ABSTRACT
Binary systems consisting of a white dwarf (WD) and a main-sequence companion with orbital periods up to ≈100 d are often thought to be formed through common envelope evolution which is ...still poorly understood. To provide new observational constraints on the physical processes involved in the formation of these objects, we are conducting a large-scale survey of close binaries consisting of a WD and an A- to K-type companion. Here, we present three systems with eccentric orbits and orbital periods between approximately 10 and 42 d discovered by our survey. Based on Hubble Space Telescope spectroscopy and high-angular resolution images obtained with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), we find that two of these systems are most likely triple systems while the remaining one could be either a binary or a hierarchical triple but none of them is a post-common envelope binary (PCEB). The discovery of these systems shows that our survey is capable to detect systems with orbital periods of the order of weeks, but all six PCEBs we have previously discovered have periods <2.5 d. We suggest that the fact that all of the systems we identify with periods of the order of weeks are not PCEBs indicates a transition between two different mechanisms responsible for the formation of very close (≲10 d) and somewhat wider WD + AFGK binaries: common envelope evolution and non-conservative stable mass transfer.
ABSTRACT
The white dwarf binary pathways survey is dedicated to studying the origin and evolution of binaries containing a white dwarf and an intermediate-mass secondary star of the spectral type A, ...F, G, or K (WD + AFGK). Here, we present CPD-65 264, a new post-common envelope binary with an orbital period of 1.37 d that contains a massive white dwarf ($0.86\pm 0.06\, \mathrm{M}_{\odot }$) and an intermediate-mass ($1.00\pm 0.05\, \mathrm{M}_{\odot }$) main-sequence secondary star. We characterized the secondary star and measured the orbital period using high-resolution optical spectroscopy. The white dwarf parameters are determined from HST spectroscopy. In addition, TESS observations revealed that up to 19 per cent of the surface of the secondary is covered with starspots. Small period changes found in the light curve indicate that the secondary is the second example of a G-type secondary star in a post-common envelope binary with latitudinal differential rotation. Given the relatively large mass of the white dwarf and the short orbital period, future mass transfer will be dynamically and thermally stable and the system will evolve into a cataclysmic variable. The formation of the system can be understood assuming common envelope evolution without contributions from energy sources besides orbital energy. CPD-65 264 is the seventh post-common envelope binaries with intermediate-mass secondaries that can be understood assuming a small efficiency in the common envelope energy equation, in agreement with findings for post-common envelope binaries with M-dwarf or substellar companions.
ABSTRACT
We present time-resolved optical and ultraviolet (UV) spectroscopy and photometry of V1460 Her, an eclipsing cataclysmic variable with a 4.99-h orbital period and an overluminous K5-type ...donor star. The optical spectra show emission lines from an accretion disc along with absorption lines from the donor. We use these to measure radial velocities, which, together with constraints upon the orbital inclination from photometry, imply masses of $M_1=0.869\pm 0.006\, \mathrm{M}_\odot$ and $M_2=0.295\pm 0.004\, \mathrm{M}_\odot$ for the white dwarf and the donor. The radius of the donor, $R_2=0.43\pm 0.002\, \mathrm{\it R}_\odot$, is ≈50 per cent larger than expected given its mass, while its spectral type is much earlier than the M3.5 type that would be expected from a main-sequence star with a similar mass. Hubble Space Telescope (HST) spectra show strong N v 1240-Å emission but no C iv 1550-Å emission, evidence for CNO-processed material. The donor is therefore a bloated, overluminous remnant of a thermal time-scale stage of high mass transfer and has yet to reestablish thermal equilibrium. Remarkably, the HST UV data also show a strong 30 per cent peak-to-peak, $38.9\,$s pulsation that we explain as being due to the spin of the white dwarf, potentially putting V1460 Her in a similar category to the propeller system AE Aqr in terms of its spin frequency and evolutionary path. AE Aqr also features a post-thermal time-scale mass donor, and V1460 Her may therefore be its weak magnetic field analogue since the accretion disc is still present, with the white dwarf spin-up a result of a recent high accretion rate.
ABSTRACT
This article reports quasi-continuous transiting events towards WD 1054–226 at d = 36.2 pc and V = 16.0 mag, based on simultaneous, high-cadence, multiwavelength imaging photometry using ...ULTRACAM over 18 nights from 2019 to 2020 March. The predominant period is 25.02 h and corresponds to a circular orbit with blackbody Teq = 323 K, where a planetary surface can nominally support liquid water. The light curves reveal remarkable night-to-night similarity, with changes on longer time-scales, and lack any transit-free segments of unocculted starlight. The most pronounced dimming components occur every 23.1 min – exactly the 65th harmonic of the fundamental period – with depths of up to several per cent, and no evident colour dependence. Myriad additional harmonics are present, as well as at least two transiting features with independent periods. High-resolution optical spectra are consistent with stable, photospheric absorption by multiple, refractory metal species, with no indication of circumstellar gas. Spitzer observations demonstrate a lack of detectable dust emission, suggesting that the otherwise hidden circumstellar disc orbiting WD 1054–226 may be typical of polluted white dwarfs, and detected only via favourable geometry. Future observations are required to constrain the orbital eccentricity, but even if periastron is near the Roche limit, sublimation cannot drive mass loss in refractory parent bodies, and collisional disintegration is necessary for dust production.
ABSTRACT
White dwarfs with emission lines from gaseous debris discs are among the rarest examples of planetary remnant hosts, but at the same time they are key objects for studying the final ...evolutionary stage of planetary systems. Making use of the large number of white dwarfs identified in Gaia Data Release 2 (DR2), we are conducting a survey of planetary remnants and here we present the first results of our search: six white dwarfs with gaseous debris discs. This first publication focuses on the main observational properties of these objects and highlights their most unique features. Three systems in particular stand out: WD J084602.47+570328.64 displays an exceptionally strong infrared excess that defies the standard model of a geometrically thin, optically thick dusty debris disc; WD J213350.72+242805.93 is the hottest gaseous debris disc host known with $\mbox{$T_{\mathrm{eff}}$}=29\,282$ K; and WD J052914.32–340108.11 in which we identify a record number of 51 emission lines from five elements. These discoveries shed light on the underlying diversity in gaseous debris disc systems and bring the total number of these objects to 21. With these numbers we can now start looking at the properties of these systems as a class of objects rather than on a case-by-case basis.
ABSTRACT
Virtually all binaries consisting of a white dwarf with a non-degenerate companion can be classified as either close post-interaction systems (with orbital periods of a few days or less), or ...wide systems (with periods longer than decades), in which both components have effectively evolved as single stars. Binaries with periods between these two extremes can help constrain common envelope efficiency, or highlight alternative pathways towards the creation of compact binaries. To date such binaries have remained mostly elusive. Here we present three white dwarfs in binaries with evolved subgiant stars with orbital periods of 41, 52, and 461 d. Using Hubble Space Telescope spectroscopy we find that all three systems contain low mass white dwarfs (≤0.4 M⊙). One system, TYC 8394−1331−1, is the inner binary of a hierarchical triple, where the white dwarf plus subgiant binary is orbited by a more distant companion star. These binaries were likely formed from a phase of stable but non-conservative mass transfer, as opposed to common envelope evolution. All three systems will undergo a common envelope phase in the future, but the two shorter period systems are expected to merge during this event, while the longest period system is likely to survive and create a close binary with two low mass white dwarfs.
ABSTRACT
White dwarfs with an F, G, or K type companion represent the last common ancestor for a plethora of exotic systems throughout the galaxy, though to this point very few of them have been ...fully characterized in terms of orbital period and component masses, despite the fact several thousand have been identified. Gaia data release 3 has examined many hundreds of thousands of systems, and as such we can use this, in conjunction with our previous UV excess catalogues, to perform spectral energy distribution fitting in order to obtain a sample of 206 binaries likely to contain a white dwarf, complete with orbital periods, and either a direct measurement of the component masses for astrometric systems, or a lower limit on the component masses for spectroscopic systems. Of this sample of 206, four have previously been observed with Hubble Space Telescope spectroscopically in the ultraviolet, which has confirmed the presence of a white dwarf, and we find excellent agreement between the dynamical and spectroscopic masses of the white dwarfs in these systems. We find that white dwarf plus F, G, or K binaries can have a wide range of orbital periods, from less than a day to many hundreds of days. A large number of our systems are likely post-stable mass transfer systems based on their mass/period relationships, while others are difficult to explain either via stable mass transfer or standard common envelope evolution.
Abstract
We present a spectroscopic survey of 248 white dwarf candidates within 40 pc of the Sun; of these 244 are in the Southern hemisphere. Observations were performed mostly with the Very Large ...Telescope (X-Shooter) and Southern Astrophysical Research Telescope. Almost all candidates were selected from Gaia Data Release 3 (DR3). We find a total of 246 confirmed white dwarfs, 209 of which had no previously published spectra, and two main-sequence star contaminants. Of these, 100 white dwarfs display hydrogen Balmer lines, 69 have featureless spectra, and two show only neutral helium lines. Additionally, 14 white dwarfs display traces of carbon, while 37 have traces of other elements that are heavier than helium. We observe 35 magnetic white dwarfs through the detection of Zeeman splitting of their hydrogen Balmer or metal spectral lines. High spectroscopic completeness (> 97 per cent) has now been reached, such that we have 1058 confirmed Gaia DR3 white dwarfs out of 1083 candidates within 40 pc of the Sun at all declinations.
The INT Galactic Plane Survey (IGAPS) is the merger of the optical photometric surveys, IPHAS and UVEX, based on data from the
Isaac Newton
Telescope (INT) obtained between 2003 and 2018. Here, we ...present the IGAPS point source catalogue. It contains 295.4 million rows providing photometry in the filters,
i
,
r
, narrow-band H
α
,
g
, and
U
RGO
. The IGAPS footprint fills the Galactic coordinate range, |
b
| < 5° and 30° <
ℓ
< 215°. A uniform calibration, referred to as the Pan-STARRS system, is applied to
g
,
r
, and
i
, while the H
α
calibration is linked to
r
and then is reconciled via field overlaps. The astrometry in all five bands has been recalculated in the reference frame of
Gaia
Data Release 2. Down to
i
∼ 20 mag (Vega system), most stars are also detected in
g
,
r
, and H
α
. As exposures in the
r
band were obtained in both the IPHAS and UVEX surveys, typically a few years apart, the catalogue includes two distinct
r
measures,
r
I
and
r
U
. The
r
10
σ
limiting magnitude is approximately 21, with median seeing of 1.1 arcsec. Between approximately 13th and 19th mag in all bands, the photometry is internally reproducible to within 0.02 mag. Stars brighter than
r
= 19.5 mag are tested for narrow-band H
α
excess signalling line emission, and for variation exceeding |
r
I
−
r
U
| = 0.2 mag. We find and flag 8292 candidate emission line stars and over 53 000 variables (both at > 5
σ
confidence).
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