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

Smartt, S. J. and Valenti, S. and Fraser, M. and Inserra, C. and Young, D. R. and Sullivan, M. and Pastorello, A. and Benetti, S. and Gal-Yam, A. and Knapic, C. and Molinaro, M. and Smareglia, R. and Smith, K. W. and Taubenberger, S. and Yaron, O. and Anderson, J. P. and Ashall, C. and Balland, C. and Baltay, C. and Barbarino, C. and Bauer, F. E. and Baumont, S. and Bersier, D. and Blagorodnova, N. and Bongard, S. and Botticella, M. T. and Bufano, F. and Bulla, M. and Cappellaro, E. and Campbell, H. and Cellier-Holzem, F. and Chen, T. -W. and Childress, M. J. and Clocchiatti, A. and Contreras, C. and Dall'Ora, M. and Danziger, J. and de Jaeger, T. and De Cia, A. and Della Valle, M. and Dennefeld, M. and Elias-Rosa, N. and Elman, N. and Feindt, U. and Fleury, M. and Gall, E. and Gonzalez-Gaitan, S. and Galbany, L. and Morales Garoffolo, A. and Greggio, L. and Guillou, L. L. and Hachinger, S. and Hadjiyska, E. and Hage, P. E. and Hillebrandt, W. and Hodgkin, S. and Hsiao, E. Y. and James, P. A. and Jerkstrand, A. and Kangas, T. and Kankare, E. and Kotak, R. and Kromer, M. and Kuncarayakti, H. and Leloudas, G. and Lundqvist, P. and Lyman, J. D. and Hook, I. M. and Maguire, K. and Manulis, I. and Margheim, S. J. and Mattila, S. and Maund, J. R. and Mazzali, P. A. and McCrum, M. and McKinnon, R. and Moreno-Raya, M. E. and Nicholl, M. and Nugent, P. and Pain, R. and Pignata, G. and Phillips, M. M. and Polshaw, J. and Pumo, M. L. and Rabinowitz, D. and Reilly, E. and Romero-Canizales, C. and Scalzo, R. and Schmidt, B. and Schulze, S. and Sim, S. and Sollerman, J. and Taddia, F. and Tartaglia, L. and Terreran, G. and Tomasella, L. and Turatto, M. and Walton, N. A. and Walker, E. and Wyrzykowski, L. and Yuan, F. and Zampieri, L. (2015) PESSTO:survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects. Astronomy and Astrophysics, 579. ISSN 0004-6361

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 angstrom between 3345-9995 angstrom. A subset of the brighter science targets are selected for SOFI spectroscopy with the blue and red grisms (0.935-2.53 mu m and resolutions 23-33 angstrom) 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 similar to 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.