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Kuhi, L. V.

Publications and source records attributed to Kuhi, L. V..

4 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

X-ray photometry and spectroscopy of T Tauri stars

Follow-up Einstein X-ray observations of four fields containing pre-main-sequence stars are presented. A search has been made for evidence of variability on time scales of hours and of 1 year. A large, slow flare in AS 205, and the X-ray disappearance of AA Tau are reported. Otherwise, T Tauri stars appear no more variable in X-rays than do active solar-like stars. An attempt has been made to determine spectral parameters for a number of the brighter sources. X-ray absorption column densities are consistent with those inferred from A(v), and T(x) of about 10-million K, in all cases. The importance of these observations for models of T Tauri stars and their coronae is considered.

Walter, F. M.↗
NASA NTRS1981

The smothered coronae of T Tauri stars

Einstein IPC observations of 10 fields containing pre-main-sequence stars are presented. The detection of significant soft X-ray flux from eight cataloged T Tauri stars plus the optical identification of two new T Tauri-like stars associated with X-ray sources are reported. It is demonstrated than an inverse correlation between the H-alpha equivalent width and the detection of X-ray flux exists. This is interpreted in terms of a model wherein the X-ray emission arises in a corona similar to that of active late-type stars, which is small compared to the extent of the circumstellar envelope. It is postulated that the lack of correlation of X-ray flux (or H-alpha) with A(v) is due to a lack of grains in the envelopes of the more active T Tauri stars.

Walter, F. M.↗
NASA NTRS1981

Continuing changes in the peculiar nebulous object PV Cephei

Changes in the nebular structure, optical spectrum and stellar brightness of the faint star PV Cephei and the nebulosity associated with it are discussed. Iris photometry of the starlike object at the tip of the fan-shaped nebula reveals irregular variability of approximately 4 magnitudes in the red. Stellar spectra in the region 4300-6750 A taken from December 1976 to April 1980 are similar to the richest emission line spectra of T Tauri stars, while nebular spectra indicate a lack of spherical symmetry. Observations obtained in the infrared reveal a source offset by a few arcsec from the apex of the fan, which is identified with the illuminating star. Radial velocities of CO emission indicate that PV Cep is at the same distance as NGC 7023, and independent estimates lead to an estimated value of 500 pc. Such a distance corresponds to a bolometric luminosity approximately 100 times that of the sun. It is suggested that PV Cep is a T Tauri star that has recently broken through its circumstellar cocoon at a time when highly erratic variability and a strong stellar wind characterize the star.

Cohen, M.↗