Explanipedia

The SALT survey of helium-rich hot subdwarfs: final sample and classification Open

C. S. Jeffery, M. Dorsch, A. Philip Monai, E. J. Snowdon, I. M. Monageng , et al. · 2025

A medium-resolution spectroscopic survey of helium-rich hot subdwarfs has been carried out using the Southern African Large Telescope (SALT). Objectives include the discovery of exotic hot subdwarfs, resolving distinct subclasses, identify…

The diverse morphology of gravitational wave signals from merging neutron-star white-dwarf binaries Open

Shenghua Yu, Youjun Lu, C. S. Jeffery, Dongdong Liu, Jie Yang , et al. · 2025

In sufficiently compact neutron star-white dwarf (NSWD) binary systems, orbital decay means the white dwarf eventually fills its shrinking Roche lobe, initiating a phase of mass transfer. The exchange of angular momentum-both internal and …

K2 observations of five pulsating subdwarf-B stars with white dwarf companions Open

M. D. Reed, A. S. Baran, J. H. Telting, R. H. Østensen, C. S. Jeffery , et al. · 2025

We report seismic analyses of five pulsating subdwarf B (sdBV) stars observed during Kepler’s K2 mission, each with a white dwarf companion. We find three of the five to be g-mode-dominated hybrid pulsators. For the other two, we only dete…

K2 observations of five pulsating subdwarf B stars with white dwarf companions Open

M. D. Reed, A. S. Baran, J. H. Telting, R. H. Ostensen, C. S. Jeffery , et al. · 2025

We report seismic analyses of five pulsating subdwarf B (sdBV) stars observed during Kepler's K2 mission, each with a white dwarf companion. We find three of the five to be g-mode-dominated hybrid pulsators. For the other two, we only dete…

Linear and non-linear models for large-amplitude radial pulsation in faint blue stars (BLAPs) Open

C. S. Jeffery · 2025

The recent discovery of large-amplitude pulsations in faint blue stars (BLAPs) provides both challenges for stellar pulsation theory and opportunities to explore the late evolution of low-mass stars. This paper explores the radial-mode sta…

A search for close binary systems in the SALT survey of hydrogen-deficient stars using TESS Open

E. J. Snowdon, C. S. Jeffery, Saskia Schlagenhauf, M. Dorsch · 2025

The TESS periodograms of the SALT survey catalogue of hydrogen-deficient stars were searched for evidence of short-period variability. Periodic light-curve variations were identified in 16 stars out of 153 catalogue objects, of which 10 we…

A search for close binary systems in the SALT survey of hydrogen-deficient stars using {\it TESS} Open

E. J. Snowdon, C. S. Jeffery, Saskia Schlagenhauf, M. Dorsch · 2025

The {\it TESS} periodograms of the SALT survey catalogue of hydrogen-deficient stars were searched for evidence of short-period variability. Periodic light curve variations were identified in 16 stars out of 153 catalogue objects, of which…

Discovery of three magnetic helium-rich hot subdwarfs with SALT Open

M. Dorsch, C. S. Jeffery, A. Philip Monai, Christopher A. Tout, E. J. Snowdon , et al. · 2024

Magnetic fields with strengths ranging from 300 to 500 kG have recently been discovered in a group of four extremely similar helium-rich hot subdwarf (He-sdO) stars. In addition to their strong magnetic fields, these He-sdO stars are chara…

Discovery of three magnetic helium-rich hot subdwarfs with SALT Open

M. Dorsch, C. S. Jeffery, A. Philip Monai, Christopher A. Tout, E. J. Snowdon , et al. · 2024

Magnetic fields with strengths ranging from 300 to 500 kG have recently been discovered in a group of four extremely similar helium-enriched hot subdwarf (He-sdO) stars. Besides their strong magnetic fields, these He-sdO stars are characte…

Quantifying spatial peat depth with seismic micronodes and the implications for carbon stock estimates Open

Jack Muir, C. S. Jeffery, Joe D. Collins, Alice Marks, Nathan Brake , et al. · 2024

Peatlands are a major store of soil carbon, due to their high concentration of carbon-rich decayed plant material. Consequently, accurate assessment of peat volumes is important for determining land-use carbon budgets, especially in the No…

EC 19529−4430: SALT identifies the most carbon- and metal-poor extreme helium star Open

C. S. Jeffery, Laura J. A. Scott, A. Philip Monai, B. Miszalski, Vincent M. Woolf · 2024

EC 19529−4430 was identified as a helium-rich star in the Edinburgh–Cape (EC) Survey of faint-blue objects and subsequently resolved as a metal-poor extreme helium (EHe) star in the Southern African Large Telescope (SALT) survey of chemica…

EC 19529-4430: SALT identifies the most carbon- and metal-poor extreme helium star Open

C. S. Jeffery, Laura Scott, A. Philip Monai, B. Miszalski, Vincent M. Woolf · 2024

EC 19529-4430 was identified as a helium-rich star in the Edinburgh-Cape Survey of faint-blue objects and subsequently resolved as a metal-poor extreme helium (EHe) star in the SALT survey of chemically-peculiar hot subdwarfs. This paper p…

Spectroscopic diagnostics of lead stratification in hot subdwarf atmospheres Open

Laura J. A. Scott, C. S. Jeffery, Conor M Byrne, M. Dorsch · 2024

Heavy metal subdwarfs are a class of hot subdwarfs with very high abundances of heavy elements, typically around 10 000 times solar. They include stars, which are strongly enhanced in either lead or zirconium, as well as other elements. Ve…

Spectroscopic diagnostics of lead stratification in hot subdwarf atmospheres Open

Laura J. A. Scott, C. S. Jeffery, Conor M Byrne, M. Dorsch · 2024

Heavy metal subdwarfs are a class of hot subdwarfs with very high abundances of heavy elements, typically around 10 000 times solar. They include stars which are strongly enhanced in either lead or zirconium, as well as other elements. Ver…

A 500 pc volume-limited sample of hot subluminous stars I. Space density, scale height, and population properties Open

Harry Dawson, S. Geier, U. Heber, Ingrid Pelisoli, M. Dorsch , et al. · 2024

We present the first volume-limited sample of spectroscopically confirmed hot subluminous stars out to 500 pc, defined using the accurate parallax measurements from the {\em Gaia} space mission data release 3 (DR3). The sample comprises a …

A 500 pc volume-limited sample of hot subluminous stars Open

Harry Dawson, S. Geier, U. Heber, Ingrid Pelisoli, M. Dorsch , et al. · 2024

We present the first volume-limited sample of spectroscopically confirmed hot subluminous stars out to 500 pc, defined using the accurate parallax measurements from the Gaia space mission data release 3 (DR3). The sample comprises a total …

Quantifying spatial peat depth with seismic micronodes and the implications for carbon stock estimates Open

Tarje Nissen‐Meyer, Jack Muir, C. S. Jeffery, Joe D. Collins, Alice Marks , et al. · 2024

Peatlands are a major store of soil carbon, due to their high concentration of carbon-rich decayed plant material. Consequently, accurate assessment of peat volumes are important for determining land-use carbon budgets. Determination of ca…

The effect of cannabinoids on wound healing: A review Open

Aniruddha C. Parikh, C. S. Jeffery, Zainab Sandhu, Benjamin P. Brownlee, Lurdes Queimado , et al. · 2024

Background and Aims Cannabis and its various derivatives are commonly used for both recreational and medicinal purposes. Cannabinoids have been shown to have anti‐inflammatory properties. Inflammation is an important component of wound hea…

The Formation of Blue Large-amplitude Pulsators from White-dwarf Main-sequence Star Mergers Open

Xianfei Zhang, C. S. Jeffery, Jie Su, Shaolan Bi · 2023

Blue large-amplitude pulsators (BLAPs) are hot low-mass stars that show large-amplitude light variations likely due to radial oscillations driven by iron group opacities. Period changes provide evidence of both secular contraction and expa…

The formation of blue large-amplitude pulsators from white-dwarf main-sequence star mergers Open

Xianfei Zhang, C. S. Jeffery, Jie Su, Shaolan Bi · 2023

Blue large-amplitude pulsators (BLAPs) are hot low-mass stars which show large-amplitude light variations likely due to radial oscillations driven by iron-group opacities. Period changes provide evidence of both secular contraction and exp…

The distribution, kinematics, and luminosities of extreme helium stars as probes of their origin and evolution Open

A. Philip Monai, Pierre Martin, C. S. Jeffery · 2023

Hydrogen-deficient stars include the cool R CrB variable (RCBs) and hydrogen-deficient carbon (HdCs) giants through extreme helium stars (EHes) to the very hot helium-rich subdwarfs (He-sdO and O(He) stars) and white dwarfs. With surfaces …

The distribution, kinematics and luminosities of extreme helium stars as probes of their origin and evolution Open

A. Philip Monai, Pablo Martín‐Ramos, C. S. Jeffery · 2023

Hydrogen deficient stars include the cool R CrB variable (RCBs) and hydrogen-deficient carbon (HdCs) giants through extreme helium stars (EHes) to the very hot helium-rich subdwarfs (He-sdO and O(He) stars) and white dwarfs. With surfaces …

Ton S 415: a close binary containing an intermediate helium subdwarf discovered with SALT and TESS Open

E. J. Snowdon, C. S. Jeffery, Saskia Schlagenhauf, M. Dorsch, I. M. Monageng · 2023

Hot subdwarfs are early-type low-mass stars lying between the main sequence and the white dwarf sequence. The majority have helium-burning cores and helium-poor surfaces. A minority have helium-rich surfaces. A few, including Ton S 415, ha…

Abundance analysis of a nitrogen-rich extreme-helium hot subdwarf from the SALT survey Open

L. J. A. Scott., C. S. Jeffery, D. Farren, C. Tap, M. Dorsch · 2023

We have performed a detailed spectral analysis of the helium-rich hot subdwarf EC 20187-4939 using data obtained in the SALT survey of helium-rich hot subdwarfs. We have measured its effective temperature, surface gravity and chemical abun…

The SALT survey of chemically-peculiar hot subdwarfs Open

C. S. Jeffery, I. M. Monageng, B. Miszalski, E. J. Snowdon, Laura J. A. Scott , et al. · 2023

The Southern African Large Telescope (SALT) has surveyed a sample of 300 chemically-peculiar hot subdwarfs with a view to explore evolutionary pathways and connections between a large variety of stars. Observations have been obtained for t…

Kepler, K2, and TESS observations: ensemble and comparative asteroseismology Open

M. D. Reed, A. S. Baran, R. H. Østensen, J. H. Telting, C. S. Jeffery · 2023

The original Kepler mission detected 18 pulsating subdwarf B (sdBV) stars, K2 observed 161 of our proposed targets with 41 sdB stars found to show p- or g-mode pulsations, and TESS has observed about 1,000 of our proposed targets. All thes…

The close binary fraction of He-rich hot subdwarfs from SALT and TESS Open

E. J. Snowdon, C. S. Jeffery, Saskia Schlagenhauf · 2023

The Southern African Large Telescope (SALT) survey of He-rich hot subdwarfs has identi-fied several binary candidates from variable or anomalous radial velocities, or unusually high rotational velocities. Many SALT survey objects have also…

Hot white dwarfs and pre-white dwarfs discovered with SALT Open

C. S. Jeffery, K. Werner, D. Kilkenny, B. Miszalski, I. M. Monageng , et al. · 2022

The Southern African Large Telescope survey of helium-rich hot subdwarfs aims to explore evolutionary pathways among groups of highly evolved stars. The selection criteria mean that several hot white dwarfs and related objects have also be…

TESS uncloaks the secondaries in hydrogen-deficient binaries Open

C. S. Jeffery · 2022

$\upsilon$ Sgr is the prototype of four known hydrogen-deficient binary (HdB) systems. These are characterised by a hydrogen-deficient A-type primary, variable hydrogen emission lines, and a normally unseen secondary presumed to be an uppe…

Spectroscopic analysis of BPS CS 22940-0009: connecting evolved helium stars Open

E. J. Snowdon, Laura J. A. Scott, C. S. Jeffery, Vincent M. Woolf · 2022

BPS CS 22940-0009 is a helium-rich B-star that shares characteristics with both helium-rich B subdwarfs and extreme helium stars. The optical spectrum of BPS CS 22940-0009 has been analysed from SALT observations. The atmospheric parameter…

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