The Algol System SZ Herculis: Physical Nature and Orbital Behavior

Abstract

Multiband CCD photometric observations of SZ Her were obtained between 2008 February and May. The light curve was completely covered and indicated a significant temperature difference between both components. The light-curve synthesis presented in this paper indicates that the eclipsing binary is a classical Algol-type system with parameters of $q$=0.472, $i$=87${}^{\circ }$.57, and $\Delta$($T_1$--$T_2$)=2,381 K; the primary component fills approximately 77% of its limiting lobe and is slightly larger than the lobe-filling secondary. More than 1,100 times of minimum light spanning more than one century were used to study an orbital behavior of the binary system. It was found that the orbital period of SZ Her has varied due to a combination of two periodic variations with cycle lengths of $P_3$=85.8 yr and $P_4$=42.5 yr and semi-amplitudes of $K_3$=0.013 d and $K_4$=0.007 d, respectively. The most reasonable explanation for them is a pair of light-time effects (LITEs) driven by the possible existence of two M-type companions with minimum masses of $M_3$=0.22 M${}_{\odot }$ and $M_4$=0.19 M${}_{\odot }$, that are located close to the 2:1 mean motion resonance. If two additional bodies exist, then the overall dynamics of the multiple system may provide a significant clue to the formation and evolution of the eclipsing pair.

23 pages, including 5 figures and 7 tables, accepted for publication in AJ

References in corpus (4)

• The first WASP public data release
• The sdB+M Eclipsing System HW Virginis and its Circumbinary Planets
• Homogeneous studies of transiting extrasolar planets. II. Physical properties
• WZ Cygni: a Marginal Contact Binary in a Triple System?

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• The Eclipsing System EP Andromedae and its Circumbinary Companions
• An Orbital Stability Study of the Proposed Companions of SW Lyncis
• On the RZ Draconis Sub-stellar Circumbinary Companions Stability Study of the Proposed Sub-stellar Circumbinary System
• Pulsation and Rotation of the EL CVn-type Eclipsing Binary 1SWASP J024743.37-251549.2