The doubly eclipsing quintuple low-mass star system 1SWASP J093010.78+533859.5 (1504.07065v1)

Abstract: Our discovery of 1SWASP J093010.78+533859.5 as a probable doubly eclipsing quadruple system containing a contact binary with P~0.23 d and a detached binary with P~1.31 d was announced in 2013. Subsequently Koo et al. confirmed the detached binary spectroscopically and identified a fifth set of static spectral lines at its location, corresponding to a further non-eclipsing component of the system. Here we present new spectroscopic and photometric observations, allowing confirmation of the contact binary and improved modelling of all four eclipsing components. The detached binary is found to contain components of masses 0.837(8) and 0.674(7) M_sol, with radii of 0.832(18) and 0.669(18) R_sol and effective temperatures of 5185(-20,+25) and 4325(-15,+20) K respectively, the contact system has masses 0.86(2) and 0.341(11) M_sol, radii of 0.79(4) and 0.52(5) R_sol respectively, and a common T_eff of 4700(50) K. The fifth star is of similar temperature and spectral type to the primaries in the two binaries. Long-term photometric observations indicate the presence of a spot on one component of the detached binary, moving at an apparent rate of approximately one rotation every two years. Both binaries have consistent system velocities around -11 to -12 km/s, which match the average radial velocity of the fifth star, consistent distance estimates for both subsystems of d=78(3) and d=73(4) pc are also found, and (with some further assumptions) of d=83(9) pc for the fifth star. These findings strongly support the claim that both binaries (and very probably all five stars) are gravitationally bound in a single system. The consistent angles of inclination found for the two binaries (88.2(3) and 86(4) degrees) may also indicate that they originally formed by fragmentation (~9-10 Gyr ago) from a single protostellar disk and subsequently remained in the same orbital plane.

• The paper presents comprehensive measurements of J093010’s contact and detached binaries, determining precise masses, radii, and temperatures.
• It employs light curve analysis, radial velocity measurements, and long-term photometric monitoring to derive detailed system parameters.
• The study offers valuable insights into the formation and dynamical stability of complex multiple star systems, supporting protostellar fragmentation models.

Analysis of the Doubly Eclipsing Quintuple Low-Mass Star System 1SWASP J093010.78+533859.5

The presented research offers a comprehensive paper of the doubly eclipsing quintuple low-mass star system 1SWASP J093010.78+533859.5 (hereafter J093010), focusing on the dual eclipsing binary subsystems and a non-eclipsing fifth component. This system's unique configuration renders it a valuable target for studying stellar formation and dynamical stability in higher-order multiple systems.

Summary of Findings

The J093010 system comprises two eclipsing binaries: a contact binary with a period of approximately 0.23 days and a detached binary with a period of around 1.31 days. The contact binary is characterized by component masses of 0.86 ± 0.02 and 0.341 ± 0.011 solar masses, with corresponding radii of 0.79 ± 0.04 and 0.52 ± 0.05 solar radii. Both components share an effective temperature of around 4700 ± 50 K. The detached system, on the other hand, consists of stars with masses estimated at 0.837 ± 0.008 and 0.674 ± 0.007 solar masses and radii of 0.832 ± 0.018 and 0.669 ± 0.018 solar radii, achieved through precise modeling of light curves and radial velocities. Their respective temperatures were measured at 5185 K and 4325 K.

A fifth star, detected through static spectral lines, shares a similar spectral type and temperature with the primaries in the binaries. Its inclusion supports the assertion that all five stars are gravitationally bound. Consistent system velocities around -11 to -12 km/s and coherent distance estimates further substantiate this claim.

Long-term photometric monitoring has suggested the potential presence of a spot on one of the stars in the detached binary, inferred from observed rotational modulation.

Implications and Discussion

The stellar parameters derived provide meaningful insights into the star system's formation and evolutionary history. The inclination of the binaries, both near 90 degrees, coupled with their possible shared orbital plane, hints at formation via fragmentation from a common protostellar disk approximately 9-10 Gyr ago. The minimal metallicity deviation from solar levels reinforces this historic conjecture. This formation scenario aligns with the theories of star cluster formation where such multiple systems arise from turbulent cores.

The system's precise measurements allow for the simulation of long-term dynamical interactions, serving as an empirical testbed for star formation models, especially those predicting the outcome of close binary interactions and contact phase longevity under the influence of outer companions.

Future Directions

The research lays foundational work for further investigations, including:

• Spectroscopic Monitoring: Continued and comprehensive spectroscopic observations could help refine component parameters and detect additional subtle effects such as apsidal motion or spot dynamics.
• Astrometric Studies: Precision astrometric measurements might reveal potential hierarchical stability or resonant interactions.
• Theoretical Simulations: Utilizing advanced N-body simulations may provide insights into the impact of the fifth star and predict the system’s future stability and evolution pathways.

As observational capabilities improve, systems like J093010 could play a pivotal role in enhancing our comprehension of complex stellar dynamics and the intricacies of multi-system evolution. The results from this system could also contribute to the calibration of models used to understand the formation of tight quadruple and quintuple systems in galactic environments.