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Improved Photometry for the DASCH Pipeline

Tang, Sumin and Grindlay, Jonathan and Los, Edward and Servillat, Mathieu (2013) Improved Photometry for the DASCH Pipeline. Publications of the Astronomical Society of the Pacific, 125 (929). pp. 857-865. ISSN 0004-6280. doi:10.1086/671760.

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The Digital Access to a Sky Century@Harvard (DASCH) project is digitizing the ∼500,000 glass plate images obtained (full sky) by the Harvard College Observatory from 1885 to 1992. Astrometry and photometry for each resolved object are derived with photometric rms values of ∼0.15 mag for the initial photometry analysis pipeline. Here we describe new developments for DASCH photometry, applied to the Kepler field, that have yielded further improvements, including better identification of image blends and plate defects by measuring image profiles and astrometric deviations. A local calibration procedure using nearby stars in a similar magnitude range as the program star (similar to what has been done for visual photometry from the plates) yields additional improvement for a net photometric rms of ∼0.1 mag. We also describe statistical measures of light curves that are now used in the DASCH pipeline processing to identify new variables autonomously. The DASCH photometry methods described here are used in the pipeline processing for the data releases of DASCH data, as well as for a forthcoming paper on the long-term variables discovered by DASCH in the Kepler field.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle Paper
Tang, Sumin0000-0002-6225-8918
Grindlay, Jonathan0000-0002-1323-5314
Servillat, Mathieu0000-0001-5443-4128
Additional Information:© 2013 The Astronomical Society of the Pacific. Received 2013 April 28; accepted 2013 June 03; published 2013 June 27. We thank the referee, George Djorgovski, for many helpful comments and suggestions that improved the paper. There are many colleagues who have helped out. In particular we thank our team members Alison Doane, Bob Simcoe, Jaime Pepper, David Sliski, and Silas Laycock for their work on DASCH. We would also like to thank many volunteers who have helped digitize logbooks, clean and scan plates (http://hea‑www.harvard .edu/DASCH/team.php). This work was supported in part by NSF grants AST0407380 and AST0909073 and now also the Cornel and Cynthia K. Sarosdy Fund for DASCH. This research has made use of the APASS database, located at the AAVSO Web site. Funding for APASS has been provided by the Robert Martin Ayers Sciences Fund.
Funding AgencyGrant Number
Cornel and Cynthia K. Sarosdy FundUNSPECIFIED
Robert Martin Ayers Sciences FundUNSPECIFIED
Subject Keywords:Data Analysis and Techniques
Issue or Number:929
Record Number:CaltechAUTHORS:20130830-105457910
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Official Citation:Improved Photometry for the DASCH Pipeline Sumin Tang, Jonathan Grindlay, Edward Los and Mathieu Servillat Publications of the Astronomical Society of the Pacific , Vol. 125, No. 929 (July 2013), pp. 857-865 Published by: The University of Chicago Press on behalf of the Astronomical Society of the Pacific Article DOI: 10.1086/671760 Article Stable URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41028
Deposited By: Tony Diaz
Deposited On:30 Aug 2013 18:10
Last Modified:10 Nov 2021 04:25

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