Search Publications

Variable stars in Palomar 13; an evaporating globular cluster

Arellano Ferro, A.; Muneer, S.; Giridhar, Sunetra +3 more

We present new CCD VI photometry of the distant globular cluster Pal 13. Fourier decomposition of the light curves of the three cluster member RRab stars lead to estimations of [Fe/H] = -1.65, and a distance of 23.67 ± 0.57 kpc. Light and colour near minimum phases for RRab stars leads to an estimate of E(B - V) = 0.104 ± 0.001. A V /(V - I) colou…

Effect of low anisotropy on cosmological models by using supernova data

Hossienkhani, H.; Yousefi, H.; Azimi, N.

By using the supernovae type Ia (SNIa) data we study influence of the anisotropy (although low) on the evolution of the universe and compare ΛCDM model with 6 representative parametrizations of the recent Hubble expansion history H(z). To compare these models we use the maximum likelihood method for find that the best fit dynamical w(z) and q(z) o…

PPMXL and Gaia morphological analysis of Melotte 22 (Pleiades) and Melotte 25 (Hyades)

Elsanhoury, W. H.; Nouh, M. I.

In this article, we present a morphological study of two extended open clusters in the sky, Melotte 22 and Melotte 25 using J, H, and K_s photometry with Gaia DR2 and PPMXL proper motions. Various photometric and kinematic astrophysical parameters have been determined.

Based on proper motions of these clusters, we extract our member…

Analysis of a detached eclipsing binary at near the turnoff point of the open cluster NGC 6791 in Kepler field

Çakırlı, Ö.; Dervişoğlu, A.; Yontan, T. +2 more

We analyzed high-precision Kepler photometry and high-resolution UVES and GIRAFFE spectroscopy from ESO Science Archieve for a double-lined eclipsing binary star in the field of the high metallicity old open cluster NGC 6791. Earlier measurements of the masses and radii of the detached system were not accurate enough for photometric and spectrosco…

Photometric observations of the W UMa stars CSS J113505.5+332031, ASAS J142124+1813.1 and HR Boo

Michel, R.; Kjurkchieva, D.

Multicolor photometric observations of the W UMa binaries CSS J113505.5+332031, ASAS J142124+1813.1 and HR Boo are presented. They led to improvement of the orbital periods of CSS J113505.5+332031 and HR Boo. The light curve solutions revealed that all the targets are overcontact binaries with moderate fill-out factors whose components are of G an…

Variable absorption line in XTE J1810-197

Göğüş, Ersin; Güver, Tolga; Vurgun, Eda +1 more

We report the results of a long-term spectral and timing study of the first transient magnetar, XTE J1810-197 which was discovered in 2003, when its X-ray luminosity increased ≈ 100 fold. We fit X-ray spectra of all archival X-ray observations using a two-component blackbody model, where the cool component is most likely originating from the whole…

Microquasar V404 Cyg /GS 2023+338: MASTER optical observations during the June and December 2015 super-outbursts

Rebolo, R.; Wang, X.; Buckley, D. A. H. +22 more

We present several thousands homogeneous photometric (WBVRI and polarization) observations of the microquasar black hole binary V404 Cyg, obtained by the MASTER Global Robotic Network (Lipunov et al. 2010). MASTER were the first telescopes to optically monitor the microquasar after its gamma-ray onset from 18 h 34 m 09 s UT on June 15, 2015 (), un…

Photometry study in period variation and orbital parameter of two W UMa eclipsing binaries: AV Crb and EK Aqr

Han, Xianming L.; Lu, Hong-peng; Zhang, Li-yun +2 more

We report new light curves of two eclipsing binaries of AV Crb and EK Aqr obtained in 2017 and 2018 using Holcomb and SARA telescopes. We obtain the updated ephemeris and find a continuous period decrease (AV Crb) and increase (EK Aqr), respectively. We used the 2015 version Wilson-Devinney method to analyze the light curves and asymmetries. The e…

PY Boo and NSVS 7328383: Two totally-eclipsing W UMa stars with small mass ratios and close parameters

Popov, Velimir A.; Petrov, Nikola I.; Kjurkchieva, Diana P.

Photometric observations of the W UMa binaries PY Boo and NSVS 7328383 with periods of around 0.27 d are presented. The light curve solutions reveal that the components of both targets are stars of K type (temperatures T₁=4770 K, T₂=5080 K and T₁=5146 K, T₂=5056 K, respectively,) and undergo total eclips…

OT UMa and GU leo: Two middle-contact w UMa binaries with similar stellar components

Michel, Raul; Kjurkchieva, Diana; Guerrero, Carlos

We present photometric observations of the W UMa binaries OT UMa and UG Leo. Our results from the light curve solutions are: (i) The two targets show partial eclipses; (ii) The components OT UMa and UG Leo are of G spectral type; (iii) Detailed q-search analysis was carried out for determination of the mass ratios; (iv) The two binaries are of W s…