arXiv subjects

K. Inight

Publications and source records attributed to K. Inight.

8 recordsLinked to original sources

arXiv2026

The DESI Data Release 1 white dwarf catalogue

The Dark Energy Spectroscopic Instrument is conducting a redshift survey, mapping the universe in three dimensions to measure the history of cosmic expansion. As well as extragalactic objects, it is targeting millions of Milky Way stars, including white dwarfs. Using Data Release 1 we assemble the largest catalogue of spectroscopically-confirmed white dwarfs to date, whose straightforward selection function enables statistically-robust population studies. We visually inspect and fit models to spectra of 63968 objects, finding 44409 white dwarfs. We present their spectral classifications, atmospheric parameters and radial velocities. We assess survey completeness and uniformity, identify potential spectral contamination caused by flux from nearby sources entering the fibre, and assign confidence scores to our classifications to facilitate selection of statistical and observational samples. We present spectra representing most white dwarf classes, common and exotic. We conclude with recommendations and warnings regarding the use of the catalogue.

astro-ph.SR↗

arXiv2026

SRG/eROSITA X-ray selected cataclysmic variable candidates observed in SDSS-V DR20

We report on the spectroscopic observations obtained during SDSS-V DR20 of accreting compact binaries (ACB), specifically the cataclysmic variables (CVs), that were identified as likely compact binary candidates from the SRG (Spectrum Roentgen Gamma) eROSITA eRASS1 and eRASS:3 observations. Our primary aim is to obtain a complete inventory of all CVs that were detected in eRASS1 and eRASS:3, with the goal to help better understand close-binary evolution, the population density, and demographics of these systems in the Galaxy. Previous population studies had their respective limitations, with volume-limited samples suffering from low-number statistics, while magnitude-limited observations were biased to only the brighter systems. All CVs are X-ray emitters, eROSITA, therefore, presents a unique opportunity to identify CVs based on their X-ray emission. Given eROSITA's sensitivity, we expect to find most X-ray active CVs within 500 pc, and magnetic CVs to several kpc. Using X-ray data from the eROSITA together with optical data from Gaia, three different approaches were explored to identify the Gaia optical counterpart to the eROSITA X-ray source of the likely ACB. From this, unique candidates were identified and were submitted in three different cartons to SDSS-V for optical spectroscopic observations as part of the Milky Way Mapper survey. From our submitted candidates, we found 538 likely CVs. We also identified CVs that were observed in other eROSITA based cartons, in which we identified an additional 49 systems that are likely CVs and which were not in our selection. We therefore identified 587 systems as CVs from the eROSITA based SDSS-V observations. We also attempted to sub classify the CVs as dwarf-novae, novalikes, or magnetic systems based on the eROSITA X-ray data, the emission line properties in the optical SDSS-V spectra, and other data in the public domain, if available.

astro-ph.SR↗

arXiv2026

1000 cataclysmic variables identified from DESI spectroscopy

Most cataclysmic variables (CVs) are discovered when they have an outburst generating an inherent selection bias against CVs that rarely, or never, outburst. CVs discovered by virtue of their spectroscopic characteristics are particularly valuable to offset this bias and we have used an established machine-learning technique to assist in searching 98 966 000 spectra obtained by the Dark Energy Spectroscopic Survey (DESI) to find such CVs. DESI observations are much deeper than previous spectroscopic surveys and we have identified 1029 CVs, 221 of which are new including ten of the AM CVn subtype. We have spectroscopically confirmed 441 CV candidates and obtained 84 new or improved orbital periods. We present revised space density estimates based upon this new data. We have also added ten more to the eight known examples of an intriguing class of CVs which exhibit peculiar changes in accretion.

astro-ph.SR↗

arXiv2026

Evolution of a long-period Cataclysmic Variable from the viewpoint of the donor star: the case of SDSS J085210.48+783246.6

Cataclysmic variables were long considered to be close binaries consisting of a white dwarf and a Roche-lobe-filling, near-zero-age main-sequence (ZAMS) red or brown dwarf. Recent massive surveys have uncovered an increasing number of binaries with similar spectral characteristics but harboring secondary stars that have undergone nuclear evolution and partial envelope stripping, many with orbital periods far exceeding the normal upper limits for ordinary CVs. We present a detailed study of a newly discovered CV with a 17.109 h period and determine its basic stellar parameters. We also discuss the evolutionary paths leading to the formation of these extremely long-period cataclysmic variables. We consider the implications of the new evolutionary hypothesis on their further evolution into double-degenerate binaries.

astro-ph.SR↗

arXiv2025

A Sibling of AR Scorpii: SDSS J230641.47$+$244055.8 and the Observational Blueprint of White Dwarf Pulsars

Radio pulsating white dwarf (WD) systems, known as WD pulsars, are non-accreting binary systems where the rapidly spinning WD interacts with a low-mass companion producing pulsed non-thermal emission that can be observed across the entire electromagnetic spectrum. Only two such systems are known: AR Sco and eRASSU J191213.9$-$441044. Here we present the discovery of a third WD pulsar, SDSS J230641.47$+$244055.8. The optical spectrum is dominated by molecular bands from an M-dwarf companion, with additional narrow emission lines from the Balmer series and He I. The long-term optical light-curve folded on its orbital period ($P_\mathrm{orb} = 3.49$ h) exhibits large scatter (roughly 10 per cent). High-cadence photometry reveals a short period signal, which we interpret to be the spin period of the WD primary ($P_\mathrm{spin} \simeq 92$ s). The WD spin period is slightly shorter than that of AR Sco ($\rm \sim 117$ s), the WD pulsar prototype. Time-resolved spectroscopy reveals emission from the irradiated companion and Na I absorption lines approximately tracing its centre of mass, which yields a binary mass function of $f(M) \simeq 0.2 {\rm M_\odot}$. The H$\alpha$ emission includes a low-amplitude broad component, resembling the energetic emission line flashes seen in AR Sco. Using spectral templates, we classify the companion to be most likely a $\rm M4.0\pm 0.5$ star with $T_\mathrm{\rm eff} \approx 3300$ K. Modelling the stellar contribution constrains the secondary mass ($0.19\,{\rm M_\odot}\lesssim M_2\lesssim 0.28\,{\rm M_\odot}$), system distance ($\simeq1.25\,{\rm kpc}$), and inclination ($i \simeq 45-50^\circ$). We discuss the proposed evolutionary scenarios and summarize the observational properties of all three known WD pulsars, establishing a benchmark for identifying and classifying future members of this emerging class.

astro-ph.SR↗

arXiv2025

A targeted search for binary white dwarf pulsars using Gaia and WISE

After its discovery in 2016, the white dwarf binary AR Scorpii (AR Sco) remained for several years the only white dwarf system to show pulsed radio emission associated with a fast-spinning white dwarf. The evolutionary origin and the emission mechanism for AR Sco are not completely understood, with different models proposed. Testing and improving these models requires observational input. Here we report the results of a targeted search for other binary white dwarf pulsars like AR Sco. Using data from Gaia and WISE, we identified 56 candidate systems with similar properties to AR Sco, of which 26 were previously uncharacterised. These were subject to spectroscopic and photometric follow-up observations. Aside from one new binary white dwarf pulsar found, J191213.72-441045.1, which was reported in a separate work, we find no other systems whose characteristics are akin to AR Sco. The newly characterised systems are primarily young stellar objects (with 10 found) or cataclysmic variables (7 identifications), with the remaining being either blended or non-variable on short timescales.

astro-ph.SR↗

arXiv2023

Cataclysmic Variables from Sloan Digital Sky Survey V -- the search for period bouncers continues

SDSS-V is carrying out a dedicated survey for white dwarfs, single and in binaries, and we report the analysis of the spectroscopy of cataclysmic variables (CVs) and CV candidates obtained during the final plug plate observations of SDSS. We identify eight new CVs, spectroscopically confirm 53 and refute eleven published CV candidates, and we report 21 new or improved orbital periods. Combined with previously published data, the orbital period distribution of the SDSS-V CVs does not clearly exhibit a period gap. This is consistent with previous findings that spectroscopically identified CVs have a larger proportion of short-period systems compared to samples identified from photometric variability. Remarkably, despite a systematic search, we find very few period bouncers. We estimate the space density of period bouncers to be $\simeq0.2\times10^{-6}\,\mathrm{pc}^{-3}$, i.e. they represent only a few per cent of the total CV population. This suggests that during their final phase of evolution, CVs either destroy the donor, e.g. via a merger, or that they become detached and cease mass transfer.

astro-ph.SR↗

arXiv2021

Towards a volumetric census of close white dwarf binaries I.Reference samples

Close white dwarf binaries play an important role across a range of astrophysics, including thermonuclear supernovae, the Galactic low-frequency gravitational wave signal, and the chemical evolution of the Galaxy. Progress in developing a detailed understanding of the complex, multi-threaded evolutionary pathways of these systems is limited by the lack of statistically sound observational constraints on the relative fractions of various sub-populations, and their physical properties. The available samples are small, heterogeneous, and subject to a multitude of observational biases. Our overarching goal is to establish a volume-limited sample of all types of white dwarf binaries that is representative of the underlying population as well as sufficiently large to serve as a benchmark for future binary population models. In this first paper, we provide an overview of the project, and assemble reference samples within a distance limit of 300\,pc of known white dwarf binaries spanning the most common sub-classes: post-common envelope binaries containing a white dwarf plus a main sequence star, cataclysmic variables and double-degenerate binaries. We carefully vet the members of these "Gold" Samples, which span most of the evolutionary parameter space of close white dwarf binary evolution. We also explore the differences between magnitude and volume limited close white dwarf binary samples, and discuss how these systems evolve in their observational properties across the Gaia Hertzsprung-Russell diagram.

astro-ph.SR↗