Search Publications
Differences between the globular cluster systems of the Virgo and Fornax galaxy clusters
Mieske, Steffen; Dabringhausen, Jörg; Fellhauer, Michael
It is well-known that Globular cluster systems are different among galaxies. Here, we test to which degree these differences remain on the scale of galaxy clusters by comparing the globular clusters (GCs) in optical surveys of the Virgo galaxy cluster (ACSVCS) and the ACS Fornax galaxy cluster (ACSFCS) in Kolmogorov-Smirnoff Tests. Both surveys we…
A runaway T Tauri star leaving an extended trail
Luque-Escamilla, Pedro L.; Martí, Josep; Sánchez-Ayaso, Estrella
Aims: We address the problem of young stellar objects that are found too far away from possible star formation sites. Different mechanisms have been proposed before to explain this unexpected circumstance. The idea of high-velocity protostars is one of these mechanisms, although observational support is not always easy to obtain. We aim to sh…
Barium stars and their white-dwarf companions, a key to understanding evolved binaries
Escorza, A.
A rich zoo of peculiar objects forms when evolved stars with extended and loosely-bound convective envelopes, such as Asymptotic Giant Branch (AGB) stars, undergo gravitational interaction in binary systems. For example, Barium (Ba) stars are main-sequence and red-giant stars that accreted mass from the outflows of a former AGB companion. This com…
M dwarfs found in the first Byurakan spectral sky survey database. Gaia EDR3 and TESS data. Some preliminary results
Gigoyan, K. K.; Gigoyan, K. S.; Kostandyan, G. R. +5 more
In order to gain more information on the 236 M dwarfs identified in the First Byurakan Survey (FBS) low-resolution (lr) spectroscopic database, Gaia EDR3 high-accuracy astrometric and photometric data and Transiting Exoplanet Survey Satellite (TESS) data are used to characterise these M dwarfs and their possible multiplicity. Among the sample of 2…
A Search for Low-amplitude Periodic Brightness Variations in HD 168 443
Bondar', N. I.; Shlyapnikov, A. A.
The paper presents the results of studying light curves of the star HD 168443 obtained from the ground-based and space photometric observations within the ASAS, KWS surveys, and the Hipparcos mission from 1990 to 2020. During 30 years of observations, the average annual brightness of the star remained constant within the measurement errors, the me…
The Li-age relation: Calibration with open clusters and associations
Gilmore, G.; Montes, D.; Randich, S. +6 more
In this work we used a series of open clusters and associations observed by the Gaia-ESO Survey (GES) to study the use of lithium abundances (Li I spectral line at 6708 $\angstrom$) as an age indicator for pre- and main-sequence FGKM late-type stars. Previous studies of open clusters have shown that lithium depletion is not only strongly age depen…
BV photometric observations of the flickering of the dwarf nova RX And
Stoyanov, K. A.; Ivanov, V. D.; Minev, M. +3 more
We report photometry of the intranight variability of the dwarf nova RX~And in two bands ($B$ and $V$). The observations are carried out during three nights in November-December 2022 with the 50/70~cm Schmidt telescope of the Rozhen National Astronomical Observatory. The observations indicate that the amplitude of the flickering is about 0.5 mag i…
Apsidal motion and absolute parameters of GV Nor and V881 Sco based on mid-resolution spectroscopy and TESS photometry
Erdem, Ahmet; Sürgit, Derya; Engelbrecht, Chris A. +5 more
The veracity of stellar evolution models and theoretical internal structure constants may be subjected to stringent tests by using physical parameters obtained from spectroscopic and photometric observations of eclipsing binary systems that exhibit apsidal motion. Two eclipsing binary stars from the southern hemisphere with no prior published spec…
Drop in the Hard Pulsed Fraction and a Candidate Cyclotron Line in IGR J16320-4751 Seen by NuSTAR
Rahoui, F.; Tomsick, J. A.; Rodriguez, J. +10 more
We report on a timing and spectral analysis of a 50 ks NuSTAR observation of IGR J16320-4751 (= AX J1631.9-4752), a high-mass X-ray binary hosting a slowly rotating neutron star. In this observation from 2015, the spin period was 1308.8 ± 0.4 s giving a period derivative $\dot{P}\sim 2\times {10}^{-8}$ s s-1 when compared with the perio…
The origin of subdwarf B stars
Aubrey, Callum; Napiwotzki, Ralf
The origin of subdwarf B stars (sdBs) is unclear. Different formation channels are proposed including: close-binary evolution, helium-mixing on the red giant branch and the hot flasher scenario. Circumstantial evidence exists that sdBs can result from single star evolution in high metallicity populations. We investigate this possibility by using m…