scholarly journals Cataclysmic Binaries Containing a Black-Dwarf Secondary

1983 ◽  
Vol 72 ◽  
pp. 275-278
Author(s):  
H. Ritter
Keyword(s):  
Main Sequence ◽  
Probability Of Detection ◽  
Light Curves ◽  
Space Density ◽  
Cataclysmic Binaries ◽  
Low Mass ◽  
Intrinsic Luminosity

ABSTRACTCataclysmic binaries with a black-dwarf secondary can in principle be distinguished from those containing a low-mass main-sequence secondary because of the differences of the corresponding eclipse light curves. However, due to the very low intrinsic luminosity of the systems containing a black dwarf, the probability of detection turns out to be smaller than the corresponding probability for an ordinary cataclysmic binary by about 1.5 to 3 orders of magnitude. Therefore, despite the fact that the predicted space density of these objects is quite high, systems containing a black-dwarf secondary must remain essentially undetectable.

scholarly journals The Evolutionary Status of the Secondaries of Cataclysmic Binaries

1983 ◽  
Vol 72 ◽  
pp. 257-262
Author(s):  
H. Ritter
Keyword(s):  
Probability Distribution ◽  
Main Sequence ◽  
The Other ◽  
Initial Mass ◽  
Evolutionary Status ◽  
Mass Ratio ◽  
Main Sequence Stars ◽  
Cataclysmic Binaries ◽  
Low Mass ◽  
Orbital Periods

ABSTRACTIt is shown that the secondary components of cataclysmic binaries with orbital periods of less than ~10 hours are indistinguishable from ordinary low-mass main-sequence stars and that, therefore, they are essentially unevolved. On the other hand, it is shown that, depending on the mass ratio of the progenitor system, the secondary of a cataclysmic binary could be significantly evolved. The fact that nevertheless most of the observed secondaries are essentially unevolved can be accounted for by assuming that the probability distribution for the initial mass ratio is not strongly peaked towards unity mass ratio.

scholarly journals Very Low Mass Stars and Brown Dwarf Candidates in Orion OB1a and OB1b

2003 ◽  
Vol 211 ◽  
pp. 119-122
Author(s):  
Frederick M. Walter ◽  
William H. Sherry ◽  
Scott J. Wolk
Keyword(s):  
Ir Spectroscopy ◽  
Main Sequence ◽  
Brown Dwarf ◽  
Low Mass Stars ◽  
Space Density ◽  
Near Ir ◽  
Substellar Objects ◽  
Low Mass ◽  
M Stars

VRI images within the belt of Orion and the Ori OB1a association reveal a pre-main sequence locus extending to below our completeness limit of about V=21. We report here on followup JHK imaging and optical and near–IR spectroscopy of the faintest and reddest of the PMS candidates. We find that they are unreddened mid-to-late M “stars” which fall on a few million year isochrone. Masses are largely substellar, reaching as low as about 0.02 M⊙ (20 Jovian masses). The space density of the substellar objects is high.

scholarly journals Spots, flares, accretion, and obscuration in the pre-main sequence binary DQ Tau

2018 ◽  
Vol 14 (S345) ◽  
pp. 314-315
Author(s):  
Á. Kóspál ◽  
P. Ábrahám ◽  
G. Zsidi ◽  
K. Vida ◽  
R. Szabó ◽  
...  
Keyword(s):  
Real World ◽  
Main Sequence ◽  
Equal Mass ◽  
Light Curves ◽  
Multiple Systems ◽  
Spectroscopic Binary ◽  
Rotational Modulation ◽  
Stellar Flares ◽  
Low Mass ◽  
Formation And Evolution

AbstractDQ Tau is a young low-mass spectroscopic binary, consisting of two almost equal-mass stars on a 15.8 day period surrounded by a circumbinary disk. We analyzed DQ Tau’s light curves obtained by Kepler K2, the Spitzer Space Telescope, and ground-based facilities. We observed variability phenomena, including rotational modulation by stellar spots, energetic stellar flares, brightening events around periastron due to increased accretion, and short dips due to temporary circumstellar obscuration. The study on DQ Tau will help in discovering and understanding the formation and evolution of other real-world examples of “Tatooine-like” systems. This is especially important because more and more evidence points to the possibility that all Sun-like stars were born in binary or multiple systems that broke up later due to dynamical interactions.

scholarly journals Magnetic white dwarfs in post-common-envelope binaries

2021 ◽  
Vol 502 (3) ◽  
pp. 4305-4327
Author(s):  
S G Parsons ◽  
B T Gänsicke ◽  
M R Schreiber ◽  
T R Marsh ◽  
R P Ashley ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Light Curves ◽  
Magnetic Systems ◽  
Cataclysmic Binaries ◽  
Low Mass ◽  
Detached Binaries ◽  
Magnetic Cataclysmic Variables ◽  
First Time

ABSTRACT Magnitude-limited samples have shown that 20–25 per cent of cataclysmic variables contain white dwarfs with magnetic fields of Mega Gauss strength, in stark contrast to the approximately 5 per cent of single white dwarfs with similar magnetic field strengths. Moreover, the lack of identifiable progenitor systems for magnetic cataclysmic variables leads to considerable challenges when trying to understand how these systems form and evolve. Here, we present a sample of six magnetic white dwarfs in detached binaries with low-mass stellar companions where we have constrained the stellar and binary parameters including, for the first time, reliable mass estimates for these magnetic white dwarfs. We find that they are systematically more massive than non-magnetic white dwarfs in detached binaries. These magnetic white dwarfs generally have cooling ages of more than 1 Gyr and reside in systems that are very close to Roche lobe filling. Our findings are more consistent with these systems being temporarily detached cataclysmic variables, rather than pre-cataclysmic binaries, but we cannot rule out the latter possibility. We find that these systems can display unusual asymmetric light curves that may offer a way to identify them in larger numbers in future. Seven new candidate magnetic white dwarf systems are also presented, three of which have asymmetric light curves. Finally, we note that several newly identified magnetic systems have archival spectra where there is no clear evidence of magnetism, meaning that these binaries have been previously missed. Nevertheless, there remains a clear lack of younger detached magnetic white dwarf systems.

scholarly journals Evolution of Low Mass Binaries under the Influence of Gravitational Radiation

1981 ◽  
Vol 93 ◽  
pp. 185-186 ◽  
Author(s):  
A. G. Massevitch ◽  
A. V. Tutukov ◽  
L. R. Yungelson
Keyword(s):  
Mass Exchange ◽  
Gravitational Radiation ◽  
Time Scale ◽  
Driving Force ◽  
Main Sequence ◽  
X Ray ◽  
Cataclysmic Binaries ◽  
Evolutionary Changes ◽  
Low Mass ◽  
Tt Ari

Evolutionary changes of masses and periods under the influence of gravitational radiation (GR) are computed for binaries with main-sequence or degenerate hydrogen-helium (H), helium (He) and carbon (C) secondaries. Tracks in the P-M2 and P-M2 planes are determined. The orbital period of systems P with a non-degenerate dwarf filling its Roche lobe decreases until the time-scale of GR (~ 109−1010yrs) becomes shorter than the thermal time-scale τKH of the mass losing component M2. When M2 becomes ~ 0.1 M⊙, P begins to increase. This could account for the existence of the minimal P ≈ 1.3h and for the accumulation of observed cataclysmic binaries (CB) below P ≤ 2h. The GR can be the driving force for evolution of cataclysmic binaries: TT Ari, OY Car, Z Cha, and WZ Sge as their P, M2 and indicate. The rate of mass exchange driven by GR is ~ 10−9−10−10 M⊙/yrs. It is enough to feed the X-ray bursters and related objects.

scholarly journals The PMS Eclipsing Binary RXJ 0529.4+0041

2001 ◽  
Vol 200 ◽  
pp. 468-471 ◽  
Author(s):  
E. Covino ◽  
S. Catalano ◽  
A. Frasca ◽  
E. Marilli ◽  
J.M. Alcalá ◽  
...  
Keyword(s):  
Main Sequence ◽  
Light Curves ◽  
Spectroscopic Binaries ◽  
Evolutionary Models ◽  
Eclipsing Binary ◽  
Star Forming ◽  
T Tauri ◽  
Low Mass ◽  
Using Data ◽  
Orbital Solution

We report the discovery of the first low–mass pre–main sequence eclipsing binary among a sample of double-lined spectroscopic binaries in the Orion star forming region found in a previous high-resolution spectroscopic investigation on ROSAT–discovered weak-T Tauri stars. Here we present the preliminary results from the combined analysis of the spectroscopic orbit and B and V light–curves, using data available till spring 2000. We then compare the fundamental stellar parameters derived from the orbital solution with those inferred from some widely used theoretical evolutionary models.

scholarly journals The study of multipeaked type-I X-ray bursts in the neutron star low-mass X-ray binary 4U 1636 − 536 with RXTE

2020 ◽  
Vol 501 (1) ◽  
pp. 168-178
Author(s):  
Chen Li ◽  
Guobao Zhang ◽  
Mariano Méndez ◽  
Jiancheng Wang ◽  
Ming Lyu
Keyword(s):  
Neutron Star ◽  
Flux Ratio ◽  
Light Curves ◽  
Type I ◽  
X Ray ◽  
Soft State ◽  
Peak Flux ◽  
Low Mass ◽  
Two Peaks ◽  
Second Peak

ABSTRACT We have found and analysed 16 multipeaked type-I bursts from the neutron-star low-mass X-ray binary 4U 1636 − 53 with the Rossi X-ray Timing Explorer (RXTE). One of the bursts is a rare quadruple-peaked burst that was not previously reported. All 16 bursts show a multipeaked structure not only in the X-ray light curves but also in the bolometric light curves. Most of the multipeaked bursts appear in observations during the transition from the hard to the soft state in the colour–colour diagram. We find an anticorrelation between the second peak flux and the separation time between two peaks. We also find that in the double-peaked bursts the peak-flux ratio and the temperature of the thermal component in the pre-burst spectra are correlated. This indicates that the double-peaked structure in the light curve of the bursts may be affected by enhanced accretion rate in the disc, or increased temperature of the neutron star.

scholarly journals Are sdAs helium core stars?

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Ingrid Pelisoli ◽  
S. O. Kepler ◽  
Detlev Koester
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Physical Nature ◽  
Sloan Digital Sky Survey ◽  
Distance Modulus ◽  
Main Sequence Stars ◽  
Sky Survey ◽  
Balmer Lines ◽  
Low Mass ◽  
Binary Evolution

AbstractEvolved stars with a helium core can be formed by non-conservative mass exchange interaction with a companion or by strong mass loss. Their masses are smaller than 0.5 M⊙. In the database of the Sloan Digital Sky Survey (SDSS), there are several thousand stars which were classified by the pipeline as dwarf O, B and A stars. Considering the lifetimes of these classes on the main sequence, and their distance modulus at the SDSS bright saturation, if these were common main sequence stars, there would be a considerable population of young stars very far from the galactic disk. Their spectra are dominated by Balmer lines which suggest effective temperatures around 8 000-10 000 K. Several thousand have significant proper motions, indicative of distances smaller than 1 kpc. Many show surface gravity in intermediate values between main sequence and white dwarf, 4.75 < log g < 6.5, hence they have been called sdA stars. Their physical nature and evolutionary history remains a puzzle. We propose they are not H-core main sequence stars, but helium core stars and the outcomes of binary evolution. We report the discovery of two new extremely-low mass white dwarfs among the sdAs to support this statement.

scholarly journals The discovery of low-mass pre-main-sequence stars in Cepheus OB3b

2003 ◽  
Vol 341 (3) ◽  
pp. 805-822 ◽  
Author(s):  
M. Pozzo ◽  
T. Naylor ◽  
R. D. Jeffries ◽  
J. E. Drew
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Low Mass
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