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U B V I
Akkaya Oralhan, İnci
Fundamental astrophysical parameters have been derived for Berkeley 55 (Be 55) open cluster based on the UBVI charge-coupled device (CCD) photometric data observed using a AZT-22 1.5 m telescope at Maidanak Astronomical Observatory (MAO) in Uzbekistan. The mean reddening is obtained as
Detection of Strongly Turbulent Regions in the Supercorona with the Venus Express and Mars Express Satellites
Bird, M. K.; Efimov, A. I.; Lukanina, L. A. +3 more
Experiments involving the radio sounding of solar plasma with signals from the Venus Express and Mars Express spacecraft, which were carried out from October 6 to December 6, 2006, provided data on frequency fluctuations of the radio signals for the western and eastern coronal limbs. The processing of this data provided information on the intensit…
Mass Segregation as a New Indicator of Binary, IMBH, and Stellar-mass Black Hole Systems in Globular Clusters
Zhao, Gang; Wu, Wenbo
This study presents the mass segregation of 35 Galactic globular clusters (GCs) through the radial profile of the mean mass of main-sequence stars. Most of them are found to be mass segregated due to two-body relaxation effects. The GCs with a larger core to half-mass-radius ratio tend to be less mass segregated. Recent simulations show that energ…
Observations of bright stars with AstroSat soft X-ray telescope
Singh, K. P.; Dewangan, G. C.; Bhattacharyya, S. +5 more
We present observations of four bright stars observed with the AstroSat Soft X-ray Telescope (SXT). Visible light from bright stars like these can leak through the very thin filter in front of the CCD in the focal plane CCD camera of the SXT and thus making the extraction of X-ray events difficult. Here, we show how to extract the X-ray events wit…
Role of host galaxy in the formation of multiple stellar populations: analysis of NGC 1786 and NGC 1898
Goudfrooij, Paul; Niederhofer, Florian; Vanaraj, Viswajith
Even after decades of research, the origin of multiple stellar populations in globular clusters (GCs) remains enigmatic. The question as to whether the galaxy environment plays a role in their formation remains unanswered. To that extent, we analysed two classical (>10 Gyr old) Large Magellanic Cloud GCs, NGC 1786 and NGC 1898, using imaging da…
Sizes of the smallest particles at Saturn's ring edges
Colwell, Joshua E.; Esposito, Larry W.; Becker, Tracy M. +1 more
The Ultraviolet Imaging Spectrograph (UVIS) on the Cassini spacecraft observed 275 ring stellar occultations from July 2004 until August 2017. We use stellar occultation data from the UVIS High Speed Photometer (HSP) to characterize the smallest particles at ring edges by modeling observed diffraction signatures. We identify these signatures as sp…
Census of Variable Stars toward Serpens Main
Chen, Zhiwei; Li, Yao; Haas, Martin +7 more
We monitored a 3 deg2 area toward Serpens Main in the Pan-STARRS1 r, i, and z bands from 2016 April to September. Light curves of more than 11,000 stars in each band were obtained, and 143 variables have been identified. Among those, 119 variables are new discoveries, while 24 variables were previously known. We present variability clas…
Magnetic flux structuring of the quiet Sun internetwork. Center-to-limb analysis of solar-cycle variations
Faurobert, M.; Ricort, G.
Context. The small-scale magnetism of the quiet Sun has been investigated by various means in recent decades. It is now well established that the quiet Sun contains in total more magnetic flux than active regions and represents an important reservoir of magnetic energy. But the nature and evolution of these fields remain largely unknown.
Aims…
VZ Sex: X-Ray Confirmation of Its Intermediate Polar Nature
Nucita, A. A.; De Paolis, F.; Ingrosso, G. +3 more
Intermediate polars are members of the cataclysmic variable binary stars. They are characterized by a moderately magnetized white dwarf accreting matter from a cool main-sequence companion star. In many cases, this accretion gives rise to a detectable X-ray emission. VZ Sex is an interesting X-ray source whose nature needs a robust confirmation. H…
Searching for Low-mass Population III Stars Disguised as White Dwarfs
Schlaufman, Kevin C.; Chandra, Vedant
It is uncertain whether or not low-mass Population III stars ever existed. While limits on the number density of Population III stars with M* ≈ 0.8 M⊙ have been derived, using Sloan Digital Sky Survey (SDSS) data, little is known about the occurrence of Population III stars at lower masses. In the absence of reliable parallax…