Project links

  • ZTF
  • CRTS
  • Archival data
  • Research Interests

      Overview

      The Universe is an ever-changing place. My research involves understanding and characterizing the past, current, and future of astronomical sources by observing 100's of millions of sources using synoptic astronomical surveys.

      For more than two decades I have undertaken work on a wide variety of such "time-domain" projects with the aim of understanding the dynamic nature of astrophysical objects. My investigations have ranged from working on explosive transients, such as supernovae, to sources exhibiting repeated variablity, such as RR Lyrae.


      Transient Event Astronomy

      Transient event astronomy involves study of the occurance and nature of unpredictable astronomical events. Large optical surveys for transients began in the 1990's with microlensing surveys such as Macho and OGLE. Larger and more general surveys began in the 2000's with Palomar Quest, CRTS, PTF and Pan-STARRs. Current very large scale transient and variabilty surveys include ZTF and LSST. In the past I worked on the Macho project, Palomar Quest, and CRTS. I currently work on ZTF.

      The Zwicky Transient Facility (ZTF) is a time-domain survey that began at Palomar Observatory in 2017. ZTF uses a camera with a 47 square degree field of view mounted on the Oschin 48-inch Schmidt telescope. ZTF scans more than 3750 square degrees an hour to a depth of 20.5 mag to discover young supernovae, rare and exotic transients, and variable stars.

      I was co-PI of the CRTS and CRTS-II surveys which ran from Nov. 2007 to Feb. 2019. These two projects discovered of more than 15,000 transient astronomical sources, including ~4000 Supernovae. CRTS was the first large scale optical transient survey to both discover and publish transient detections within minutes of observation, as well as make all discoveries public for the benefit of the astronomical community.


      Variable Stars and Exoplanets

      For the past twenty years I have worked on variable stars. Recently, using CRTS data I have produced catalogs containing over 100,000 periodic variable star within an area 30,000 sq. deg. of the northern and southern sky.

      Halo RR Lyrae

      RR Lyrae are standard candles that can be used as probes to the Galactic evolution and structure. Some of my recent work has involved using these sources to trace the shape and extent of the outer halo of our Galaxy.

      Short Period Binaries

      Main sequence stars in binaries exhibit an orbitial period minimum of around 0.22 days. The exact cause for this minimum period remains unknown, but is likely related to the separation between where convection and conduction dominate in stars. I recently used data for tens of thousands of binaries discovered in CRTS to investigate the nature of the few stars with period below the minimum.

      White Dwarf Exoplanets

      Over the last 20 years the search for planets like our own has grown to become a major research area in astronomy with hundreds of planets now known. However, ground-based surveys are generally not sensitive to Earth-size planets. In 2008 I theorized that it would be possible to discover Earth-size or smaller planets by observing white dwarf stars. Although no candidates were found, the first clear detections of planets in such systems have recently been detected.