Palomar Transient Factory
Encyclopedia
The Palomar Transient Factory (PTF) is an astronomical wide-field survey designed to search for optical transient and variable sources. It is fully automated, including a wide-field survey camera, 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 12Kx8K, 7.8 square degree CCD
array camera re-engineered for the 1.2-m Oschin Telescope
at Palomar Observatory
. The survey camera achieved first light on 13 Dec 2008; the project completed commissioning in summer 2009, and is planned to continue until at least 2012.
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 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.
e, cataclysmic variables, Luminous red nova
e, tidal disruption flares, active galactic nuclei, transiting Extrasolar planets, RR Lyrae
variable stars, microlensing events, and solar system
bodies. PTF will fill some of the 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.
On few-day timescales the images are also ingested into a database at IPAC
. Each incoming frame is calibrated and searched for objects, before the detections are merged into a database. This database is planned to be made public after an 18 month proprietary period.
The Palomar Observatory
60-inch photometric followup telescope automatically generates colors and light curves for interesting transients detected using the 1.2 m Oschin Telescope. The PTF collaboration also uses a further 15 telescopes for photometric and spectroscopic followup.
. Arguments are given that these four events along with SN2005ap reveal the death throes of the most massive stars—pulsational pair-instability outbursts.
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.
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
array camera re-engineered for the 1.2-m Oschin Telescope
Samuel Oschin telescope
The Samuel Oschin telescope is a 48-inch aperture Schmidt camera at the Palomar Observatory in northern San Diego County, California. It consists of a 49.75-inch Schmidt corrector plate and a 72-inch mirror. The instrument is strictly a camera; there is no provision for an eyepiece to look...
at Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
. The survey camera achieved first light on 13 Dec 2008; the project completed commissioning in summer 2009, and is planned to continue until at least 2012.
PTF is a collaboration of Caltech, LBNL, Infrared Processing and Analysis Center
Infrared Processing and Analysis Center
The Infrared Processing and Analysis Center is the NASA science center responsible for the data processing, analysis, and archiving of NASA's infrared astronomy and astrophysics missions...
, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
, LCOGT, Oxford
University of Oxford
The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...
, Columbia
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...
and the Weizmann Institute. The project is led by Shrinivas Kulkarni
Shrinivas Kulkarni
Shrinivas R. Kulkarni FRS is a professor of astrophysics and planetary science at California Institute of Technology. He is on the Space Interferometry Mission science team and is the director of optical observatories at California Institute of Technology, including Palomar and Keck.Kulkarni is...
at Caltech.
Image Subtraction
Image subtraction
Image subtraction or pixel subtraction is a process whereby the digital numeric value of one pixel or whole image is subtracted from another image. This is primarily done for one of two reasons – levelling uneven sections of an image such as half an image having a shadow on it, or detecting changes...
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 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.
Scientific Goals
PTF covers a wide range of science aspects, including among others, supernovae, novaNova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
e, cataclysmic variables, Luminous red nova
Luminous red nova
A luminous red nova is a stellar explosion thought to be caused by the merger of two stars. They are characterised by a distinct red colour, and a light curve that lingers with resurgent brightness in the infrared...
e, tidal disruption flares, active galactic nuclei, transiting Extrasolar planets, RR Lyrae
RR Lyrae
RR Lyrae is a variable star in the Lyra constellation. It is the prototype of the RR Lyrae variable class of stars. It has a period of about 13 hours, and oscillates between apparent magnitudes 7 and 8. Its variable nature was discovered by the Scottish astronomer Williamina Fleming at Harvard...
variable stars, microlensing events, and solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
bodies. PTF will fill some of the 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
Four major transient detection efforts are being undertaken during the five-year project.- a 5-day cadence supernova search
- an exotic transient search with cadences between 90 seconds and 1 day.
- a half-sky survey in the H-alpha band
- a search for transiting planets in the Orion star formation region.
Transient Detection with PTF
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
IPAC
IPAC may refer to:* Institute for the Preservation of Arts and Culture , is a social enterprise devoted to the aim of promoting and preserving the traditional genre of arts in Pakistan...
. Each incoming frame is calibrated and searched for objects, before the detections are merged into a database. This database is planned to be made public after an 18 month proprietary period.
The Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
60-inch photometric followup telescope automatically generates colors and light curves for interesting transients detected using the 1.2 m Oschin Telescope. The PTF collaboration also uses a further 15 telescopes for photometric and spectroscopic followup.
2010
R. Quimby et al., submitted to Nature, embargoed for discussion in the press: "Mysterious transients unmasked as the bright blue death throes of massive stars" — Three discoveries from the PTF are presented that resolve the mystery of SCP 06F6SCP 06F6
SCP 06F6 is an astronomical object of unknown type, discovered on 21 February 2006 in the constellation Boötesduring a survey of galaxy cluster CL 1432.5+3332.8 with the Hubble Space Telescope's Advanced Camera for Surveys Wide Field Channel....
. Arguments are given that these four events along with SN2005ap reveal the death throes of the most massive stars—pulsational pair-instability outbursts.
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