Search Publications
A spectral decomposition of the variable optical, ultraviolet and X-ray continuum of NGC 5548
Zdziarski, Andrzej A.; Smith, David A.; Johnson, W. Neil +2 more
We present an analysis and decomposition of the broad-band optical/UV/X-ray/gamma-ray spectrum of the Seyfert 1 galaxy NGC 5548. The spectrum consists of an average of simultaneous optical/IUE/Ginga observations accompanied by ROSATCGRO/OSSE data from non-simultaneous observations. We show that the overall optical/UV/X-ray/gamma-ray spectrum can b…
Quantitative spectroscopy of Wolf-Rayet stars in HD97950 and R136a - the cores of giant HII regions
Crowther, P. A.; Dessart, Luc
We present quantitative analyses of Wolf-Rayet stars in the cores of two giant Hii regions - HD97950 in NGC3603 and R136a in 30 Doradus - based on archive Hubble Space Telescope (HST) spectroscopy. We confirm previous WN6h+abs classifications for components A1, B and C in HD97950, while classifications for R136a1-3 are revised from O3If^*/WN6 to W…
The EC 14026 stars - VIII. PG 1336-018: a pulsating sdB star in an HWVir-type eclipsing binary
O'Donoghue, D.; Kilkenny, D.; Lynas-Gray, A. E. +2 more
The sdB star PG 1336-018 is found to be a very short-period eclipsing binary system, remarkably similar to the previously unique system HW Vir. In addition, and unlike HW Vir, the sdB star in the PG 1336 system shows rapid oscillations of the type found in the recently discovered sdB pulsators, or EC 14026 stars. The orbital period, 0.101 0174 d, …
The equatorial disc of the Be star X Persei
Waters, L. B. F. M.; de Martino, D.; Boogert, A. C. A. +4 more
We study the long-term behaviour of the equatorial disc of the Be/X-ray binary X Persei (X Per), combining new low-resolution IUE spectra and IR photometry with UV, optical and IR observations collected from the literature. We find that the near-UV continuum level of X Per varies along with the optical brightness. From the UV observations, we also…
The EC 14026 stars - VII. PG 1605+072, a star with many pulsation modes
O'Donoghue, D.; Kilkenny, D.; Lynas-Gray, A. E. +3 more
We report the discovery of large-amplitude (~0.25 mag) pulsations in the bright (V=12.8) sdB star, PG 1605+072. The dominant period is 480s, but more than 20 periods were present on at least three separate occasions. Frequency analysis of the complete data set yields more than 30 periods. A few of these are harmonics or linear combinations of the …
On the rotation-activity correlation for active binary stars
Doyle, J. G.; Mitrou, C. K.; Gunn, A. G.
We present an investigation of rotation-activity correlations using International Ultraviolet Explorer (IUE) SWP measurements of the Civ emission line at 1550Angstroms for 72 active binary systems. We use a standard stellar evolution code to derive non-empirical Rossby numbers, R_0, for each star in our sample and compare the resulting Civ rotatio…
Long-term variability of the Be/X-ray binary A0535+26 - I. Optical and UV spectroscopy
Coe, M. J.; Steele, I. A.; Buckley, D. A. H. +11 more
The results of a 7-yr optical and UV spectroscopic study of the high-mass X-ray binary A0535+26 are presented. It was found that throughout the period of the observations the line profile of Hα showed considerable variability. A correlation between the equivalent width of Hα and both V-band magnitude and (B-V) colour excess was observed, albeit wi…
The EC14026 stars - VI. PG1047+003
O'Donoghue, D.; Kilkenny, D.; Lynas-Gray, A. E. +2 more
We report the discovery of rapid oscillations in the sdB star PG1047+003. The oscillations are multiperiodic, with nine periods in the range 104-162s. The optical spectrum of PG1047+003 is consistent with that of a single sdB star. Line profile fitting yields an effective temperature of 35000+/-1000K and log g=5.9+/-0.1, although optical photometr…
Time-dependent structure in ultraviolet absorption lines of the rapid rotators HD 64760 (B0Ib) and HD 93521 (O9.5V)
Massa, D.; Prinja, R. K.; Howarth, Ian D. +5 more
Cross-correlation provides an effective line-averaging function for spectra containing many line features, a result which can be exploited in order to perform time-series and spatial-domain analyses of absorption-line variability in data of (relatively) poor quality. We apply this method to high-resolution IUE spectra. For the known non-radial pul…
A multiwavelength study of the early evolution of the classical nova LMC 1988 1
Sonneborn, G.; Baron, E.; Hauschildt, Peter H. +3 more
LMC 1988 1 was a moderately fast, CO, dust-forming classical nova. It was observed extensively in many different wavelength regions during its early evolution. The UV, optical and infrared light curves of LMC 1988 1 are very similar to those of the Galactic Nova V1668 Cyg 1978. As in V1668 Cyg, LMC 1988 1 showed the presence of an optically thin d…