Related papers: Spot evolution on LQ Hya during 2006--2017: temper…

The plethora of photometric data collected by the Kepler space telescope has promoted the detection of tens of thousands of stellar rotation periods. However, these periods are not found to an equal extent among different spectral types.…

Finding low-mass planets around solar-type stars requires to understand the physical variability of the host star, which greatly exceeds the planet-induced radial-velocity modulation. This project aims at analyzing - observationally and…

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…

A majority part of magnetic chemically peculiar (mCP) stars of the upper main sequence exhibits strictly periodic light, magnetic, radio, and spectral variations that can be fully explained by the model of a rigidly rotating main-sequence…

Hot DQ white dwarfs constitute a new class of white dwarf stars, uncovered recently within the framework of the SDSS project. Recently, three hot DQ white dwarfs have been reported to exhibit photometric variability with periods compatible…

The convectively driven, weakly magnetized regions of the solar photosphere dominate the Sun's surface at any given time, but the temporal variations of these quiet regions of the photosphere throughout the solar cycle are still not well…

Context. We analyse multi-colour photometric and spectroscopic observations of a Young Stellar Object Gaia20bdk. Aims. We aim to investigate the exact nature of the eruptive phenomenon that the star has been experiencing since 2018.…

We observe a significant change in the TW Hya disk interior to 40~AU via archival unpolarized multi-wavelength Hubble Space Telescope/STIS and NICMOS images with an inner working angle (IWA) of 0\farcs4 (22~AU). Our images show the outer…

In this work, we probe the well known thermodynamic phase structure of black hole through the lens of its quasi-periodic oscillations (QPOs). Can QPOs be influenced by black hole phase transitions? Do they carry any signature of such…

The emergence of the disc in our Galaxy and the relation of the thick and thin disc formation and evolution is still a matter of debate. The chemo-dynamical characterization of disc stars is key to resolve this question, in particular at…

The photospheric spot activity of some of the stars with transiting planets discovered by the CoRoT space experiment is reviewed. Their out-of-transit light modulations are fitted by a spot model previously tested with the total solar…

Context. The relation between solar surface rotation and sunspot activity still remains open. Sunspot activity has dramatically reduced in solar cycle 24 and several solar activity indices and flux measurements experienced unprecedentedly…

Context. Young, solar analogue stars provide key insights into the early stages of stellar evolution, particularly in terms of magnetic activity and rotation. Their rapid rotation, high flaring rate, and enhanced surface activity make them…

We present two epochs of observations of TW Hya from the high-dispersion near-IR spectrograph ARIES at the MMT. We detect strong emission from the Brackett gamma transition of hydrogen, indicating an accretion rate substantially larger than…

We discuss ROSAT and ASCA observations of the young active star Gl355}. During the ROSAT observation a strong flare was detected with a peak flux more than an order of magnitude larger than the quiescent level. Spectral analysis of the data…

Variability observed in photometric lightcurves of late-type stars (on timescales longer than a day) is a dominant noise source in exoplanet surveys and results predominantly from surface manifestations of stellar magnetic activity, namely…

DQ Tau is a young low-mass spectroscopic binary, consisting of two almost equal-mass stars on a 15.8 d period surrounded by a circumbinary disk. Here, we analyze DQ Tau's light curves obtained by Kepler K2, the Spitzer Space Telescope, and…

We use accurate estimates of aluminium abundance provided as part of the APOGEE Data Release 17 and Gaia Early Data Release 3 astrometry to select a highly pure sample of stars with metallicity $-1.5\lesssim {\rm [Fe/H]}\lesssim 0.5$ born…

The proliferation of high time-resolution and decades-long monitoring of classical T Tauri stars provides a vast opportunity to test the variability of the star-disk connections. However, most monitoring surveys use single broad-band…

Stellar activity induces apparent radial velocity (RV) variations in late-type main-sequence stars that may hamper the detection of low-mass planets and the measurement of their mass. We use simultaneous measurements of the active planet…