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Observations of AR Sco with Chandra and AstroSat soft X-ray telescope
Singh, K. P.; Buckley, D. A. H.; Rana, V. +6 more
We present our AstroSat soft X-ray observations of a compact binary system, AR Sco, and analysis of its X-ray observations with Chandra that were taken only about a week before the AstroSat observations. An analysis of the soft X-ray (0.3–2.0 keV) data limits the modulation of the spin, orbital, or beat periods to less than 0.03 counts s
Study of Galactic structure using UVIT/AstroSat star counts
Pradhan, Ananta C.; Ghosh, S. K.; Piridi, Sonika +3 more
The structure of our Galaxy has been studied from ultraviolet (UV) star counts obtained with the Ultra-Violet Imaging Telescope (UVIT) on board the AstroSat satellite, in Far-UV (FUV) and Near-UV (NUV) bands. The F154W (BaF2) and N263M (NUVB4) filters were used in the FUV and NUV bands, respectively. The point sources are separated from…
UV photometry of spotted stars in the horizontal branch of the globular cluster NGC 2808 using AstroSat
Sahu, Snehalata; Subramaniam, Annapurni; Prabhu, Deepthi S.
A recent study of hot (20,000 to 30,000 K) extreme horizontal branch (EHB) stars in globular clusters (GCs) has led to the discovery of their variability. It is suggested that this variability is driven by the projected rotation of magnetic spots on the stellar surfaces and is expected to have higher amplitudes at shorter wavelengths. Here, we pre…
UVIT observation of Milky Way satellite galaxy Reticulum II
Thirupathi, Sivarani; Divakar, Devika K.; Doddamani, Vijayakumar H.
We present the UV photometry of one of the Ultra-Faint Dwarf (UFD) Milky Way (MW) satellite galaxies, Reticulum II, using images acquired with the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat. Reticulum II is a dark matter dominated, one of the most metal-poor and old (13.5 Gyr) satellite galaxies. High resolution spectroscopy of red gia…
A pair of UV nuclei or a compact star-forming region near the active nucleus in Mrk 766?
Singh, K. P.; Dewangan, G. C.; Deka, P. P. +1 more
We report the discovery of a bright, compact ultraviolet source at a projected separation of 1.1 kpc from the known active galactic nucleus (AGN) in Mrk 766 based on AstroSat/UVIT observations. We perform radial profile analysis and derive the UV flux almost free from the nearby contaminating sources. The new source is about 2.5 and 5.6 times fain…
Study of dynamical status of the globular cluster NGC 1851 using ultraviolet imaging telescope
Yadav, R. K. S.; Sahu, Snehalata; Subramaniam, Annapurni +1 more
We present the study of dynamical status of the globular cluster NGC 1851. A combination of multi-wavelength space and ground-based data sets are used for the present analysis. In order to select the genuine cluster members, we used the astro-photometric data available from HST and GAIA-DR2 catalogs. The BSS radial distribution of the cluster is p…
A comprehensive investigation of the variable overcontact system EH Cancri
Nelson, Robert H.; Alton, Kevin B.; StÈ©pień, Kazimierz
Precise multi-color CCD-derived photometric data were obtained from EH Cnc at two sites during 2010, 2014 and 2018 wherein each epoch used a different instrument. This has provided a unique opportunity to investigate parameter uncertainty following Roche modeling of light curves optimized by differential corrections using the Wilson–Devinney code.…
Vilnius photometry and Gaia astrometry of Melotte 105
Bilir, Selçuk; Yontan, Talar; Canbay, Remziye +1 more
Archival Vilnius CCD photometric observations are presented for the heavily reddened star cluster Melotte 105, resulting in colour-magnitude diagrams and spectral class estimates. There is considerable lack of agreement between studies for reddening, age and distance for this cluster explaining why the archival data are being made available by thi…
The influence of the cometary particles dynamics on the activity of comets
Wesołowski, M.
The paper deals with the dynamics of particles which are on the surface of the cometary nucleus. The key point is to research the behavior of the particles as a result of local sublimation. Generally, we can describe three mechanisms related to the particles behavior. Relatively small particles (of the order of micrometers) are ejected into the at…
Waves propagation in network and inter-network bright points channels between the chromosphere and transition regions with IRIS observations
Zeighami, Sima; Tavabi, Ehsan; Amirkhanlou, Elnaz
The significance increase of the plasma temperature from the solar photosphere to the corona up to 1MK is still unresolved. One of the candidates for this issue is waves and instabilities in the solar plasma. It was suggested that the energy of these waves could heat the solar atmosphere to transition-region (TR) and corona. Despite many recent ki…