Special Issue Editor

Prof. Dr. Alejandra Romero

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Guest Editor

Physics Institute, University of Rio Grande do Sul, Porto Alegre, Brazil
Interests: stellar evolution; white dwarf modeling; asteroseismology of compact stars; variable stars (photometry)

Special Issue Information

Dear Colleagues,

White dwarf stars are the most common endpoint in stellar evolution. More than 95% of all stars in the Milky Way, including our own Sun, will leave behind a white dwarf remnant. White dwarfs are abundant and long-lived celestial beings; therefore, they convey important information about the properties of galactic populations, such as galactic disks and halo and open and globular clusters.

One fundamental tool to study the properties of white dwarfs in single and multiple systems is photometry. From multiband observations, covering a wide range in frequency, to time series photometry for the study of variability, ground- and space-based facilities have paved the way to uncover information regarding the properties of the white dwarf population.

The purpose of the current volume is to review the different properties of white dwarfs and related systems that can be uncovered using photometric techniques, from both ground- and space-based observations. We welcome you to contribute with original articles or reviews on the study of white dwarf stars from photometry.

Prof. Dr. Alejandra Romero
Guest Editor

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Keywords

white dwarf catalogs
binary systems with white dwarf components
multiband photometric observations
photometric surveys
pulsations in white dwarf stars
planets or minor bodies around white dwarfs
space-based observations
ground based-observations

Published Papers (1 paper)

Research

18 pages, 870 KiB

Open AccessArticle

A Brown Dwarf Companion to the Nova-like Variable RW Tri

by Zhibin Dai, Shengbang Qian and Indika Medagangoda

Galaxies 2021, 9(4), 94; https://0-doi-org.brum.beds.ac.uk/10.3390/galaxies9040094 - 05 Nov 2021

Viewed by 1375

Abstract

The orbital period of Nova-like variable RW Tri is expected to experience a long-term evolution due to a stable mass transfer from the red dwarf to the white dwarf. By adding 297 new eclipse timings obtained from our own observations and a cross-identification of many databases, we fully reinvestigated the variations in orbital period of RW Tri, based on a total of 658 data points spanning over 80 years. The new O-C diagram demonstrates a more complicate pattern than a pure sinusoidal modulation shown in the previous O-C analyses. The best fit of the O-C variations is a quadratic-plus-sinusoidal curve with a period of 22.66 (2) years and a typical decrease rate of

\dot{P}

- 2^{d}

.32(4) × 10

^{- 9}

^{- 1}

. To explain secular orbital period decrease, the magnetic braking effect is required to cause the orbital angular moment loss in RW Tri with a mass ratio less than unity, while a conserved mass transfer is also enough for RW Tri with a mass ratio larger than unity. No matter what the mass ratio is, a slightly enhanced mass transfer rate, 2.4–5.3 × 10

^{- 9}

_{⊙}

^{- 1}

, derived from our O-C diagram, providing an evidence supporting the disk instability model and the standard/revised models of cataclysmic variable evolution, is almost the same as that obtained from the light-curve modeling. This further confirms our observed orbital period decrease and the controversial system parameter, mass transfer rate. Our updated O-C analysis further verifies the claimed cyclical changes of orbital period with a period range of 21–24 years, which is approximately one half of the results in the literature. In accordance with the light-travel time effect, this periodical variation shown in our new O-C diagram indicates a brown dwarf hidden in RW Tri at a coplanar orbit. Note that the large scatter in the data range of 0–3 × 10

^{4}

cycles requires the high-precision photometry in the longer base line in the future. Full article

(This article belongs to the Special Issue Using Photometric Observations to Uncover the Wonders of White Dwarf Stars)

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