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

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(April -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.

The Early Detection and Follow-up of the Highly Obscured Type II Supernova 2016ija/DLT16am∗

“…Most NIR spectra were provided by PESSTO using the NTT with the SOFI spectrograph (all reduced as in Smartt et al 2015). Two NIR spectra were obtained using the Gemini NIR Spectrograph (GNIRS) at Gemini North (Elias et al 2006) in cross-dispersed mode, using the 32 l mm 1 -grating and the 0 675 slit.…”

“…JHK data were also provided by PESSTO 36 using the 3.58 m NTT with the Son Of ISAAC camera (SOFI; Moorwood et al 1998) and reduced using their dedicated pipeline (see Smartt et al 2015). Further NIR photometry was provided by the NOT Unbiased Transient Survey (NUTS 37 ) with the NOT nearinfrared Camera and spectrograph (NOTCam).…”

SUPPLEMENT: “LOCALIZATION AND BROADBAND FOLLOW-UP OF THE GRAVITATIONAL-WAVE TRANSIENT GW150914” (2016, ApJL, 826, L13)

“…A few tens of transient candidates identified by the widefield telescopes were followed up on the 10 m Keck II telescope (using the DEIMOS instrument; Faber et al 2003), the 2 m Liverpool Telescope (LT; Steele et al 2004), the Palomar 200 inch Hale telescope (P200; Bracher 1998), the 3.6 m ESO New Technology Telescope (within the Public ESO Spectroscopic Survey of Transient Objects, PESSTO; Smartt et al 2015), and the University of Hawaii 2.2 m telescope (SuperNovae Integral Field Spectrograph, SNIFS). The follow-up observations of the candidate counterparts are summarized in Table 3 of the main paper.…”

Correction: Corrigendum: The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole

“…Spectra were obtained with the instruments and set-ups listed in Supplementary Table 2. The data from FLOYDS, WIFES and EFOSC2 were reduced using dedicated instrument pipelines [52][53][54] . Spectra from the Very Large Telescope+ focal reducer and low dispersion spectrograph (FORS2) and Magellan Telescope+ IMACS in the standard fashion using IRAF.…”