Palomar Transient Factory

The Palomar Transient Factory (PTF),^[1] observatory code I41, is an astronomical survey using a wide-field survey camera designed to search for optical transient and variable sources. The fully automated system includes an automated realtime data reduction pipeline, a dedicated photometric follow up telescope, and a full archive of all detected sources. The survey is performed with a 12K×8K, 7.8 square degree CCD array camera^[2] re-engineered for the 1.2-m Samuel Oschin Telescope at Palomar Observatory. The survey camera achieved first light on 13 December 2008. The project completed commissioning in summer 2009, and was planned to continue until at least 2012. PTF has since been succeeded by the Intermediate Palomar Transient Factory (iPTF).^[3]

PTF is a collaboration of Caltech, LBNL, Infrared Processing and Analysis Center, Berkeley, LCOGT, Oxford, Columbia and the Weizmann Institute. The project is led by Shrinivas Kulkarni at Caltech.

Image Subtraction for near-realtime transient detection is performed at LBNL; efforts to continue to observe interesting targets are coordinated at Caltech, and the data is processed and archived for later retrieval at the Infrared Processing and Analysis Center (IPAC). Photometric and spectroscopic followup of detected objects is undertaken by the automated Palomar 1.5-m telescope and other facilities provided by consortium members.

Time-variability studies are undertaken using the photometric/astrometric pipeline implemented at the Infrared Processing and Analysis Center (IPAC). Studies include compact binaries (AM CVn stars), RR Lyrae, cataclysmic variables, and active galactic nuclei (AGN).

Scientific goals

PTF covers a wide range of science aspects,^[4] including supernovae, novae, cataclysmic variables, Luminous red novae, tidal disruption flares, compact binaries (AM CVn star), active galactic nuclei, transiting Extrasolar planets, RR Lyrae variable stars, microlensing events, and bodies of the Solar System. PTF will fill gaps in our present-day knowledge of the optical transient phase space, extend our understanding of known source classes, and provide first detections or constraints on predicted, but not yet discovered, event populations.

Projects

The efforts being undertaken during the five-year project include:

1. a 5-day cadence supernova search
2. an exotic transient search with cadences between 90 seconds and 1 day.
3. a half-sky survey in the H-alpha band
4. a search for transiting planets in the Orion star formation region.
5. coordinated observations with the GALEX spacecraft, including a survey of the Kepler region
6. coordinated observations with the EVLA, including a survey of SDSS Stripe 82

Transient detection

Data taken with the camera are transferred to two automated reduction pipelines. A near-realtime image subtraction pipeline is run at LBNL and has the goal of identifying optical transients within minutes of images being taken. The output of this pipeline is sent to UC Berkeley where a source classifier determines a set of probabilistic statements about the scientific classification of the transients based on all available time-series and context data.

On few-day timescales the images are also ingested into a database at IPAC. Each incoming frame is calibrated and searched for objects (constant and variable), before the detections are merged into a database. Light curves of approximately 500 million objects have been accumulated. This database is planned to be made public after an 18-month proprietary period, subject to available resources.

The Palomar Observatory 60-inch photometric follow-up telescope automatically generates colors and light curves for interesting transients detected using the 1.2-meter Oschin Telescope. The PTF collaboration also uses a further 15 telescopes for photometric and spectroscopic followup.

Bibliography

2009

N. Law et al., PASP, 121, 1395:"The Palomar Transient Factory: System Overview, Performance, and First Results" — This paper summarizes the PTF project, including several months of on-sky performance tests of the new survey camera, the observing plans, and the data reduction strategy. It also includes detailes for the first 51 PTF optical transient detections, found in commissioning data.

A. Rau et al., PASP, 121, 1334: "Exploring the Optical Transient Sky with the Palomar Transient Factory" — In this article, the scientific motivation for PTF is presented and a description of the goals and expectations is provided.

2008

G. Rahmer et al., SPIE, 7014, 163: "The 12K×8K CCD mosaic camera for the Palomar Transient Factory" — This paper discusses the modifications to the CFHT 12K CCD camera, improved readout, new filter exchange mechanism, and the field flattener needed to correct for focal plane curvature.

See also

• Zooniverse — Galaxy Zoo Supernovae

References

1. Law, Nicholas M.; Kulkarni, Shrinivas R.; Dekany, Richard G.; Ofek, Eran O.; et al. (2009), "The Palomar Transient Factory: System Overview, Performance, and First Results", Publications of the Astronomical Society of the Pacific, 121 (886): 1395–1408, arXiv:0906.5350, Bibcode:2009PASP..121.1395L, doi:10.1086/648598, ISSN 0004-6280
2. Rahmer, Gustavo; Smith, Roger; Velur, Viswa; Hale, David; et al. (2008-08-15), "Ground-Based and Airborne Instrumentation for Astronomy II: 23-28 June 2008, Marseille, France", Proceedings of SPIE, 7014, Bibcode:2008SPIE.7014E.163R, doi:10.1117/12.788086, ISBN 9780819472243, ISSN 0277-786X |contribution= ignored (help)
3. "Supernova Collides With Its Companion Star". Science Daily. 20 May 2015.
4. Rau, Arne; Kulkarni1, Shrinivas R.; Law, Nicholas M.; Bloom, Joshua S.; et al. (2009), "Exploring the Optical Transient Sky with the Palomar Transient Factory", Publications of the Astronomical Society of the Pacific, 121 (886): 1334–1351, arXiv:0906.5355, Bibcode:2009PASP..121.1334R, doi:10.1086/605911, ISSN 0004-6280

External links

• Intermediate Palomar Transient Factory