Related papers: Carbon Star CGCS 673 identified as a Semi-regular …
Since the discovery of the spectral peculiarities of their prototype alpha2 Canum Venaticorum in 1897, the so-called ACV variables, which are comprised of several groups of chemically peculiar stars of the upper main sequence, have been the…
The detection of periodicities in light curves of active galacticnuclei (AGN) could have profound consequences for our understanding of the nature and radiation physics of these objects. At high energies (HE; E>100 MeV) 5 blazars (PG…
An investigation of the 200 $\times$ 200 pixel 'superstamp' images of the centres of the open clusters NGC 6791 and NGC 6819 allows for the identification and study of many variable stars that were not included in the Kepler target list.…
As part of the Young Stellar Object VARiability (YSOVAR) program, we monitored NGC 1333 for ~35 days at 3.6 and 4.5 um using the Spitzer Space Telescope. We report here on the mid-infrared variability of the point sources in the…
We present in this paper the new study of variable star AM Cnc, a short period RRab star, in orther to determine, through the light curve and the physical parameters. The Star were observed for a total of 293 sessions shooting, and exhibits…
This work presents the first long-term photometric variability survey of the intermediate-age open cluster NGC 559. Time-series V band photometric observations on 40 nights taken over more than three years with three different telescopes…
Investigation on the object reported by SIMBAD database as V683 Cas shows that this variable star corresponds to the eclipsing binary system GSC 03699-00091 (also identified as NSVS 1850718). The results of the photometric observations of…
Although dwarf carbon (dC) stars are thought universally to be binaries to explain the presence of $C_2$ in their spectra while still near main sequence luminosity, direct observational evidence for binarity is remarkably scarce. Here we…
R Coronae Borealis stars (RCBs) are rare, hydrogen-deficient, carbon-rich supergiant variable stars that are likely the evolved merger products of pairs of CO and He white dwarfs. Only 55 RCB stars are known in our galaxy and their…
We report the discovery of 3 new Double Periodic Variables based on the analysis of ASAS-SN light curves: GSD J11630570-510306, V593 Sco and TYC 6939-678-1. These systems have orbital periods between 10 and 20 days and long cycles between…
We present phase-resolved spectroscopy and photometry of a source discovered with the Chandra Galactic Bulge Survey (GBS), CXOGBSJ174444.7-260330 (aka CX93 and CX153 in the previously published GBS list). We find two possible values for the…
We present an investigation of three chemically peculiar (CP) stars and one CP star candidate which exhibit photometric periods below 12 hours. New spectroscopic observations have been acquired which confirm the peculiar nature of all…
In a shallow near-infrared survey of the dwarf Irregular galaxy, NGC 3109, near the periphery of the Local Group, we have found eight Mira variables, seven of which appear to be oxygen-rich (O-Miras). The periods range from about 430 days…
Carbon stars (with atmospheric C/O$>1$) range widely in temperature and luminosity, from low mass dwarfs to asymptotic giant branch stars (AGB). The main sequence dwarf carbon (dC) stars have inherited carbon-rich material from an AGB…
We investigate the question whether there is a real difference in the light change between stars classified as semiregular (SRV) or irregular (Lb) variables by analysing photometric light curves of 12 representatives of each class. Using…
We present moderate resolution CCD spectra and R photometry for seven KP2001 stars. We revised the spectral classification of the stars in the range 3900 - 8500 A. On the bases of light curves of the NSVS (Northern Sky Variability Survey)…
HadV98 = CoD-22 12017 = GSC 6825.253 is a variable star discovered by Katsumi Haseda. This object has been recently confirmed to be a new R CrB star (Hasselbach et al. 2002), as had been originally proposed by us at the time of the…
The short period variable star MG1-688432 has been discovered to exhibit occasional extremely high energy optical outbursts as high as 10^31 joules. Outbursts are typically of several hours duration. These events are often highly…
The SC and CS stars are thermal-pulsing AGB stars with C/O ratio close to unity. Within this small group, the Mira variable BH Cru recently evolved from spectral type SC (showing ZrO bands) to CS (showing weak C2). Wavelet analysis shows…
This work presents the charge-coupled device (CCD) photometric survey of the old open cluster NGC 188. Time-series V-band photometric observations were conducted for ten nights in January 2017 using the Nanshan One-meter Wide-field…