The time-domain spectroscopic survey: Understanding the optically variable sky with sequels in SDSS-III

John J. Ruan, Scott F. Anderson, Paul J. Green, Eric Morganson, Michael Eracleous, Adam D. Myers, Carles Badenes, Matthew A. Bershady, William N. Brandt, Kenneth C. Chambers, James R.A. Davenport, Kyle S. Dawson, Heather Flewelling, Timothy M. Heckman, Jedidah C. Isler, Nick Kaiser, Jean Paul Kneib, Chelsea L. MacLeod, Isabelle Paris, Nicholas P. RossJessie C. Runnoe, Edward F. Schlafly, Sarah J. Schmidt, Donald P. Schneider, Axel D. Schwope, Yue Shen, Keivan G. Stassun, Paula Szkody, Christoper Z. Waters, Donald G. York

Research output: Contribution to journalArticlepeer-review


The Time-Domain Spectroscopic Survey (TDSS) is an SDSS-IV eBOSS subproject primarily aimed at obtaining identification spectra of ∼220,000 optically variable objects systematically selected from SDSS/Pan-STARRS1 multi-epoch imaging. We present a preview of the science enabled by TDSS, based on TDSS spectra taken over ∼320 deg2 of sky as part of the SEQUELS survey in SDSS-III, which is in part a pilot survey for eBOSS in SDSS-IV. Using the 15,746 TDSS-selected single-epoch spectra of photometrically variable objects in SEQUELS, we determine the demographics of our variability-selected sample and investigate the unique spectral characteristics inherent in samples selected by variability. We show that variability-based selection of quasars complements color-based selection by selecting additional redder quasars and mitigates redshift biases to produce a smooth quasar redshift distribution over a wide range of redshifts. The resulting quasar sample contains systematically higher fractions of blazars and broad absorption line quasars than from color-selected samples. Similarly, we show that M dwarfs in the TDSS-selected stellar sample have systematically higher chromospheric active fractions than the underlying M-dwarf population based on their Hα emission. TDSS also contains a large number of RR Lyrae and eclipsing binary stars with main-sequence colors, including a few composite-spectrum binaries. Finally, our visual inspection of TDSS spectra uncovers a significant number of peculiar spectra, and we highlight a few cases of these interesting objects. With a factor of ∼15 more spectra, the main TDSS survey in SDSS-IV will leverage the lessons learned from these early results for a variety of time-domain science applications.

Original languageEnglish (US)
Article number137
JournalAstrophysical Journal
Issue number2
StatePublished - Jul 10 2016
Externally publishedYes


  • quasars: general
  • stars: variables: general
  • surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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