scholarly journals Multiplicity in 5 M⊙ stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 537-538
Author(s):  
Nancy Remage Evans
Keyword(s):  
Main Sequence ◽  
Mass Ratio ◽  
Subsequent Evolution ◽  
B Stars ◽  
X Ray ◽  
Triple Systems ◽  
High Fraction ◽  
Low Mass ◽  
M Stars ◽  
The Masses

AbstractBinary/multiple status can affect stars at all stages of their lifetimes: evolution onto the main sequence, properties on the main sequence, and subsequent evolution. 5 M⊙ stars have provided a wealth of information about the binary properties fairly massive stars. The combination of cool evolved primaries and hot secondaries in Cepheids (geriatric B stars) have yielded detailed information about the distribution of mass ratios. and have also provided a surprisingly high fraction of triple systems. Ground-based radial velocity orbits combined with satellite data from Hubble, FUSE, IUE, and Chandra are needed to provide full information about the systems, including the masses. As a recent example, X-ray observations can identify low mass companions which are young enough to be physical companions. Typically binary status and properties (separation, eccentricity, mass ratio) determine whether any stage of evolution takes an exotic form.

scholarly journals X-Ray Emission from Distant Stellar Clusters

1998 ◽  
Vol 188 ◽  
pp. 220-221
Author(s):  
N.S. Schulz ◽  
J.H. Kastner
Keyword(s):  
Main Sequence ◽  
Sequence Evolution ◽  
Late Type ◽  
Low Mass Stars ◽  
Dwarf Stars ◽  
X Ray ◽  
T Tauri ◽  
Low Mass ◽  
M Stars ◽  
M Dwarf Stars

Observations with the Einstein Observatory indicated that stellar X-ray activity diminishes in clusters older than 70 Myr (Pleiades). ROSAT observations of older clusters also support this result (see Caillault 1995 and references therein). The timescales over which young stars diminish in X-ray luminosity depends on spectral type (Randich et al. 1996), leading to the conclusion that X-ray activity in late type PMS depends on age and stellar mass. F and G-stars approach the main sequence much faster and the diminishing rates of X-ray activity from F to M stars start to differ considerably. Kastner et al. (1997) observed that the mean of the ratio Lx/Lbol for K and M dwarf stars increases monotonically for low-mass stars from the very early T Tauri stage through the age of the Pleiades cluster, reflecting the contraction and spin-up of such stars during pre-main sequence evolution. This ratio then decreases towards middle aged stars, as late-type main sequence stars spin down. Here we extend this result by including more distant clusters that are younger overall than those considered by Kastner et al. and also including earlier spectral types.

scholarly journals The low-mass pre-main sequence population of Scorpius OB1

2018 ◽  
Vol 615 ◽  
pp. A148 ◽  
Author(s):  
Francesco Damiani
Keyword(s):  
Total Mass ◽  
Main Sequence ◽  
Near Infrared ◽  
Large Population ◽  
X Ray ◽  
Uv Excess ◽  
Low Mass ◽  
Ob Associations ◽  
The Rich ◽  
A New Technique

Context. The low-mass members of OB associations, expected to be a major component of their total population, are in most cases poorly studied because of the difficulty of selecting these faint stars in crowded sky regions. Our knowledge of many OB associations relies on only a relatively small number of massive members. Aims. We study here the Sco OB1 association, with the aim of a better characterization of its properties, such as global size and shape, member clusters and their morphology, age and formation history, and total mass. Methods. We use deep optical and near-infrared (NIR) photometry from the VPHAS+ and VVV surveys, over a wide area (2.6° × 2.6°), complemented by Spitzer infrared (IR) data, and Chandra and XMM-Newton X-ray data. A new technique is developed to find clusters of pre-main sequence M-type stars using suitable color-color diagrams, complementing existing selection techniques using narrow-band Hα photometry or NIR and ultraviolet (UV) excesses, and X-ray data. Results. We find a large population of approximately 4000 candidate low-mass Sco OB1 members whose spatial properties correlate well with those of Hα-emission, NIR-excess, UV-excess, and X-ray detected members, and unresolved X-ray emission. The low-mass population is spread among several interconnected subgroups: they coincide with the HII regions G345.45+1.50 and IC4628, and the rich clusters NGC 6231 and Trumpler 24, with an additional subcluster intermediate between these two. The total mass of Sco OB1 is estimated to be ~ 8500 M⊙. Indication of a sequence of star-formation events is found, from South (NGC 6231) to North (G345.45+1.50). We suggest that the diluted appearance of Trumpler 24 indicates that the cluster is now dissolving into the field, and that tidal stripping by NGC 6231 nearby contributes to the process.

scholarly journals V479 And: CV, LMXB, or Symbiotic?

2011 ◽  
Vol 7 (S281) ◽  
pp. 113-116
Author(s):  
Diego González Buitrago ◽  
Gagik Tovmassian ◽  
Juan Echevarría ◽  
Sergey Zharikov ◽  
Takamitsu Miyaji ◽  
...  
Keyword(s):  
Orbital Period ◽  
Main Sequence ◽  
Compact Object ◽  
Close Binary System ◽  
Close Binary ◽  
Stellar Winds ◽  
Primary Star ◽  
Giant Star ◽  
X Ray ◽  
Low Mass

AbstractV479 And is a 14.26 hour, close binary system, comprised of a G8-K0 star departing from the main sequence and a compact primary star accreting matter from the donor. The object is an X-ray source, modulated with the orbital period. This, and the presence of an intense He II line, leads us to speculate that the compact object is a magnetic white dwarf. However, we do not find strong constraints on the upper mass limit of the compact object, and we may have a neutron star in a low mass X-ray binary instead of a cataclysmic variable. The orbital period is certainly too short for the donor star to be an evolved giant star, so classifying this object as a symbiotic binary may be a big stretch; however there is an evidence that the mass transfer occurs via stellar winds, rather than through the L1 point of Roche filling secondary, a phenomenon more common for symbiotic stars.

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 HST-FGS Astrometry of the Low Mass Binary L722-22

1999 ◽  
Vol 172 ◽  
pp. 405-407
Author(s):  
L.G. Taff ◽  
John L. Hershey
Keyword(s):  
Main Sequence ◽  
Hubble Space Telescope ◽  
Brown Dwarf ◽  
One Dimensional ◽  
Photographic Images ◽  
System A ◽  
Data Points ◽  
Low Mass ◽  
The Masses ◽  
M Dwarf

The M dwarf L722-22 (= LHS 1047) was discovered to be a binary system by Ianna 20 years ago. The analysis of the ground- based data indicated a mass 0.06M⊙ for the secondary. This is below the nominal stellar mass limit of 0.08M⊙. The importance of potential “brown-dwarf” candidates, and the fact that the masses of both components place them near the end of the main sequence, made this system a prime object for further, intensive, study.This close (separation 0."3), faint (V = 11.m5, 14.m4) binary was near the limit for ground-based work. The residuals of an individual night’s photographic data were typically at the 50% level. Also, the photographic images are completely blended. The few one-dimensional speckle data points yielded a merged, asymmetric image profile. Finally, this system is too faint for HIPPARCOS. Our proposal for Hubble Space Telescope Fine Guidance Sensor (FGS) observing was approved in 1992.

scholarly journals X-ray Flare Rate of T Tauri Stars in Taurus

1995 ◽  
Vol 151 ◽  
pp. 216-217
Author(s):  
R. Neuhäuser ◽  
Th. Preibisch
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
T Tauri Stars ◽  
Medium Size ◽  
Late Type ◽  
Large Sample ◽  
X Ray ◽  
T Tauri ◽  
Sky Survey ◽  
Low Mass

AbstractWe study the X-ray emission of several hundred (young, low-mass, late-type, pre-main sequence) T Tauri stars (TTS) in the Taurus T association, a nearby well-studied region of ongoing star formation. We report on X-ray emission variability of TTS as observed with the flux-limited ROSAT All-Sky Survey (RASS). Since RASS observations are spatially unbiased, we can investigate the X-ray flare rate of TTS on a large sample. We find that large flares are very rare (once per year), while medium-size flares can occur once in ∼ 40 days.

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 Discovery of Three Very Low Mass Binary Systems: An Adaptive Optics Survey of M6.0–M7.5 Stars

2003 ◽  
Vol 211 ◽  
pp. 257-260
Author(s):  
Nick Siegler ◽  
Laird M. Close ◽  
Eric E. Mamajek ◽  
Melanie Freed
Keyword(s):  
Adaptive Optics ◽  
Binary Systems ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Solar Mass ◽  
Low Mass ◽  
M Stars ◽  
Adaptive Optics System

We have used the adaptive optics system Hōkūpa'a at Gemini North to search for companions from a flux-limited (Ks > 12) survey of 30 nearby M6.0–M7.5 dwarfs. Our observations, which are sensitive to companions with separations > 0.1″ (~ 2.8 AU), detect 3 new binary systems. This implies an overall binary fraction of 9±4% for M6.0–M7.5 binaries. This binary frequency is somewhat less than the 19±7% measured for late M stars and ~ 20% for L stars, but is still statistically consistent. However, the result is significantly lower than the binary fractions observed amongst solar mass main sequence stars (~60%) and early M stars (~35%).

scholarly journals A LOW-MASS MAIN-SEQUENCE STAR AND ACCRETION DISK IN THE VERY FAINT X-RAY TRANSIENT M15 X-3

2015 ◽  
Vol 807 (1) ◽  
pp. 52 ◽  
Author(s):  
R. M. Arnason ◽  
G. R. Sivakoff ◽  
C. O. Heinke ◽  
H. N. Cohn ◽  
P. M. Lugger
Keyword(s):  
Accretion Disk ◽  
Main Sequence ◽  
Main Sequence Star ◽  
X Ray ◽  
Low Mass
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