Secondary stars in CVs: the theoretical perspective

Kolb, U.; Baraffe, I.

doi:10.1016/s1387-6473(00)00021-x

Cited by 17 publications

(28 citation statements)

References 22 publications

(18 reference statements)

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“…Silber et al (1994) found that the optical spectrum of V2301 Oph taken at mid‐eclipse was most similar to an M6 V spectral type. Based on the theoretical models of Kolb & Baraffe (2000), such a spectral type implies a secondary star mass, M 2 = 0.10 M ⊙ . The same models also predict the spectral type of the secondary star as a function of orbital period.…”

Section: The Light Curvesmentioning

confidence: 88%

“…The same models also predict the spectral type of the secondary star as a function of orbital period. For an orbital period appropriate to V2301 Oph (113 min) the models predict a secondary of spectral type of ∼M4.5 (Baraffe & Kolb 2000), which implies M 2 = 0.15 M ⊙ (Kolb & Baraffe 2000). For M 2 = 0.10 and 0.15 M ⊙ and q = 0.15 (Reynolds et al 2005), this implies M 1 = 0.67 and 1.0 M ⊙ , respectively.…”

Section: The Light Curvesmentioning

confidence: 98%

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XMM-Newton observations of the eclipsing polar V2301 Oph

Ramsay

Cropper

2007

Monthly Notices of the Royal Astronomical Society

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We present XMM-Newton observations of the eclipsing polar V2301 Oph which cover nearly 2.5 binary orbital cycles and 2 eclipses. This polar is believed to have the lowest magnetic field strength (7 MG) of any known polar. We find evidence for structure in the X-ray eclipse profile which shows a `standstill' feature lasting 26+/-4 sec. This allows us to place an upper limit on the mass of the white dwarf of ~1.2 Msun. We find no evidence for QPOs in the frequency range 0.02-10 Hz. This coupled with the absence of QPOs in RXTE data suggest that, if present, any oscillations in the shock front have a minimal effect on the resultant X-ray flux. We find no evidence for a distinct soft X-ray component in its spectrum - it therefore joins another 7 systems which do not show this component. We suggest that those systems which are asynchronous, have low mass transfer rates, or have accretion occurring over a relatively large fraction of the white dwarf are more likely to show this effect. We find that the specific mass transfer rate has to be close to 0.1 g cm^-2 s^-1 to predict masses which are consistent with that derived from our eclipse analysis. This maybe due to the fact that the low magnetic field strength allows accretion to take place along a wide range of azimuth.Comment: Accepted MNRA

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Section: The Light Curvesmentioning

confidence: 88%

Section: The Light Curvesmentioning

confidence: 98%

XMM-Newton observations of the eclipsing polar V2301 Oph

Ramsay

Cropper

2007

Monthly Notices of the Royal Astronomical Society

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“…In the case of an X-ray heated star, the radius can be increased by a factor as large as two (Hameury et al 1993), while an evolved main sequence star scenario also implies a significantly larger stellar radius (Kolb & Baraffe 2000) (see our cautionary statement in Sect. 3.4).…”

Section: The Radius Of the Secondarymentioning

confidence: 99%

Determination of the basic parameters of the dwarf nova EY Cygni

Echevarría¹,

Michel²,

Costero³

et al. 2006

A&A

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Context. High-dispersion spectroscopy of EY Cyg obtained from data spanning twelve years show, for the first time, the radial velocity curves from both emission and absorption line systems, yielding semi-amplitudes K em = 24 ± 4 km s −1 and K abs = 54 ± 2 km s −1 . The orbital period of this system is found to be 0.4593249(1) d. The masses of the stars, their mass ratio and their separation are found to be M 1 sinand a sin i = 0.71 ± 0.04 R . We also found that the spectral type of the secondary star is around K0, consistent with an early determination by Kraft (1962). Aims. From the spectral type of the secondary star and simple comparisons with single main sequence stars, we conclude that the radius of the secondary star is about 30 per cent larger than a main sequence star of the same mass. Methods. We also present VRI CCD photometric observations, some of them simultaneous with the spectroscopic runs. The photometric data shows several light modulations, including a sinusoidal behaviour with twice the frequency of the orbital period, characteristic of the modulation coming from an elongated, irradiated secondary star. Low and high states during quiescence are also detected and discussed. Results. From several constrains, we obtain tight limits for the inclination angle of the binary system between 13 and 15 degrees, with a best value of 14 degrees obtained from the sinusoidal light curve analysis. Conclusions. From the above results we derive masses M 1 = 1.10 ± 0.09 M , M 2 = 0.49 ± 0.09 M , and a binary separation a = 2.9 ± 0.1 R .

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“…These two relations, using the improved orbital period, give M 2 = 1.14 M ⊙ and M 2 = 1.07 M ⊙ , respectively. The spectral types labelled on the left‐hand side of the diagram correspond to the zero‐age main sequence (ZAMS) stellar models discussed by Kolb & Baraffe (2000), while those shown on the right‐hand side correspond to evolved stars that are still within the main‐sequence band (see Kolb & Baraffe 2000 for detailed explanations). Points in the white area are then within these limits as we expect that the primary star will not exceed the Chandrasekhar limit, and that the secondary star will not be on the MS (Echevarría 1983; Beuermann et al 1998).…”

Section: The M1–m2 Diagrammentioning

confidence: 99%

High-dispersion absorption-line spectroscopy of AE Aqr

Echevarría

Smith

Costero

et al. 2008

Monthly Notices of the Royal Astronomical Society

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High‐dispersion time‐resolved spectroscopy of the unique magnetic cataclysmic variable AE Aqr is presented. A radial velocity analysis of the absorption lines yields K2= 168.7 ± 1 km s−1. Substantial deviations of the radial velocity curve from a sinusoid are interpreted in terms of intensity variations over the secondary star's surface. A complex rotational velocity curve as a function of orbital phase is detected which has a modulation frequency of twice the orbital frequency, leading to an estimate of the binary inclination angle that is close to 70°. The minimum and maximum rotational velocities are used to indirectly derive a mass ratio of q= 0.6 and a radial velocity semi‐amplitude of the white dwarf of K1= 101 ± 3 km s−1. We present an atmospheric temperature indicator, based on the absorption‐line ratio of Fe i and Cr i lines, whose variation indicates that the secondary star varies from K0 to K4 as a function of orbital phase. The ephemeris of the system has been revised, using more than 1000 radial velocity measurements, published over nearly five decades. From the derived radial velocity semi‐amplitudes and the estimated inclination angle, we calculate that the masses of the stars are M1= 0.63 ± 0.05 M⊙; M2= 0.37 ± 0.04 M⊙, and their separation is a= 2.33 ± 0.02 R⊙. Our analysis indicates the presence of a late‐type star whose radius is larger, by a factor of nearly 2, than the radius of a normal main‐sequence star of the same mass. Finally, we discuss the possibility that the measured variations in the rotational velocity, temperature and spectral type of the secondary star as functions of orbital phase may, like the radial velocity variations, be attributable to regions of enhanced absorption on the star's surface.

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Secondary stars in CVs: the theoretical perspective

Cited by 17 publications

References 22 publications

XMM-Newton observations of the eclipsing polar V2301 Oph

XMM-Newton observations of the eclipsing polar V2301 Oph

Determination of the basic parameters of the dwarf nova EY Cygni

High-dispersion absorption-line spectroscopy of AE Aqr

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