A 15.7-Minute AM CVn Binary Discovered in K2

Green, Matthew; Hermes, J. J.; Marsh, T. R.; Steeghs, D.; Bell, Keaton J.; Littlefair, S. P.; Parsons, S. G.; Dennihy, E.; Fuchs, J.; Reding, Joshua S.; Kaiser, Bastian; Ashley, R. P.; Breedt, E.; Dhillon, V. S.; Fusillo, N. P. Gentile; Kerry, P.; Sahman, D. I.

doi:10.1093/mnras/sty1032

Cited by 21 publications

(29 citation statements)

References 60 publications

(75 reference statements)

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“…The physical cause of this feature is uncertain. Similar features have been seen in some short-period 1 To date, two AM CVn binaries have measurements of q by eclipse photometry, four by spectroscopy, and nine by the superhump method (Green et al 2018b, and references therein). 2 Several versions of the empirical superhump relationship are available.…”

Section: Introductionsupporting

confidence: 52%

Phase-resolved spectroscopy of Gaia14aae: line emission from near the white dwarf surface

Green

Marsh

Steeghs

et al. 2019

Monthly Notices of the Royal Astronomical Society

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AM CVn binaries are a class of ultracompact, hydrogen-deficient binaries, each consisting of a white dwarf accreting helium-dominated material from a degenerate or semi-degenerate donor star. Of the 56 known systems, only Gaia14aae undergoes complete eclipses of its central white dwarf, allowing the parameters of its stellar components to be tightly constrained. Here, we present phase-resolved optical spectroscopy of Gaia14aae. We use the spectra to test the assumption that the narrow emission feature known as the 'central spike' traces the motion of the central white dwarf. We measure a central spike velocity amplitude of 13.8 ± 3.2 km/s, which agrees at the 1 σ level with the predicted value of 17.6 ± 1.0 km/s based on eclipse-derived system parameters. The orbital phase offset of the central spike from its expected position is 4 ± 15 • , consistent with 0 • . Doppler maps of the He i lines in Gaia14aae show two accretion disc bright spots, as seen in many AM CVn systems. The formation mechanism for the second spot remains unclear. We detect no hydrogen in the system, but we estimate a 3 σ limit on Hα emission with an equivalent width of -1.14Å. Our detection of nitrogen and oxygen with no corresponding detection of carbon, in conjunction with evidence from recent studies, mildly favours a formation channel in which Gaia14aae is descended from a cataclysmic variable with a significantly evolved donor. Parameter Value Mass ratio, q 0.0287(20) Inclination, i ( • ) 86.3(3) Orbital separation, a (R ) 0.430(3) Accretor mass, M 1 (M ) 0.87(2) Donor mass, M 2 (M ) 0.0250(13) Accretor radius, R 1 (R ) 0.0092(3) Donor radius, R 2 (R ) 0.060(10) Disc radius, R disc (R ) 0.264(3) Bright spot separation, R spot (R ) 0.187 (2) Accretor orbital velocity, K WD (km/s) 17.6 ± 1.0

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Section: Introductionsupporting

confidence: 52%

Phase-resolved spectroscopy of Gaia14aae: line emission from near the white dwarf surface

Green

Marsh

Steeghs

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Some of these may be quasi-periodic variability originating in the disc (Fontaine et al 2011;Kupfer et al 2015). However, many CVs and some AM CVn binaries show a photometric signature coincident with the orbital period of the binary (Armstrong et al 2012;Green et al 2018b). Alongside this, many AM CVn binaries and short-period CVs show a photometric signature known as the 'superhump' period.…”

Section: Namementioning

confidence: 99%

“…This superhump period is generally a few per cent longer than the orbital period. The disc precession itself is sometimes seen photometrically (Green et al 2018b), but as the timescale is of order 12 hours such detections are often not possible from single-site, ground-based photometry.…”

Section: Namementioning

confidence: 99%

“…The evolution of AM CVn binaries is uncertain, with three proposed channels (see Solheim 2010 for an overview, and Green et al 2018b andRamsay et al 2018 for recent results). In two of these channels, the binary goes through two phases of common envelope evolution (Ivanova et al 2013), leaving either a double white dwarf binary (Paczyński 1967;Deloye et al 2007) or a binary consisting of a white dwarf and a helium-burning star whose atmosphere has been stripped during the common envelope evolution (Savonije et al 1986;Iben & Tutukov 1987;Yungelson 2008).…”

mentioning

confidence: 99%

“…Note that this number does not include those systems for which an indirect estimate of the orbital period has been made, based either on its superhump period (see the discussion in the following section) or on its outburst properties (Levitan et al 2015). Only 17 AM CVn binaries (Green et al 2018b) and six sub-period minimum He CVs (Table 1) have published mass ratio measurements.…”

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confidence: 99%

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Spectroscopic and photometric periods of six ultracompact accreting binaries

Green

Marsh

Carter

et al. 2020

Monthly Notices of the Royal Astronomical Society

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ABSTRACT Ultracompact accreting binary systems each consist of a stellar remnant accreting helium-enriched material from a compact donor star. Such binaries include two related sub-classes, AM CVn-type binaries and helium cataclysmic variables, in both of which the central star is a white dwarf. We present a spectroscopic and photometric study of six accreting binaries with orbital periods in the range of 40–70 min, including phase-resolved VLT spectroscopy and high-speed ULTRACAM photometry. Four of these are AM CVn systems and two are helium cataclysmic variables. For four of these binaries we are able to identify orbital periods (of which three are spectroscopic). SDSS J1505+0659 has an orbital period of 67.8 min, significantly longer than previously believed, and longer than any other known AM CVn binary. We identify a Wide-field Infrared Survey Explorer (WISE) infrared excess in SDSS J1505+0659 that we believe to be the first direct detection of an AM CVn donor star in a non-direct impacting binary. The mass ratio of SDSS J1505+0659 is consistent with a white dwarf donor. CRTS J1028–0819 has an orbital period of 52.1 min, the shortest period of any helium cataclysmic variable. MOA 2010-BLG-087 is co-aligned with a K-class star that dominates its spectrum. ASASSN-14ei and ASASSN-14mv both show a remarkable number of echo outbursts following superoutbursts (13 and 10 echo outbursts respectively). ASASSN-14ei shows an increased outburst rate over the years following its superoutburst, perhaps resulting from an increased accretion rate.

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Astrophysics with the Laser Interferometer Space Antenna

et al. 2023

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The Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy, and, as such, it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and space-born instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA’s first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed; ultra-compact stellar-mass binaries, massive black hole binaries, and extreme or interme-diate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help making progress in the different areas. New research avenues that LISA itself, or its joint exploitation with upcoming studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe.

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A 15.7-Minute AM CVn Binary Discovered in K2

Cited by 21 publications

References 60 publications

Phase-resolved spectroscopy of Gaia14aae: line emission from near the white dwarf surface

Phase-resolved spectroscopy of Gaia14aae: line emission from near the white dwarf surface

Spectroscopic and photometric periods of six ultracompact accreting binaries

Astrophysics with the Laser Interferometer Space Antenna

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