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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.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

SU-E-T-305: Study of the Eclipse Electron Monte Carlo Algorithm for Patient Specific MU Calculations

Purpose: To evaluate the Eclipse electron Monte Carlo (eMC) algorithm based on patient specific monitor unit (MU) calculations, and to propose a new factor which quantitatively predicts the discrepancy of MUs between the eMC algorithm and hand calculations. Methods: Electron treatments were planned for 61 patients on Eclipse (Version 10.0) using the eMC algorithm for Varian TrueBeam linear accelerators. For each patient, the same treatment beam angle was kept for a point dose calculation at dmax performed with the reference condition, which used an open beam with a 15×15 cm2 size cone and 100 SSD. A patient specific correction factor (PCF) was obtained by getting the ratio between this point dose and the calibration dose, which is 1 cGy per MU delivered at dmax. The hand calculation results were corrected by the PCFs and compared with MUs from the treatment plans. Results: The MU from the treatment plans were in average (7.1±6.1)% higher than the hand calculations. The average MU difference between the corrected hand calculations and the eMC treatment plans was (0.07±3.48)%. A correlation coefficient of 0.8 was found between (1-PCF) and the percentage difference between the treatment plan and hand calculations. Most outliers were treatment plans with small beam opening (< 4 cm) and low energy beams (6 and 9 MeV). Conclusion: For CT-based patient treatment plans, the eMC algorithm tends to generate a larger MU than hand calculations. Caution should be taken for eMC patient plans with small field sizes and low energy beams. We hypothesize that the PCF ratio reflects the influence of patient surface curvature and tissue inhomogeneity to patient specific percent depth dose (PDD) curve and MU calculations in eMC algorithm.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-P-16: A Feasibility Study of Using Eclipse AAA for SRS Treatement

Purpose: To commission Varian Eclipse AAA for SRS treatment and compare the accuracy with Brainlab iPlan system for clinical cases measured with radiochromic film. Methods: A 6MV AAA clinical model for a Varian TrueBeam STx is used as baseline. The focal spot and field size of the baseline model(BASE) are (1.75,0.75) and 40×40cm{sup 2} respectively. Maximum field sizes, output factors(S{sub t}), FWHM focal spot and secondary source sizes are systematically adjusted to obtain an optimized model(OPT) by comparing the calculated PDD’s, profiles, and output factors with measurements taken with a stereotactic diode(SD) and, cc01 and cc04 ion chambers in Blue Phantom. In-phantom dose distributions of clinical SRS fields are calculated using the OPT and the clinical Brainlab iPlan pencil-beam. Within the 90% isodose-line(ROI), the average dose difference between the calculations and radiochromic film measurements are assessed. Results: The maximum field, focal spot and secondary source sizes for the OPT are 15×15cm{sup 2}, (0,0), and 32.3mm respectively. The OPT St input at 1.0 and 2.0cm fields are increased by 4.5% and 1.5% from BASE. The calculated output of the BASE and OPT underestimate by 16.1%–3.2% respectively at 0.5×0.5cm{sup 2} field and 3.1%−0.02% respectively at 1.0×1.0cm{sup 2} field. The depth doses at 10cm are within 3.5% and 0.4% of measurements for 0.5×0.5 and 1.0×1.0cm{sup 2}. The ROI dose of OPT and iPlan are within 1.6% and 0.6% of film measurements for 3.0cm clinical fields. For 1.0cm fields, the ROI dose of OPT underestimate 0.0–2.0% and iPlan overestimates 1.7–2.9% relative to measurements. Conclusion: The small field dose calculation of Eclipse AAA algorithm can be significantly improved by carefully adjusting the input parameters. The larger deviation of the OPT for 0.5×0.5cm{sup 2} field from measurements can be attributed to the lowest 1.0cm field size input limit of AAA. The OPT compares reasonably well with the iPlan pencil-beam and measurements.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-196: Comparative Analysis of Surface Dose Measurements Using MOSFET Detector and Dose Predicted by Eclipse - AAA with Varying Dose Calculation Grid Size

Purpose: Skin dose can be the limiting factor and fairly common reason to interrupt the treatment, especially for treating head-and-neck with Intensity-modulated-radiation-therapy(IMRT) or Volumetrically-modulated - arc-therapy (VMAT) and breast with tangentially-directed-beams. Aim of this study was to investigate accuracy of near-surface dose predicted by Eclipse treatment-planning-system (TPS) using Anisotropic-Analytic Algorithm (AAA)with varying calculation grid-size and comparing with metal-oxide-semiconductor-field-effect-transistors(MOSFETs)measurements for a range of clinical-conditions (open-field,dynamic-wedge, physical-wedge, IMRT,VMAT). Methods: QUASAR™-Body-Phantom was used in this study with oval curved-surfaces to mimic breast, chest wall and head-and-neck sites.A CT-scan was obtained with five radio-opaque markers(ROM) placed on the surface of phantom to mimic the range of incident angles for measurements and dose prediction using 2mm slice thickness.At each ROM, small structure(1mmx2mm) were contoured to obtain mean-doses from TPS.Calculations were performed for open-field,dynamic-wedge,physical-wedge,IMRT and VMAT using Varian-21EX,6&15MV photons using twogrid-sizes:2.5mm and 1mm.Calibration checks were performed to ensure that MOSFETs response were within ±5%.Surface-doses were measured at five locations and compared with TPS calculations. Results: For 6MV: 2.5mm grid-size,mean calculated doses(MCD)were higher by 10%(±7.6),10%(±7.6),20%(±8.5),40%(±7.5),30%(±6.9) and for 1mm grid-size MCD were higher by 0%(±5.7),0%(±4.2),0%(±5.5),1.2%(±5.0),1.1% (±7.8) for open-field,dynamic-wedge,physical-wedge,IMRT,VMAT respectively.For 15MV: 2.5mm grid-size,MCD were higher by 30%(±14.6),30%(±14.6),30%(±14.0),40%(±11.0),30%(±3.5)and for 1mm grid-size MCD were higher by 10% (±10.6), 10%(±9.8),10%(±8.0),30%(±7.8),10%(±3.8) for open-field, dynamic-wedge, physical-wedge, IMRT, VMAT respectively.For 6MV, 86% and 56% of all measured values agreed better than ±20% for 1mm and 2.5mm grid-sizes respectively. For 18MV, 56% and 18% of all measured-values agreed better than ±20% for 1mm and 2.5mm grid-sizes respectively. Conclusion: Reliable Skin-dose calculations by TPS can be very difficult due to steep dose-gradient and inaccurate beam-modelling in buildup region.Our results showed that Eclipse over-estimates surface-dose.Impact of grid-size is also significant,surface-dose increased up to 40% from 1mm to 2.5mm,however, 1mm calculated-values closely agrees with measurements. Due to large uncertnities in skin-dose predictions from TPS, outmost caution must be exercised when skin dose is evaluated,a sufficiently smaller grid-size(1mm)can improve the accuracy and MOSFETs can be used for verification.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-277: Dose Calculation Comparisons Between Monaco, Pinnacle and Eclipse Treatment Planning Systems

Purpose: Monaco treatment planning system (TPS) version 5.0 uses a Monte-Carlo based dose calculation engine. The aim of this study is to verify and compare the Monaco based dose calculations with both Pinnacle{sup 3} collapsed cone convolution superposition (CCC) and Eclipse analytical anisotropic algorithm (AAA) calculations. Methods: For this study, previously treated SBRT lung, head and neck and abdomen patients were chosen to compare dose calculations between Pinnacle, Monaco and Eclipse. Plans were chosen from those that had been treated using the Elekta VersaHD or a NovalisTX linac. The plans included 3D conventional and IMRT beams using 6MV and 6MV Flattening filter free (FFF) photon beams. The original plans calculated with CCCS or AAA along with the recalculated ones using MC from the three TPS were exported into Velocity software for inter-comparison. Results: To compare the dose calculations, Mean Lung Dose (MLD), lung V5 and V20 values, and PTV Heterogeneity indexes (HI) and Conformity indexes (CI) were all calculated and recorded from the dose volume histograms (DVH). For each patient, the CI values were identical but there were differences in all other parameters. The HI was computed higher by 5 and 4% for calculated plans AAA and CCCS respectively, compared to the MC ones. The DVH graphs showed large differences between the CCCS and AAA and Monaco for 3D FFF, VMAT and IMRT plans. Better DVH agreement between was observed for 3D conventional plans. Conclusion: Better agreement was observed between CCCS and MC calculations than AAA and MC calculations. Those differences were more profound as the field size was decreasing and in the presence of inhomogeneities.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-SPS-05: Experimental Validation of Peripheral Dose Distribution of Electron Beams for Eclipse Electron Monte Carlo Algorithm

Purpose: In this study, the two available calculation algorithms of the Varian Eclipse treatment planning system(TPS), the electron Monte Carlo(eMC) and General Gaussian Pencil Beam(GGPB) algorithms were used to compare measured and calculated peripheral dose distribution of electron beams. Methods: Peripheral dose measurements were carried out for 6, 9, 12, 15, 18 and 22 MeV electron beams of Varian Triology machine using parallel plate ionization chamber and EBT3 films in the slab phantom. Measurements were performed for 6×6, 10×10 and 25×25cm{sup 2} cone sizes at dmax of each energy up to 20cm beyond the field edges. Using the same film batch, the net OD to dose calibration curve was obtained for each energy. Films were scanned 48 hours after irradiation using an Epson 1000XL flatbed scanner. Dose distribution measured using parallel plate ionization chamber and EBT3 film and calculated by eMC and GGPB algorithms were compared. The measured and calculated data were then compared to find which algorithm calculates peripheral dose distribution more accurately. Results: The agreement between measurement and eMC was better than GGPB. The TPS underestimated the out of field doses. The difference between measured and calculated doses increase with the cone size. The largest deviation between calculated and parallel plate ionization chamber measured dose is less than 4.93% for eMC, but it can increase up to 7.51% for GGPB. For film measurement, the minimum gamma analysis passing rates between measured and calculated dose distributions were 98.2% and 92.7% for eMC and GGPB respectively for all field sizes and energies. Conclusion: Our results show that the Monte Carlo algorithm for electron planning in Eclipse is more accurate than previous algorithms for peripheral dose distributions. It must be emphasized that the use of GGPB for planning large field treatments with 6 MeV could lead to inaccuracies of clinical significance.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-256: 4D IMRT Planning Using An Early Prototype GPU-Enabled Eclipse Workstation

Purpose: True 4D IMRT planning, based on simultaneous spatiotemporal optimization has been shown to significantly improve plan quality in lung radiotherapy. However, the high computational complexity associated with such planning represents a significant barrier to widespread clinical deployment. We introduce an early prototype GPU-enabled Eclipse workstation for inverse planning. To our knowledge, this is the first GPUintegrated Eclipse system demonstrating the potential for clinical translation of GPU computing on a major commercially-available TPS. Methods: The prototype system comprised of four NVIDIA Tesla K80 GPUs, with a maximum processing capability of 8.5 Tflops per K80 card. The system architecture consisted of three key modules: (i) a GPU-based inverse planning module using a highly-parallelizable, swarm intelligence-based global optimization algorithm, (ii) a GPU-based open-source b-spline deformable image registration module, Elastix, and (iii) a CUDA-based data management module. For evaluation, aperture fluence weights in an IMRT plan were optimized over 9 beams,166 apertures and 10 respiratory phases (14940 variables) for a lung cancer case (GTV = 95 cc, right lower lobe, 15 mm cranio-caudal motion). Sensitivity of the planning time and memory expense to parameter variations was quantified. Results: GPU-based inverse planning was significantly accelerated compared to its CPU counterpart (36 vs 488 min, for 10 phases, 10 search agents and 10 iterations). The optimized IMRT plan significantly improved OAR sparing compared to the original internal target volume (ITV)-based clinical plan, while maintaining prescribed tumor coverage. The dose-sparing improvements were: Esophagus Dmax 50%, Heart Dmax 42% and Spinal cord Dmax 25%. Conclusion: Our early prototype system demonstrates that through massive parallelization, computationally intense tasks such as 4D treatment planning can be accomplished in clinically feasible timeframes. With further optimization, such systems are expected to enable the eventual clinical translation of higher-dimensional and complex treatment planning strategies to significantly improve plan quality. This work was partially supported through research funding from National Institutes of Health (R01CA169102) and Varian Medical Systems, Palo Alto, CA, USA.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

The Factory and the Beehive. III. PTFEB132.707+19.810, A Low-mass Eclipsing Binary in Praesepe Observed by PTF and K2

Theoretical models of stars constitute the fundamental bedrock upon which much of astrophysics is built, but large swaths of model parameter space remain uncalibrated by observations. The best calibrators are eclipsing binaries in clusters, allowing measurement of masses, radii, luminosities, and temperatures for stars of known metallicity and age. We present the discovery and detailed characterization of PTFEB132.707+19.810, a P = 6.0 day eclipsing binary in the Praesepe cluster (τ ∼ 600–800 Myr; [Fe/H] = 0.14 ± 0.04). The system contains two late-type stars (SpT{sub P} = M3.5 ± 0.2; SpT{sub S} = M4.3 ± 0.7) with precise masses (M{sub p}=0.3953±0.0020 M {sub ⊙}; M{sub s}=0.2098 ±0.0014 M {sub ⊙}) and radii (R{sub p}=0.363±0.008 R {sub ⊙}; R{sub s}=0.272±0.012 R {sub ⊙}). Neither star meets the predictions of stellar evolutionary models. The primary has the expected radius but is cooler and less luminous, while the secondary has the expected luminosity but is cooler and substantially larger (by 20%). The system is not tidally locked or circularized. Exploiting a fortuitous 4:5 commensurability between P {sub orb} and P{sub rot,prim}, we demonstrate that fitting errors from the unknown spot configuration only change the inferred radii by ≲1%–2%. We also analyze subsets of data to test the robustness of radius measurements; the radius sum is more robust to systematic errors and preferable for model comparisons. We also test plausible changes in limb darkening and find corresponding uncertainties of ∼1%. Finally, we validate our pipeline using extant data for GU Boo, finding that our independent results match previous radii to within the mutual uncertainties (2%–3%). We therefore suggest that the substantial discrepancies are astrophysical; since they are larger than those for old field stars, they may be tied to the intermediate age of PTFEB132.707+19.810.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Evaluating the Impact of the 2017 Solar Eclipse on U.S. Western Interconnection Operations

With support from the U.S. Department of Energy (DOE) Solar Energy Technologies Office (SETO), the National Renewable Energy Laboratory (NREL) partnered with Peak Reliability to evaluate the impact of the August 21, 2017 total solar eclipse on the reliability and grid operations in the Western Electricity Coordinating Council (WECC) territory.

14 SOLAR ENERGY↗
DOE OSTI2017

Why Don’t We See Solar Eclipses More Often?

August 21 will mark the first total solar eclipse visible from the continental U.S. in 38 years. And it’s the first one that will be observable across the entire contiguous United States since 1918. So, yes, it’s a big deal. Why don’t we see them more often?

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Absolute properties of the eclipsing binary VV CORVI

We have obtained red-wavelength spectroscopy and Johnson B and V differential photoelectric photometry of the eclipsing binary VV Crv = HR 4821. The system is the secondary of the common proper motion double star ADS 8627, which has a separation of 5.''2. VV Crv has an orbital period of 3.144536 days and a low but non-zero eccentricity of 0.085. With the Wilson-Devinney program we have determined a simultaneous solution of our spectroscopic and photometric observations. Those orbital elements produce masses of M {sub 1} = 1.978 ± 0.010 M {sub ☉} and M {sub 2} = 1.513 ± 0.008 M {sub ☉}, and radii of R {sub 1} = 3.375 ± 0.010 R {sub ☉} and R {sub 2} = 1.650 ± 0.008 R {sub ☉} for the primary and secondary, respectively. The effective temperatures of the two components are 6500 K (fixed) and 6638 K, so the star we call the primary is the more massive but cooler and larger component. A comparison with evolutionary tracks indicates that the components are metal rich with [Fe/H] = 0.3, and the system has an age of 1.2 Gyr. The primary is near the end of its main-sequence lifetime and is rotating significantly faster than its pseudosynchronous velocity. The secondary is still well ensconced on the main sequence and is rotating more slowly than its pseudosynchronous rate.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

On the SW Sex-type eclipsing cataclysmic variable SDSS0756+0858

We conducted a spectroscopic and photometric study of SDSS J075653.11+085831. X-ray observations were also attempted. We determined the orbital period of this binary system to be 3.29 hr. It is a deep eclipsing system, whose spectra show mostly single-peaked, Balmer emission lines and a rather intense He II line. There is also the presence of faint (often double-peaked) He I emission lines as well as several absorption lines, Mg I being the most prominent. All of these features point toward the affiliation of this object with the growing number of SW Sex-type objects. We developed a phenomenological model of an SW Sex system to reproduce the observed photometric and spectral features.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Absolute properties of the eclipsing binary star AP Andromedae

AP And is a well-detached F5 eclipsing binary star for which only a very limited amount of information was available before this publication. We have obtained very extensive measurements of the light curve (19,097 differential V magnitude observations) and a radial velocity curve (83 spectroscopic observations) which allow us to fit orbits and determine the absolute properties of the components very accurately: masses of 1.277 ± 0.004 and 1.251 ± 0.004 M {sub ☉}, radii of 1.233 ± 0.006 and 1.1953 ± 0.005 R {sub ☉}, and temperatures of 6565 ± 150 K and 6495 ± 150 K. The distance to the system is about 400 ± 30 pc. Comparison with the theoretical properties of the stellar evolutionary models of the Yonsei-Yale series of Yi et al. shows good agreement between the observations and the theory at an age of about 500 Myr and a slightly sub-solar metallicity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Study of eclipsing binary and multiple systems in ob associations. II. The cygnus ob region: V443 Cyg, V456 Cyg, and V2107 Cyg

Three presumably young eclipsing binary systems in the direction of the Cygnus OB1, OB3, and OB9 associations are studied. Component spectra are reconstructed and their orbits are determined using light curves and spectra disentangling techniques. V443 Cyg and V456 Cyg have circular orbits while the light curve of V2107 Cyg imposes a slightly eccentric orbit (e = 0.045 ± 0.03). V443 Cyg harbors F-type stars, not young early-A stars as previously suggested in the literature based solely on photometry. It appears to be situated in the foreground (distance 0.6 ± 0.2 kpc) of the young stellar populations in Cygnus. V456 Cyg, at a distance of 0.50 ± 0.03 kpc, consists of a slightly metal-weak A-type star and an early-F star. The age of both systems, on or very near to the main sequence, remains uncertain by an order of magnitude. V2107 Cyg is a more massive system (8.9 ± 2 and 4.5 ± 1.2 M {sub ☉}) at 1.5 ± 0.5 kpc and, also kinematically, a strong candidate-member of Cyg OB1. The more massive component is slightly evolved and appears to undergo non-radial βCep-type pulsations. The Doppler signal of the secondary is barely detectable. A more extensive, asteroseismological study is necessary to fix masses more precisely. Nevertheless, the position of the primary in the H-R diagram confines the age reasonably well to 20 ± 5 Myr, indicating that for Cyg OB1 has a similar extent of star formation history as that established for Cyg OB2.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

A strict test of stellar evolution models: The absolute dimensions of the massive benchmark eclipsing binary V578 Mon

We determine the absolute dimensions of the eclipsing binary V578 Mon, a detached system of two early B-type stars (B0V + B1V, P = 2.40848 days) in the star-forming region NGC 2244 of the Rosette Nebula. From the light curve analysis of 40 yr of photometry and the analysis of HERMES spectra, we find radii of 5.41 ± 0.04 R{sub ☉} and 4.29 ± 0.05 R{sub ☉}, and temperatures of 30,000 ± 500 K and 25,750 ± 435 K, respectively. We find that our disentangled component spectra for V578 Mon agree well with previous spectral disentangling from the literature. We also reconfirm the previous spectroscopic orbit of V578 Mon finding that masses of 14.54 ± 0.08 M{sub ☉} and 10.29 ± 0.06 M{sub ☉} are fully compatible with the new analysis. We compare the absolute dimensions to the rotating models of the Geneva and Utrecht groups and the models of the Granada group. We find that all three sets of models marginally reproduce the absolute dimensions of both stars with a common age within the uncertainty for gravity-effective temperature isochrones. However, there are some apparent age discrepancies for the corresponding mass-radius isochrones. Models with larger convective overshoot, >0.35, worked best. Combined with our previously determined apsidal motion of 0.07089{sub −0.00013}{sup +0.00021} deg cycle{sup –1}, we compute the internal structure constants (tidal Love number) for the Newtonian and general relativistic contribution to the apsidal motion as log k {sub 2} = –1.975 ± 0.017 and log k {sub 2} = –3.412 ± 0.018, respectively. We find the relativistic contribution to the apsidal motion to be small, <4%. We find that the prediction of log k {sub 2,theo} = –2.005 ± 0.025 of the Granada models fully agrees with our observed log k {sub 2}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Absolute properties of the eclipsing binary star V501 Herculis

V501 Her is a well detached G3 eclipsing binary star with a period of 8.597687 days for which we have determined very accurate light and radial-velocity curves using robotic telescopes. Results of these data indicate that the component stars have masses of 1.269 ± 0.004 and 1.211 ± 0.003 solar masses, radii of 2.001 ± 0.003 and 1.511 ± 0.003 solar radii, and temperatures of 5683 ± 100 K and 5720 ± 100 K, respectively. Comparison with the Yonsei-Yale series of evolutionary models results in good agreement at an age of about 5.1 Gyr for a somewhat metal-rich composition. Those models indicate that the more massive, larger, slightly cooler star is just beyond core hydrogen exhaustion while the less massive, smaller, slightly hotter star has not quite reached core hydrogen exhaustion. The orbit is not yet circularized, and the components are rotating at or near their pseudosynchronous velocities. The distance to the system is 420 ± 30 pc.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Absolute properties of the eclipsing binary star IM Persei

IM Per is a detached A7 eccentric eclipsing binary star. We have obtained extensive measurements of the light curve (28,225 differential magnitude observations) and radial velocity curve (81 spectroscopic observations) which allow us to fit orbits and determine the absolute properties of the components very accurately: masses of 1.7831 ± 0.0094 and 1.7741 ± 0.0097 solar masses, and radii of 2.409 ± 0.018 and 2.366 ± 0.017 solar radii. The orbital period is 2.25422694(15) days and the eccentricity is 0.0473(26). A faint third component was detected in the analysis of the light curves, and also directly observed in the spectra. The observed rate of apsidal motion is consistent with theory (U = 151.4 ± 8.4 year). We determine a distance to the system of 566 ± 46 pc.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Photometric investigation of the totally eclipsing contact binary V12 in the intermediate-age open cluster NGC 7789

NGC 7789 is an intermediate-age open cluster with an age similar to the mean age of contact binary stars. V12 is a bright W UMa-type binary star with an orbital period of 0.3917 days. The first complete light curves of V12 in the V, R, and I bands are presented and analyzed with the Wilson–Devinney (W-D) method. The results show that V12 is an intermediate-contact binary (f=43.0(±2.2)%) with a mass ratio of 3.848, and it is a W-type contact binary where the less massive component is slightly hotter than the more massive one. The asymmetry of the light curves is explained by the presence of a dark spot on the more massive component. The derived orbital inclination (i=83{sub .}{sup ∘}6) indicates that it is a totally eclipsing binary, which suggests that the determined parameters are reliable. The orbital period may show a long-term increase at a rate of P-dot =+2.48(±0.17)×10{sup −6} days yr{sup −1} that reveals a rapid mass transfer from the less massive component to the more massive one. However, more observations are needed to confirm this conclusion. The presence of an intermediate-contact binary in an intermediate-age open cluster may suggest that some contact binaries have a very short pre-contact timescale. The presence of a third body and/or stellar collision may help to shorten the pre-contact evolution.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

TIME-SERIES SPECTROSCOPY OF THE ECLIPSING BINARY Y CAM WITH A PULSATING COMPONENT

We present the physical properties of the semi-detached Algol-type eclipsing binary Y Cam based on high resolution spectra obtained using the Bohyunsan Optical Echelle Spectrograph. This is the first spectroscopic monitoring data obtained for this interesting binary system, which has a δ Sct-type pulsating component. We obtained a total of 59 spectra over 14 nights from 2009 December to 2011 March. Double-lined spectral features from the hot primary and cool secondary components were well identified. We determined the effective temperatures of the two stars to be T{sub eff,1} = 8000 ± 250 K and T{sub eff,2} = 4629 ± 150 K. The projected rotational velocities are v{sub 1}sin i{sub 1} = 51 ± 4 km s{sup −1} and v{sub 2}sin i{sub 2} = 50 ± 10 km s{sup −1}, which are very similar to a synchronous rotation with the orbital motion. Physical parameters of each component were derived by analyzing our radial velocity data together with previous photometric light curves from the literature. The masses and radii are M{sub 1} = 2.08 ± 0.09 M{sub ⊙}, M{sub 2} = 0.48 ± 0.03 M{sub ⊙}, R{sub 1} = 3.14 ± 0.05 R{sub ⊙}, and R{sub 2} = 3.33 ± 0.05 R{sub ⊙}, respectively. A comparison of these parameters with the theoretical evolution tracks showed that the primary component is located between the zero-age main sequence and the terminal-age main sequence, while the low-mass secondary is noticeably evolved. This indicates that the two components have experienced mass exchange with each other and the primary has undergone an evolution process different from that of single δ Sct-type pulsators.

79 ASTRONOMY AND ASTROPHYSICS↗