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Probing quasar viewing angle with the variability structure function
Tang, Ji-Jia; Wolf, Christian; Tonry, John +3 more
Given the anisotropic emission from quasar accretion discs, their viewing angle affects estimates of the quasar luminosity, black hole mass, and Eddington ratio. Discs appear overluminous when viewed pole-on and underluminous when viewed at high inclination. In radio-quiet quasars, the viewing angle is usually unknown, although spectroscopic indic…
The Core Starbursts of the Galaxy NGC 3628: Radio Very Long Baseline Interferometry and X-Ray Studies
Yang, Xiaolong; Ou, Ziwei
We present radio very long baseline interferometry (VLBI) and X-ray studies of the starburst galaxy NGC 3628. The VLBI observation at 1.5 GHz reveals seven compact (0.7-7 pc) radio sources in the central ~250 pc region of NGC 3628. Based on their morphology, high radio-brightness temperatures (105-107 K), and steep radio spec…
A Statistical Analysis of Deflection of Coronal Mass Ejections in the Field of View of LASCO Coronagraphs
Gopalswamy, Nat; Yashiro, Seiji; Michalek, Grzegorz +1 more
Coronal mass ejections (CMEs) can generate the most severe geomagnetic disturbances. One of the most critical factors affecting a CME's geoeffectiveness is its trajectory. It is crucial to determine whether and when CME will hit Earth. It is commonly assumed that CMEs experience a deflection of propagation in the corona and in interplanetary space…
Photometric and Period Variation study of two contact binaries ASAS J034931-0431.2 and KIC 11413213
Jagirdar, Rukmini; Devarapalli, Shanti Priya; Wakgari, Dereje
We present the first photometric analysis of ASAS J034931-0431.2 and KIC 11413213, two short-period eclipsing contact binaries. Photometric analysis using the Wilson-Devinney method was performed using TESS, Kepler 2, and Gaia DR3 data available. Based on the collected times of minima, period variation studies were carried out and the orbital peri…
Observational Constraints on Close Binary Star Evolution. I. Putative Contact Binaries with Long Periods and High Mass Ratios
Kobulnicky, Henry A.; Cook, Evan M.
Evolutionary and structural models for contact binary stars make quantitative predictions about the distribution of systems in the mass ratio (q)-orbital period (P) plane. Specifically, contact binaries containing primaries with convective envelopes are predicted to be absent at mass ratios larger than a critical threshold that is a function of or…
A CCD search for variable stars in the open cluster NGC 6611
Leiton, R.; Kołaczkowski, Z.; Kalari, V. M. +3 more
We present the results of the UBVIC variability survey in the young open cluster NGC 6611 based on observations obtained during 34 nights spanning one year. In total, we found 95 variable stars. Most of these stars are classified as periodic and irregular pre-main sequence (PMS) stars. The analysis of the JHKS 2MASS photometr…
A Search for Exoplanets around Northern Circumpolar Stars. VIII. Filtering Out a Planet Cycle from the Multi-Period Radial Velocity Variations in M Giant HD 36384
Lee, Byeong-Cheol; Park, Myeong-Gu; Lim, Beomdu +6 more
This paper is written as a follow-up observations to reinterpret the radial velocity (RV) of HD 36384, where the existence of planetary systems is known to be ambiguous. In giants, it is, in general, difficult to distinguish the signals of planetary companions from those of stellar activities. Thus, known exoplanetary giant hosts are relatively ra…
Berkeley 68 ve Stock 20 Açık Kümelerinin Yer ve Uzay Tabanlı Teleskop Verileriyle İncelenmesi
Yontan, Talar
Bu çalışmada Berkeley 68 (Be 68) ve Stock 20 açık kümelerinin ayrıntılı fotometrik ve astrometrik çalışması yapılmıştır. İki kümenin analizlerinde, CCD UBV fotometrik ile Gaia'nın üçüncü veri sürümünde (Gaia DR3) yayımladığı astrometrik ve fotometrik verileri birlikte kullanılmıştır. Yıldızların kümeye üyelik hesaplamaları sonucunda olasılık değer…
Phase spirals in cosmological simulations of Milky Way sized galaxies
Antoja, T.; Ramos, P.; García-Conde, B. +1 more
The Gaia DR2 revealed the phase spirals in the Z - Vz plane, whose origin is still under study, but linked to the Sagittarius dwarf galaxy tidal interaction. In our work, we detect phase spirals in the vertical projection Z - Vz of the disc's stellar particles for the first time in the zoom-in cosmological simulation GARROTXA which includes hydrod…
The True Nature of the Brightest Local Triple Stellar Candidates within 100 pc in the Galaxy
Al-Wardat, Mashhoor A.; Annuar, A.; Yousef, Z. T. +1 more
We present a study of a sample of bright (V ≤ 10 mag) and close (d ≤ 100 pc) triple-stellar system candidates in the galaxy, consisting of eight systems in total. Our aim is to determine their actual multiplicity and the physical properties of each stellar component in the systems. The sample was analyzed using a complex spectrophotometric techniq…