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

Rodriguez, Antonio C.; Kulkarni, S. R.; Prince, Thomas A.; Szkody, Paula; Burdge, Kevin B.; Caiazzo, Ilaria; Roestel, Jan van; Vanderbosch, Zachary P.; El-Badry, Kareem; Bellm, Eric C.; Gänsicke, B. T.; Graham, M. J.; Mahabal, A.; Masci, Frank J.; Mróz, P.; Riddle, Reed; Rusholme, B.

doi:10.3847/1538-4357/acbb6f

Cited by 12 publications

(2 citation statements)

References 69 publications

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“…I have shown elsewhere that this diagram can be used to discover two important classes of CVs: magnetic CVs and ultracompact AM CVns. In Rodriguez et al (2023b), we discovered two polars using a crossmatch of the SRG/ eROSITA eFEDS catalog with Gaia and ZTF. In (Rodriguez et al 2023a), we discovered an eclipsing AM CVn which showed little optical variability due to poor photometric coverage.…”

Section: Other Srg/erosita Systems: Magnetic Cvs and Am Cvnsmentioning

confidence: 99%

From Active Stars to Black Holes: A Discovery Tool for Galactic X-Ray Sources

Rodriguez

2024

PASP

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Galactic X-ray sources are diverse, ranging from active M dwarfs to compact object binaries, and everything in between. The X-ray landscape of today is rich, with point source catalogs such as those from XMM-Newton, Chandra, and Swift, each with ≳105 sources and growing. Furthermore, X-ray astronomy is on the verge of being transformed through data releases from the all-sky SRG/eROSITA survey. Many X-ray sources can be associated with an optical counterpart, which in the era of Gaia, can be determined to be Galactic or extragalactic through parallax and proper motion information. Here, I present a simple diagram—the “X-ray Main Sequence,” which distinguishes between compact objects and active stars based on their optical color and X-ray-to-optical flux ratio (F X/F opt). As a proof of concept, I present optical spectroscopy of six exotic accreting WDs discovered using the X-ray Main Sequence as applied to the XMM-Newton catalog. Looking ahead to surveys of the near future, I additionally present SDSS-V optical spectroscopy of new systems discovered using the X-ray Main Sequence as applied to the SRG/eROSITA eFEDS catalog.

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Section: Other Srg/erosita Systems: Magnetic Cvs and Am Cvnsmentioning

confidence: 99%

From Active Stars to Black Holes: A Discovery Tool for Galactic X-Ray Sources

Rodriguez

2024

PASP

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“…CVs and AM CVns among them were discovered in the past through the all-sky Roentgen Satellite (ROSAT) X-ray survey (Truemper 1982;Verbunt et al 1997;Voges et al 1999;Ramsay et al 2002). The ongoing Extended Roentgen Survey with an Imaging Telescope Array (eROSITA) telescope on board the Spektrum-Roentgen-Gamma (SRG; Predehl et al 2021;Sunyaev et al 2021) mission goes ∼15 times deeper than ROSAT, with improved localization of X-ray sources, and has already led to the discovery of new CVs (e.g., Bikmaev et al 2022;Schwope et al 2022;Rodriguez et al 2023). Some CVs were discovered using the Mikhail Pavlinsky ART-XC telescope (Pavlinsky et al 2021) on board the SRG observatory (e.g., Zaznobin et al 2022).…”

Section: Introductionmentioning

confidence: 99%

SRGeJ045359.9+622444: A 55 Minute Period Eclipsing AM Canum Venaticorum Star Discovered from a Joint SRG/eROSITA + ZTF Search

Rodriguez,

Galiullin,

Gilfanov

et al. 2023

ApJ

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AM Canum Venaticorum (AM CVn) systems are ultracompact binaries where a white dwarf accretes from a helium-rich degenerate or semidegenerate donor. Some AM CVn systems will be among the loudest sources of gravitational waves for the upcoming Laser Interferometer Space Antenna; yet the formation channel of AM CVns remains uncertain. We report the study and characterization of a new eclipsing AM CVn, SRGeJ045359.9+622444 (hereafter, SRGeJ0453), discovered from a joint Spektrum-Roentgen-Gamma (SRG) Extended Roentgen Survey with an Imaging Telescope Array (eROSITA) mission and Zwicky Transient Facility program to identify cataclysmic variables (CVs). We obtained optical photometry to confirm the eclipse of SRGeJ0453 and determine the orbital period to be P orb = 55.0802 ± 0.0003 min . We constrain the binary parameters by modeling the high-speed photometry and radial-velocity curves and find M donor = 0.044 ± 0.024M ⊙ and R donor = 0.078 ± 0.012R ⊙. The X-ray spectrum is approximated by a power-law model with an unusually flat photon index of Γ ∼ 1 previously seen in magnetic CVs with SRG/eROSITA, but verifying that the magnetic nature of SRGeJ0453 requires further investigation. Optical spectroscopy suggests that the donor star of SRGeJ0453 could have initially been a He star or a He white dwarf. SRGeJ0453 is the ninth eclipsing AM CVn system published to date, and its lack of optical outbursts have made it elusive in previous surveys. The discovery of SRGeJ0453 using joint X-ray and optical surveys highlights the potential for discovering similar systems in the near future.

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Compact white dwarf binaries in the combined SRG/eROSITA/SDSS eFEDS survey

Schwope,

Kurpas,

Baecke

et al. 2024

A&A

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X-ray surveys combined with optical follow-up observations are used to generate complete flux-limited samples of the main X-ray emitting source classes. on the Spectrum-Roentgen-Gamma (SRG) mission provides sufficient sensitivity to build significantly enhanced samples of rare X-ray emitting sources. We strive to identify and classify compact white dwarf binaries, cataclysmic variables (CVs), and related objects, which were detected in the sky area of eFEDS, the Final Equatorial Depths Survey, and they were observed in the plate program of SDSS-V. Compact white dwarf binaries were selected from spectra obtained in the early SDSS-V plate program. A dedicated set of SDSS plate observations were carried out in the eFEDS field, providing spectroscopic classifications for a significant fraction of the optically bright end ($r<22.5$) of the X-ray sample. The identification and subclassification rests on visual inspections of the SDSS spectra, spectral variability, color-magnitude and color-color diagrams involving optical and X-ray fluxes, optical variability, and literature work. Upon visual inspection of SDSS spectra and various auxiliary data products, we have identified 26 accreting compact white dwarf binaries (aCWDBs) in eFEDS, of which 24 are proven X-ray emitters. Among those 26 objects, there are 12 dwarf novae, three WZ Sge-like disk-accreting nonmagnetic CVs with low accretion rates, five likely nonmagnetic high accretion rate nova-like CVs, two magnetic CVs of the polar subcategory, and three double degenerates (AM CVn objects). Period bouncing candidates and magnetic systems are rarer than expected in this sample, but it is too small for a thorough statistical analysis. Fourteen of the systems are new discoveries, of which five are fainter than the magnitude limit. Thirteen aCWDBs have measured or estimated orbital periods, of which five were presented here. Through a Zeeman analysis, we revise the magnetic field estimate of the polar system J0926$+0105$, which is likely a low-field polar at $B=16$\,MG. We quantified the success of X-ray versus optical/UV selection of compact white dwarf binaries which will be relevant for the full SDSS-V survey. We also identified six white dwarf main sequence (WDMS) systems, among them there is one confirmed pre-CV at an orbital period of 17.6 hours and another pre-CV candidate. This work presents successful initial work in building large samples of all kinds of accreting and X-ray emitting compact white dwarf binaries that will be continued over the full hemisphere in the years to come.

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

Cited by 12 publications

References 69 publications

From Active Stars to Black Holes: A Discovery Tool for Galactic X-Ray Sources

From Active Stars to Black Holes: A Discovery Tool for Galactic X-Ray Sources

SRGeJ045359.9+622444: A 55 Minute Period Eclipsing AM Canum Venaticorum Star Discovered from a Joint SRG/eROSITA + ZTF Search

Compact white dwarf binaries in the combined SRG/eROSITA/SDSS eFEDS survey

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