Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe Fifth Edition of the General Catalogue of Variable Stars: Experiences in the Constellation of Centaurus
49
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We have recently announced that the General Catalogue of Variable Stars enters the stage of its fifth, purely electronic edition (GCVS 5.1). Recently, we have incorporated a new, completely revised version for 1408 variable stars in the constellation of Centaurus into the GCVS 5.1. Working on this revision, we used current possibilities of data mining, suggested new variability types for many variable stars, found new light elements for a large number of periodic variables. This paper describes the work fulfilled during the preparation of the GCVS 5.1 version for Centaurus, discusses in detail a number of cases most significant astrophysically.
rate research
Read More
Planetary nebulae represent a potential late stage of stellar evolution, however the central stars (CSPNe) are relatively faint and therefore pertinent information is merely available for <20% of the Galactic sample. Consequently, the literature was surveyed to construct a new catalogue of 620 CSPNe featuring important spectral classifications and information. The catalogue supersedes the existing iteration by 25%, and includes physical parameters such as luminosity, surface gravity, temperature, magnitude estimates, and references for published spectra. The marked statistical improvement enabled the following pertinent conclusions to be determined: the H-rich/H-poor ratio is 2:1, there is a deficiency of CSPNe with types [WC 5-6], and nearly 80% of binary central stars belong to the H-rich group. The last finding suggests that evolutionary scenarios leading to the formation of binary central stars interfere with the conditions required for the formation of H-poor CSPN. Approximately 50% of the sample with derived values of log L, log Teff, and log g, exhibit masses and ages consistent with single stellar evolutionary models. The implication is that single stars are indeed able to form planetary nebulae. Moreover, it is shown that H-poor CSPNe are formed by higher mass progenitors. The catalogue is available through the Vizier database.
A paper about variable stars with possible multiple occurrence in the VSX catalogue is presented. Our main criteria for identification of such duplicities were the angular distance among stars (below 1 arcmin) and close periods of objects. In our approach, we also considered double or half values of periods to reveal possible misclassification among stars with similar light curve shapes. The probability of false identification is expressed by the parameter R giving the relative difference between periods. We found 1487 pairs of stars in angular distance lower than 1 arcmin with period difference R lower than 0.1 %, which are high-probable candidates on duplicates. From this sample, 354 pairs have exactly the same periods (R = 0.0 %) and should be considered as definite duplicates. The main contribution of certain duplicates comes from the Catalina Sky Survey (73 pairs have two names with CSS acronym) and from the BEST projects (71 pairs). Distribution of identified duplicates on the sky is not homogeneous but contains surprising depression in Galactic plane.
The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims to find sdBs with compact companions like massive white dwarfs, neutron stars or black holes. Here we provide classifications, atmospheric parameters and a complete radial velocity (RV) catalogue containing 1914 single measurements for an sample of 177 hot subluminous stars discovered based on SDSS DR7. 110 stars show significant RV variability, while 67 qualify as candidates. We constrain the fraction of close massive compact companions {of hydrogen-rich hot subdwarfs} in our sample to be smaller than $sim1.3%$, which is already close to the theoretical predictions. However, the sample might still contain such binaries with longer periods exceeding $sim8,{rm d}$. We detect a mismatch between the $Delta RV_{rm max}$-distribution of the sdB and the more evolved sdOB and sdO stars, which challenges our understanding of their evolutionary connection. Furthermore, irregular RV variations of unknown origin with amplitudes of up to $sim180,{rm km,s^{-1}}$ on timescales of years, days and even hours have been detected in some He-sdO stars. They might be connected to irregular photometric variations in some cases.
The 2nd edition of the Roma-BZCAT is available on line at the ASDC website (http://www.asdc.asi.it/bzcat) and in the NED database. In this short paper we describe the major updates from the first edition.
Magnetized stars exhibit periodic variations of their longitudinal global magnetic fields, $B_e$, owing to rotation. Here, we present the second catalog of averaged stellar magnetic rotational phase curves and their parameters derived from a compilation of the published observational data and personal communications for 350 stars of various spectral types, which were published up to the end of December 2019. Magnetic Ap and Bp stars constitute the most numerous subset in the catalog (215 objects). Phase curves were obtained by fitting either a sinusoid or a double sine wave to series of the observed $B_e$ measurements using the least squares method. For some stars, we present magnetic phase curves derived from time series of the surface magnetic field, $B_s$, or obtained improved values of the rotational period, $P_{rm rot}$. We have also identified eight stars in our catalog that host planets or planetary systems.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
