相关论文: AB Dor: Coronal imaging and activity cycles

Throughout an activity cycle, magnetic structures rise to the stellar surface, evolve and decay. Tracing their evolution on a stellar corona allows us to characterize the X-ray cycles. However, directly mapping magnetic structures is…

The most popular models for the complex phase and time lags in the rapid aperiodic variability of Galactic X-ray binaries are based Comptonization of soft seed photons in a hot corona, where small-scale flares are induced by flares of the…

Using K2 data, we have identified 23 very low mass members of the $\rho$ Oph and Upper Scorpius star-forming region as having periodic photometric variability not easily explained by well-established physical mechanisms such as star spots,…

Observations of magnetic activity indicators in solar-type stars exhibit a relationship with rotation with an increase until a "saturation" level and a moderate decrease in activity in the very fastest rotators ("supersaturation"). While…

We present a study of the frequency of transient brightenings in the core of solar active regions as observed in the Fe XVIII line component of AIA/SDO 94 A filter images. The Fe XVIII emission is isolated using an empirical correction to…

Relativistically blurred reflection from the accretion disc provides a powerful probe of the extreme environments close to supermassive black holes; the inner regions of the accretion flow and the corona that produces the intense X-ray…

The frequent flaring events in the X-ray and the NIR radiation of Sgr A* seem not to be periodic in time. However, statistical regularities, here termed "modulations by a pacemaker", are found in the recorded arrival times of both types of…

AB Dor is a young solar-type star with a surface large-scale magnetic field $10^2$ to $10^3$ times stronger than the that of the Sun. Although strong magnetic fields are thought to inhibit coronal mass ejections (CMEs), dimming signatures…

Observations of various solar-type stars along decades revealed that they can have magnetic cycles, just like our Sun. An investigation of the relation between their cycle length and rotation period can shed light on the dynamo mechanisms…

We investigate the decayless regime of coronal kink oscillations recently discovered in the Solar Dynamics Observatory (SDO)/AIA data. In contrast to decaying kink oscillations that are excited by impulsive dynamical processes, this type of…

The CoRoT satellite has recently discovered a hot Jupiter that transits across the disc of a F9V star called CoRoT-6 with a period of 8.886 days. We model the photospheric activity of the star and use the maps of the active regions to study…

The diagram of indices of coronal and chromospheric activity allowed us to reveal stars where solar-type activity appears and regular cycles are forming. Using new consideration of a relation between coronal activity and the rotation rate,…

Recent intensive monitoring campaigns of active galactic nuclei (AGN) have provided simultaneous X-ray, UV, and optical data of unprecedented quality. The observations reveal a strong correlation between the UV and optical variability, but…

We use high-resolution images of the sun obtained by the SDO/AIA instrument to study the evolution of the coronal loops in a flaring solar active region. During 15 February 2011 a X-2.2 class flare occurred in NOAA 11158, a…

We analyse the 2021 outburst from the black hole X-ray binary GX339-4 observed by NICER around the hard to soft transition, when the system exhibits flip-flops between two distinct luminosity states: a bright state with a 5-6 Hz…

We report the discovery and characterization of high-speed (>100 km/s) horizontal flows in solar active regions, making use of the Sun-as-a-star spectroscopy in the range 5-105 nm provided by the EVE (Extreme Ultraviolet Variability…

The aim of this paper is to study the latitudinal variation in the solar rotation in soft X-ray corona. The time series bins are formed on different latitude regions of the solar full disk (SFD) images that extend from 80 degree South to 80…

Long-term photometric measurements in a sample of ultrashort-period (P~0.5 days or less) single and binary stars of different interior structures are analysed. A loose correlation exists between the rotational rate and cycle lengths of…

We are conducting a comprehensive investigation of V815 Her using photometric and spectroscopic data to understand the origin of the activity and what influences it in the short and long term. Using TESS photometry we performed light curve…

We present optical monitoring of the neutron star low-mass X-ray binary Swift J1858.6-0814 during its 2018-2020 outburst and subsequent quiescence. We find that there was strong optical variability present throughout the entire outburst…