Related papers: Time-series Paschen-beta spectroscopy of SU Auriga…

The more massive counterparts of T Tauri stars, Herbig Ae/Be stars, are known to vary in a complex way with no variability mechanism clearly identified. We attempt to characterize the optical variability of HD~37806 (MWC 120) on time scales…

The C II] feature at ~2325 Angstrom is very prominent in the spectra of T Tauri stars (TTSs). This feature is a quintuplet of semiforbidden transitions excited at electron temperatures around 10,000 K that, together with the nearby Si II]…

Context. The prototypical low-mass young stellar object, T Tauri, is a well-studied multiple system with at least three components. Aims. We aim to explore the T Tau system with the highest spatial resolution, study the time evolution of…

We carried out a new and sensitive search for long-period variability in the prototype of the Mira class of long-period pulsating variables, o Ceti (Mira A), the closest and brightest Mira variable. We conducted this search using an…

We present results from a Near Infrared multi-epoch spectroscopic campaign to detect a young low-mass companion to a T Tauri star. AS 205A is a late-type dwarf (~K5) of ~1 Msun that belongs to a triple system. Independent photometric…

We present the results of an extensive analysis of the ``ASCA'' AO2 observation of the Seyfert 1 galaxy NGC4051. The target exhibits broadband [0.5--10 keV] variability by a factor $\sim 8$ on time scales $\sim 10^4 s$, with a typical…

We present Gemini-NIFS, VLT-SINFONI and Keck-OSIRIS observations of near-infrared [Fe II] emission associated with the well-studied jets from three active T Tauri stars; RW Aur A, RY Tau and DG Tau taken from 2012-2021. We primarily covered…

Light curves of young star systems show photometric variability due to different kinematic, and physical processes. One of the main contributors to the photometric variability is the changing mass accretion rate, which regulates the…

Between 1996 and 2002, we have carried out a spectral monitoring program for the Seyfert galaxy NGC 5548. High quality spectra (S/N>50), covering the spectral range (4000-7500)AA were obtained with the 6 m and 1 m telescopes of SAO (Russia)…

We present the first extensive photometric results of CL Aur from our BVRI CCD photometry made on 22 nights from 2003 November through 2005 February. Fifteen new timings of minimum light were obtained. During the past 104 years, the orbital…

We examined the VSNET light curve of the ER UMa-type star V1159 Ori. We detected a large variation of the supercycle (the interval between successive superoutbursts) between extremes of 44.6 and 53.3 d. The outburst activity was also found…

The migration of profile sub-peaks identified in time-monitored optical emission lines of Wolf-Rayet star spectra provides a direct diagnostic of the dynamics of their stellar winds via a measured line-of-sight velocity change per unit…

Using phase resolved spectroscopic observations obtained with the Ultraviolet and Visual Echelle Spectrograph on ESO's Kueyen Very Large Telescope supplemented by spectroscopic observations obtained with the Boller and Chivens Spectrograph…

The TeV blazar PKS 2155-304 was monitored with the X-ray satellite ASCA in 1994 May, as part of a multiwavelength campaign from the radio to X-ray bands. At the beginning of the two-day continuous observation, we detected a large flare,…

Broad absorption lines (BALs) in quasar spectra are prominent signatures of high-velocity outflows, which might be present in all quasars and could be a major contributor to feedback to galaxy evolution. Studying the variability in these…

We have used laser guide star adaptive optics and a near-infrared dual-channel imaging polarimeter to observe light scattered in the circumstellar environment of Herbig Ae/Be stars on scales of 100-300 AU. We discover a strongly polarized,…

As a continuation of our previous studies in 2007 and 2008, new photometric observations of the T Tauri star TW Hya obtained by the MOST satellite and the ASAS project over 40 days in 2009 with temporal resolution of 0.2 days are presented.…

We discovered multiple high-velocity (ranging from -900 to -650 km/s) and narrow (FWHM = 15 km/s) absorption components corresponding to both the D2 and the D1 lines of Na I on a high dispersion spectrum of V1280 Sco observed on 2009 May 9…

We obtained high temporal resolution spectroscopy of the unusual binary system AR Sco covering nearly an orbit. The H$\alpha$ emission shows a complex line structure similar to that seen in some polars during quiescence. Such emission is…

Classical T Tauri stars with ages of less than 10 Myr possess accretion discs. Magnetohydrodynamic processes at the boundary between the disc and the stellar magnetosphere control the accretion and ejections gas flows. We carried out a long…