Search Publications
Distance, Luminosity and evolutionary status of epsilon Aurigae (F0Iaep) from Gaia DR2 parallax
Muneer, S.; Parthasarathy, M.
From Gaia DR2 parallax of epsilon Aurigae the distance, Mv, Mbol, and log(L*/LMsun) are found to be 445 parsecs, -6.5 mag, -6.5 mag, and 4.5 respectively. These results clearly indicate that epsilon Aurigae (F0Iae) is post-AGB star. The progenitor of epsilon Aurigae is most likely an intermediate mass star of 4 to 5 solar masses or the progenitor …
Cassini CIRS and ISS opposition effects of Saturn's rings - I. C ring narrow or broad surge?
Déau, E.; Colwell, J. E.; El Moutamid, M. +6 more
We focus on the thermal and optical opposition effects of Saturn's C ring seen by Cassini CIRS (Composite InfraRed Spectrometer) at 15.7 {µ}m and ISS (Imaging Science Subsystem) at 0.6 {µ}m. The opposition surge is a brightness peak observed at low phase angle (α → 0°). Saturn rings' opposition surge was recently observed in reflected …
Investigation of the Outburst Activity of the Black Hole Candidate GRS 1739-278
Lutovinov, A. A.; Mereminskiy, I. A.; Filippova, E. V. +2 more
We have performed a joint spectral and timing analysis of the outburst of GRS 1739-278 in 2014 based on Swift and INTEGRAL data. We show that during this outburst the system exhibited both intermediate states: hard and soft. Peaks of quasi-periodic oscillations (QPOs) in the frequency range 0.1-5 Hz classified as type-C QPOs have been detected fro…
Opposite Polarity Magnetic Fields and Convective Downflows in a Simulated Sunspot Penumbra
Rempel, Matthias; Bharti, Lokesh
Recent numerical simulations and observations of sunspots show a significant amount of opposite polarity magnetic fields within the sunspot penumbra. Most of the opposite polarity fields are associated with convective downflows. We present an analysis of 3D MHD simulations through forward modeling of synthetic Stokes profiles of the Fe I 6301.5 Å …
AU Pegasi revisited: period evolution and orbital elements of a peculiar Type II Cepheid
Szabados, László; Csörnyei, Géza
New analysis on the period changes of Type II Cepheid AU Peg is presented. The available recent photometric measurements were collected and analysed with various methods. The period has been found to be constant for certain time intervals, although increasing in overall, in contrast with the previous expectations, which suggested the period change…
Search for Evolutionary Changes in the Periods of Cepheids: CF Cas
Berdnikov, L. N.; Pastukhova, E. N.
For the classical Cepheid CF Cas we have constructed an O- C diagram spanning a time interval of 129 years. The O- C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary decrease in the period, dP/ dt = -0.050 (±0.006) syr-1…
Energy‑dependent timing studies of the low‑hard state of black hole X‑ray binaries with XMM‑Newton
Kong, Albert K. H.; Stiele, Holger
Almost all low‑mass black hole X‑ray binaries are transient sources. Most of these sources show a hysteresis: they evolve from the low‑hard state through intermediate state(s) into the high‑soft state and then return to the hard state at lower luminosity, again passing through the intermediate states. However, there are outbursts that remain in th…
Discovery and Period Analysis of Seven Variable Stars
Polakis, T.
Tens of thousands of images have been acquired during the course of asteroid photometry observations at Command Module Observatory (MPC V02). Nightly sets of these images were analyzed using a software routine that locates field stars whose brightness shows anomalously high photometric scatter. A total of 32 variable stars were identified by this …
Venus crater-related radar-dark parabolas and neighboring terrains: A comparison of 1-µm emissivity and microwave properties
Basilevsky, A. T.; Markiewicz, W. J.; Shalygin, E. V. +2 more
This work presents a comparative study of microwave properties and 1-µm emissivity for five Venus crater-associated radar-dark parabolas along with neighboring plains and some other geologic units. Craters of interest are Adivar, Bassi, Bathsheba, Sitwell, and du Chatelet with nearby crater Caccini having non-parabolic radar-dark halo. Micro…
Spectroscopy of Globular Clusters in the Spheroidal Dwarf Galaxy IKN
Sharina, M. E.; Shimansky, V. V.
Moderate resolution spectra of four globular clusters in the dwarf spheroidal galaxy IKN obtained with the 6-m telescope of the Special Astrophysical Observatory have been used to determine the radial velocities, ages, and metallicities of the clusters, and also to derive the first approximate estimates of the abundances of Mg, Ca, and C. Cross-co…