Catalina Real-Time Transient Survey

Catalina Real-Time Transient Survey
Name	Catalina Real-Time Transient Survey
Acronym	CRTS
Start date	2007
Telescopes	Mount Lemmon Survey, Catalina Sky Survey, Siding Spring Observatory
Operators	University of Arizona, Catalina Sky Survey
Wavelength	Optical
Area	All-sky (primarily northern hemisphere)
Discoveries	Supernovae; cataclysmic variables; blazars; flaring stars; tidal disruption events

Catalina Real-Time Transient Survey is a time-domain optical survey that conducted automated real-time searches for transient and variable sources using telescopes associated with the Catalina Sky Survey. It provided rapid alerts and follow-up targets to the astronomical community, contributing to transient astronomy alongside projects such as Pan-STARRS, Zwicky Transient Facility, All-Sky Automated Survey for SuperNovae, and Gaia. The survey operated in an era of growing synoptic facilities including Sloan Digital Sky Survey, Palomar Transient Factory, and Large Synoptic Survey Telescope planning, enabling multi-wavelength coordination with observatories such as Chandra X-ray Observatory, Fermi Gamma-ray Space Telescope, and Very Large Array.

Overview

CRTS used wide-field imaging to discover optical transients and variables across large sky areas, emphasizing rapid public dissemination of candidates for follow-up by groups like Las Cumbres Observatory, Keck Observatory, Very Large Telescope, and amateur networks affiliated with American Association of Variable Star Observers. The survey played a role in identifying transient phenomena also studied by facilities including Hubble Space Telescope, XMM-Newton, Swift Observatory, and radio facilities such as Atacama Large Millimeter Array. Leadership and contributors included individuals and institutions linked to University of Arizona, Harvard-Smithsonian Center for Astrophysics, and other institutes active in time-domain research.

Survey Operations and Instrumentation

CRTS exploited imaging from multiple instruments: the 0.68-m Schmidt on Catalina Station (part of the Catalina Sky Survey), the 1.5-m telescope on Mount Lemmon, and ancillary data from the Siding Spring Survey telescope during southern campaigns. The instrumentation strategy echoed design elements from programs at Palomar Observatory and Kitt Peak National Observatory and interfaced with catalogs like Two Micron All Sky Survey and Sloan Digital Sky Survey for cross-identification. Operations combined nightly cadence scheduling, image differencing pipelines, and automated vetting routines developed by teams associated with NASA-funded research groups and university observatories.

Detection and Data Processing

Detection relied on image subtraction and real-time alert generation, using reference images and catalogs such as USNO-B1.0, Guide Star Catalog, and SIMBAD to filter known sources. Automated classification incorporated cross-matches with catalogs from missions like ROSAT, GALEX, and WISE to distinguish supernovae, cataclysmic variables, active galactic nuclei, and flaring stars. Data processing pipelines shared methodology with projects led by groups at Lawrence Berkeley National Laboratory and institutions linked to the development of the Virtual Observatory framework, enabling query access for collaborators at California Institute of Technology, Massachusetts Institute of Technology, and Max Planck Society research groups.

Notable Discoveries and Scientific Impact

CRTS announced thousands of optical transients spanning supernovae identified for follow-up at Keck Observatory and Gemini Observatory, rare tidal disruption event candidates later observed with XMM-Newton and Hubble Space Telescope, and numerous cataclysmic variables monitored by American Association of Variable Star Observers contributors. Discoveries included rapidly evolving transients studied in context with theory groups at University of Cambridge and Stanford University, and blazar flares coordinated with the Fermi Gamma-ray Space Telescope team and radio arrays such as Very Long Baseline Array. CRTS results were cited in multi-wavelength campaigns involving the Pierre Auger Observatory community for high-energy counterpart searches and informed survey strategies at next-generation projects like Vera C. Rubin Observatory. The survey also enriched catalogs used by stellar variability researchers at Oxford University and cosmology groups comparing Type Ia supernova samples across surveys including Supernova Legacy Survey and Dark Energy Survey.

Collaborations and Data Access

CRTS maintained a policy of rapid public alerts that fostered collaboration with professional observatories and amateur astronomers affiliated with International Astronomical Union networks and organizations such as American Astronomical Society. Data products and candidate lists were ingested by brokers and services similar to those run by Zooniverse citizen science projects and archival centers such as NASA/IPAC Infrared Science Archive and institutional repositories at University of Arizona. International partners included research groups from institutions like Australian National University and University of Cambridge, enabling southern-sky coverage via coordination with Siding Spring Observatory.

Limitations and Challenges

CRTS faced limitations common to synoptic surveys: modest aperture telescopes constrained depth compared with facilities like Subaru Telescope and Hubble Space Telescope, leading to sensitivity trade-offs between sky coverage and limiting magnitude. The cadence and bandpass choices limited characterization of rapidly evolving transients relative to multi-filter campaigns by Pan-STARRS and spectroscopy resources at Keck Observatory or Gemini Observatory, while contamination from variable stars cataloged in Two Micron All Sky Survey and moving objects cataloged by Minor Planet Center required substantial vetting. Operational challenges included automated classification ambiguities addressed through community follow-up, telescope scheduling conflicts with Catalina Sky Survey minor-planet searches, and the evolving landscape of data brokers exemplified by services from LSST preparatory teams.

Category:Astronomical surveys