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Discovery of Two Polars from a Crossmatch of ZTF and the SRG/eFEDS X-ray Catalog

Rodriguez, Antonio C. and Kulkarni, Shrinivas R. and Prince, Thomas A. and Szkody, Paula and Burdge, Kevin B. and Caiazzo, Ilaria and van Roestel, Jan and Vanderbosch, Zachary P. and El-Badry, Kareem and Bellm, Eric C. and Gänsicke, Boris T. and Graham, Matthew J. and Mahabal, Ashish A. and Masci, Frank J. and Mróz, Przemek and Riddle, Reed and Rusholme, Ben (2022) Discovery of Two Polars from a Crossmatch of ZTF and the SRG/eFEDS X-ray Catalog. . (Unpublished)

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Magnetic CVs are luminous Galactic X-ray sources but have been difficult to find in purely optical surveys due to their lack of outburst behavior. The eROSITA telescope aboard the Spektr-RG (SRG) mission is conducting an all-sky X-ray survey and recently released the public eROSITA Final Equatorial Depth Survey (eFEDS) catalog. We crossmatched the eFEDS catalog with photometry from the Zwicky Transient Facility (ZTF) and discovered two new magnetic cataclysmic variables (CVs). We obtained high-cadence optical photometry and phase-resolved spectroscopy for each magnetic CV candidate and found them both to be polars. Among the newly discovered magnetic CVs is ZTFJ0850+0443, an eclipsing polar with orbital period P_(orb) = 1.72 hr, white dwarf mass M_(WD) = 0.81 ± 0.08 M_⊙ and accretion rate M˙∼10⁻¹¹ M_⊙/yr. We suggest that ZTFJ0850+0443 is a low magnetic field strength polar, with B_(WD) ≲ 10 MG. We also discovered a non-eclipsing polar, ZTFJ0926+0105, with orbital period P_(orb) = 1.48 hr, magnetic field strength B_(WD)≳ 26 MG, and accretion rate M˙ ∼10⁻¹² M_⊙/yr.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Rodriguez, Antonio C.0000-0003-4189-9668
Kulkarni, Shrinivas R.0000-0001-5390-8563
Prince, Thomas A.0000-0002-8850-3627
Szkody, Paula0000-0003-4373-7777
Burdge, Kevin B.0000-0002-7226-836X
Caiazzo, Ilaria0000-0002-4770-5388
van Roestel, Jan0000-0002-2626-2872
Vanderbosch, Zachary P.0000-0002-0853-3464
El-Badry, Kareem0000-0002-6871-1752
Bellm, Eric C.0000-0001-8018-5348
Gänsicke, Boris T.0000-0002-2761-3005
Graham, Matthew J.0000-0002-3168-0139
Mahabal, Ashish A.0000-0003-2242-0244
Masci, Frank J.0000-0002-8532-9395
Mróz, Przemek0000-0001-7016-1692
Riddle, Reed0000-0002-0387-370X
Rusholme, Ben0000-0001-7648-4142
Additional Information:Attribution 4.0 International (CC BY 4.0). ACR thanks the ZTF Variable Star Group for useful comments and discussions. ACR also thanks Axel Schwope, Paul Groot, Frank Verbunt, and Jim Fuller for insightful conversations that led to an improved final manuscript. This work is based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. Major funding has been provided by the U.S National Science Foundation under Grant No. AST-1440341 and by the ZTF partner institutions: the California Institute of Technology, the Oskar Klein Centre, the Weizmann Institute of Science, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron, the University of Wisconsin-Milwaukee, and the TANGO Program of the University System of Taiwan. The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). Some observations were made with the Apache Point 3.5m telescope, which is owned and operated be the Astrophysical Research Corporation. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular, the institutions participating in the Gaia Multilateral Agreement. This work is based on data from eROSITA, the soft X-ray instrument aboard SRG, a joint Russian-German science mission supported by the Russian Space Agency (Roskosmos), in the interests of the Russian Academy of Sciences represented by its Space Research Institute (IKI), and the Deutsches Zentrum für Luft- und Raumfahrt (DLR). The SRG spacecraft was built by Lavochkin Association (NPOL) and its subcontractors, and is operated by NPOL with support from the Max Planck Institute for Extraterrestrial Physics (MPE). The development and construction of the eROSITA X-ray instrument was led by MPE, with contributions from the Dr. Karl Remeis Observatory Bamberg & ECAP (FAU Erlangen-Nuernberg), the University of Hamburg Observatory, the Leibniz Institute for Astrophysics Potsdam (AIP), and the Institute for Astronomy and Astrophysics of the University of Tübingen, with the support of DLR and the Max Planck Society. The Argelander Institute for Astronomy of the University of Bonn and the Ludwig Maximilians Universität Munich also participated in the science preparation for eROSITA.
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
ZTF partner institutionsUNSPECIFIED
Heising-Simons Foundation12540303
Gaia Multilateral AgreementUNSPECIFIED
Russian Academy of SciencesUNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
Max Planck Institute for Extraterrestrial PhysicsUNSPECIFIED
Max Planck SocietyUNSPECIFIED
Record Number:CaltechAUTHORS:20230130-184121391
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118975
Deposited By: George Porter
Deposited On:30 Jan 2023 20:37
Last Modified:30 Jan 2023 20:37

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