Search Publications
Searching for overlooked TDEs in the 4XMM catalogue
Risaliti, Guido; Sacchi, Andrea; Miniutti, Giovanni
Tidal disruption events (TDEs) are usually discovered as bright transients, either in the X‑ray or optical/UV band. These events are often characterized by a "super‑soft" emission in the X‑ray band, which has not been observed in any other extragalactic source, with few exceptions (novae and supersoft active galactic nuclei, AGN), which can howeve…
X‑HESS: A large sample of highly accreting serendipitous AGN under the XMM‑Newton microscope
Guainazzi, M.; Piconcelli, E.; Tombesi, F. +3 more
The bulk of X‑ray spectroscopic studies of active galactic nuclei (AGN) are focused on local () sources with low‑to‑moderate (<0.3) Eddington ratio (). It is then mandatory to overcome this limitation and improve our understanding of highly accreting AGN. In this work, we present the preliminary results from the analysis of a sample of high‑ ra…
Gaia search for stellar companions of TESS Objects of Interest III
Mugrauer, Markus; Michel, Kai-Uwe; Zander, Jule
The latest results from our ongoing multiplicity study of (Community) TESS Objects of Interest are presented, using astro- and photometric data from the ESA-Gaia mission, to detect stellar companions of these stars and characterize their properties. A total of 124 binary and 7 hierarchical triple star systems were detected among 2175 targets, whos…
Large-scale asymmetry in galaxy spin directions: Analysis of galaxies with spectra in DES, SDSS, and DESI Legacy Survey
Shamir, Lior
Multiple previous studies using several different probes have shown considerable evidence for the existence of cosmological-scale anisotropy and a Hubble-scale axis. One of the probes that show such evidence is the distribution of the directions toward which galaxies spin. The advantage of the analysis of the distribution of galaxy spin directions…
Effects of flares on the habitable zones of M dwarfs accessible to TESS planet detections
Stelzer, B.; Raetz, Stefanie; Bogner, M.
Photometric space missions like Kepler and TESS continuously discover new exoplanets and advance the search for a second habitable world. The light curves recorded by these telescopes also reveal signs of magnetic activity, such as star spot modulation and flares, which can influence habitability. Searching for these characteristics, we analyzed T…
First eROSITA-TESS results for M dwarfs: Mass dependence of the X-ray activity rotation relation and an assessment of sensitivity limits
Stelzer, B.; Raetz, St.; Magaudda, E.
We present a study of the activity-rotation relation for M dwarf stars, using new X-ray data from the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission (SRG), combined with photometric rotation periods from the Transiting Exoplanet Survey Satellite (TESS). The stars used in this work are…
Optical spectroscopy of the Be/black hole binary MWC 656 - interaction of a black hole with a circumstellar disc
Bode, Michael F.; Stefanov, Stefan Y.; Marchev, Dragomir +7 more
We present new spectroscopic observations of the Be/black hole binary MWC 656 obtained during the period 2015-2021. We measure the equivalent width of Hα (EWα), Hβ (EWβ), and the distance between the peaks of Hα (ΔVα), Hβ (ΔVβ), and FeII (ΔVFeII) lines. Combining new and old data, we find that…
X-exoplanets coronal models and planet photoevaporation
Sanz-Forcada, Jorge
Follow‑up observations of the binary system γ Cep
Mugrauer, Markus; Buder, Sven; Ginski, Christian +2 more
We present new imaging and spectroscopic observations of the exoplanet host star $\gamma$ Cep A, and of its low-mass stellar companion $\gamma$ Cep B. We used AstraLux/CAHA to follow the orbital motion of the companion around its primary, whose radial velocity was determined with spectra of the star, taken with the spectrograph FLECHAS at the Univ…
Characterizing X-ray activity cycles of young solar-like stars with solar observations
Stelzer, Beate; Orlando, Salvatore; Coffaro, Martina
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 feasible only for the Sun, while such structures are spatially unresolved with present-day X-ray instruments on ste…