Related papers: HETGS Spectroscopy of a Coronally Active Contact B…
Short-period binaries represent extreme cases in the generation of stellar coronae via a rotational dynamo. Such stars are important for probing the origin and nature of coronae in the regimes of rapid rotation and activity saturation. VW…
Spectroscopy with the Chandra High Energy Transmission Grating Spectrometer provides details on X-ray emission and activity from young and cool stars through resolution of emission lines from a variety of ions. We are beginning to see…
We present a detailed X-ray analysis and imaging of stellar coronae of five coronally connected eclipsing binaries, namely, 44 Boo, DV Psc, ER Vul, XY UMa, and TX Cnc. Both components of these binaries are found to be active. The X-ray…
Recent papers published in the last years contributed to resolve the enigma on the hypothetical Be nature of the hot pulsating star $\beta$ Cep. This star shows variable emission in the H$\alpha$ line, typical for Be stars, but its…
We have studied the coronal X-ray emission of the recently discovered short-period eclipsing binary HD 9770 with the BeppoSAX satellite. The data from the Low Energy and Medium Energy Concentrator Spectrometers (LECS & MECS) onboard…
A survey of 28 stars using EUV spectra has been conducted to establish the structure of stellar coronae in active binary systems from the EMD, electron densities, and scale sizes. Observations obtained by the EUVE during 9 years of…
Context. Despite the fact that VW Cephei is one of the well-studied contact binaries in the literature, there is no fully consistent model available that can explain every observed property of this system. Aims. Our motivation is to obtain…
EUVE satellite spectroscopic observations (SW, MW and LW bands covering 80 - 160, 170 - 350 and 450 A with resolutions 0.5, 1 and 2 A) and photometric observations (Deep Sky Survey, broad-band 70 - 140 A) have been obtained for two contact,…
Theta 1 Ori E is a young, moderate mass binary system, a rarely observed case of spectral-type G-giants of about 3 Solar masses, which are still collapsing towards the main sequence. We have obtained high resolution X-ray spectra with…
Ground-based optical photometry of the counterparts of High-Mass X-ray Binaries (HMXBs) has revealed the presence of periodic modulations on timescales of ~0.3-0.5 d. More recent space-based observations Corot and TESS of OB and Be stars…
The first photometric analysis of V811 Cep was carried out. The first complete light curves of V, R and I bands are given. The analysis was carried out by Wilson-Devinney (W-D) program, and the results show that V811 Cep is a median-contact…
We observed the coronally active eclipsing binary, AR Lac, with the High Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV spectra and…
The Chandra X-ray observatory monitored the single cool star, AB Doradus, continuously for a period lasting 88ksec (1.98 Prot) in 2002 December with the LETG/HRC-S. The X-ray lightcurve shows significant rotational modulation. It can be…
New CCD photometry during 4 successive years from 2005 is presented for the eclipsing binary GW Cep, together with reasonable explanations for the light and period variations. All historical light curves, obtained over a 30-year interval,…
Close binary systems undergoing mass transfer or common envelope interactions can account for the morphological properties of some planetary nebulae. The search for close binary companions in planetary nebulae is hindered by the difficulty…
An analysis of Lyman series lines arising from hydrogen-like oxygen and neon ions in the coronae of the active RS CVn-type binaries II Peg and IM Peg, observed using the {\it Chandra} High Resolution Transmission Grating Spectrograph, shows…
We present the first detailed X-ray study and simultaneous optical observations of the active fast rotating star FR Cnc. The X-ray spectra are found to be explained by two-temperature plasma model with temperature of cool and hot components…
High resolution spectra of the active binary Capella (G8 III + G1 III) covering the energy range 0.4-8.0 keV (1.5-30 Angstroms) show a large number of emission lines, demonstrating the performance of the HETGS. A preliminary application of…
Radial-velocity measurements and sine-curve fits to the orbital radial velocity variations are presented for ten close binary systems: EG Cep,V1191 Cyg, V1003 Her, BD+7_3142, V357 Peg, V407 Peg, V1123 Tau, V1128 Tau, HH UMa, and PY Vir.…
EL CVn-type eclipsing binaries are composed of a massive A-type main-sequence primary star and a hotter B-type secondary star. This paper presents the time-series photometric and asteroseismic results of the EL CVn-type star 1SWASP…