Observations and Light Curve Solutions of Ultrashort-Period Eclipsing Binaries

Abstract

Photometric observations in V and I bands and low-dispersion spectra of ten ultrashort-period binaries (NSVS 2175434, NSVS 2607629, NSVS 5038135, NSVS 8040227, NSVS 9747584, NSVS 4876238, ASAS 071829-0336.7, SWASP 074658.62+224448.5, NSVS 2729229, NSVS 10632802) are presented. One of them, NSVS 2729229, is newly discovered target. The results from modeling and analysis of our observations revealed that: (i) Eight targets have overcontact configurations with considerable fillout factor (up to 0.5) while NSVS 4876238 and ASAS 0718-03 have almost contact configurations; (ii) NSVS 4876238 is rare ultrashortperiod binary of detached type; (iii) all stellar components are late dwarfs; (iv) the temperature difference of the components of each target does not exceed 400 K; (v) NSVS 2175434 and SWASP 074658.62+224448.5 exhibit total eclipses and their parameters could be assumed as well-determined; (v) NSVS 2729229 shows emission in the Hα line. Masses, radii and luminosities of the stellar components were estimated by the empirical relation "period, orbital axis" for short-and ultrashort-period binaries. We found linear relations mass-luminosity and mass-radius for the stellar components of our targets.

Contact binaries at the short period cut-off – I. Statistics and the first photometric investigations of 10 totally eclipsing systems

“…We should declare that the parameters of the spot were set as fixed, during third light search, in order to quickly determine a convergent solution. The final T 1 and T 2 were determined by the following equations (Coughlin et al 2011;Kjurkchieva et al 2018a),…”

The Photometric Study of Six W UMa Systems and Investigation of the Mass-Radius Relations for Contact Binary Stars

“…Their result declared that unlike secondary components, the primary components of cool contact binaries follow the MRR of MS stars. Another study by Kjurkchieva et al (2018) found that the calculated mass-luminosity relation is not as precise as the mass-radius relation in the selected sample of 10 ultrashort-period overcontact binaries. Li et al (2020) in a statistical study of 380 Kepler contact binary systems found that the linear MRR of the primary and secondary stars is identical and that the primary stars are found generally on the ZAMS line.…”

The first light curve modeling and orbital period change investigation of nine contact binaries around the short period cut-off

“…Actually, this average value is neither the primary's nor the secondary's, it should be a quadrature temperature of the two components. Therefore, when modeling the light curves of these systems, we set this temperature as the primary's (primary means the hotter component), T 1 = T m , and the final temperatures of the primary and secondary components were derived by using the following equations (Kjurkchieva et al 2018):…”

“…The orbital period investigation (Lohr et al 2013a;Koen 2014) of 1SWASP J234401.81−212229.1 has proved that it is a hierarchical multiple-star system. In order to check whether 1SWASP J074658.62+224448.5 and 1SWASP J075102.16+342405.3 exhibit cyclic variation in the orbital period, we reanalyzed their O −C diagrams by using all the available eclipsing times including the data of NSVS, SuperWASP, CSS, ASAS-SN, Jiang et al (2015aJiang et al ( , 2015b, and Kjurkchieva et al (2018). Using the same linear ephemerides those given by Jiang et al (2015aJiang et al ( , 2015b, we calculated the O −C values of the two systems and constructed the O − C diagrams displayed in Figure 6.…”