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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

INTERFEROMETRY OF ϵ AURIGAE: CHARACTERIZATION OF THE ASYMMETRIC ECLIPSING DISK

We report on a total of 106 nights of optical interferometric observations of the ϵ Aurigae system taken during the last 14 years by four beam combiners at three different interferometric facilities. This long sequence of data provides an ideal assessment of the system prior to, during, and after the recent 2009–2011 eclipse. We have reconstructed model-independent images from the 10 in-eclipse epochs which show that a disk-like object is indeed responsible for the eclipse. Using new three-dimensional, time-dependent modeling software, we derive the properties of the F-star (diameter, limb darkening), determine previously unknown orbital elements (Ω, i), and access the global structures of the optically thick portion of the eclipsing disk using both geometric models and approximations of astrophysically relevant density distributions. These models may be useful in future hydrodynamical modeling of the system. Finally, we address several outstanding research questions including mid-eclipse brightening, possible shrinking of the F-type primary, and any warps or sub-features within the disk.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

SU-F-T-436: A Method to Evaluate Dosimetric Properties of SFGRT in Eclipse TPS

Purpose: The objective was to develop a method for dose distribution calculation of spatially-fractionated-GRID-radiotherapy (SFGRT) in Eclipse treatment-planning-system (TPS). Methods: Patient treatment-plans with SFGRT for bulky tumors were generated in Varian Eclipse version11. A virtual structure based on the GRID pattern was created and registered to a patient CT image dataset. The virtual GRID structure was positioned on the iso-center level together with matching beam geometries to simulate a commercially available GRID block made of brass. This method overcame the difficulty in treatment-planning and dose-calculation due to the lack o-the option to insert a GRID block add-on in Eclipse TPS. The patient treatment-planning displayed GRID effects on the target, critical structures, and dose distribution. The dose calculations were compared to the measurement results in phantom. Results: The GRID block structure was created to follow the beam divergence to the patient CT images. The inserted virtual GRID block made it possible to calculate the dose distributions and profiles at various depths in Eclipse. The virtual GRID block was added as an option to TPS. The 3D representation of the isodose distribution of the spatially-fractionated beam was generated in axial, coronal, and sagittal planes. Physics of GRID can be different from that for fields shaped by regular blocks because the charge-particle-equilibrium cannot be guaranteed for small field openings. Output factor (OF) measurement was required to calculate the MU to deliver the prescribed dose. The calculated OF based on the virtual GRID agreed well with the measured OF in phantom. Conclusion: The method to create the virtual GRID block has been proposed for the first time in Eclipse TPS. The dosedistributions, in-plane and cross-plane profiles in PTV can be displayed in 3D-space. The calculated OF’s based on the virtual GRID model compare well to the measured OF’s for SFGRT clinical use.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Clear-Sky Probability for the August 21, 2017, Total Solar Eclipse Using the NREL National Solar Radiation Database

The National Renewable Energy Laboratory (NREL) and collaborators have created a clear-sky probability analysis to help guide viewers of the August 21, 2017, total solar eclipse, the first continent-spanning eclipse in nearly 100 years in the United States. Using cloud and solar data from NREL's National Solar Radiation Database (NSRDB), the analysis provides cloudless sky probabilities specific to the date and time of the eclipse. Although this paper is not intended to be an eclipse weather forecast, the detailed maps can help guide eclipse enthusiasts to likely optimal viewing locations. Additionally, high-resolution data are presented for the centerline of the path of totality, representing the likelihood for cloudless skies and atmospheric clarity. The NSRDB provides industry, academia, and other stakeholders with high-resolution solar irradiance data to support feasibility analyses for photovoltaic and concentrating solar power generation projects.

14 SOLAR ENERGY↗
DOE OSTI2016

Two eclipsing ultraluminous X-ray sources in M51

We present the discovery, from archival Chandra and XMM-Newton data, of X-ray eclipses in two ultraluminous X-ray sources (ULXs), located in the same region of the galaxy M51: CXOM51 J132940.0+471237 (ULX-1, for simplicity) and CXOM51 J132939.5+471244 (ULX-2). Three eclipses were detected for ULX-1 and two for ULX-2. The presence of eclipses puts strong constraints on the viewing angle, suggesting that both ULXs are seen almost edge-on and are certainly not beamed toward us. Despite the similar viewing angles and luminosities (L{sub X}≈2×10{sup 39} erg s{sup −1} in the 0.3–8 keV band for both sources), their X-ray properties are different. ULX-1 has a soft spectrum, well fitted by Comptonization emission from a medium with electron temperature kT{sub e}≈1 keV. ULX-2 is harder, well fitted by a slim disk with kT{sub in}≈1.5–1.8 keV and normalization consistent with a ∼10 M {sub ⊙} black hole. ULX-1 has a significant contribution from multi-temperature thermal-plasma emission (L{sub X,mekal}≈2×10{sup 38} erg s{sup −1}). About 10% of this emission remains visible during the eclipses, proving that the emitting gas comes from a region slightly more extended than the size of the donor star. From the sequence and duration of the Chandra observations in and out of eclipse, we constrain the binary period of ULX-1 to be either ≈6.3 days, or ≈12.5–13 days. If the donor star fills its Roche lobe (a plausible assumption for ULXs), both cases require an evolved donor, most likely a blue supergiant, given the young age of the stellar population in that Galactic environment.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

A new γ-ray loud, eclipsing low-mass X-ray binary

We report the discovery of an eclipsing low-mass X-ray binary at the center of the 3FGL error ellipse of the unassociated Fermi/Large Area Telescope γ-ray source 3FGL J0427.9–6704. Photometry from OGLE and the SMARTS 1.3 m telescope and spectroscopy from the SOAR telescope have allowed us to classify the system as an eclipsing low-mass X-ray binary (P = 8.8 hr) with a main-sequence donor and a neutron-star accretor. Broad double-peaked H and He emission lines suggest the ongoing presence of an accretion disk. Remarkably, the system shows separate sets of absorption lines associated with the accretion disk and the secondary, and we use their radial velocities to find evidence for a massive (∼1.8–1.9 M {sub ⊙}) neutron-star primary. In addition to a total X-ray eclipse with a duration of ∼2200 s observed with NuSTAR, the X-ray light curve also shows properties similar to those observed among known transitional millisecond pulsars: short-term variability, a hard power-law spectrum (Γ∼1.7), and a comparable 0.5–10 keV luminosity (∼2.4×10{sup 33} erg s{sup −1}). We find tentative evidence for a partial (∼60%) γ-ray eclipse at the same phase as the X-ray eclipse, suggesting the γ-ray emission may not be confined to the immediate region of the compact object. The favorable inclination of this binary is promising for future efforts to determine the origin of γ-rays among accreting neutron stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Long-term CCD Photometry and Physical Properties of the sdB+M Eclipsing System 2M 1533+3759

New CCD photometry of seven successive years from 2010 is presented for the HW Vir-type eclipsing binary 2M 1533+3759. Using the VI light curves together with the radial-velocity data given by For et al., we determined the absolute parameters of each component to be M {sub 1} = 0.442 ± 0.012 M {sub ⊙}, M {sub 2} = 0.124 ± 0.005 M {sub ⊙}, R {sub 1} = 0.172 ± 0.002 R {sub ⊙}, R {sub 2} = 0.157 ± 0.002 R {sub ⊙}, L {sub 1} = 19.4 ± 1.4 L {sub ⊙}, and L {sub 2} = 0.002 ± 0.002 L {sub ⊙}. These indicate that 2M 1533+3759 is a detached system consisting of a normal sdB primary and an M7 dwarf companion. Detailed analyses of 377 minimum epochs, including our 111 timings, showed that the orbital period of the system remains constant during the past 12 years. Inspecting both types of minima, we found a delay of 3.9 ± 1.0 s in the arrival times of the secondary eclipses relative to the primary eclipse times. This delay is in satisfactory agreement with the predicted Rømer delay of 2.7 ± 1.4 s, and the result is the second measurement in sdB+M eclipsing binaries. The time shift of the secondary eclipse can be explained by some combination of the Rømer delay and a non-zero eccentricity. Then the binary star would have a very small eccentricity of ecos ω≃0.0001.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

X-Ray Eclipses of Active Galactic Nuclei

X-ray variation is a ubiquitous feature of active galactic nuclei (AGNs); however, its origin is not well understood. In this paper, we show that the X-ray flux variations in some AGNs, and correspondingly, the power spectral densities (PSDs) of the variations, may be interpreted as being caused by absorptions of eclipsing clouds or clumps in the broad-line region (BLR) and the dusty torus. By performing Monte Carlo simulations for a number of plausible cloud models, we systematically investigate the statistics of the X-ray variations resulting from the cloud eclipsing and the PSDs of the variations. For these models, we show that the number of eclipsing events can be significant and the absorption column densities due to those eclipsing clouds can be in the range from 10{sup 21} to 10{sup 24} cm{sup −2}, leading to significant X-ray variations. We find that the PSDs obtained from the mock observations for the X-ray flux and the absorption column density resulting from these models can be described by a broken double power law, similar to those directly measured from observations of some AGNs. The shape of the PSDs depend strongly on the kinematic structures and the intrinsic properties of the clouds in AGNs. We demonstrate that the X-ray eclipsing model can naturally lead to a strong correlation between the break frequencies (and correspondingly the break timescales) of the PSDs and the masses of the massive black holes (MBHs) in the model AGNs, which can be well consistent with the one obtained from observations. Future studies of the PSDs of the AGN X-ray (and possibly also the optical-UV) flux and column density variations may provide a powerful tool to constrain the structure of the BLR and the torus and to estimate the MBH masses in AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2005

A Case Study in High Contrast Coronagraph for Planet Discovery: The Eclipse Concept and Support Laboratory Experience

Eclipse is a proposed NASA Discovery mission to perform a sensitive imaging survey of nearby planetary systems, including a survey for jovian-sized planets orbiting Sun-like stars to distances of 15 pc. We outline the science objectives of the Eclipse mission and review recent developments in the key enabling technologies. Eclipse is a space telescope concept for high-contrast visible-wavelength imaging and spectrophotometry. Its design incorporates a telescope with an unobscured aperture of 1.8 meters, a coronographic camera for suppression of diffracted light, and precise active wavefront correction for the suppression of scattered background light. For reference, Eclipse is designed to reduce the diffracted and scattered starlight between 0.33 and 1.5 arcseconds from the star by three orders of magnitude compared to any HST instrument. The Eclipse mission provides precursor science exploration and technology experience in support of NASA's Terrestrial Planet Finder (TPF) program.

coronagraphic imaging testbed↗
NASA NTRS2017

Effects of the 2017 Solar Eclipse on HF Radio Propagation and the D-Region Ionosphere: Citizen Science Investigation

August 21, 2017 provided a unique opportunity to investigate the effects of the total solar eclipse on high frequency (HF) radio propagation and ionospheric variability. In Marshall Space Flight Center's partnership with the US Space and Rocket Center (USSRC) and Austin Peay State University (APSU), we engaged students and citizen scientists in an investigation of the eclipse effects on the mid-latitude ionosphere. Activities included implementing and configuring software, monitoring the HF Amateur Radio frequency bands and collecting radio transmission data on days before, the day of, and days after the eclipse to build a continuous record of changing propagation conditions as the moon's shadow marched across the United States. Post-eclipse radio propagation analysis provided insights into ionospheric variability due to the eclipse. We report on results, interpretation, and conclusions of these investigations.

Radio Propagatio↗
NASA NTRS2022

Thermospheric Nitric Oxide Cooling Responses to the 14 December 2020 Solar Eclipse

The behaviors of the nitric oxide (NO) cooling in the lower thermosphere during the 14 December 2020 solar eclipse are studied using Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) measurements and WACCM-X simulations. We found that NO cooling rate decreases during the solar eclipse in both SABER measurements and WACCM-X simulations. The maximum decrease of the NO cooling is 40% in SABER measurements and 25% in WACCM-X simulations. The NO cooling process is initiated almost entirely through the collisions with atomic oxygen (O) which depends linearly on NO and O densities and non-linearly on the neutral temperature. During the eclipse, the NO concentration and temperature decreases are larger than that of O concentration. Consequently, the eclipse-time NO concentration and temperature decreases are the major drivers of the NO cooling rate decrease. The decreases of the temperature and the NO concentration contribute comparably to the eclipse-time NO cooling rate decrease.

solar eclipse↗
NASA NTRSDate not supplied

By the Light of Eclipses: Bringing NASA Content to Underserved Audiences

The August 21, 2017 total solar eclipse saw a collaboration between NASA/Marshall Space Flight Center (MSFC) scientists, Austin Peay State University in Clarksville, Tennessee, the U.S. Space and Rocket Center, and The INSPIRE (Interactive NASA Space Physics Ionosphere Experiments) Project. Leveraging that collaboration, we expanded to southwest Texas to be in the paths of annularity and totality for the October 14, 2023 and the April 8, 2024 eclipse, respectively. Observations were made in Eagle Pass, Uvalde, and Garner State Park, Texas with the help of students and professors from Sul Ross State University, and Southwest Texas Junior College, as well as Park Rangers in Garner State Park. Through these eclipses we supported Citizen Science projects SunSketcher, Globe Eclipse, and iNaturalist, participated in multiple education and outreach events prior to and after the eclipses and presented our experiences to the Seventh Annual Science of Stem Literacy Conference held at Sul Ross State University in Alpine, Texas. This presentation will report those experiences and the impact to the community.

Eclipses↗
DOE OSTI2017

Impact of the 2017 Solar Eclipse on the Smart Grid

With the increasing interest in using solar energy as a major contributor to the use of renewable generation, and with the focus on using smart grids to optimize the use of electrical energy based on demand and resources from different locations, the need arises to know the moons position in the sky with respect to the sun. When a solar eclipse occurs, the moon disk might totally or partially shade the sun disk, which can affect the irradiance level from the sun disk, consequently affecting a resource on the electric grid. The moons position can then provide smart grid users with information about how potential total or partial solar eclipses might affect different locations on the grid so that other resources on the grid can be directed to where they might be needed when such phenomena occurs. At least five solar eclipses occur yearly at different locations on Earth, they can last 3 hours or more depending on the location, and they can affect smart grid users. On August 21, 2017, a partial and full solar eclipse occurred in many locations in the United States, including at the National Renewable Energy Laboratory in Golden, Colorado. Solar irradiance measurements during the eclipse were compared to the data generated by a model for validation at eight locations.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2023

Neutron star mass estimates from gamma-ray eclipses in spider millisecond pulsar binaries

Reliable neutron star mass measurements are key to determining the equation of state of cold nuclear matter, but such measurements are rare. Black widows and redbacks are compact binaries consisting of millisecond pulsars and semi-degenerate companion stars. Spectroscopy of the optically bright companions can determine their radial velocities, providing inclination-dependent pulsar mass estimates. Although inclinations can be inferred from subtle features in optical light curves, such estimates may be systematically biased due to incomplete heating models and poorly understood variability. Using data from the Fermi Large Area Telescope, we have searched for gamma-ray eclipses from 49 spider systems, discovering significant eclipses in 7 systems, including the prototypical black widow PSR B1957+20. Gamma-ray eclipses require direct occultation of the pulsar by the companion, and so the detection, or significant exclusion, of a gamma-ray eclipse strictly limits the binary inclination angle, providing new robust, model-independent pulsar mass constraints. For PSR B1957+20, the eclipse implies a much lighter pulsar (1.81 ± 0.07 solar masses) than inferred from optical light curve modelling.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Periodic eclipses of the young star PDS 110 discovered with WASP and KELT photometry

We report the discovery of eclipses by circumstellar disc material associated with the young star PDS 110 in the Ori OB1a association using the SuperWASP and Kilodegree Extremely Little Telescope surveys. PDS 110 (HD 290380, IRAS 05209-0107) is a rare Fe/Ge-type star, an ~10 Myr-old accreting intermediate-mass star showing strong infrared excess (L IR /L bol 0.25). Two extremely similar eclipses with a depth of 30 per cent and duration ~25 d were observed in 2008 November and 2011 January. We interpret the eclipses as caused by the same structure with an orbital period of 808 ± 2 d. Shearing over a single orbit rules out diffuse dust clumps as the cause, favouring the hypothesis of a companion at ~2 au. The characteristics of the eclipses are consistent with transits by an unseen low-mass (1.8–70 MJup) planet or brown dwarf with a circumsecondary disc of diameter ~0.3 au. The next eclipse event is predicted to take place in 2017 September and could be monitored by amateur and professional observatories across the world.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

SU-E-T-344: Validation and Clinical Experience of Eclipse Electron Monte Carlo Algorithm (EMC)

Purpose: The purpose of this study is to validate Eclipse Electron Monte Carlo (Algorithm for routine clinical uses. Methods: The PTW inhomogeneity phantom (T40037) with different combination of heterogeneous slabs has been CT-scanned with Philips Brilliance 16 slice scanner. The phantom contains blocks of Rando Alderson materials mimicking lung, Polystyrene (Tissue), PTFE (Bone) and PMAA. The phantom has 30×30×2.5 cm base plate with 2cm recesses to insert inhomogeneity. The detector systems used in this study are diode, tlds and Gafchromic EBT2 films. The diode and tlds were included in CT scans. The CT sets are transferred to Eclipse treatment planning system. Several plans have been created with Eclipse Monte Carlo (EMC) algorithm 11.0.21. Measurements have been carried out in Varian TrueBeam machine for energy from 6–22mev. Results: The measured and calculated doses agreed very well for tissue like media. The agreement was reasonably okay for the presence of lung inhomogeneity. The point dose agreement was within 3.5% and Gamma passing rate at 3%/3mm was greater than 93% except for 6Mev(85%). The disagreement can reach as high as 10% in the presence of bone inhomogeneity. This is due to eclipse reporting dose to the medium as opposed to the dose to the water as in conventional calculation engines. Conclusion: Care must be taken when using Varian Eclipse EMC algorithm for dose calculation for routine clinical uses. The algorithm dose not report dose to water in which most of the clinical experiences are based on rather it just reports dose to medium directly. In the presence of inhomogeneity such as bone, the dose discrepancy can be as high as 10% or even more depending on the location of normalization point or volume. As Radiation oncology as an empirical science, care must be taken before using EMC reported monitor units for clinical uses.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-P-39: End-To-End Validation of a 6 MV High Dose Rate Photon Beam, Configured for Eclipse AAA Algorithm Using Golden Beam Data, for SBRT Treatments Using RapidArc

Purpose: To use end-to-end testing to validate a 6 MV high dose rate photon beam, configured for Eclipse AAA algorithm using Golden Beam Data (GBD), for SBRT treatments using RapidArc. Methods: Beam data was configured for Varian Eclipse AAA algorithm using the GBD provided by the vendor. Transverse and diagonals dose profiles, PDDs and output factors down to a field size of 2×2 cm2 were measured on a Varian Trilogy Linac and compared with GBD library using 2% 2mm 1D gamma analysis. The MLC transmission factor and dosimetric leaf gap were determined to characterize the MLC in Eclipse. Mechanical and dosimetric tests were performed combining different gantry rotation speeds, dose rates and leaf speeds to evaluate the delivery system performance according to VMAT accuracy requirements. An end-to-end test was implemented planning several SBRT RapidArc treatments on a CIRS 002LFC IMRT Thorax Phantom. The CT scanner calibration curve was acquired and loaded in Eclipse. PTW 31013 ionization chamber was used with Keithley 35617EBS electrometer for absolute point dose measurements in water and lung equivalent inserts. TPS calculated planar dose distributions were compared to those measured using EPID and MapCheck, as an independent verification method. Results were evaluated with gamma criteria of 2% dose difference and 2mm DTA for 95% of points. Results: GBD set vs. measured data passed 2% 2mm 1D gamma analysis even for small fields. Machine performance tests show results are independent of machine delivery configuration, as expected. Absolute point dosimetry comparison resulted within 4% for the worst case scenario in lung. Over 97% of the points evaluated in dose distributions passed gamma index analysis. Conclusion: Eclipse AAA algorithm configuration of the 6 MV high dose rate photon beam using GBD proved efficient. End-to-end test dose calculation results indicate it can be used clinically for SBRT using RapidArc.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

β Cephei Pulsations in the High-mass Eclipsing System CW Cephei

CW Cep is an early B-type eclipsing binary with mass measurement precisions better than 1%. We report the discovery of pulsation signatures in the Transiting Exoplanet Survey Satellite time-series data of the system observed during Sectors 17 and 18. Our binary modeling indicates that the target star is a partially eclipsing detached system with masses of 12.95 M {sub ⊙} and 11.88 M {sub ⊙} and radii of 5.52 R {sub ⊙} and 5.09 R {sub ⊙} in an eccentric orbit of e = 0.0305. The distance to the eclipsing system, 928 ± 36 pc, is much more precise than the Gaia distance of 962 ± 453 pc. Applying multifrequency analyses to the residual light curve in the outside-eclipse part, we detected 13 significant signals in two frequency regions. Six frequencies below 1 day{sup −1} appeared to be mostly orbital harmonic and combination terms, or sidelobes due to insufficient removal of the binary effects. In contrast, seven frequencies clustered around 2.73 day{sup −1} and 5.34 day{sup −1} could be considered β Cep–type pulsations. Our results represent the second discovery of β Cep pulsations present in double-lined eclipsing binaries with precise masses and, hence, CW Cep serves as an important test bed for the asteroseismic modeling of high-mass stars.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Tidally Excited Modes and δ Scuti Pulsations in the Eclipsing Triple Star IM Persei

IM Per is a triple star system whose eclipsing pair masses and radii are accurate to within 1%. The Transiting Exoplanet Survey Satellite (TESS) light curve of the program target exhibits partial eclipses and multiple oscillations with millimagnitude-level amplitudes. It is found that the oscillations affect eclipse timing measurements. Binary modeling of the high-quality TESS data indicates that the eclipsing components of the triple system are twin dwarfs with parameters of M {sub 2}/M {sub 1} = 0.995, R {sub 2}/R {sub 1} = 0.901, and Δ(T{sub eff,1}–T{sub eff,2}) = 12 K in an eccentric (e = 0.049), detached configuration. The third light of l {sub 3} = 0.054 may mostly come from a G-type tertiary companion. Our predicted parallax of 1.52 ± 0.09 mas is concurrent with the Gaia measurement of 1.52 ± 0.05 mas. Multifrequency analysis of the outside-eclipse residuals reveals 22 significant pulsation signals: 4 in the gravity-mode region (0.03−2.22 day{sup −1}) and 18 in the pressure-mode region (9.19−25.12 day{sup −1}). Of the low frequencies, f {sub 11} and f {sub 14} are orbital harmonics that can be identified as tidally excited modes. The pulsation periods and constants for the high frequencies, and the position in the Cepheid instability strip demonstrate that the pulsating component of IM Per is a δ Sct variable.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗