Revealing the Nature of Algol Disks through Optical and UV Spectroscopy, Synthetic Spectra, and Tomography of TT Hydrae

We have developed a systematic procedure to study the disks in Algol-type binaries using spectroscopic analysis, synthetic spectra, and tomography. We analyzed 119 H-alpha spectra of TT Hya, an Algol-type eclipsing interacting binary, collected from 1985-2001. The new radial velocities enabled us to derive reliable orbital elements, including a small non-zero eccentricity, and to improve the accuracy of the absolute dimensions of the system. High resolution IUE spectra were also analyzed to study the formation of the ultraviolet lines and continuum. Synthetic spectra of the iron curtain using our new shellspec program enabled us to derive a characteristic disk temperature of 7000K. We have demonstrated that the UV emission lines seen during total primary eclipse cannot originate from the accretion disk, but most likely arise from a hotter disk-stream interaction region. The synthetic spectra of the stars, disk, and stream allowed us to derive a lower limit to the mass transfer rate of 2e-10 solar masses per year. Doppler tomography of the observed H-alpha profiles revealed a distinct accretion disk. The difference spectra produced by subtracting the synthetic spectra of the stars resulted in an image of the disk, which virtually disappeared once the composite synthetic spectra of the stars and disk were used to calculate the difference spectra. An intensity enhancement of the resulting tomogram revealed images of the gas stream and an emission arc. We successfully modeled the gas stream using shellspec and associated the emission arc with an asymmetry in the accretion disk.Comment: 46 pages, 15 figures, 6 tables, accepted by Ap

Optical photometry and X-ray monitoring of the "Cool Algol" BD+05 706: Determination of the physical properties

We present new photometric observations in the BVRI bands of the double-lined eclipsing binary BD+05 706 conducted over three observing seasons, as well as new X-ray observations obtained with the ROSAT satellite covering a full orbital cycle (P = 18.9 days). A detailed light-curve analysis of the optical data shows the system to be semidetached, confirming indications from an earlier analysis by Torres et al. (1998), with the less massive and cooler star filling its Roche lobe. The system is a member of the rare class of cool Algol systems, which are different from the "classical" Algol systems in that the mass-gaining component is also a late-type star rather than a B- or A-type star. By combining the new photometry with a reanalysis of the spectroscopic observations reported by Torres et al. (1998) we derive accurate absolute masses for the components of M1 = 2.633 +/- 0.028 Msun and M2 = 0.5412 +/- 0.0093 Msun, radii of R1 = 7.55 +/- 0.20 Rsun and R2 = 11.02 +/- 0.21 Rsun, as well as effective temperatures of 5000 +/- 100 K and 4640 +/- 150 K for the primary and secondary, respectively. There are obvious signs of activity (spottedness) in the optical light curve of the binary. Our X-ray light curve clearly shows the primary eclipse but not the secondary eclipse, suggesting that the primary star is the dominant source of the activity in the system. The depth and duration of the eclipse allow us to infer some of the properties of the X-ray emitting region around that star.Comment: 38 pages including 8 figures and 11 tables. To appear in The Astronomical Journal, June 200

CoRoT photometry and high-resolution spectroscopy of the interacting eclipsing binary AU Mon

Analyses of very accurate CoRoT space photometry, past Johnson V photoelectric photometry and high-resolution \'echelle spectra led to the determination of improved and consistent fundamental stellar properties of both components of AU Mon. We derived new, accurate ephemerides for both the orbital motion (with a period of 11.113d) and the long-term, overall brightness variation (with a period of 416.9d) of this strongly interacting Be + G semi-detached binary. It is shown that this long-term variation must be due to attenuation of the total light by some variable circumbinary material. We derived the binary mass ratio $M_{\rm G}/M_{\rm B}$ = 0.17\p0.03 based on the assumption that the G-type secondary fills its Roche lobe and rotates synchronously. Using this value of the mass ratio as well as the radial velocities of the G-star, we obtained a consistent light curve model and improved estimates of the stellar masses, radii, luminosities and effective temperatures. We demonstrate that the observed lines of the B-type primary may not be of photospheric origin. We also discover rapid and periodic light changes visible in the high-quality residual CoRoT light curves. AU Mon is put into perspective by a comparison with known binaries exhibiting long-term cyclic light changes.Comment: Accepted for publication in MNRA

The most plausible explanation of the cyclical period changes in close binaries: the case of the RS CVn-type binary WW Dra

We searched the orbital period changes in 182 EA-type (including the 101 Algol systems used by \cite{hal89}), 43 EB-type and 53 EW-type binaries with known both the mass ratio and the spectral type of their secondary components. We reproduced and improved the same diagram as Hall's (1989) according to the new collected data. Our plots do not support the conclusion derived by \cite{hal89} that all cases of cyclical period changes are restricted to binaries having the secondary component with spectral types later than F5. The presence of period changes also among stars with secondary component of early type indicates that the magnetic activity is one cause, but not the only one, for the period variation. It is discovered that cyclic period changes, likely due to the presence of a third body are more frequent in EW-type binaries among close binaries. Therefore, the most plausible explanation of the cyclical period changes is the LTTE via the presence of a third body. By using the century-long historical record of the times of light minimum, we analyzed the cyclical period change in the Algol binary WW Dra. It is found that the orbital period of the binary shows a $\sim112.2 \textbf{\textrm{yr}}$ cyclic variation with an amplitude of $\sim0.1977\textbf{\textrm{days}}$. The cyclic oscillation can be attributed to the LTTE via a third body with a mass no less than $6.43 M_{\odot}$. However, no spectral lines of the third body were discovered indicating that it may be a candidate black hole. The third body is orbiting the binary at a distance shorter than 14.4 AU and it may play an important role in the evolution of this system.Comment: 9 pages, 5 figures, published by MNRA

AU Monocerotis–improved elements

From an analysis, using Wilson-Devinney method, of the corrected yellow light curve of the semi detached eclipsing binary system AU Monocerotis (AU Mon), obtained by Lorenzi (1980b), an improved value for the mass ratio, q, equal to 0.1985 and reliable geometrical elements were derived.They give the absolute elements as: ${m_{\rm h}/m_\odot}\rm=5.93\pm0.31$; ${m_{\rm c}/m_\odot}=\rm1.18\pm0.16$; $R_{\rm h}/R_\odot=5.28\pm0.16$; $R_{\rm c}/R_\odot=10.04\pm0.74$; ${\rm Log}\ L_{\rm h}/L_\odot=3.16\pm0.14$; ${\rm Log}\ L_{\rm c}/L_\odot=2.07\pm0.21$; ${\rm Log}\ g_{\rm h}=3.76\pm0.06$; and ${\rm Log}\ g_{\rm c}=2.51\pm0.02$. When compared to main sequence stars of similar mass, the primary is found to have normal luminosity, bigger size and lower temperature while the secondary is found to have higher luminosity, bigger size and normal temperature for their masses. On the HR diagram of the normal main sequence stars, the primary is found to lie near but above the main sequence (brighter by 1\hbox{.\!\!^{\rm m}}4). The secondary component is far above the main sequence and is overluminous by about 4\hbox{.\!\!^{\rm m}}5

A rediscussion on the eclipsing binary YY Canis Minoris

We have reanalysed the UBV light curves of [Abhyankar (1962b)] using the 1993 version of Wilson-Devinney computer programme with a view to derive a consistent solution in all the three passbands and to answer the discordant opinions on the general picture of YY CMi. Initially, a preliminary unspotted solution was obtained and a photometric mass ratio was derived. From the present analysis, we obtained a mass ratio of $q=0.89$ which differs from the mass ratio of 0.8 derived by [Giuricin & Mardirossian (1981)] and 0.65 derived by [Abhyankar (1962b)] but agrees with the value of 0.885 derived by [Niarchos et al. (1998)]. Finally, the light curves were modelled by introducing a spot on the cooler secondary component to represent the observed light curve asymmetries. Assuming the mass of the primary component to be $1.56\ m_\odot$(F1V), the absolute elements of YY CMi are found to be $m_{\rm c}=1.39\ m_\odot$, $R_{\rm h}=2.52\ R_\odot$, $R_{\rm c}=2.38\ R_\odot$, ${\rm Log}\ L_{\rm h}=1.13\ L_\odot$, ${\rm Log}\ L_{\rm c}=0.86\ L_\odot$, ${\rm Log}\ g_{\rm h}=3.83$ and ${\rm Log} g_{\rm c}=3.83$. The primary and secondary components are found to be slightly overluminous and bigger in size when compared to stars of the same mass. In the H-R diagram ($\log\ T_{\rm e}$ versus $\log\ L$, ZAMS), both the components are above but near the ZAMS suggesting that both of them have left the main sequence and have come into contact. Our results essentially agree with those of [Niarchos et al. (1998)] based on V passband only

Photometric observations of the RS CVn binary σ Cr.B

This article does not have an abstract

Photometry of HD 23838

This article does not have an abstract