Search Publications
Early magnetic B-type stars: X-ray emission and wind properties
Hamann, W. -R.; Oskinova, L. M.; Ignace, R. +3 more
We present a comprehensive study of X-ray emission by, and wind properties of, massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three early-type B-type stars, ξ1 CMa, V2052 Oph and ζ Cas, with recently discovered magnetic fields. We report the first detection of X-ray emission from V2052 Oph and ζ…
The winds of hydrogen-rich central stars of planetary nebulae
Bianchi, L.; Herald, J. E.
We have modelled far-UV, UV and optical spectra of a sample of 10 hydrogen-rich central stars of planetary nebulae (CSPN) using stellar atmosphere codes to derive their photospheric and wind parameters. The resulting stellar temperatures range from 40 to 120 kK, well spanning the CSPN evolutionary phase and allowing certain trends to be discerned.…
The basal chromospheric Mg II h+k flux of evolved stars: probing the energy dissipation of giant chromospheres
Pérez Martínez, M. Isabel; Schröder, K. -P.; Cuntz, M.
Of a total of 177 cool G, K and M giants and supergiants, we measured the Mg II h+k line emission of extended chromospheres in high-resolution (LWR) International Ultraviolet Explorer (IUE) spectra by using the IUE final data archive at the Space Telescope Science Institute (STScI) and derived the respective stellar surface fluxes. They represent …
Discovery of the first τ Sco analogues: HD 66665 and HD 63425
Wade, G. A.; Ignace, R.; Marcolino, W. L. F. +3 more
The B0.2 V magnetic star τ Sco stands out from the larger population of massive OB stars due to its high X-ray activity, peculiar wind diagnostics and highly complex magnetic field. This Letter presents the discovery of the first two τ Sco analogues - HD 66665 and HD 63425, identified by the striking similarity of their ultraviolet (UV) spectra to…
Pulsations in the atmosphere of the rapidly oscillating star 33 Lib
Shulyak, D.; Ryabchikova, T.; Hareter, M. +4 more
In 2009, the rapidly oscillating peculiar A-type (roAp) star 33 Lib was the target of an intense observing campaign, combining ground-based spectroscopy with space photometry obtained with the Microvariability and Oscillation of STars (MOST) satellite. We collected 780 spectra using the Echelle Spectro Polarimetric Device for the Observation of St…
XMM-Newton first X-ray detection of the low-ionization broad absorption line quasar PG 1700+518
Vignali, C.; Schartel, N.; Ballo, L. +1 more
We report the first high-energy detection of PG 1700+518, a well-known low-ionization broad absorption line quasar (quasi-stellar object, QSO). Due to previous X-ray non-detection, it was classified as soft X-ray weak QSO. We observed PG 1700+518 with XMM-Newton for about 60 ks divided in three exposures. The spectrum below 2 keV is very steep, Γ∼…
Period switching in the symbiotic star BX Mon
Formiggini, Liliana; Leibowitz, Elia M.
We report on a detailed analysis of the optical light curve (LC) of the symbiotic system BX Mon, the data of which were gathered from the literature. The LC covers the period from 1889 December to 2009 March, with a gap of no observations between 1940 March and 1972 February. The LC is characterized by strong oscillations of peak-to-peak amplitude…
Simple stellar population models including blue stragglers
Deng, Licai; de Grijs, Richard; Kroupa, Pavel +1 more
Observations show that nearly all star clusters and stellar populations contain blue straggler stars (BSs). BSs in a cluster can significantly enhance the integrated spectrum of the host population, preferentially at short wavelengths, and render it much bluer in photometric colours. Current theoretical simple stellar population (SSP) models const…