Search Publications
Near-simultaneous Ultraviolet and Optical Spectrophotometry of T Tauri Stars
Goodrich, Robert W.; Herbig, G. H.
A set of near-simultaneous ultraviolet and optical spectra and UBVR(J)I(J) photometry of five T Tauri stars has been analyzed for the shape of the energy distribution shortward of 3000 A. The far-ultraviolet continua of these stars are very much stronger than the level of light scattered from longer wavelengths in the IUE spectrograph. The results…
Activity in F Stars
Simon, Theodore; Boesgaard, Ann Merchant; Wolff, Sidney C.
Measurements of He I 5876 A and IUE measurements of chromospheric and transition region lines in a large sample of F-type stars are presented. The data show that activity is detectable in nearly all early F-type stars and differs in several of its characteristics from that typically seen in cooler stars with slow rotation and fully developed conve…
The Discovery of 3.9 Hour Periodic Dips in the X-Ray Intensity of XB 1254-690
Parmar, A. N.; Pakull, M.; Courvoisier, T. J. -L. +1 more
The low-mass X-ray binary XB 1254 - 690 has been discovered to show irregular dips in X-ray intensity that recur with a period of 3.9 hr consistent with the optical period derived independently. The spectral changes observed during dipping are complex and can be successfully described using a two-component model. One of these components may be X-r…
Simultaneous X-Ray and Infrared Observations of Cygnus X-3
White, N. E.; Mason, K. O.; Cordova, F. A.
Cygnus X-3 has been observed simultaneously in the X-ray and infrared spectral bands. A series of short flares were detected in the infrared. The most intense of these involve a doubling of the 2.2 micron flux. No counterparts of the flares were unequivocably detected in the X-ray band; the ratio of the flare energy emitted in the 1.5-10.0 keV and…
The Evolution of the 1984 Outburst of the Transient X-Ray Source 4U 1630-47
Stella, L.; Parmar, A. N.; White, N. E.
The results of a series of EXOSAT observations of the X-ray transient 4U 1630 - 47 during an outburst in 1984 are presented. The source decayed over an interval of about 100 days from a maximum 1-50 keV luminosity of about 2.8 x 10 to the 38th to about 4 x 10 to the 36th erg/s (for an assumed distance of 10 kpc). The 1-50 keV spectrum was best rep…
Observation of the Onset of an Emission Episode in the Be Star MU Centauri
Peters, G. J.
A series of recent CCD observations which shows the rapid development of Hα emission in the pulsating, transient Be star µ Cen in only 2 days and thus establishes a time scale for the physical changes in the photosphere that lead to the outburst, are presented. On 1985 March 25, Hα was in pure absorption in µ Cen but by 1985 March 27 a…
A 6 Second Periodic X-Ray Source in Carina
Charles, P. A.; Smale, A. P.; Seward, F. D.
A serendipitous source, 1E 1048.1-5937, was discovered during Einstein imaging observations of the Carina nebula. On July 13, 1979, this source had an intensity of 0.14 IPC counts/s, and the signal was 65 percent pulsed with a period of 6.44 s. An earlier observation failed to detect any source with strength greater than 1/10 the above signal. The…
The Ultraviolet Excess of Quasars. III. The Highly Polarized Quasars PKS 0736+017 and PKS 1510-089
Malkan, M. A.; Moore, R. L.
Ultraviolet/optical/infrared spectrophotometry of the highly-polarized quasars (HPQ's) PKS 0736 + 047 and PKS 1510 089 is analyzed. A blazer continuum component like that in BL Lac objects (e.g. with violent variability, high polarization, and a steep power-law shape) contributes about half the visual light of 1510 - 089, and at least three-quarte…
Identification of two southern X-ray emitting cataclysmic variables.
Buckley, D. A. H.; Schwartz, D. A.; Tuohy, I. R. +2 more
The optical identification of two faint HEAO 1 X-ray sources with previously uncataloged cataclysmic variables is reported. The two cataclysmic variables, 1H 0542 - 407 and H0534 - 581, have average V magnitudes of about 15.7 and about 14.9, and have similar high excitation spectra with moderate to strong He II 4686 A emission. X-ray measurements …
Simultaneous EXOSAT and IUE Observations of Fairall 9: Short and Long-Term Variability
Piro, L.; Perola, G. C.; Boksenberg, A. +11 more
Simultaneous observations of the Seyfert I galaxy Fairall 9 (F9) were performed with Exosat and IUE during October 1983 and 1984. A decrease in the flux of the source by more than a factor of 2 was observed at all wavelengths between the two epochs. Furthermore, in the X-ray (0.05-10-keV) band, variability of the order of 50 percent on a time scal…