A Systematic Search for Outbursting AM CVn Systems with the Zwicky Transient Facility

Creators: van Roestel, Jan; Creter, Leah; Kupfer, Thomas; Szkody, Paula; Fuller, Jim; Green, Matthew J.; Rich, R. Michael; Sepikas, John; Burdge, Kevin; Caiazzo, Ilaria; Mróz, Przemek; Prince, Thomas A.; Duev, Dmitry A.; Graham, Matthew J.; Shupe, David L.; Laher, Russ R.; Mahabal, Ashish A.; Masci, Frank J.

Abstract

AM CVn systems are a rare type of accreting binary that consists of a white dwarf and a helium-rich, degenerate donor star. Using the Zwicky Transient Facility (ZTF), we searched for new AM CVn systems by focusing on blue, outbursting stars. We first selected outbursting stars using the ZTF alerts. We cross matched the candidates with Gaia and Pan-STARRS catalogs. The initial selection of candidates based on the Gaia BP-RP contains 1751 unknown objects. We used the Pan-STARRS g-r and r-i color in combination with the Gaia color to identify 59 strong AM CVn candidates. We obtained identification spectra of 35 sources, of which 18 are high-priority candidates, and discovered nine new AM CVn systems and one magnetic CV that shows only He-ii lines. Using the outburst recurrence time, we estimate the orbital periods of the nine new AM CVn systems that are in the range of 29–50 minutes. We conclude that targeted follow up of blue, outbursting sources is an efficient method to find new AM CVn systems and we plan to follow up all candidates we identified to systematically study the population of outbursting AM CVn systems.

Additional Information

© 2021. The American Astronomical Society. Received 2021 May 8; revised 2021 May 24; accepted 2021 May 26; published 2021 August 19. This paper is dedicated in part to the memory of Dr. Bill Whitney who was above all a great teacher and educator. For over 68 yr from Caltech to MIT to JPL and back to Caltech, Bill has guided and nurtured both students and faculty from across the country and world, with a love of physics, science, and education. Bill was one of the founders of the Caltech Summer Undergraduate Research Fellowship (SURF) in 1979 under the principle that undergraduates can productively contribute to research, which was considered very novel at the time. Since then, the SURF undergraduate model has been replicated by many leading universities benefiting many thousands of students and faculty alike. Bill's deep recognition for the efficacy of multigenerational science education is reflected in this paper as contributing author and SURF student Leah Creter is the student of also contributing author Dr. John Sepikas who in turn was the student of Dr. Bill Whitney. Nothing would have made Dr. Whitney more proud. J.v.R. is partially supported by NASA-LISA grant 80NSSC19K0325. Based on observations obtained with the Samuel Oschin Telescope 48 inch at the Palomar Observatory as part of the Zwicky Transient Facility project. Z.T.F. is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France; Astroquery (Ginsburg et al. 2019); and Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013, 2018). Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. Based on observations made with the William Herchel Telescope (WHT) operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofsica de Canarias. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular, the institutions participating in the Gaia Multilateral Agreement. The Pan-STARRS1 Surveys (PS1) have been made possible through contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg, and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen's University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under grant No. AST-1238877, the University of Maryland, and Eotvos Lorand University (ELTE). Facilities: P48(ZTF) - , WHT:4.2 m (ACAM) - , Keck II:10 m (LRIS&DEIMOS) - , P200:5.0 m (CHIMERA) - , Shane:3.0 m (Kast) - . Software: penquins, astropy & astroquery (Astropy Collaboration et al. 2013, 2018), Lpipe (Perley 2019), PypeIt (Prochaska et al. 2020).

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