Related papers: Decoding the X-ray flare from MAXI J0709-159 using…

We present time-resolved spectroscopy of the soft X-ray transient XTE J2123-058 in outburst. Spectral coverage of 3700-6700A was achieved spanning two orbits of the binary. The strongest emission lines are HeII 4686A and CIII/NIII 4640A…

We detected a giant X-ray flare from the RS-CVn type binary star UX Ari using MAXI on 2020 August 17 and started a series of NICER observations 89 minutes later. For a week, the entire duration of the flare was covered with 32 snapshot…

We present new results from a study of high quality, red spectra of the massive binary star system HD 1383 (B0.5 Ib + B0.5 Ib). We determined radial velocities and revised orbital elements (P = 20.28184 +/- 0.0002 d) and made Doppler…

The field containing the candidate High Mass X-ray Binary IGR J01363+6610 was observed by XMM-Newton on 2009 July 31 for 28 ks. A Be star was previously suggested as the possible counterpart of the INTEGRAL source, and although Chandra,…

We present observations and models of the behaviour of the HI and HeI lines between 1.6 and 2.2um in a small sample of compact HII regions. As in our previous papers on planetary nebulae, we find that the `pure' 1.7007um 4^3D-3^3P and…

We report the discovery of a large amplitude (factor of $\sim$100) X-ray transient (IC 10 X-2, CXOU J002020.99+591758.6) in the nearby dwarf starburst galaxy IC10 during our Chandra monitoring project. Based on the X-ray timing and spectral…

We review the X-ray observations of hot subdwarf stars. While no X-ray emission has been detected yet from binaries containing B-type subdwarfs, interesting results have been obtained in the case of the two luminous O-type subdwarfs HD…

We present a hard X-ray observation of the TeV gamma-ray binary candidate HESS J1832-093 coincident with supernova remnant (SNR) G22.7-0.2 using the Nuclear Spectroscopic Telescope Array (NuSTAR). Non-thermal X-ray emission from XMMU…

We report the detection of a long-duration optical flare in the recenltly discovered, X-ray selected, chromospherically binary 2RE J0743+224. The high resolution echelle spectroscopic observations taken in 12-21th January 1998 exhibit a…

Using the Livermore X-ray Spectral Synthesizer, which calculates spectral models of highly charged ions based on HULLAC atomic data, we investigate the temperature, density, and photoexcitation dependence of the I(11.92 A)/I(11.77 A) line…

HD 49798 is a hydrogen depleted subdwarf O6 star and has an X-ray pulsating companion (RX J0648.0-4418). The X-ray pulsating companion is a massive white dwarf. Employing Eggleton's stellar evolution code with the optically thick wind…

In this paper we report on the real nature of the star HD 145792, classified as He weak in {\it ``The General Catalogue of Ap and Am stars''}. By means of [email protected] high resolution spectroscopic data, we refined the atmospheric…

The Lobster Eye Imager for Astronomy (LEIA) detected a new X-ray transient on 2022 November 7, identified as a superflare event occurring on a nearby K-type giant star HD 251108. The flux increase was also detected in follow-up observations…

Abridged. Here we report on the X-ray activity of the primary star, HD189733 A, using a new XMM-Newton observation and a comparison with the previous X-ray observations. The spectrum in the quiescent intervals is described by two…

The bright eclipsing and bursting low-mass X-ray binary EXO 0748-676 has been observed at several occasions by XMM-Newton during the initial calibration and performance verification (CAL/PV) phase. We present here the results obtained from…

We present the optical to near-infrared spectrum of MAXI J1659-152, during the onset of its 2010 X-ray outburst. The spectrum was obtained with X-shooter on the ESO - Very Large Telescope (VLT) early in the outburst simultaneous with high…

We report on the detection and follow-up multi-wavelength observations of the new X-ray transient MAXI J1807+132 with the MAXI/GSC, Swift, and ground-based optical telescopes. The source was first recognized with the MAXI/GSC on 2017 March…

An uncatalogued bright X-ray transient was detected with MAXI on November 9, 2024, named MAXI J1752$-$457. The NinjaSat X-ray observatory promptly observed the source from November 10 to 18 while the small angular separation from the Sun…

We obtained an optical spectrum of a star we identify as the optical counterpart of the M31 Chandra source CXO J004318.8+412016, because of prominent emission lines of the Balmer series, of neutral helium, and a He II line at 4686 Angstrom.…

Using data obtained during the RATS-Kepler project we identified one short duration flare in a 1 hour sequence of ground based photometry of the dwarf star KIC 5474065. Observations made using GTC show it is a star with a M4 V spectral…