Related papers: X-ray activity phased with planet motion in HD 189…

We investigate quasi-periodic coronal pulsations during the decay phase of an X 3.2 class flare on 14 May 2013, using soft X-ray data from the RHESSI satellite. Periodogram analyses of soft X-ray light curves show that 53 s and 72 s periods…

Late-type stars interact with their close-in planets through their coronal magnetic fields. We introduce a theory for the interaction between the stellar and planetary fields focussing on the processes that release magnetic energy in the…

We present the first observation of planet-induced stellar X-ray activity, identified for the HD 179949 system, using Chandra / ACIS-S. The HD 179949 system consists of a close-in giant planet orbiting an F9V star. Previous ground-based…

XSS J12270-4859 (henceforth J12270) is the first low-mass X-ray binary to exhibit a transition, taking place at the end of 2012, from an X-ray active state to a radio pulsar state. The X-ray emission based on archival XMM-Newton…

Solar and stellar flares are powerful events which produce intense radiation across the electromagnetic spectrum. Multiwavelength observations are highly important for understanding the nature of flares, because different flare-related…

We demonstrate that resonant shattering flares can occur during close passages of neutron stars in eccentric or hyperbolic encounters. We provide updated estimates for the rate of close encounters of compact objects in dense stellar…

The XMM-Newton satellite has made four observations of the core of M31 as part of a survey that will span the entire galaxy. The majority of the X-ray emission is contributed by point sources, chiefly X-ray Binaries (XB). Exciting early…

For over 10 years, we have carried out a precise radial velocity (RV) survey to find substellar companions around evolved G,K-type stars to extend our knowledge of planet formation and evolution. We performed high precision RV measurements…

We present the analysis of phase-resolved X-ray and optical observations of the peculiar hot star HD191612 (Of?p). This star is known to display line-profile variations that are recurrent with a period of 538d and its spectrum was found to…

We present the results of a detailed analysis of multi-wavelength observations of a very impulsive solar flare 1B/M6.7, which occurred on 10 March, 2001 in NOAA AR 9368 (N27 W42). The observations show that the flare is very impulsive with…

The activity levels of stars are influenced by several stellar properties, such as stellar rotation, spectral type and the presence of stellar companions. In analogy to binaries, planetary companions are also thought to be able to cause…

Several phenomenological aspects of low-luminosity neutron star transients, such as atolls, remain poorly understood. One such source, MAXI J1807+132, entered its latest outburst in July 2023. To thoroughly characterize this outburst, we…

Detecting heavy atoms in the inflated atmospheres of giant exoplanets that orbit close to their parent stars is a key factor for understanding their bulk composition, and the processes that drive their expansion and interaction with the…

We have used high-speed spectroscopy of the rapidly oscillating Ap (roAp) star HD99563 to study the pulsation amplitude and phase behaviour of elements in its stratified atmosphere over one 2.91-d rotation cycle. We identify spectral…

The discovery of a short-period giant planet (a hot Jupiter) around the primary component of the triple star system HD 188753 has often been considered as an important observational evidence and as a serious challenge to planet-formation…

We report the detection of transits by the 3.1 M_Jup companion to the V=8.17 G0V star HD 17156. The transit was observed by three independant observers on Sept. 9/10, 2007 (two in central Italy and one in the Canary Islands), who obtained…

The peak amplitude of linear polarization detected recently from an extrasolar hot giant planet HD 189733b, is a few times of $10^{-4}$, more than an order of magnitude higher than all theoretical predictions. Rayleigh scattering off $H_2$…

We present a case study of the solar flare (SOL2001-10-02T17:31) that showed quasi-periodic pulsations (QPPs) in hard X-rays with two simultaneously excited periods, P_1 = 26-31 s and P_2 = 110 s. Complete evolution of the flare recorded by…

KIC 7341653 is one of several late-type M dwarfs observed in the main mission of Kepler with peculiar infrared colors placing them in the domain of suspected young stellar objects (YSO). It is likely associated with a powerful X-ray emitter…

Much effort has been invested in recent years, both observationally and theoretically, to understand the interacting processes taking place in planetary systems consisting of a hot Jupiter orbiting its star within 10 stellar radii. Several…