PESSTO: survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects^⋆,⋆⋆

¹ Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast, BT7 1NN, UK
e-mail: s.smartt@qub.ac.uk
² Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102, Goleta, California 93117, USA
³ Department of Physics, University of California Santa Barbara, Santa Barbara, CA 93106, USA
⁴ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁵ School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
⁶ INAF–Osservatorio Astronomico di Padova, Vicolo del l’Osservatorio 5, 35122 Padova, Italy
⁷ Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot, Israel
⁸ INAF–Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34143 Trieste, Italy
⁹ Max-Planck-Institut fur Astrophysik, Karl-Schwarzschildstr. 1, 85748 Garching, Germany
¹⁰ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago
¹¹ Laboratoire de Physique Nucléaire et des Hautes Énergies, Université Pierre et Marie Curie Paris 6, Université Paris Diderot Paris 7, CNRS-IN2P3, 4 place Jussieu, 75252 Paris Cedex 05, France
¹² Physics Department, Yale University, New Haven, CT 06520, USA
¹³ INAF–Osservatorio astronomico di Capodimonte, V. Moiariello 16, 80131 Napoli, Italy
¹⁴ Dip. di Fisica and ICRA, Sapienza Universit ă di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
¹⁵ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22, Chile
¹⁶ Millennium Institute of Astrophysics, Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
¹⁷ Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, Colorado 80301, USA
¹⁸ Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF, UK
¹⁹ Departamento de Ciencias Fisicas, Universidad Andres Bello. Avda. Republica 252, Santiago, Chile
²⁰ Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia
²¹ Institut d’Astrophysique de Paris, CNRS, and Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
²² Institut de Ciencies de l’Espai (IEEC-CSIC), Facultat de Cincies, Campus UAB, 08193 Bellaterra, Spain
²³ Departamentode Astronomía – Universidad de Chile, Camino el Observatorio 1515, Santiago, Chile
²⁴ Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Vaisalantie 20, 21500 Piikkio, Finland
²⁵ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen, Denmark
²⁶ Department of Astronomy and the Oskar Klein Centre, Stockholm University, AlbaNova, 106 91 Stockholm, Sweden
²⁷ University of Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
²⁸ INAF Astronomical Observatory of Rome, via Frascati 33, 00040 Monte Porzio Catone (RM), Italy
²⁹ European Southern Observatory, KarlSchwarzschildStrasse 2, 85748 Garching, Germany
³⁰ Gemini Observatory, Southern Operations Center, Casilla 603, La Serena, Chile
³¹ Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
³² ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia
³³ Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Emil-Fischer-Str. 31, 97074 Würzburg, Germany
³⁴ Institut für Mathematik, Universität Würzburg, Emil-Fischer-Str. 30, 97074 Würzburg, Germany
³⁵ Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
³⁶ Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Väiäläntie 20, 21500 Piikkiö, Finland
³⁷ Millennium Institute of Astrophysics, Universidad de Chile, Casilla 36-D, Santiago, Chile
³⁸ Università degli Studi di Padova, Dipartimento di Fisica e Astronomia, Vicolo dellOsservatorio 2, 35122 Padova, Italy
³⁹ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
⁴⁰ Physikalisches Institut, Universität Bonn, Nußallee 12, 53115 Bonn, Germany
⁴¹ Department of Astronomy, University of California, Berkeley, CA 94720, USA
⁴² Departamento de Investigación Básica, CIEMAT, Av da. Complutense 40, 28040 Madrid, Spain
⁴³ Carnegie Observatories, Las Campanas Observatory, Colina El Pino, Casilla 601, Chile
⁴⁴ Department of Physics and Astronomy, Aarhus University, Ny Munkegade, 8000 Aarhus C, Denmark
⁴⁵ Department of Physics, University of Warwick, Coventry CV4 7AL, UK

Received: 29 October 2014
Accepted: 17 April 2015

Abstract

Context. The Public European Southern Observatory Spectroscopic Survey of Transient Objects (PESSTO) began as a public spectroscopic survey in April 2012. PESSTO classifies transients from publicly available sources and wide-field surveys, and selects science targets for detailed spectroscopic and photometric follow-up. PESSTO runs for nine months of the year, January – April and August – December inclusive, and typically has allocations of 10 nights per month.

Aims. We describe the data reduction strategy and data products that are publicly available through the ESO archive as the Spectroscopic Survey data release 1 (SSDR1).

Methods. PESSTO uses the New Technology Telescope with the instruments EFOSC2 and SOFI to provide optical and NIR spectroscopy and imaging. We target supernovae and optical transients brighter than 20.5^m for classification. Science targets are selected for follow-up based on the PESSTO science goal of extending knowledge of the extremes of the supernova population. We use standard EFOSC2 set-ups providing spectra with resolutions of 13–18 Å between 3345−9995 Å. A subset of the brighter science targets are selected for SOFI spectroscopy with the blue and red grisms (0.935−2.53 μm and resolutions 23−33 Å) and imaging with broadband JHK_s filters.

Results. This first data release (SSDR1) contains flux calibrated spectra from the first year (April 2012–2013). A total of 221 confirmed supernovae were classified, and we released calibrated optical spectra and classifications publicly within 24 h of the data being taken (via WISeREP). The data in SSDR1 replace those released spectra. They have more reliable and quantifiable flux calibrations, correction for telluric absorption, and are made available in standard ESO Phase 3 formats. We estimate the absolute accuracy of the flux calibrations for EFOSC2 across the whole survey in SSDR1 to be typically ~15%, although a number of spectra will have less reliable absolute flux calibration because of weather and slit losses. Acquisition images for each spectrum are available which, in principle, can allow the user to refine the absolute flux calibration. The standard NIR reduction process does not produce high accuracy absolute spectrophotometry but synthetic photometry with accompanying JHK_s imaging can improve this. Whenever possible, reduced SOFI images are provided to allow this.

Conclusions. Future data releases will focus on improving the automated flux calibration of the data products. The rapid turnaround between discovery and classification and access to reliable pipeline processed data products has allowed early science papers in the first few months of the survey.