E. Fernández Lajús

Instituto de Astrofísica de La Plata

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R. Gamen

Universidad Nacional de La Plata

C. Fariña

Isaac Newton Group

R. H. Barbá

University of La Serena

S.‐B. Qian

University of Chinese Academy of Sciences

Virpi Sinikka Niemelä

Instituto de Ciencias Astronómicas, de la Tierra y del Espacio

L.-Y. Zhu

Xi'an University of Architecture and Technology

R. P. Di Sisto

Consejo Nacional de Investigaciones Científicas y Técnicas

N. Salerno

Universidad Nacional de La Plata

J. P. Calderón

Consejo Nacional de Investigaciones Científicas y Técnicas

Claudio Llinares

Institute of Astrophysics and Space Sciences

Cooperative Institutions

Consejo Nacional de Investigaciones Científicas y Técnicas

117

Centre National de la Recherche Scientifique

104

Max Planck Society

Universidad Nacional de La Plata

Chinese Academy of Sciences

Australian National University

University of Sydney

Commonwealth Scientific and Industrial Research Organisation

Argentine National Observatory

Institute of Astronomy

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Análisis de sistemas binarios con período variable

Boletin de la Asociacion Argentina de Astronomia La Plata Argentina (2017)

G. Ferrero R. Gamen G. Baume A. W. Blain C. Cebral

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Confirmation and revision on the orbital period change of the possible type Ia supernova progenitor V617 Sagittarii

Publications of the Astronomical Society of Japan (2014)

Guang Shi Sheng-Bang Qian E. Fernández Lajús

Abstract This work reports new photometric results of eclipsing cataclysmic variable V617 Sagittarii (V617 Sgr). We analyzed the orbital period change of V617 Sgr by employing three new (since 2010) CCD eclipse timings along with all the available data from the literature. It was found that the orbital period of V617 Sgr undergoes an obvious long-term increase, which confirms the result revealed by Steiner et al. (2006). The rate of orbital period increase was calculated to be ${\dot{P}}$ = +2.14(0.05) × 10−7 d yr−1. This suggests the lifetime of the secondary star will end in a timescale of 0.97 × 106 yr faster than that predicted previously. In particular, a cyclic variation with a period of 4.5 yr and an amplitude of 2.3 min may appear in the O − C diagram. Dominated by the wind-accretion mechanism, high mass transfer from the low mass secondary to the white dwarf is expected to continue in the V Sge-type star V617 Sgr during its long-term evolution. The mass transfer rate $|\skew4\dot{M}_{ \, {\rm tr}}|$ was estimated to be in the range of about 2.2 × 10−7 to 5.2 × 10−7 M⊙ yr−1. Accordingly, the already massive (≥ 1.2 M⊙) white dwarf primary will process stable nuclear burning, accrete a fraction of the mass from its companion to reach the standard Chandrasekhar mass limit (≃ 1.38 M⊙), and ultimately produce a type Ia supernova (SN Ia) within about 4–8 × 105 yr or earlier.

Orbital period

Chandrasekhar limit

Eclipse

10.1093/pasj/pst009

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Monitoreo fotométrico de η Carinæ desde el OALP Temporadas de observación 2011-2012

Boletin de la Asociacion Argentina de Astronomia La Plata Argentina (2012)

E. Fernández Lajús F. Giudici X. S. Ramos M. C. Scalia N. E. Salerno

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Optical photometric monitoring of Eta Carinae at La Plata. Period 2003-2005

Boletin de la Asociacion Argentina de Astronomia La Plata Argentina (2005)

E. Fernández Lajús M. Schwartz A. Torres-Forné N. Salerno C. Fariña

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Orbital Period Variations in HT Cas: Evidence for Additional Angular Momentum Loss and a High-eccentricity Giant Planet

The Astrophysical Journal (2023)

Z.-T. Han S. Qian Qifei Han Lei Zang Boonrucksar Soonthornthum

Abstract We present a timing study of the short-period eclipsing cataclysmic variable (CV) HT Cas. Based on new eclipse times derived from our photometric monitoring and archival optical data, combined with historical timings, spanning ∼42 yr, we detect a secular decrease in the orbital period at a rate of P ̇ = − 1.32 × 10 − 12 ss − 1 and a cyclic period wiggle with an amplitude of 79.3 s and a period of 30.28 yr. We find that neither gravitational radiation nor magnetic braking can explain the observed decrease rate, suggesting the presence of additional angular momentum loss (AML). The empirical consequential AML (eCAML) model developed by Schreiber et al. can well match the observed orbital decay in HT Cas, and the physical mechanism for eCAML is most likely attributable to the frictional AML following nova eruptions. As for the cyclic variation, the best explanation is the influence of an unseen companion in orbit around the binary. The derived orbital parameters reveal that the hypothetical third body could be a giant planet with mass of M 3 ≃ 14 M Jup that is moving on a highly eccentric orbit ( e = 0.82). Taken together the results of the present study suggest that HT Cas is a unique triple system containing a high-eccentricity giant planet and it has the potential to become an ideal laboratory in which to test models of CV evolution.

10.3847/1538-4357/acdd6e

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VISTA Variables in the Vía Láctea (VVV): Halfway Status and Results

arXiv (Cornell University) (2014)

M. Hempel D. Minniti Istvan Dékány R. K. Saito P. W. Lucas

The VISTA Variables in the Vía Láctea (VVV) survey is one of six public ESO surveys, and is now in its 4th year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variables stars, microlensing events, new star clusters), others concerning more exotic objects, e.g. novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the actual status of the survey, as well some of the results based on the VVV data, are presented.

Gravitational microlensing

10.48550/arxiv.1406.3241

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Light Curve Analysis of the AP Dor Binary System using Ground-Based and TESS Observations

arXiv (Cornell University) (2023)

Atila Poro E. Fernández Lajús Mohammad Madani Golshan Sabbaghian F. Nasrollahzadeh

The short-period AP Dor eclipsing binary's first in-depth and multiband photometric solutions are presented. We made use of our eight nights of ground-based at a southern hemisphere observatory, and twelve sectors of TESS observations. We extracted eight and 1322 minima from our observations and TESS, respectively. We suggested a new linear ephemeris based on the trend of orbital period variations using the Markov chain Monte Carlo (MCMC) approach. The PHysics Of Eclipsing BinariEs (PHOEBE) Python code and the MCMC approach were used for the light curve analysis. This system did not require a starspot for the light curve solutions. We calculated the absolute parameters of the system using Gaia DR3 parallax method. The orbital angular momentum (J_0) of the AP Dor indicates that this system is located in a region of contact binaries. According to our results, this system is an overcontact binary system with a mass ratio of 0.584, a fillout factor of 48\%, and an inclination of 53deg. The positions of AP Dor stars on the Hertzsprung-Russell (HR) diagram are represented.

Orbital period

Contact binary

Ephemeris

Starspot

Parallax

10.48550/arxiv.2306.02904

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BVRI photometric monitoring of η Carinae

RMxAC (2006)

E. Fernández Lajús M. Schwartz A. Torres-Forné N. Salerno C. Fariña

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