THE CHROMOSPHERIC ACTIVITY OF [HH97] FS Aur-79: A CLOSE BINARY WITH LATE-TYPE ACTIVE (dK7e+dM3e) COMPONENTS

The 4 known AM Her stars or polars (AM Her, ANUMa, W Pup, and 2A0311-227) are characterized by large circular polarizations of 10-35%, (Tapia 1977a, b, Krzeminski and Serkowski 1977), an emission line spectrum with strong H and He lines (Crampton and Cowley 1977, Greenstein et al. 1977), complex photometric variations (Szkody 1978, Priedhorsky and Krzeminski 1978, Warner & Nather 1972), long term high and low states and short orbital periods (80-180 min.). Models of these systems envision a close binary containing a magnetic white dwarf primary (B ~ 108G) and late type main sequence secondary transferring material into an accretion funnel over one or both poles of the white dwarf (Stockman et al. 1977, Lamb & Masters 1979, Liebert et al. 1978).

Download Full-text

Eclipse mapping of late-type close binary stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/287.3.556 ◽

1997 ◽

Vol 287 (3) ◽

pp. 556-566 ◽

Cited By ~ 48

Author(s):

A. C. Cameron

Keyword(s):

Binary Stars ◽

Close Binary ◽

Late Type ◽

Close Binary Stars

Download Full-text

12 years of stellar activity observations in Argentina

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312005029 ◽

2011 ◽

Vol 7 (S286) ◽

pp. 317-323 ◽

Cited By ~ 1

Author(s):

P. J. D. Mauas ◽

A. Buccino ◽

R. Díaz ◽

M. Vieytes ◽

R. Petrucci ◽

...

Keyword(s):

Spectral Range ◽

Conversion Factor ◽

Activity Levels ◽

Late Type ◽

Cyclic Activity ◽

Chromospheric Activity ◽

Activity Measurements ◽

Radiative Losses ◽

Hydrogen Lines ◽

Observational Program

AbstractWe present an observational program we started in 1999, to systematically obtain mid-resolution spectra of late-type stars, to study in particular chromospheric activity. In particular, we found cyclic activity in four dM stars, including Prox-Cen. We directly derived the conversion factor that translates the known S index to flux in the Ca II cores, and extend its calibration to a wider spectral range. We investigated the relation between the activity measurements in the calcium and hydrogen lines, and found that the usual correlation observed is the product of the dependence of each flux on stellar color, and it is not always preserved when simultaneous observations of a particular star are considered. We also used our observations to model the chromospheres of stars of different spectral types and activity levels, and found that the integrated chromospheric radiative losses, normalized to the surface luminosity, show a unique trend for G and K dwarfs when plotted against the S index.

Download Full-text

Analysis of 11 late-type close binary systems

Astrophysics and Space Science ◽

10.1007/bf00650265 ◽

1984 ◽

Vol 99 (1-2) ◽

pp. 411-411

Author(s):

K. C. Leung ◽

D. S. Zhai ◽

R. X. Zhang ◽

Q. Y. Liu ◽

J. T. Zhang ◽

...

Keyword(s):

Binary Systems ◽

Close Binary ◽

Late Type ◽

Close Binary Systems

Download Full-text

Lithium Depletion in Late-Type Stars Through Wind-Driven Mixing

Highlights of Astronomy ◽

10.1017/s1539299600011758 ◽

1995 ◽

Vol 10 ◽

pp. 461-462 ◽

Cited By ~ 1

Author(s):

J.-P. Zahn

Keyword(s):

Binary Stars ◽

Causal Link ◽

Close Binary ◽

Late Type ◽

Lithium Abundance ◽

Convective Envelope ◽

Halo Stars ◽

Close Binary Stars ◽

Nuclear Burning ◽

Lithium Depletion

A well established property of late-type stars is that their rotation rate and their lithium abundance both decline with age. We understand why such stars are spun down while losing so little mass (Schatzman 1962), but we are still working on a theory which would explain all aspects of the observed lithium depletion. Although most agree that some kind of mixing must occur below the convective envelope of late-type stars, which transports 7Li to the depth where it is destroyed through nuclear burning, the physical process which is responsible for this transport is still in debate. However the most recent observations of the lithium abundance in close binary stars clearly show that there is a causal link between the destruction of lithium and the loss of angular momentum: consistently, tidally-locked binaries tend to display more lithium than single stars of the same effective temperature, as observed in the Hyades (Soderblom et al. 1990, Thorburn et al. 1993) and among old disk stars and halo stars (Spite et al. 1994).

Download Full-text

Metallicity effects on the chromospheric activity-age relation for late-type dwarfs

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.1998.01597.x ◽

1998 ◽

Vol 298 (2) ◽

pp. 332-346 ◽

Cited By ~ 68

Author(s):

H. J. Rocha-Pinto ◽

W. J. Maciel

Keyword(s):

Late Type ◽

Chromospheric Activity ◽

Age Relation

Download Full-text

Analysis of 11 Late-Type Close Binary Systems

International Astronomical Union Colloquium ◽

10.1017/s025292110008876x ◽

1984 ◽

Vol 80 ◽

pp. 411-411

Author(s):

K. C. Lfung ◽

D. S. Zhai ◽

R. X. Zhang ◽

Q. Y. Liu ◽

J. T. Zhang ◽

...

Keyword(s):

United States ◽

Preliminary Report ◽

Binary Systems ◽

Computational Analysis ◽

The United States ◽

Close Binary ◽

Late Type ◽

Joint Research ◽

Joint Research Project ◽

University Of Nebraska Lincoln

AbstractThis is a preliminary report on the joint research project between 3 observatories: Beijing, Yunnan, and Behlen Observatories from China and the United States. The systems we have been dealing with are primary of late spectral types and with short periods. Most.of the observations were secured from the observatories in China. The computational analysis is carried out in University of Nebraska, Lincoln. The photometric solutions are based on the Wilson and Devinney method. Out of 11 systems analyzed 6 of them: AO Cam. ER Ori. BX Peg, BB Peg, U Peg, and SW Lac are found to be contact systems. All of them are having their primary eclipses at occultation. Therefore they can be classified as W-type WUMa systems. They also show other W-type characteristics.

Download Full-text