Eclipsing System Research Articles

THE NEW ECLIPSING POST COMMON-ENVELOPE BINARY SDSS J074548.63+263123.4

The common-envelope process is a complicated phase in binary evolution. A lot of effort has been dedicated to study the common-envelope stage, but many questions related to this process are yet to be answered. If one member of the binary survives the common-envelope phase, the binary will emerge as a white dwarf accompanied by a low-mass main sequence star in close orbit, often referred as a post common-envelope binary (PCEB). SDSS J0745+2631 is among the list of newly found PCEBs from the Sloan Digital Sky Survey (SDSS). This star is proposed to be a strong eclipsing system candidate due to the ellipsoidal modulation in its light curve. In this work, we aim to confirm the eclipsing nature of SDSS J0745+2631 and to determine the stellar and orbital parameters using the software Binary Maker 3.0 (BM3.0). We detected the primary eclipse in the light curve of SDSS J0745+2631 in our follow-up observation from January 2014 using the ULTRASPEC instrument at the Thai National Observatory. The data obtained on 7th and 8th January 2014 in g filter show an evident drop in brightness during the eclipse of the white dwarf, but this eclipse is less prominent in the data taken on the next night using a clear filter. According to our preliminary model, we find that SDSS J0745+2631 hosts a rather hot white dwarf with an effective temperature of 11500K. The companion star is a red dwarf star with a temperature of 3800K and radius of 0.3100 <TEX>$R_{\odot}$</TEX>. The red dwarf star almost fills its Roche lobe, causing a large ellipsoidal modulation. The mass ratio of the binary given by the Binary Maker 3.0 (BM3.0) model is M2/M1 = 0.33.

A COORDINATED X-RAY AND OPTICAL CAMPAIGN OF THE NEAREST MASSIVE ECLIPSING BINARY,δORIONIS Aa. IV. A MULTIWAVELENGTH, NON-LTE SPECTROSCOPIC ANALYSIS

Eclipsing systems of massive stars allow one to explore the properties of their components in great detail. We perform a multi-wavelength, non-LTE analysis of the three components of the massive multiple system $\delta$ Ori A, focusing on the fundamental stellar properties, stellar winds, and X-ray characteristics of the system. The primary's distance-independent parameters turn out to be characteristic for its spectral type (O9.5 II), but usage of the ${\rm \it Hipparcos}$ parallax yields surprisingly low values for the mass, radius, and luminosity. Consistent values follow only if $\delta$ Ori lies at about twice the ${\rm \it Hipparcos}$ distance, in the vicinity of the $\sigma$-Orionis cluster. The primary and tertiary dominate the spectrum and leave the secondary only marginally detectable. We estimate the V-band magnitude difference between primary and secondary to be $\Delta V \approx 2.\!\!^{\rm m}8$. The inferred parameters suggest the secondary is an early B-type dwarf ($\approx$ B1 V), while the tertiary is an early B-type subgiant ($\approx$ B0 IV). We find evidence for rapid turbulent velocities ($\sim 200$ km ${\rm s}^{-1}$) and wind inhomogeneities, partially optically thick, in the primary's wind. The bulk of the X-ray emission likely emerges from the primary's stellar wind ($\log L_{\text{X}} / L_{\text{Bol}} \approx -6.85$), initiating close to the stellar surface at $R_0 \sim 1.1\,R_*$. Accounting for clumping, the mass-loss rate of the primary is found to be $\log \dot{M} \approx -6.4\,[M_\odot\,{\rm yr}^{-1}]$, which agrees with hydrodynamic predictions, and provides a consistent picture along the X-ray, UV, optical and radio spectral domains.

THE MASS–RADIUS RELATION OF YOUNG STARS. I. USCO 5, AN M4.5 ECLIPSING BINARY IN UPPER SCORPIUS OBSERVED BY K2

We present the discovery that UScoCTIO 5, a known spectroscopic binary in the Upper Scorpius star-forming region (P = 34 days, ), is an eclipsing system with both primary and secondary eclipses apparent in K2 light curves obtained during Campaign 2. We have simultaneously fit the eclipse profiles from the K2 light curves and the existing RV data to demonstrate that UScoCTIO 5 consists of a pair of nearly identical M4.5 stars with , , , and . The radii are broadly consistent with pre-main-sequence ages predicted by stellar evolutionary models, but none agree to within the uncertainties. All models predict systematically incorrect masses at the 25%?50% level for the HR diagram position of these mid-M dwarfs, suggesting significant modifications to mass-dependent outcomes of star and planet formation. The form of the discrepancy for most model sets is not that they predict luminosities that are too low, but rather that they predict temperatures that are too high, suggesting that the models do not fully encompass the physics of energy transport (via convection and/or missing opacities) and/or a miscalibration of the SpT? scale. The simplest modification to the models (changing to match observations) would yield an older age for this system, in line with the recently proposed older age of Upper Scorpius (? ? 11 Myr).

CC Sculptoris: Eclipsing SU UMa-type intermediate polar

Abstract We observed the 2014 superoutburst of the SU UMa-type intermediate polar CC Scl. We detected superhumps with a mean period of 0.05998(2) d during the superoutburst plateau and during three nights after the fading. During the post-superoutburst stage after three nights, a stable superhump period of 0.059523(6) d was detected. We found that this object is an eclipsing system with an orbital period of 0.058567233(8) d. By assuming that the disk radius in the post-superoutburst phase is similar to those in other SU UMa-type dwarf novae, we obtained a mass ratio of q = 0.072(3) from the dynamical precession rate of the accretion disk. The eclipse profile during outbursts can be modeled by an inclination of 80 $_{.}^{\circ}$6 ± 0 $_{.}^{\circ}$5. The 2014 superoutburst was preceded by a precursor outburst and the overall appearance of the outburst was similar to superoutbursts in ordinary SU UMa-type dwarf novae. We showed that the standard thermal-tidal instability model can explain the outburst behavior in this system and suggest that inner truncation of the disk by magnetism of the white dwarf does not strongly affect the behavior in the outer part of the disk.

JHKLM-Observations of the Unique Eclipsing System ε Aur During a Secondary Minimum

Photometric data in the JHKLM near infrared bands obtained in 1999-2000 are presented for the long-period eclipsing system e Aur. The time of secondary eclipse (when the F21 supergiant eclipses a dust disk surrounding the more massive component of the system) is calculated using the latest orbital elements of the system. A brightness minimum with an amplitude of ~0m.05 is observed in all bands at the phase of the expected secondary eclipse (φ = 0.606). The nearest subsequent time of a secondary eclipse, which will occur in December 2026-February 2027, is calculated. It is shown that during the secondary minimum the B5V star currently proposed as the secondary component cannot be eclipsed. It is proposed that the eclipsed component should be a hot star surrounded by a gas-dust cloud and with luminosity and radius exceeding the typical values for Main sequence stars.

Characterizing distant worlds with asterodensity profiling

Eclipsing systems, such as transiting exoplanets, allow one to measure the mean stellar density of the host star under various idealized assumptions. Asterodensity profiling (AP) compares this density to an independently determined value in order to check the validity of the assumptions and ultimately derive useful parameters. Several physical effects can cause said assumptions to become invalid, with the most well-known example being the so-called photoeccentric effect. In this work, we provide analytic expressions for five other effects which induce AP deviations: the photoblend, -spot, -timing, -duration and -mass effects. We find that these effects can easily reproduce large AP deviations and so we caution that extracting the eccentricity distribution is only viable with careful consideration of the prior distributions for these other effects. We also re-investigate the photoeccentric effect and derive a single-domain minimum eccentricity expression and the parameter range for which analytic formulae are valid. The latter result shows that the assumptions underlying the analytic model for the photoeccentric effect break down for close-in, highly eccentric planets, meaning that extreme care must be taken in this regime. Finally, we demonstrate that contaminated light fraction can be solved for, indicating that AP could be a potent tool for planet validation.

Orbital, superhump and superorbital periods in the cataclysmic variables AQ Mensae and IM Eridani

We report photometric detections of orbital and superorbital signals, and negative orbital sidebands, in the light curves of the nova-like cataclysmic variables AQ Mensae and IM Eridani. The frequencies of the orbital, superorbital, and sideband signals are 7.0686 (3), 0.263 (3), and 7.332 (3) cycles per day (c/d) in AQ Mensae, and 6.870 (1), 0.354 (7), and 7.226 (1) c/d in IM Eridani. We also find a spectroscopic orbital frequency in IM Eridani of 6.86649 (2) c/d. These observations can be reproduced by invoking an accretion disc that is tilted with respect to the orbital plane. This model works well for X-ray binaries, in which irradiation by a primary neutron star can account for the disc's tilt. A likely tilt mechanism has yet to be identified in CVs, yet the growing collection of observational evidence indicates that the phenomenon of tilt is indeed at work in this class of object. The results presented in this paper bring the number of CVs known to display signals associated with retrograde disc precession to twelve. We also find AQ Mensae to be an eclipsing system. The eclipse depths are highly variable, which suggests that the eclipses are grazing. This finding raises the possibility of probing variations in disc tilt by studying systematic variations in the eclipse profile.

Life after eruption – II. The eclipsing old nova V728 Scorpii

The old nova V728 Sco has been recently recovered via photometric and spectroscopic observations, 150 years after the nova eruption. The spectral properties pointed to a high-inclination system with a comparatively low mass-transfer rate. In this paper we show that the object is an eclipsing system with an orbital period of 3.32 h. It has enhanced long-term variability that can be interpreted as 'stunted' dwarf-nova-type outbursts. Using the ingress and egress times of the eclipsed components we calculate the radius of the central object. The latter turns out to be significantly larger than a white dwarf and we identify it with a hot inner disc. The implications for models on the behaviour of post-novae are discussed.

HD 181068: a triply eclipsing system with intrinsically variable red giant component

We present the analysis of HD 181068 which is one of the first triply eclipsing triple system discovered. Using Kepler photometry, ground based spectroscopic and interferometric measurements, we determined the stellar and orbital parameters of the system. We show that the oscillations observed in the red giant component of the system are tidally forced oscillations, while one of the most surprising results is that it does not show solar-like oscillations.

A transiting companion to the eclipsing binary KIC002856960

We present an early result from an automated search of Kepler eclipsing binary systems for circumbinary companions. An intriguing tertiary signal has been discovered in the short period eclipsing binary KIC002856960. This third body leads to transit-like features in the light curve occurring every 204.2 days, while the two other components of the system display eclipses on a 6.2 hour period. The variations due to the tertiary body last for a duration of \sim1.26 days, or 4.9 binary orbital periods. During each crossing of the binary orbit with the tertiary body, multiple individual transits are observed as the close binary stars repeatedly move in and out of alignment with the tertiary object. We are at this stage unable to distinguish between a planetary companion to a close eclipsing binary, or a hierarchical triply eclipsing system of three stars. Both possibilities are explored, and the light curves presented.

Application of the Direct Distance Estimation procedure to eclipsing binaries in star clusters

AbstractWe alert the community to a paradigm method to calibrate a range of standard candles by means of well-calibrated photometry of eclipsing binaries in star clusters. In particular, we re-examine systems studied as part of our Binaries-in-Clusters program, and previously analyzed with earlier versions of the Wilson–Devinney light-curve modeling program. We make use of the 2010 version of this program, which incorporates a procedure to estimate the distance to an eclipsing system directly, as a system parameter, and is thus dependent on the data and analysis model alone. As such, the derived distance is accorded a standard error, independent of any additional assumptions or approximations that such analyses conventionally require.

Photoelectric Radial Velocities, Paper XVIII Spectroscopic Orbits for Another 52 Binaries in the Hyades Field

Spectroscopic orbits are presented for 52 stars in the Hyades field, of which 41 prove to be actual members of the Hyades (with some reservations in two cases). Most of the stars concerned have not had orbits published for them previously. Three of them are of higher multiplicity. The already-known double-lined eclipsing system van Bueren 22 is demonstrated to be a triple system, as was obliquely announced 25 years ago; its ‘outer’ orbit, which has a period of about 8 years, is now determined. Van Bueren 75 is already known to be triple, but here the visual secondary is shown to be the (single-lined) spectroscopic sub-system, and an independent spectroscopic solution is given for the 40-year orbit of what has hitherto been regarded as the ‘visual’ pair. Van Bueren 102, for which a close visual companion was discovered comparatively recently, is a single-lined binary whose γ -velocity has shown a steady drift over at least the last 30 (probably 50) years. Three stars, vB 39, 50 and 59, have notably high eccentricities of 0.85, 0.98 and 0.94, respectively; they have quite long periods (especially vB 50, which is over 100 years), and every one of them contrived to pass the whole of its recent periastron passage (about 180° of true anomaly) between seasons, at the time of year when the Hyades are unobservable!

Detection of an increasing orbital period in the subdwarf B eclipsing system NSVS 14256825

New timings of eclipses made in 2010 and 2011 are presented for the hot subdwarf B (sdB) eclipsing binary NSVS 14256825. Composed of an sdB star and a much cooler companion, with a period near 0.1104 days, this system is very similar to the prototype sdB eclipsing binary HW Vir. The new observations show that the binary period of NSVS 14256825 is rapidly increasing at a rate of about 12 × 10 −12 days orbit −1 .

Features of the orbital variability in the brightness of the WZ Sge type dwarf nova V1108 Her

Results are presented from photometric studies of the dwarf nova V1108 Her conducted at the primary focus of the 2.6-m G. A. Shajn Telescope at the Crimean Astrophysical Observatory during June-July 2008, 4 years after the 2004 outburst. An orbital period of 0.05672(4) days is found for the system. An analysis of observations made earlier during the 2004 outburst reveals an orbital signal which indicates that V1108 Her is an eclipsing system. The mass ratio of the secondary component to the white dwarf is estimated to be q = 0.068, which makes it highly likely that the secondary component of this system is a brown dwarf. The orbital light curves indicate a complex structure for the accretion disk whose radius has reached a 2:1 resonance. An explanation is suggested for a quasi-periodic modulation in the brightness at 1/4 of the orbital period observed in V1108 Her and other WZ Sge systems.

Eccentricity of Selected Eclipsing Systems

AbstractThis paper presents the results of verification of known stars showing evidence of orbital eccentricity and apsidal motion.

DISCOVERY OF AN ACCRETING MILLISECOND PULSAR IN THE ECLIPSING BINARY SYSTEM SWIFT J1749.4–2807

We report on the discovery and the timing analysis of the first eclipsing accretion-powered millisecond X-ray pulsar (AMXP): SWIFT J1749.4–2807. The neutron star rotates at a frequency of ∼517.9 Hz and is in a binary system with an orbital period of 8.8 hr and a projected semimajor axis of ∼1.90 lt-s. Assuming a neutron star between 0.8 and 2.2 M☉ and using the mass function of the system and the eclipse half-angle, we constrain the mass of the companion and the inclination of the system to be in the ∼0.46–0.81 M☉ and ∼ 744–773 range, respectively. To date, this is the tightest constraint on the orbital inclination of any AMXP. As in other AMXPs, the pulse profile shows harmonic content up to the third overtone. However, this is the first AMXP to show a first overtone with rms amplitudes between ∼6% and ∼23%, which is the strongest ever seen and which can be more than two times stronger than the fundamental. The fact that SWIFT J1749.4–2807 is an eclipsing system that shows uncommonly strong harmonic content suggests that it might be the best source to date to set constraints on neutron star properties including compactness and geometry.

CAL 87 – an evolved wind-driven supersoft X-ray binary

Context. Compact binary supersoft X-ray sources (CBSS) are explained as being associated with hydrostatic nuclear burning on the surface of a white dwarf with high accretion rate. This high mass transfer rate has been suggested to be caused by dynamical instability, expected when the donor star is more massive than the accreting object. When the orbital period is smaller than ∼ 6h , this mechanism does not work and the CBSS with such periods are believed to be fed by a distinct mechanism: the wind-driven accretion. Such a mechanism has been proposed to explain the properties of objects like SMC 13, T Pyx and V617 Sgr. One observational property that offers a critical test for discriminating between the above two possibilities is the orbital period change. Aims. As systems with wind-driven accretion evolve with increasing periods, some of them may reach quite long orbital periods. The above critical test may, therefore, also be applied to orbital periods longer than 6 h. CAL 87 is an eclipsing system in the LMC with an orbital period of 10.6 h that could provide the opportunity for testing the hypothesis of the system being powered by wind-driven accretion. Methods. We obtained eclipse timings for this system and show that its orbital period increases with a rate of P/ u P =+ 7.2(±1.3) × 10 6 years. Results. Contrary to the common belief, we conclude that CAL 87 is the first confirmed case of a wind-driven CBSS with an orbital

Infrared Spectroscopy of Symbiotic Stars. V. First Orbits for Three S-Type Systems: Henize 2-173, CL Scorpii, and AS 270

Infrared radial velocities have been used to compute first orbits of the M giants in three southern S-type symbiotic systems. Of the three, Hen 2-173 has the longest orbital period, 911 days, and also has a noncircular orbit with an eccentricity of 0.21. The large value of its mass function suggests that Hen 2-173 may be an eclipsing system. For CL Sco our spectroscopic orbital period of 626 days is essentially identical to the previously determined light variability period of 625 days, and we have adopted the latter. AS 270 has an orbital period of similar length, 671 days, and both CL Sco and AS 270 have circular orbits. Only CL Sco has been extensively investigated previously, and we compare our results with the conclusions of Kenyon & Webbink. We also have examined the period-eccentricity relation for 30 S-type symbiotics. Circular orbits are found for 81% of the systems with orbital periods up to 800 days, while they occur for only 22% with periods greater than 800 days. This distribution is quite unlike that for G and K giants; rather, it is similar to that for barium stars, another type of mass-transfer binary, which also consists of a late-type giant and a white dwarf companion.

Spectroscopy of Old Nova Candidates

We present optical spectroscopy for several old nova candidates that hitherto lacked such observations. V842 Cen, V630 Sgr, XX Tau, CQ Vel, and V840 Oph show typical CV spectra, but V529 Ori is probably misclassified.V630 Sgr is an eclipsing system with an orbital period of 2.83 h. In spite of the high inclination, the emission lines are not, double-peaked at the resolution of 1 mm.

Detection of Two-armed Spiral Shocks on the Accretion Disk of the Eclipsing Fast Nova V1494 Aquilae

We have modeled the unusual orbital light curve of V1494 Aquilae (Nova Aquilae 1999 No.2) and found that such an unusual orbital light curve can be reproduced when there exist two-armed, spiral shocks on the accretion disk. V1494 Aql is a fast classical nova and found to be an eclipsing system with the orbital period of 0.1346138 days in the late phase of the nova outburst. Its orbital light curve shows a small bump at orbital phase 0.2, a small dip at 0.3, sometimes a small bump at 0.4, and a large bump at 0.6-0.7 outside eclipse. Such a double- or triple-wave pattern outside eclipse has never been observed even though overall patterns look like some supersoft X-ray sources or eclipsing polars. We have calculated orbital light curves including the irradiation effects of the accretion disk and the companion by the hot white dwarf. These unusual patterns can be reproduced when we assume two-armed spiral shocks on the accretion disk. Especially, triple-wave patterns are naturally obtained. This result strongly suggests the existence of two-armed spiral shocks on the accretion disk in the late phase of the nova outburst.