Unidad de Excelencia ’María de Maeztu’) through grant CEX2019-000918-M. This work is supported by Polish NCN grants: Daina No. 2017/27/L/ST9/03221, Harmonia No. 2018/30/M/ST9/00311, Preludium No. 2017/25/N/ST9/01253 and MNiSW grant DIR/WK/2018/12 as well as the European Commission’s Horizon2020 OPTICON grant No. 730890. The Authors would like to thank the Warsaw University OGLE project for their continuous support in this work. AB acknowledges financial support from the Netherlands Research School for Astronomy (NOVA). AG acknowledges the financial support from the Slovenian Research Agency (grants P1-0031, I0-0033, J1-8136, J1-2460). AH was funded in part by the Leverhulme Trust through grant RPG-2012-541 and by the European Research Council grant 320360. AP acknowledges support from the NCN grant no. 2016/21/B/ST9/01126. CM acknowledges support from Jim and Hiroko Sherwin. DAK acknowledges support from the Spanish research projects AYA 2014-58381-P, AYA2017-89384-P, from Juan de la Cierva Incorporación fellowship IJCI-2015-26153, and from Spanish National Research Project RTI2018-098104-J-I00 (GRBPhot). EB and STH are funded by the Science and Technology Facilities Council grant ST/S000623/1. TW was funded in part by European Research Council grant 320360 and by European Commission grant 730980. GC acknowledges the Agenzia Spaziale Italiana (ASI) for its continuing support through contract 2018-24-HH.0 to the Italian Istituto Nazionale di Astrofisica (INAF). GD acknowledges the observing grant support from the Institute of Astronomy and Rozhen NAO BAS through the bilateral joint research project “Gaia Celestial Reference Frame (CRF) and fast variable astronomical objects” (during 2020-2022, leader is G. Damljanovic), and support by the Ministry of Education, Science and Technological Development of the Republic of Serbia (contract no. 451-03-68/2020-14/200002). G. Marton acknowledges support from the EC Horizon 2020 project OPTICON (730890) and the ESA PRODEX contract no. 4000129910. MF is supported by a Royal Society - Science Foundation Ireland University Research Fellowship NB acknowledges support from the research programme VENI, with project number 016.192.277, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO). NI is partially supported by Polish NCN DAINA grant no. 2017/27/L/ST9/03221. PAW acknowledges research funding from the South African National Research Foundation. RWW was funded by the Science and Technology Facilities Council grant ST/P000541/1. V.A.R.M.R. acknowledges financial support from Radboud Excellence Initiative, the Fundação para a Ciência e a Tecnologia (FCT) in the form of an exploratory project of reference IF/00498/2015/CP1302/CT0001, FCT and the Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) through national funds and when applicable co-funded EU funds under the project UIDB/EEA/50008/2020, and supported by Enabling Green E-science for the Square Kilometre Array Research Infrastructure (ENGAGE-SKA), POCI-01-0145-FEDER-022217, and PHOBOS, POCI-01-0145-FEDER-029932, funded by Programa Operacional Competitividade e Internacionalização (COMPETE 2020) and FCT, Portugal. ZKR acknowledges funding from the Netherlands Research School for Astronomy (NOVA). ZN acknowledges support from the ESA PRODEX contract nr. 4000129910.
Funding AgencyGrant Number
Gaia Multilateral AgreementUNSPECIFIED
Particle Physics and Astronomy Research Council (PPARC)UNSPECIFIED
United Kingdom Space Agency (UKSA)PP/D006511/1
United Kingdom Space Agency (UKSA)PP/D006546/1
United Kingdom Space Agency (UKSA)PP/D006570/1
Science and Technology Facilities Council (STFC)ST/I000852/1
Science and Technology Facilities Council (STFC)ST/J005045/1
Science and Technology Facilities Council (STFC)ST/K00056X/1
Science and Technology Facilities Council (STFC)ST/K000209/1
Science and Technology Facilities Council (STFC)ST/K000756/1
Science and Technology Facilities Council (STFC)ST/L006561/1
Science and Technology Facilities Council (STFC)ST/N000595/1
Science and Technology Facilities Council (STFC)ST/S000623/1
Science and Technology Facilities Council (STFC)ST/N000641/1
Science and Technology Facilities Council (STFC)ST/N000978/1
Science and Technology Facilities Council (STFC)ST/N001117/1
Science and Technology Facilities Council (STFC)ST/S000089/1
Science and Technology Facilities Council (STFC)ST/S000976/1
Science and Technology Facilities Council (STFC)ST/S001123/1
Science and Technology Facilities Council (STFC)ST/S001948/1
Science and Technology Facilities Council (STFC)ST/S002103/1
Science and Technology Facilities Council (STFC)ST/V000969/1
Ministerio de Economía, Industria y Competitividad (MINECO)RTI2018-095076-B-C21
Centro de Excelencia Severo OchoaCEX2019-000918-M
National Science Centre (Poland)2017/27/L/ST9/03221
National Science Centre (Poland)2018/30/M/ST9/00311
National Science Centre (Poland)2017/25/N/ST9/01253
Ministerstwo Nauki i Szkolnictwa Wyższego (MNiSW)DIR/WK/2018/12
European Research Council (ERC)730890
Nederlandse Onderzoekschool Voor Astronomie (NOVA)UNSPECIFIED
Slovenian Research AgencyP1-0031
Slovenian Research AgencyI0-0033
Slovenian Research AgencyJ1-8136
Slovenian Research AgencyJ1-2460
Leverhulme TrustRPG-2012-541
European Research Council (ERC)320360
National Science Centre (Poland)2016/21/B/ST9/01126
Jim and Hiroko SherwinUNSPECIFIED
Ministerio de Educación y Ciencia (MEC)AYA 2014-58381-P
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2017-89384-P
Juan de la Cierva IncorporaciónIJCI-2015-26153
Ministerio de Ciencia e Innovación (MCINN)RTI2018-098104-J-I00
Science and Technology Facilities Council (STFC)ST/S000623/1
European Research Council (ERC)320360
European Research Council (ERC)730980
Agenzia Spaziale Italiana (ASI)2018-24-HH.0
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Institute of AstronomyUNSPECIFIED
National Astronomical Observatory RozhenUNSPECIFIED
Ministry of Education, Science and Technological Development (Serbia)451-03-68/2020-14/200002
European Research Council (ERC)730890
European Space Agency (ESA)4000129910
Science Foundation, IrelandUNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)016.192.277
National Science Centre (Poland)2017/27/L/ST9/03221
National Research Foundation (South Africa)UNSPECIFIED
Science and Technology Facilities Council (STFC)ST/P000541/1
Fundação para a Ciência e a Tecnologia (FCT)IF/00498/2015/CP1302/CT0001
Ministério da Ciência, Tecnologia e Ensino Superior (MCTES)UIDB/EEA/50008/2020
Square Kilometer Array Research InfrastructurePOCI-01-0145-FEDER-022217
Square Kilometer Array Research InfrastructurePOCI-01-0145-FEDER-029932
Programa Operacional Competitividade e InternacionalizaçãoUNSPECIFIED
Subject Keywords:surveys – supernovae: general – quasars: general – stars: variables: general
Record Number:CaltechAUTHORS:20210920-160728903
Persistent URL:
Official Citation:Gaia Early Data Release 3 - Gaia photometric science alerts. S. T. Hodgkin, D. L. Harrison, E. Breedt, T. Wevers, G. Rixon, A. Delgado, A. Yoldas, Z. Kostrzewa-Rutkowska, Ł. Wyrzykowski, M. van Leeuwen, N. Blagorodnova, H. Campbell, D. Eappachen, M. Fraser, N. Ihanec, S. E. Koposov, K. Kruszyńska, G. Marton, K. A. Rybicki, A. G. A. Brown, P. W. Burgess, G. Busso, S. Cowell, F. De Angeli, C. Diener, D. W. Evans, G. Gilmore, G. Holland, P. G. Jonker, F. van Leeuwen, F. Mignard, P. J. Osborne, J. Portell, T. Prusti, P. J. Richards, M. Riello, G. M. Seabroke, N. A. Walton, P. Ábrahám, G. Altavilla, S. G. Baker, U. Bastian, P. O’Brien, J. de Bruijne, T. Butterley, J. M. Carrasco, J. Castañeda, J. S. Clark, G. Clementini, C. M. Copperwheat, M. Cropper, G. Damljanovic, M. Davidson, C. J. Davis, M. Dennefeld, V. S. Dhillon, C. Dolding, M. Dominik, P. Esquej, L. Eyer, C. Fabricius, M. Fridman, D. Froebrich, N. Garralda, A. Gomboc, J. J. González-Vidal, R. Guerra, N. C. Hambly, L. K. Hardy, B. Holl, A. Hourihane, J. Japelj, D. A. Kann, C. Kiss, C. Knigge, U. Kolb, S. Komossa, Á. Kóspál, G. Kovács, M. Kun, G. Leto, F. Lewis, S. P. Littlefair, A. A. Mahabal, C. G. Mundell, Z. Nagy, D. Padeletti, L. Palaversa, A. Pigulski, M. L. Pretorius, W. van Reeven, V. A. R. M. Ribeiro, M. Roelens, N. Rowell, N. Schartel, A. Scholz, A. Schwope, B. M. Sipőcz, S. J. Smartt, M. D. Smith, I. Serraller, D. Steeghs, M. Sullivan, L. Szabados, E. Szegedi-Elek, P. Tisserand, L. Tomasella, S. van Velzen, P. A. Whitelock, R. W. Wilson and D. R. Young. A&A, 652 (2021) A76; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110960
Deposited By: Tony Diaz
Deposited On:20 Sep 2021 18:37
Last Modified:20 Sep 2021 18:37

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