Discovery of a high state AM CVn binary in the Galactic Bulge Survey

Wevers, T.; Torres, M. A. P.; Jonker, P. G.; Wetuski, J.; Nelemans, G.; Steeghs, D.; Maccarone, Thomas J.; Heinke, C. O.; Hynes, R. I.; Udalski, A.; Kostrzewa-Rutkowska, Z.; Groot, P.; Gazer, R.; Szymański, M. K.; Britt, C. T.; Wyrzykowski, Ł.; Poleski, R.

doi:10.1093/mnrasl/slw141

Cited by 21 publications

(9 citation statements)

References 29 publications

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“…A log of these observations is given in Table 1. A number of previous studies have made use of all or part of these observations, which primarily focused on the identification of discrete X-ray sources and the quantification of their statistical properties (Revnivtsev et al 2009;Hong et al 2009;Revnivtsev et al 2011;Hong 2012;Morihana et al 2013;Wevers et al 2016).…”

Section: Chandra Observationsmentioning

confidence: 99%

Periodic X-ray Sources in the Galactic Bulge: Application of the Gregory-Loredo Algorithm

Bao,

2020

Preprint

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We present a systematic study of periodic X-ray sources in the Limiting Window (LW), a ∼70 arcmin 2 field representative of the inner Galactic bulge and the target of ∼1 Ms Chandra observations. Using the Gregory-Loredo algorithm, which applies Bayes's theorem to the phase-folded light curve and is well-suited for irregularly sampled X-ray data, we detect 25 periodic signals in 23 discrete sources, among which 15 signals are new discoveries and two sources show dual periods. The vast majority of the 23 periodic sources are classified as magnetic cataclysmic variables (CVs), based on their period range, X-ray luminosities, spectral properties, and phase-folded light curves that are characteristic of spin modulation. Meanwhile, there is a paucity of non-magnetic CVs seen as periodic sources, which can be understood as due to a low detection efficiency for eclipsing sources. Under reasonable assumptions about the geometry of magnetic CVs and a large set of simulated X-ray light curves, we estimate the fraction of magnetic CVs in the inner Galactic bulge to be 23%, which is similar to that in the solar neighborhood. There is an apparent lack of long-period ( 3.3 hours) CVs in the LW, when contrasted with the range of known CVs in the solar neighborhood. We suggest that this might be an age effect, in the sense that CVs in the inner bulge are more evolved systems and have substantially shrunk their orbits.

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Section: Chandra Observationsmentioning

confidence: 99%

Periodic X-ray Sources in the Galactic Bulge: Application of the Gregory-Loredo Algorithm

Bao,

2020

Preprint

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“…At slightly longer periods (10  P  22 minutes), the accretion flow forms an accretion disk. The accretion rate is high and the systems are in a constant "high state" (e.g., Roelofs et al 2006b;Kupfer et al 2015;Wevers et al 2016;Green et al 2018b). Intermediate period systems (22  P  45 minutes) form an accretion disk and behave similarly to hydrogen-rich CVs; they show outbursts and superoutbursts (Kotko et al 2012), as well as flickering in their light curves (see Duffy et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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

Roestel

Creter

Kupfer

et al. 2021

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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.

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“…a constant high state where an optically thick accretion disc with helium absorption lines dominates the observed optical flux. HP Lib is a member of this class of high-state AM CVn systems, and other members include AM CVn itself, SDSS J1908, CXOGBS J1751, and SDSS J1351 (Fontaine et al 2011;Kupfer et al 2015;Wevers et al 2016;Green et al 2018a). At the longest orbital periods ≥ 40 − 50 min, AM CVn systems have low accretion rates and are in a permanent low state with an optically thin accretion disc exhibiting helium emission lines (e.g.…”

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confidence: 99%

Periodicities in the K2 light curve of HP Librae

Solanki

Kupfer

Blaes

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We analyse Kepler/K2 lightcurve data of the AM CVn system HP Librae. We detect with confidence four photometric periodicities in the system: the orbital frequency, both positive and negative superhumps, and the positive apsidal precession frequency of the accretion disc. This is only the second time that the apsidal precession frequency has ever been directly detected in the photometry of a helium accreting system, after SDSS J135154.46-064309.0. We present phase-folded lightcurves and sliding power spectra of each of the four periodicities. We measure rates of change of the positive superhump period of ∼10−7 days/day. We also redetect a QPO at ∼300 cyc/day, a feature that has been stable over decades, and show that it is harmonically related to two other QPOs, the lowest of which is centered on the superhump/orbital frequency. The continuum power spectrum is consistent with a single power law with no evidence of any breaks within our observed frequency range.

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Discovery of a high state AM CVn binary in the Galactic Bulge Survey

Cited by 21 publications

References 29 publications

Periodic X-ray Sources in the Galactic Bulge: Application of the Gregory-Loredo Algorithm

Periodic X-ray Sources in the Galactic Bulge: Application of the Gregory-Loredo Algorithm

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

Periodicities in the K2 light curve of HP Librae

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