V1097 Her, an overcontact (W-type) eclipsing binary, has a short period, a relatively low degree of contact (or fill-out parameter), and an increasing period.It has now been classified: for the more luminous star a spectral type of F8.5V±1 has been determined.B,V,Ic light curves and, for the first time, radial velocity curves for the overcontact binary V1097 Her have been obtained; these have been subjected to a Wilson-Devinney analysis, yielding fundamental parameters; in particular masses of 0.41 ± 0.01 and 1.11 ± 0.02 M⊙ and luminosities of 0.77 ± 0.01 and 1.75 ± 0.03 L⊙ respectively.The distance estimate of r = 237 ± 11 pc is consistent with the Gaia value of r = 250.3± 1.4 pc (Bailer-Jones et al., 2018; Gaia Collaboration, 2018).A period analysis, again believed to be the first ever, has been undertaken, revealing a constant rate of period increase of dP/dt = (1.85 ± 0.11) × 10 -7 d/yr.
DG Ari (ASAS J025521+1539.4) is a variable star that was found in the search of binary stars with periods longer than 30 days in ASAS catalogue .The source shows two periodic component in its light curve.We estimate both, the orbital period, and the long-term cycle using PDM.Additionally, we present a match with the soft X-ray source 1RXSJ025521.3+153951located at similar position.According with these results, we discuss about its nature as a RS CVn candidate.
We present a new period study and light-curve solutions for the A-Type W UMa binary GSC 3208 1986. Contrary to a previous claim by R.G. Samec et al. of a rapidly decreasing period, the system's period is increasing moderately on a timescale of two million years. The light curve is variable on the time scale of years, which can be understood by changes in how much it overfills its Roche lobe.
We have obtained uvbyβ photoelectric photometry with the 0.84 m telescope of the San Pedro Martir Observatory, México, for the stars HD220735 and HD30110 which were found to be new variable stars.For these stars we determined some of their physical characteristics, such as effective temperature and surface gravity.
In mid-2018, efforts were renewed to check on the highly active mass-transfer process shown by the classical Algol system R Arae.We present new light curves and times of light minimum from this project.We also extend R Arae's period O-C diagram to include the new results.The new data are consistent with the strong mass transfer scenario of Reed (2011).Recent and ongoing studies of this interesting system are referred to.
Recently, brightness variations occurring on twice the accretion disk precession period in the old nova and permanent superhump system V603 Aql have been observed by Bruch & Cook (2018). In an attempt to detect a similar effect in other cataclysmic variables reported to contain permanent superhumps the novalike variable UU Aqr was observed during 11 nights in September 2018. While no traces of superhumps were seen in the data, rendering the quest for variations related to the disk precession period obsolete, the system exhibits regular variations with a period of ~4 days.
We present a new period study and light-curve solutions for the A-Type W UMa binary GSC 3208 1986. Contrary to a previous claim by R.G. Samec et al. of a rapidly decreasing period, the system's period is increasing moderately on a timescale of two million years. The light curve is variable on the time scale of years, which can be understood by changes in how much it overfills its Roche lobe.
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 300 and 600 days.
High precision light curves were obtained for the GSC 03612-1565 = V2647 Cyg eclipsing binary system in 2009 and in 2018.The solution for these curves allowed to estimate the limb darkening coefficients and spectral classes of components (F5V-F8V).Also a new ephemeris was computed, it is very different in comparison to a previous study by Otero et al. (2006).The circular orbit instead the elliptical was found.
Revisit of the CCD archive obtained during long-time monitoring of the white dwarf WD1145+015 at Tien-Shan Observatory revealed a new variable star, identified as Gaia DR2 3796400796427214848.It was inferred that this star is of spectral type G7V-G8V.The amount of photometric data allows performing detailed analysis of this target, revealing its rotational-modulation variability.The period of variation is 6.33 h which makes this star an ultra-fast rotator.The stability of variability might be due to "magnetic saturation" of the angular momentum loss.Yet another possible interpretation of the brightness variation is an elliptical variable binary system.
RZ Com (GSC 1990(GSC -2841) is a short period (P = 0.3385 d) W UMa-type binary system, type-W, which has had, over the years, two spectroscopic and numerous light curve studies.The various mass determinations show a large scatter.Here we present the results of new light curve and radial velocity observations, and a fresh analysis by the Wilson-Devinney 2003 code.We have been able to obtain a unified model for photometric five datasets, each used one or more filters.The main model parameters such as mass ratio, temperature, potential, and inclination were in close agreement, as were derived quantities such as mass, stellar radius, etc.Only the spot parameters differed, as one might expect.Further, we determined a distance estimate, r = 204 ± 5 pc, in good agreement with the Gaia value of r = 203.1 ± 3.7 pc.We also presented four new eclipse timings, performed a renewed period analysis attaining a LiTE fit.With that we determined a rate of intrinsic period change dP/dt = 3.86(2) × 10 -8 days/year, and-assuming conservative processes-a rate of mass exchange dm1/dt = -4.1(3)× 10 -8 M⊙/year which means that the less massive star is losing mass to its companion.
CCD photometric data collected at UnderOak Observatory (UO) and Desert Bloom Observatory (DBO) in three bandpasses (B, V and IC) produced 10 new times of minimum for AU Ser which were used to revise the linear ephemeris.These results captured in 2011 and 2018 reinforced a longstanding observation that the shape of the light curve from this W UMa binary system (P=0.386497d) is highly variable.Significantly skewed peaks and differences at maximum light were detected during quadrature which could only be simulated during Roche modeling by positioning a hot spot on the secondary star close to the neck between both constituents.Historically this system has been variously classified as an F8, G5 and K0 system; however, this study supports more recent reports that AU Ser is best described as spectral type K1V-K2V.A fresh assessment of eclipse time residuals over the past 80 years has provided additional insight regarding cyclical changes in orbital period experienced by this interesting variable star.
From Gaia DR2 parallax of ǫ Aurigae the distance, Mv, M bol , and log(L * /L⊙sun) are found to be 445 parsecs, -6.5 mag, -6.5 mag, and 4.5 respectively.These results clearly indicate that ǫ Aurigae (F0Iae) is post-AGB star.The progenitor of ǫ Aurigae is most likely an intermediate mass star of 4 to 5 solar masses or the progenitor may be a star which is lower limit of a super-AGB star.
We report the detection of 30.5 min low-amplitude (A=0.003mag) δ Scuti-type pulsations in an A5V-A7V type component of the detached eclipsing binary system TU CMa.
We present the first part of a new Name-List of variable stars containing information on 1291 variable stars recently designated in the system of the General Catalogue of Variable Stars.With the exception of Novae and other unusual variables named upon request from the IAU CBAT or by our initiative, these stars are in the range of J2000.0 right ascensions from 0 hours to 18 hours 00 minutes.The paper also announces GCVS designations for 324 known variables in 10 globular clusters.
In three seasons of 2015-2018 we carried out a series of visible and near infrared (NIR) photometry of SU Aur. In course of this photometric monitoring we detected an event of a deep fading of the star in spring of 2018. In this paper we present preliminary analysis of our photometry.
The identification of the variable stars published on IBVS #3573 has ben revised on the basis of the original (unpublished) finding charts.Cross check with the 2MASS catalog has been made to get more accurate coordinates and to confirm their nature from their J -H, H -K colors.The Mira stars, given their known periods, could be used with the astrometric parallaxes of the forthcoming Gaia catalog to improve the Period-Luminosity relation.
