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A Time of Minimum and Rotational Velocity for TT Hydrae
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| The nature of TT Hydrae
Photometric solutions are made of previously published photoelectriclight curves of TT Hydrae. The WINK model is employed to give radii ofrA = 0.0894 and rB = 0.2431, and an orbitalinclination of i = 84.4 deg. Spectrophotometry is presented and analyzedto give revised spectral types of B9.5 V and phase-variable G9 to K1III-IV, and temperatures of TA = 9800K and TB =4850 - 4670K. There is anomalous photometric behavior indicative ofcircumstellar material surrounding the primary component. Thenear-ultraviolet excess seen during totality is verified byspectrophotometry, and found to extend to ?4200 Å.Photospheric features of Si II, Mg II, and He I are consistent with aB9.5 V classification for the hotter star, and give a v sin i of 168 kms-1. The metallic-line spectrum (similar to an A2) and sharphydrogen-line cores, both associated with the hotter star, arise almosttotally from circumstellar material. The mass ratio is combined with apreliminary spectroscopic orbit for the cooler star to derive thecomponent properties: MA = 2.25 M_sun;, MB = 0.41M_sun;, RA = 1.90 R_sun;, and RB = 5.17 R_sun; Theradiative properties imply that the system is 193 pc distant.
| Absolute dimensions of TT Hydrae
The photometric elements of the Algol type binary TT Hydrae derived fromUBV observations during 1973-77 (Kulkarni and Abhyankar, 1978) have beencombined with the spectroscopic elements given by Sanford (1937) andSahade and Cesco (1946) to obtain the absolute dimensions of the system.It is found that the spectroscopic orbital elements given by Sanfordrepresent the evolutionary status of the secondary component better thanthose of Sahade and Cesco. The primary appears to be an Al V mainsequence star of mass approximately 3 to 4 solar masses and radiusapproximately 2.3 solar radii. The secondary fills its Roche lobe; itcan be represented by a K0 III star of mass approximately 0.8 solar massand radius approximately 6.0 solar radii. Better spectroscopic data areneeded for confirmation of these results.
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