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<i>δ</i> Sct-type pulsations in eclipsing binary systems: Y Cam
Rodrí,guez, E.,Garcí,a, J. M.,Costa, V.,Lampens, P.,van Cauteren, P.,Mkrtichian, D. E.,Olson, E. C.,Amado, P. J.,Daszyń,ska-Daszkiewicz, J.,Turcu, V.,Kim, S.-L.,Zhou, A. Y.,Ló,p Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.408 No.4
<P>ABSTRACT</P><P>We present the results of a three-continent multisite photometric campaign carried out on the Algol-type eclipsing binary system Y Cam, in which the primary component is a multiperiodic δ Sct-type pulsator. The observations consist of 86 nights and more than 450 h of useful data collected mainly during the Northern winter 2002–2003. This means that this is the most extensive time series for such kind of systems obtained so far. These observations were collected mostly in the Johnson V filter, but they also include, for the first time, nearly complete binary light curves in simultaneous Strömgren <I>uvby</I> filters together with a few Crawford Hβ data obtained around the orbital phase of the first quadrature. A detailed photometric analysis is presented for both binarity and pulsation. The results indicate a semidetached system with the secondary filling its Roche lobe. No significant contribution from a third body is found. The residuals from the computed binary solution were then used to investigate the pulsational content of the primary component. The frequency analysis of the out-of-primary-eclipse data leads to a set of eight significant and independent pulsational peaks in a well-defined region of the frequency domain. This means that this is the largest set of excited modes discovered so far in the pulsating component of such kind of systems. The possibility of aliasing problems during the present run or short-term time-scale amplitude variations in some of them was investigated with null results. Indeed the results indicate that <I>f</I><SUB>1</SUB> and <I>f</I><SUB>3</SUB> form a frequency doublet with a beat period of <I>P</I><SUB>beat</SUB>= 17.065 d. Our results confirm the frequencies already detected by earlier authors and show the presence of some additional significant peaks. The observed amplitudes during the present run are also consistent with those derived from older data sets. We perform a preliminary mode identification for most of the frequencies on the basis of the collected multicolour photometry, the observed frequency spacings and the mode visibility in eclipsing binaries.</P>
Multi-site, multi-year monitoring of the oscillating Algol-type eclipsing binary CT Herculis
Lampens, P.,Strigachev, A.,Kim, S.-L.,Rodrí,guez, E.,Ló,pez-Gonzá,lez, M. J.,Vidal-Saí,nz, J.,Mkrtichian, D.,Koo, J.-R.,Kang, Y. B.,Van Cauteren, P.,Wils, P.,Kraicheva, Z.,Dimi EDP Sciences 2011 Astronomy and astrophysics Vol.534 No.2
<P>We present the results of a multi-site photometric campaign carried out in 20042008 for the Algol-type eclipsing binary system CT Her, the primary component of which displays δ Scuti-type oscillations. Our data consist of differential light curves collected in the filters B and V, which were analysed using the method of Wilson-Devinney (PHOEBE). After identifying an adequate binary model and removing the best-fit light-curve solution, we performed a Fourier analysis of the residual B and V light curves to investigate the pulsational behaviour. We confirm the presence of rapid pulsations with a main period of 27.2 min. Up to eight significant frequencies with semi-amplitudes in the range 3 to 1 mmag were detected, all of which lie in the frequency range 43.553.5 d<SUP>−1</SUP>. This result is independent of the choice of the primary’s effective temperature (8200 or 8700 K) since the light-curve models of the binary are very similar in both cases. This is yet another case of a complex frequency spectrum observed for an accreting δ Scuti-type star (after Y Cam). In addition, we demonstrate that the amplitudes of several pulsation frequencies provide evidence of variability on timescales as short as 12 years, perhaps even less. Moreover, our analysis takes into account some recently acquired spectra, from which we obtained the corresponding radial velocities for the years 20072009. Investigation of the OC diagram shows that further monitoring of the epochs of eclipse minima of CT Her will cast new light on the evolution of its orbital period.</P>
SPECTROSCOPIC ANALYSIS OF THE R CANIS MAJORIS BINARY SYSTEM
A-THANO, N.,MKRTICHIAN, D.E.,KOMONJINDA, S. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
R Canis Majoris is a bright, short-period ($1^d$.1359) Algol-type eclipsing binary. For a long time, it was considered to be a low-mass binary star with $M_1=1.1M_{\odot}$ and $M_2=0.17M_{\odot}$ primary and secondary components, respectively (Tomkin, 1985). Glazunova, Yushchenko & Mkrtichian (2009) found new masses for the primary and secondary components of $M_1=1.81M_{\odot}$ and $M_2=0.23M_{\odot}$, respectively and resolved a long-standing problem with the low masses of components for this binary. Budding and Butland (2011) confirmed the results of Glazunova, Yushchenko & Mkrtichian and obtained improved orbits and masses. New spectroscopic observations of R CMa were done during 8 nights on December 2012 with the 2.4-meter telescope of the Thai National Observatory (TNO) and fibre-fed medium resolution echelle spectrograph. We obtained new, accurate orbital radial velocities of the two components of this binary system. Results of these investigations and the new orbital parameters are presented.
Detection of planet candidates around K giants. HD 40956, HD 111591, and HD 113996
Jeong, G.,Lee, B.-C.,Han, I.,Omiya, M.,Izumiura, H.,Sato, B.,Harakawa, H.,Kambe, E.,Mkrtichian, D. Springer-Verlag 2018 Astronomy and astrophysics Vol.610 No.-
<P><I>Aims. </I>The purpose of this paper is to detect and investigate the nature of long-term radial velocity (RV) variations of K-type giants and to confirm planetary companions around the stars. </P><P><I>Methods. </I>We have conducted two planet search programs by precise RV measurement using the 1.8 m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) and the 1.88 m telescope at Okayama Astrophysical Observatory (OAO). The BOAO program searches for planets around 55 early K giants. The OAO program is looking for 190 G-K type giants. </P><P><I>Results. </I>In this paper, we report the detection of long-period RV variations of three K giant stars, HD 40956, HD 111591, and HD 113996. We investigated the cause of the observed RV variations and conclude the substellar companions are most likely the cause of the RV variations. The orbital analyses yield <I>P</I> = 578.6 ± 3.3 d, <I>m</I> sin <I>i</I> = 2.7 ± 0.6 <I>M</I>J, <I>a</I> = 1.4 ± 0.1 AU for HD 40956; <I>P</I> = 1056.4 ± 14.3 d, <I>m</I> sin <I>i</I> = 4.4 ± 0.4 <I>M</I>J, <I>a</I> = 2.5 ± 0.1 AU for HD 111591; <I>P</I> = 610.2 ± 3.8 d, <I>m</I> sin <I>i</I> = 6.3 ± 1.0 <I>M</I>J, <I>a</I> = 1.6 ± 0.1 AU for HD 113996. </P>
SPECTROSCOPIC ANALYSIS OF THE RS CVn STAR EI Eri
KEERATIBHARAT, J.,MKRTICHIAN, D.E.,KOMONJINDA, S. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
We present results of a new high-resolution spectroscopic study of the RS CVn-type binary system EI Eridani (HD26337). We used high S/N ratio LSD profiles to measure a new RV orbit of the primary component and new orbital parameters. We found evidence of strong spectral line profile variations at time intervals indicating the existence of short-lived (few days) spots on the surface of the primary component. We measured a projected rotation velocity of star of 53.2 km/s.