Spectroscopic and photometric periods of six ultracompact accreting binaries

Green, Matthew; Marsh, T. R.; Carter, Philip J.; Steeghs, D.; Breedt, E.; Dhillon, V.; Littlefair, S.; Parsons, S. G.; Kerry, P.; Fusillo, N. P. Gentile; Ashley, R. P.; Bours, Madelon C. P.; Cunningham, Tim; Dyer, M.; Gänsicke, B. T.; Izquierdo, Paula; Pala, A. F.; Pattama, Chuangwit; Outmani, Sabrina; Sahman, D. I.; Sukaum, Boonchoo; Wild, J. F.

doi:10.1093/mnras/staa1509

Cited by 25 publications

(26 citation statements)

References 94 publications

(118 reference statements)

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“…Like precursors, this could mean that echo outbursts or rebrightening phases are common in SOs of AM CVns. We see echo outbursts for systems of orbital period from 25-32 min, but systems with longer orbital period (43, 46 min) also have shown echo outbursts discovered by other facilities (Rivera Sandoval & Maccarone 2019; Green et al 2020), meaning that there is no apparent correlation between the orbital period and the appearance of echo outbursts.…”

Section: Echo Outburstsmentioning

confidence: 58%

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TACOS: TESS AM CVn Outbursts Survey

Marcano

Sandoval

Maccarone

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Using TESS we are doing a systematic study of outbursting AM CVn systems to place some limits on the current outbursts models. We present the TESS light curve (LC) for 9 AM CVns showing both superoutbursts (SOs) and normal outbursts (NOs). The continuous coverage of the outbursts with TESS allows us to place stringent limits on the duration and structures of the SOs and the NOs. We present evidence that in at least some of the systems enhanced mass transfer (EMT) has to be taken into account to explain the observed LC of the SOs and rebrighthening phase after the SOs. For others, the colour evolution from simultaneous observations in g and r with ZTF differs from previously reported colour evolution of longer period AM CVns where EMT is responsible for the SO. We also find that due to the lack of sufficiently high cadence coverage the duration of many systems might have been overestimated in previous ground-based surveys. We report the SO duration for 6 AM CVns. We also found that precursors are a common feature of SOs in AM CVns and are seen in the LC of 5 of the 6 reported SOs. Finally the 10-minute and 2-minute cadence LCs from TESS also allowed us to find two new candidate orbital periods of AM CVns, both of which are in reasonably good agreement with the predictions for their periods based on their past outburst histories.

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Section: Echo Outburstsmentioning

confidence: 58%

“…Echo outbursts have been detected before in AM CVns (e.g. Green et al 2020). Here, we used the continuous observations of TESS to study in more detail the echo outbursts of these systems.…”

Section: Echo Outburstsmentioning

confidence: 99%

TACOS: TESS AM CVn Outbursts Survey

Marcano

Sandoval

Maccarone

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Based on a spectrum that shows strong He-II emission and possibly Hα, Breedt et al (2014) speculate that this system is a He CV (see also Green et al 2020). We also obtained a spectrum with ACAM and see a strong, double-peaked He-II line.…”

Section: Ztf18aakvnlwmentioning

confidence: 67%

“…We checked the literature on known AM CVn systems and identified 20 candidates as known AM CVn systems. To better understand where AM CVn systems are located in color space, we added all published AM CVn binaries to the list (Ramsay et al 2018;Green et al 2020;Isogai et al 2021;van Roestel 2021), including 57 systems that did not appear in our alert query (they are not included in the numbers given in Figure 1 and Table 1). For the remaining candidates, we used Simbad 11 to determine if a candidate was already identified as a hydrogen-rich CV.…”

Section: Identification Of Known Sourcesmentioning

confidence: 99%

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

Roestel

Creter

Kupfer

et al. 2021

Self Cite

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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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“…This is due to the finely tuned starting parameters and long timescales required to remove all visible hydrogen from these systems (Nelson et al 2018). However, there are known helium CVs which are potential progenitors of the channel (Thorstensen et al 2002;Breedt et al 2012;Carter et al 2013b;Green et al 2020).…”

Section: Formation Channelsmentioning

confidence: 99%

Discovery and characterization of five new eclipsing AM CVn systems

van Roestel,

Kupfer,

Green

et al. 2021

Preprint

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AM CVn systems are ultra-compact, hydrogen-depleted and helium-rich, accreting binaries with degenerate or semi-degenerate donors. We report the discovery of five new eclipsing AM CVn systems with orbital periods of 61.5, 55.5, 53.3, 37.4, and 35.4 minutes. These systems were discovered by searching for deep eclipses in the Zwicky Transient Facility (ZTF) lightcurves of white dwarfs selected using Gaia parallaxes. We obtained phase-resolved spectroscopy to confirm that all systems are AM CVn binaries, and we obtained high-speed photometry to confirm the eclipse and characterize the systems. The spectra of two longperiod systems (61.5 and 53.3 minutes) show many emission and absorption lines, indicating the presence of N, O, Na, Mg, Si, and Ca, and also the K and Zn, elements which have never been detected in AM CVn systems before. By modelling the high-speed photometry, we measured the mass and radius of the donor star, potentially constraining the evolutionary channel that formed these AM CVn systems. We determined that the average mass of the accreting white dwarf is ≈ 0.8 M , and that the white dwarfs in long-period systems are hotter than predicted by recently updated theoretical models. The donors have a high entropy and are a factor of ≈ 2 more massive compared to zero-entropy donors at the same orbital period. The large donor radius is most consistent with He-star progenitors, although the observed spectral features seem to contradict this. The discovery of 5 new eclipsing AM CVn systems is consistent with the known observed AM CVn space density and estimated ZTF recovery efficiency. Based on this estimate, we expect to find another 1-4 eclipsing AM CVn systems as ZTF continues to obtain data. This will further increase our understanding of the population, but will require high precision data to better characterize these 5 systems and any new discoveries.

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Spectroscopic and photometric periods of six ultracompact accreting binaries

Cited by 25 publications

References 94 publications

TACOS: TESS AM CVn Outbursts Survey

TACOS: TESS AM CVn Outbursts Survey

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

Discovery and characterization of five new eclipsing AM CVn systems

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