scholarly journals Revised Stellar Parameters for V471 Tau, A Post-common Envelope Binary in the Hyades

2021 ◽  
Vol 163 (1) ◽  
pp. 34
Author(s):  
Philip S. Muirhead ◽  
Jason Nordhaus ◽  
Maria R. Drout
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Hubble Space Telescope ◽  
Main Sequence Star ◽  
Velocity Measurements ◽  
Single Star ◽  
Orbital Parameters ◽  
Common Envelope ◽  
Star Evolution ◽  
First Time

Abstract V471 Tau is a post-common-envelope binary consisting of an eclipsing DA white dwarf and a K-type main-sequence star in the Hyades star cluster. We analyzed publicly available photometry and spectroscopy of V471 Tau to revise the stellar and orbital parameters of the system. We used archival K2 photometry, archival Hubble Space Telescope spectroscopy, and published radial-velocity measurements of the K-type star. Employing Gaussian processes to fit for rotational modulation of the system flux by the main-sequence star, we recovered the transits of the white dwarf in front of the main-sequence star for the first time. The transits are shallower than would be expected from purely geometric occultations owing to gravitational microlensing during transit, which places an additional constraint on the white-dwarf mass. Our revised mass and radius for the main-sequence star is consistent with single-star evolutionary models given the age and metallicity of the Hyades. However, as noted previously in the literature, the white dwarf is too massive and too hot to be the result of single-star evolution given the age of the Hyades, and may be the product of a merger scenario. We independently estimate the conditions of the system at the time of common envelope that would result in the measured orbital parameters today.

scholarly journals Origins of Type Ibn SNe 2006jc/2015G in interacting binaries and implications for pre-SN eruptions

2019 ◽  
Vol 491 (4) ◽  
pp. 6000-6019 ◽  
Author(s):  
Ning-Chen Sun ◽  
Jusytn R Maund ◽  
Ryosuke Hirai ◽  
Paul A Crowther ◽  
Philipp Podsiadlowski
Keyword(s):  
Main Sequence ◽  
Hubble Space Telescope ◽  
Optical Observations ◽  
Initial Mass ◽  
Binary Interaction ◽  
Lower Mass ◽  
Single Star ◽  
Circumstellar Material ◽  
Luminous Blue Variables ◽  
Star Evolution

ABSTRACT Type Ibn supernovae (SNe Ibn) are intriguing stellar explosions whose spectra exhibit narrow helium lines with little hydrogen. They trace the presence of circumstellar material (CSM) formed via pre-SN eruptions of their stripped-envelope progenitors. Early work has generally assumed that SNe Ibn come from massive Wolf–Rayet (WR) stars via single-star evolution. In this paper, we report ultraviolet (UV) and optical observations of two nearby Type Ibn SNe 2006jc and 2015G conducted with the Hubble Space Telescope (HST) at late times. A point source is detected at the position of SN 2006jc, and we confirm the conclusion of Maund et al. that it is the progenitor’s binary companion. Its position on the Hertzsprung–Russell (HR) diagram corresponds to a star that has evolved off the main sequence (MS); further analysis implies a low initial mass for the companion star (M2 ≤ 12.3$^{+2.3}_{-1.5}$ M⊙) and a secondary-to-primary initial mass ratio very close to unity (q = M2/M1 ∼ 1); the SN progenitor’s hydrogen envelope had been stripped through binary interaction. We do not detect the binary companion of SN 2015G. For both SNe, the surrounding stellar populations have relatively old ages and argue against any massive WR stars as their progenitors. These results suggest that SNe Ibn may have lower mass origins in interacting binaries. As a result, they also provide evidence that the giant eruptions commonly seen in massive luminous blue variables (LBVs) can also occur in much lower mass, stripped-envelope stars just before core collapse.

scholarly journals Classical Novae – Before and After Outburst

1988 ◽  
Vol 108 ◽  
pp. 226-231
Author(s):  
Mario Livio
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Orbital Parameters ◽  
Classical Novae ◽  
Classical Nova ◽  
Before And After ◽  
Low Mass ◽  
Orbital Periods ◽  
Thermonuclear Runaway ◽  
Nova Outburst

Classical nova (CN) and dwarf nova (DN) systems have the same binary components (a low-mass main sequence star and a white dwarf) and the same orbital periods. An important question that therefore arises is: are these systems really different ? (and if so, what is the fundamental difference ?) or, are these the same systems, metamorphosing from one class to the other ?The first thing to note in this respect is that the white dwarfs in DN systems are believed to accrete continuously (both at quiescence and during eruptions). At the same time, both analytic (e.g. Fujimoto 1982) and numerical calculations show, that when sufficient mass accumulates on the white dwarf, a thermonuclear runaway (TNR) is obtained and a nova outburst ensues (see e.g. reviews by Gallagher and Starrfield 1978, Truran 1982). It is thus only natural, to ask the question, is the fact that we have not seen a DN undergo a CN outburst (in about 50 years of almost complete coverage) consistent with observations of DN systems ? In an attempt to answer this question, we have calculated the probability for a nova outburst not to occur (in 50 years) in 86 DN systems (for which at least some of the orbital parameters are known).

scholarly journals The HST large programme on NGC 6752 – III. Detection of the peak of the white dwarf luminosity function

2019 ◽  
Vol 488 (3) ◽  
pp. 3857-3865
Author(s):  
L R Bedin ◽  
M Salaris ◽  
J Anderson ◽  
M Libralato ◽  
D Apai ◽  
...  
Keyword(s):  
Globular Cluster ◽  
White Dwarf ◽  
Luminosity Function ◽  
Main Sequence ◽  
Hubble Space Telescope ◽  
Horizontal Branch ◽  
Space Telescope

ABSTRACT We report on the white dwarf (WD) cooling sequence of the old globular cluster NGC 6752, which is chemically complex and hosts a blue horizontal branch. This is one of the last globular cluster WD cooling sequences accessible to imaging by the Hubble Space Telescope. Our photometry and completeness tests show that we have reached the peak of the luminosity function of the WD cooling sequence, at a magnitude mF606W  = 29.4 ± 0.1, which is consistent with a formal age of ∼14 Gyr. This age is also consistent with the age from fits to the main-sequence turn-off (13–14 Gyr), reinforcing our conclusion that we observe the expected accumulation of WDs along the cooling sequence.

scholarly journals The Ejecta of Classical Novae

2001 ◽  
Vol 205 ◽  
pp. 260-263
Author(s):  
T.J. O'Brien ◽  
R.J. Davis ◽  
M.F. Bode ◽  
S. P. S. Eyres ◽  
J.M. Porter
Keyword(s):  
Coherent Structures ◽  
White Dwarf ◽  
Binary Stars ◽  
Hubble Space Telescope ◽  
Classical Novae ◽  
Common Envelope ◽  
Physical Mechanisms ◽  
The Common ◽  
Thermonuclear Runaway ◽  
Prolate Ellipsoidal

Classical novae are interacting binary stars in which a thermonuclear runaway in material accreted onto a white dwarf from a companion red dwarf results in the ejection of around 10−4M⊙ at hundreds to thousands of kilometres per second. Recent Hubble Space Telescope and MERLIN imaging of the expanding ejecta from several classical novae are presented. In general the ejecta are clumpy but often display coherent structures, most notably equatorial rings of enhanced emission encircling prolate ellipsoidal shells. Physical mechanisms (including the common envelope phase and anisotropic irradiation of the shell) which may result in the generation of these structures are discussed.

scholarly journals Evolution Models of Helium White Dwarf–Main-sequence Star Merger Remnants

2017 ◽  
Vol 835 (2) ◽  
pp. 242 ◽  
Author(s):  
Xianfei Zhang ◽  
Philip D. Hall ◽  
C. Simon Jeffery ◽  
Shaolan Bi
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Main Sequence Star

scholarly journals Gaia Data Release 2 catalogue of extremely low-mass white dwarf candidates

2019 ◽  
Vol 488 (2) ◽  
pp. 2892-2903 ◽  
Author(s):  
Ingrid Pelisoli ◽  
Joris Vos
Keyword(s):  
White Dwarf ◽  
Theoretical Models ◽  
Dwarf Stars ◽  
Single Star ◽  
Common Envelope ◽  
White Dwarf Stars ◽  
Final Sample ◽  
Data Release ◽  
Low Mass ◽  
Binary Evolution

ABSTRACT Extremely low-mass white dwarf stars (ELMs) are M < 0.3 M⊙ helium-core white dwarfs born either as a result of a common-envelope phase or after a stable Roche lobe overflow episode in a multiple system. The Universe is not old enough for ELMs to have formed through single-star evolution channels. As remnants of binary evolution, ELMs can shed light onto the poorly understood phase of common-envelope evolution and provide constraints to the physics of mass accretion. Most known ELMs will merge in less than a Hubble time, providing an important contribution to the signal to be detected by upcoming space-based gravitational wave detectors. There are currently less than 150 known ELMs; most were selected by colour, focusing on hot objects, in a magnitude-limited survey of the Northern hemisphere only. Recent theoretical models have predicted a much larger space density for ELMs than estimated observationally based on this limited sample. In order to perform meaningful comparisons with theoretical models and test their predictions, a larger well-defined sample is required. In this work, we present a catalogue of ELM candidates selected from the second data release of Gaia (DR2). We have used predictions from theoretical models and analysed the properties of the known sample to map the space spanned by ELMs in the Gaia Hertzsprung–Russell diagram. Defining a set of colour cuts and quality flags, we have obtained a final sample of 5762 ELM candidates down to Teff ≈ 5000 K.

scholarly journals Sakurai’s Object, V605 Aql and FG Sge: An Evolutionary Sequence Revealed

2002 ◽  
Vol 187 ◽  
pp. 193-199
Author(s):  
Timothy M. Lawlor ◽  
James MacDonald
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Mixing Efficiency ◽  
Evolutionary Sequence ◽  
Evolutionary Time ◽  
Convective Mixing ◽  
The Difference ◽  
Born Again ◽  
First Time ◽  
Uniform Composition

AbstractWe have completed a grid of stellar evolution calculations to study the behavior of the born again phenomenon. All our evolutionary sequences begin with a uniform composition 1 M⊙ star on the pre-main sequence Hayashi phase and end on the white dwarf cooling track. We find a very late thermal pulse occurs in 10 – 15 percent of cases. Our models supply an answer to the question of why the born again stars V4334 Sgr (Sakurai’s Object) and V605 Aql have a significantly shorter evolutionary time scale than the otherwise similar born again star FG Sge. Models with low convective mixing efficiency, η = 10–4, first evolve quickly to the AGB, return to the blue, and then evolve more slowly back to the AGB for a second time before finally returning to the white dwarf cooling track. The difference in evolution time scales can then be explained by proposing that Sakurai’s Object is evolving to the AGB for the first time but FG Sge has been observed during its second return to the AGB.

scholarly journals Applegate mechanism in post-common-envelope binaries: Investigating the role of rotation

2018 ◽  
Vol 615 ◽  
pp. A81 ◽  
Author(s):  
F. H. Navarrete ◽  
D. R. G. Schleicher ◽  
J. Zamponi Fuentealba ◽  
M. Völschow
Keyword(s):  
Orbital Period ◽  
Rotation Rate ◽  
Main Sequence ◽  
Magnetic Activity ◽  
Main Sequence Star ◽  
Common Envelope ◽  
Rotation Rates ◽  
Critical Rotation ◽  
Period Variations ◽  
Time Variations

Context. Eclipsing time variations are observed in many close binary systems. In particular, for several post-common-envelope binaries (PCEBs) that consist of a white dwarf and a main sequence star, the observed-minus-calculated (O–C) diagram suggests that real or apparent orbital period variations are driven by Jupiter-mass planets or as a result of magnetic activity, the so-called Applegate mechanism. The latter explains orbital period variations as a result of changes in the stellar quadrupole moment due to magnetic activity. Aims. In this work we explore the feasibility of driving eclipsing time variations via the Applegate mechanism for a sample of PCEB systems, including a range of different rotation rates. Methods. We used the MESA code to evolve 12 stars with different masses and rotation rates. We applied simple dynamo models to their radial profiles to investigate the scale at which the predicted activity cycle matches the observed modulation period, and quantifiy the uncertainty. We further calculated the required energies to drive the Applegate mechanism. Results. We show that the Applegate mechanism is energetically feasible in 5 PCEB systems. In RX J2130.6+4710, it may be feasible as well considering the uncertainties. We note that these are the systems with the highest rotation rate compared to the critical rotation rate of the main-sequence star. Conclusions. The results suggest that the ratio of physical to critical rotation rate in the main sequence star is an important indicator for the feasibility of Applegate’s mechanism, but exploring larger samples will be necessary to probe this hypothesis.

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