Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “eclipse”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

The detached eclipsing binary KV 29 and the age of the open cluster M11

We present an extensive set of photometry and radial velocities for the detached eclipsing binary KV 29 in the intermediate-aged open cluster M11 (NGC 6705). Spectroscopy shows that the system is double lined, and all available evidence (proper motion, photometry, and position on the color–magnitude diagram) indicates that it is a member of the cluster. We find the period of the binary to be 4.64276 ± 0.00001 days. We find masses 3.604{sub −0.011}{sup +0.002}M{sub ⊙} and 1.837{sub −0.006}{sup +0.001}M{sub ⊙} and radii 5.392{sub −0.035}{sup +0.018}R{sub ⊙} and 1.656{sub −0.044}{sup +0.007}R{sub ⊙} for the primary and secondary stars, respectively. Because the primary star in the binary is rapidly evolving and is brighter than the cluster turnoff in a color–magnitude diagram, the measurement of its mass leads to a strong constraint on the cluster age. We find the age of M11 to be 222{sub −3}{sup +2}±15 Myr, where the quoted uncertainties come from statistical errors in the calculated masses and radii, and systematic uncertainties due to the ambiguity of the metallicity of the open cluster and variations within the isochrone models concerning heavy elements and convective overshooting.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

The K2 M67 Study: A Curiously Young Star in an Eclipsing Binary in an Old Open Cluster

We present an analysis of a slightly eccentric (e = 0.05), partially eclipsing, long-period (P = 69.73 days) main-sequence binary system (WOCS 12009, Sanders 1247) in the benchmark old open cluster M67. Using Kepler K2 and ground-based photometry, along with a large set of new and reanalyzed spectra, we derived highly precise masses (1.111 ± 0.015 and 0.748 ± 0.005 M {sub ⊙}) and radii (1.071 ± 0.008 ± 0.003 and 0.713 ± 0.019 ± 0.026 R {sub ⊙}, with statistical and systematic error estimates) for the stars. The radius of the secondary star is in agreement with theory. The primary, however, is approximately 15% smaller than reasonable isochrones for the cluster predict. Our best explanation is that the primary star was produced from the merger of two stars, as this can also account for the nondetection of photospheric lithium and its higher temperature relative to other cluster main-sequence stars at the same V magnitude. To understand the dynamical characteristics (low measured rotational line broadening of the primary star and low eccentricity of the current binary orbit), we believe that the most probable (but not the only) explanation is the tidal evolution of a close binary within a primordial triple system (possibly after a period of Kozai–Lidov oscillations), leading to merger approximately 1 Gyr ago. This star appears to be a future blue straggler that is being revealed as the cluster ages and the most massive main-sequence stars die out.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Photometric Solutions of Three Eclipsing Binary Stars Observed from Dome A, Antarctica

Based on spectroscopic observations for the eclipsing binaries CSTAR 036162 and CSTAR 055495 with the WiFeS/2.3 m telescope at SSO and CSTAR 057775 with the Mage/Magellan I at LCO in 2017, stellar parameters are derived. More than 100 nights of almost-continuous light curves reduced from the time-series photometric observations by CSTAR at Dome A of Antarctic in i in 2008 and in g and r in 2009, respectively, are applied to find photometric solutions for the three binaries with the Wilson–Devinney code. The results show that CSTAR 036162 is a detached configuration with the mass ratio q = 0.354 ± 0.0009, while CSTAR 055495 is a semi-detached binary system with the unusual q = 0.946 ± 0.0006, which indicates that CSTAR 055495 may be a rare binary system with mass ratio close to one and the secondary component filling its Roche Lobe. This implies that a mass-ratio reversal has just occurred and CSTAR 055495 is in a rapid mass-transfer stage. Finally, CSTAR 057775 is believed to be an A-type W UMa binary with q = 0.301 ± 0.0008 and a fill-out factor of f = 0.742(8).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Time-series Spectroscopy of the Oscillating Eclipsing Algol System V392 Orionis

We present the results from a detailed analysis of our high-resolution spectra and historical photometric observations of the semidetached eclipsing binary V392 Ori with a δ Scuti (δ Sct) pulsating component. A total of 31 spectroscopic observations were carried out at both the Bohyunsan Optical Astronomy Observatory in Korea and the Thai National Observatory in Thailand during the 2016 and 2017 observing seasons. The radial velocities (RVs) of the primary and the faint secondary components were determined, and the effective temperature and projected rotational velocity of the former star were measured as T {sub eff,1} = 8500 ± 160 K and v {sub 1} sin i = 148 ± 13 km s{sup −1}, respectively, through a comparison of the observed spectra and stellar atmosphere models. The physical properties of V392 Ori were determined by analysis of our RVs together with the existing multiband light curves. The results are the following: masses of M {sub 1} = 2.28 ± 0.30 M {sub ⊙} and M {sub 2} = 0.49 ± 0.10 M {sub ⊙}, and radii of R {sub 1} = 2.08 ± 0.09 R {sub ⊙} and R {sub 2} = 1.15 ± 0.05 R {sub ⊙}. The primary star located inside the main-sequence band exhibits a δ Sct-type pulsation. On the contrary, the less massive secondary component is significantly oversized and overluminous for its mass and temperature.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

The Pre-He White Dwarfs in Eclipsing Binaries. I. WASP 0131+28

We report the first BV light curves and high-resolution spectra of the post-mass transfer binary star WASP 0131+28 to study the absolute properties of extremely low-mass white dwarfs. From the observed spectra, the double-lined radial velocities were derived, and the effective temperature and rotational velocity of the brighter, more massive primary were found to be T{sub eff,1}=10,000±200 K and v{sub 1}sin i = 55 ± 10 km s{sup −1}, respectively. The combined analysis of the Transiting Exoplanet Survey Satellite (TESS) archive data and ours yielded the accurate fundamental parameters of the program target. The masses were derived to about 1.0% accuracy and the radii to 0.6%, or better. The secondary component's parameters of M{sub 2}=0.200±0.002 M{sub ⊙}, R{sub 2}=0.528±0.003 R{sub ⊙}, T{sub eff,2} = 11,186 ± 235 K, and L{sub 2}=3.9±0.3 L{sub ⊙} are in excellent agreement with the evolutionary sequence for a helium-core white dwarf of mass 0.203 M{sub ⊙}, and indicates that this star is halfway through the constant luminosity phase. The results presented in this article demonstrate that WASP 0131+28 is an EL CVn eclipsing binary in a thin disk, which is formed from the stable Roche-lobe overflow channel and composed of a main-sequence dwarf with a spectral type A0 and a pre-He white dwarf.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

A KELT–TESS Eclipsing Binary in a Young Triple System Associated with the Local “Stellar String” Theia 301

HD 54236 is a nearby, wide common-proper-motion visual pair that has been previously identified as likely being very young by virtue of strong X-ray emission and lithium absorption. Here, we report the discovery that the brighter member of the wide pair, HD 54236A, is itself an eclipsing binary (EB), comprising two near-equal solar-mass stars on a 2.4 days orbit. It represents a potentially valuable opportunity to expand the number of benchmark-grade EBs at young stellar ages. Using new observations of Ca ii H and K emission and lithium absorption in the wide K-dwarf companion, HD 54236B, we obtain a robust age estimate of 225 ± 50 Myr for the system. This age estimate and Gaia proper motions show HD 54236 is associated with Theia 301, a newly discovered local “stellar string,” which itself may be related to the AB Dor moving group through shared stellar members. Applying this age estimate to AB Dor itself alleviates reported tension between observation and theory that arises for the luminosity of AB Dor C when younger age estimates are used.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

γ DORADUS PULSATIONS IN THE ECLIPSING BINARY STAR KIC 6048106

We present the Kepler photometry of KIC 6048106, which is exhibiting the O’Connell effect and multiperiodic pulsations. Including a starspot on either of the components, light-curve synthesis indicates that this system is a semi-detached Algol with a mass ratio of 0.211, an orbital inclination of 73.°9, and a large temperature difference of 2534 K. To examine in detail both the spot variations and pulsations, we separately analyzed the Kepler time-series data at the interval of an orbital period in an iterative way. The results reveal that the variable asymmetries of the light maxima can be interpreted as the changes with time of a magnetic cool spot on the secondary component. Multiple frequency analyses were performed in the outside-eclipse light residuals after removal of the binarity effects from the observed Kepler data. We detected 30 frequencies with signal to noise amplitude ratios larger than 4.0, of which six ( f {sub 2}– f {sub 6} and f {sub 10}) can be identified as high-order (17 ≤ n ≤ 25) low-degree ( ℓ = 2) gravity-mode pulsations that were stable during the observing run of 200 days. In contrast, the other frequencies may be harmonic and combination terms. For the six frequencies, the pulsation periods and pulsation constants are in the ranges of 0.352–0.506 days and 0.232–0.333 days, respectively. These values and the position on the Hertzsprung–Russell diagram demonstrate that the primary star is a γ Dor variable. The evolutionary status and the pulsation nature of KIC 6048106 are discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Accurate Orbital Solution for the New and Metal-poor Eclipsing Binary Tycho 5227-1023-1

The orbit and physical parameters of the previously unsolved double-lined eclipsing binary Tyc 5227-1023-1, discovered during the search for RR Lyr variable candidate members of the Aquarius stream, are derived using high-resolution échelle spectroscopy and V,i{sup ′} photometry. A synthetic spectral analysis of both components has been performed, yielding metallicity [M/H] = −0.63 ± 0.11 for both stars and a temperature for the secondary that is in close agreement with the one from the orbital solution, while the temperature of the primary is determined from photometry (T{sub 1}=6350 K). The masses and radii (M{sub 1}=0.96±0.02,M{sub 2}=0.84±0.01 M{sub ⊙}, R{sub 1}=1.39±0.01,R{sub 2}=0.98±0.01 R{sub ⊙}) reveal that both stars have already slightly evolved away from the main-sequence band, having an age of about 7 Gyr, and the results of the synthetic spectral analysis support the claim of corotation with the orbital motion. The radial velocity of the system is −60±2 km s{sup −1}, while its distance, computed from orbital parameters and the derived reddening E{sub B−V}=0.053, is 496 ± 35 pc. Even though Tyc 5227-1023-1 was initially treated as a possible member of the Aquarius stream, the results presented here disagree with reported values for this ancient structure and suggest a likely membership of the thick disk.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Coevality in Young Eclipsing Binaries

The ages of the components in very short period pre-main-sequence (PMS) binaries are essential to an understanding of their formation. We considered a sample of seven PMS eclipsing binaries (EBs) with ages 1–6.3 MY and component masses 0.2–1.4 M{sub ⊙}. The very high precision with which their masses and radii have been measured and the capability provided by the Modules for Experiments in Stellar Astrophysics to calculate their evolutionary tracks at exactly the measured masses allows the determination of age differences of the components independent of their luminosities and effective temperatures. We found that the components of five EBs, ASAS J052821+0338.5, Parenago 1802, JW 380, CoRoT 223992193, and UScoCTIO 5, formed within 0.3 MY of each other. The parameters for the components of V1174 Ori imply an implausible large age difference of 2.7 MY and should be reconsidered. The seventh EB in our sample, RX J0529.4+0041 fell outside the applicability of our analysis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

New Low-mass Eclipsing Binary Systems in Praesepe Discovered by K2

We present the discovery and characterization of four low-mass (M<0.6 M{sub ⊙}) eclipsing binary (EB) systems in the sub-Gyr old Praesepe open cluster using Kepler/K2 time series photometry and Keck/HIRES spectroscopy. We present a new Gaussian process EB model, GP–EBOP, as well as a method of simultaneously determining effective temperatures and distances for EBs. Three of the reported systems (AD 3814, AD 2615 and AD 1508) are detached and double-lined, and precise solutions are presented for the first two. We determine masses and radii to 1%–3% precision for AD 3814 and to 5%–6% for AD 2615. Together with effective temperatures determined to ∼50 K precision, we test the PARSEC v1.2 and BHAC15 stellar evolution models. Our EB parameters are more consistent with the PARSEC models, primarily because the BHAC15 temperature scale is hotter than our data over the mid-M-dwarf mass range probed. Both ADs 3814 and 2615, which have orbital periods of 6.0 and 11.6 days, are circularized but not synchronized. This suggests that either synchronization proceeds more slowly in fully convective stars than the theory of equilibrium tides predicts, or magnetic braking is currently playing a more important role than tidal forces in the spin evolution of these binaries. The fourth system (AD 3116) comprises a brown dwarf transiting a mid-M-dwarf, which is the first such system discovered in a sub-Gyr open cluster. Finally, these new discoveries increase the number of characterized EBs in sub-Gyr open clusters by 20% (40%) below M<1.5 M {sub ⊙} (M<0.6 M {sub ⊙}).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Discovery of a Detached, Eclipsing 40 Minute Period Double White Dwarf Binary and a Friend: Implications for He+CO White Dwarf Mergers

We report the discovery of two detached double white dwarf (WD) binaries, SDSS J082239.546+304857.19 and SDSS J104336.275+055149.90, with orbital periods of 40 and 46 minutes, respectively. The 40 minute system is eclipsing; it is composed of a 0.30 M {sub ⊙} and a 0.52 M {sub ⊙} WD. The 46 minute system is a likely LISA verification binary. The short 20 ± 2 Myr and ∼34 Myr gravitational-wave merger times of the two binaries imply that many more such systems have formed and merged over the age of the Milky Way. We update the estimated Milky Way He+CO WD binary merger rate and affirm our previously published result: He+CO WD binaries merge at a rate at least 40 times greater than the formation rate of stable mass-transfer AM CVn binaries, and so the majority must have unstable mass-transfer. The implication is that spin–orbit coupling in He+CO WD mergers is weak, or perhaps nova-like outbursts drive He+CO WDs into merger, as proposed by Shen.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The SDSS-HET Survey of Kepler Eclipsing Binaries. A Sample of Four Benchmark Binaries

The purpose of this work is to extend a sample of accurately modeled, benchmark-grade eclipsing binaries (EBs) with accurately determined masses and radii. We select four "well-behaved" Kepler binaries, KIC 2306740, KIC 4076952, KIC 5193386 and KIC 5288543, each with at least eight double-lined spectra from the Apache Point Observatory Galactic Evolution Experiment instrument that is part of the Sloan Digital Sky Surveys III and IV, and from the Hobby–Eberly High Resolution Spectrograph. We obtain masses and radii with uncertainties of 2.5% or less for all four systems. Three of these systems have orbital periods longer than 9 days, and thus populate an undersampled region of the parameter space for extremely well-characterized detached EBs. We compare the derived masses and radii against MESA MIST isochrones to determine the ages of the systems. All systems were found to be coeval, showing that the results are consistent across MESA MIST and PHOEBE .

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Multi-period G-mode pulsations of a pre-He-WD star in the eclipsing binary KIC 9164561

We report the discovery of a new pulsating pre-He-WD in the EL CVn-type binary KIC 9164561. Light curve modeling and frequency analysis of the binary system were carried out based on short-cadence Kepler photometry. Combined with the radial-velocity solution, revised physical parameters of the binary system were determined. The component KIC 9164561B was confirmed to be a pre-He-WD star with M = 0.213±0.012M{sub ⊙}, R = 0.283±0.006R{sub ⊙}, and T{sub eff} = 10650±200 K. In addition to the light changes due to an eclipse, pulsational light variations of the pre-He-WD star were detected. The Fourier analysis reveals at least 52 frequencies, with the dominant one at 313.4 μHz. A brief mode identification indicates that the pre-He-WD star pulsates in g-modes with an average period spacing of ΔΠ{sub l=1} = 80.87 s. Moreover, a number of multiplets due to rotational splitting were identified from the frequency spectra. The rotational period of the pulsating pre-He-WD star was found to equal to the orbital period, indicating that KIC 9164561B is in synchronous rotation.

79 ASTRONOMY AND ASTROPHYSICS↗