Search NASA⌕ Search

SEARCH · Search NASA

Results for “optical binary”

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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

ASCA Observations of the Barnard 209 Dark Cloud and an Intense X-Ray Flare on V773 Tauri

ASCA (Advanced Satellite for Cosmology and Astrophysics) detected an intense X-ray flare on the weak-lined T Tauri star V773 Tau (=HD 283447) during a 30 ks observation of the Barnard 209 dark cloud in 1995 September. This star is a spectroscopic binary and shows signs of strong magnetic surface activity including a spot-modulated optical light curve. The flare was seen only during its decay phase but is still one of the strongest ever recorded from a T Tauri star with a peak luminosity L(sub x) = 10(exp 32.4) ergs/s (0.5-10 keV), a maximum temperature of at least 42 million K, and energy release of greater than 10(exp 37) ergs. A shorter ASCA observation taken five months later showed V773 Tau in a quiescent state (L(sub x)= 10(exp 31.0) ergs/s) and detected variable emission from the infrared binary IRAS 04113+2758. The differential emission measure (DEM) distribution during the V773 Tau flare shows a bimodal temperature structure that is almost totally dominated by hot plasma at an average temperature of approx. 37 million K. Using information from time-resolved spectra, we examine the flare decay in terms of solar flare models (cooling loops and two-ribbon flares) and also consider possible nonsolar behavior (interbinary flares, star-disk flares, and rotational X-ray modulation). Solar models are unable to reproduce the unusual convex-shaped X-ray light curve, which decays slowly over a timespan of at least 1 day. However, the light curve decay is accurately modeled as a sinusoid with an inferred X-ray period of 2.97 days, which is nearly identical to the optical rotation period(s) of the two K-type components. This provides tantalizing evidence that the flaring region was undergoing rotational occultation, but periodic X-ray variability is not yet proven since our ASCA observation spans only one-third of a rotation cycle.

Skinner, Stephen L.↗
DOE OSTI2015

Pan-chromatic observations of the remarkable nova Large Magellanic Cloud 2012

We present the results of an intensive multiwavelength campaign on nova LMC 2012. This nova evolved very rapidly in all observed wavelengths. The time to fall two magnitudes in the V band was only 2 days. In X-rays the super soft phase began 13 ± 5 days after discovery and ended around day 50 after discovery. During the super soft phase, the Swift/XRT and Chandra spectra were consistent with the underlying white dwarf (WD) being very hot, ∼1 MK, and luminous, ∼10{sup 38} erg s{sup −1}. The UV, optical, and near-IR photometry showed a periodic variation after the initial and rapid fading had ended. Timing analysis revealed a consistent 19.24 ± 0.03 hr period in all UV, optical, and near-IR bands with amplitudes of ∼0.3 mag which we associate with the orbital period of the central binary. No periods were detected in the corresponding X-ray data sets. A moderately high inclination system, i = 60 ± 10{sup ∘}, was inferred from the early optical emission lines. The HST/STIS UV spectra were highly unusual with only the N v (1240 Å) line present and superposed on a blue continuum. The lack of emission lines and the observed UV and optical continua from four epochs can be fit with a low mass ejection event, ∼10{sup −6} M{sub ⊙}, from a hot and massive WD near the Chandrasekhar limit. The WD, in turn, significantly illuminated its subgiant companion which provided the bulk of the observed UV/optical continuum emission at the later dates. The inferred extreme WD characteristics and low mass ejection event favor nova LMC 2012 being a recurrent nova of the U Sco subclass.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE X-RAY TRANSIENT 2XMMi J003833.3+402133: A CANDIDATE MAGNETAR AT HIGH GALACTIC LATITUDE

We present detailed analysis of the transient X-ray source 2XMMi J003833.3+402133 detected by XMM-Newton in 2008 January during a survey of M31. The X-ray spectrum is well fitted by either a steep power law plus a blackbody model or a double blackbody model. Prior observations with XMM-Newton, Chandra, Swift, and ROSAT spanning 1991-2007, as well as an additional Swift observation in 2011, all failed to detect this source. No counterpart was detected in deep optical imaging with the Canada-France-Hawaii Telescope down to a 3{sigma} lower limit of g = 26.5 mag. This source has previously been identified as a black hole X-ray binary in M31. While this remains a possibility, the transient behavior, X-ray spectrum, and lack of an optical counterpart are equally consistent with a magnetar interpretation for 2XMMi J003833.3+402133. The derived luminosity and blackbody emitting radius at the distance of M31 argue against an extragalactic location, implying that if it is indeed a magnetar it is located within the Milky Way but 22 Degree-Sign out of the plane. The high Galactic latitude could be explained if 2XMMi J003833.3+402133 were an old magnetar, or if its progenitor was a runaway star that traveled away from the plane prior to going supernova.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Birth of a Be star: an APOGEE search for Be stars forming through binary mass transfer

ABSTRACT Motivated by recent suggestions that many Be stars form through binary mass transfer, we searched the APOGEE survey for Be stars with bloated, stripped companions. From a well-defined parent sample of 297 Be stars, we identified one mass-transfer binary, HD 15124. The object consists of a main-sequence Be star ($M_{\rm Be}=5.3\pm 0.6\, {\rm M}_{\odot }$) with a low-mass ($M_{\rm donor}=0.92\pm 0.22\, {\rm M}_{\odot }$), subgiant companion on a 5.47-d orbit. The emission lines originate in an accretion disc caused by ongoing mass transfer, not from a decretion disc as in classical Be stars. Both stars have surface abundances bearing imprint of CNO processing in the donor’s core: the surface helium fraction is YHe ≈ 0.6, and the nitrogen-to-carbon ratio is 1000 times the solar value. The system’s properties are well-matched by binary evolution models in which mass transfer begins while a $3-5\, {\rm M}_{\odot }$ donor leaves the main sequence, with the originally less massive component becoming the Be star. These models predict that the system will soon become a detached Be + stripped star binary like HR 6819 and LB-1, with the stripped donor eventually contracting to become a core helium-burning sdO/B star. Discovery of one object in this short-lived (∼1 Myr) evolutionary phase implies the existence of many more that have already passed through it and are now Be + sdO/B binaries. We infer that $(10-60)\, {{\ \rm per\ cent}}$ of Be stars have stripped companions, most of which are $\sim 100\, \times$ fainter than the Be stars in the optical. Together with the dearth of main-sequence companions to Be stars and recent discovery of numerous Be + sdO/B binaries in the UV, our results imply that binarity plays an important role in the formation of Be stars.

El-Badry, Kareem (ORCID:0000000268711752)↗
DOE OSTI2017

Fermi/LAT detection of a transient gamma-ray flare in the vicinity of the binary star DG CVn

Solar flares are regularly detected by the Large Area Telescope (LAT) on board the Fermi satellite, however no γ-ray emission from other stellar eruptions has ever been captured. The Swift detection in 2014 April of a powerful outburst originating from DG CVn, with associated optical and radio emissions, enticed us to search for possible 0.1–100 GeV emission from this flaring nearby binary star using the Fermi /LAT. No γ-ray emission is detected from DG CVn in 2014, but we report a significant γ-ray excess in 2012 November, at a position consistent with that of the binary. There are no reports of contemporary flaring at other wavelengths from DG CVn or any other source within the error circle of the γ-ray source. As a result, we argue that the γ-ray flare is more likely to have been associated with a background blazar than with DG CVn and identify a candidate for follow-up study.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

IMAGING DISK DISTORTION OF BE BINARY SYSTEM {delta} SCORPII NEAR PERIASTRON

The highly eccentric Be binary system {delta} Sco reached periastron during early 2011 July, when the distance between the primary and secondary was a few times the size of the primary disk in the H band. This opened a window of opportunity to study how the gaseous disks around Be stars respond to gravitational disturbance. We first refine the binary parameters with the best orbital phase coverage data from the Navy Precision Optical Interferometer. Then we present the first imaging results of the disk after the periastron, based on seven nights of five telescope observations with the MIRC combiner at the CHARA array. We found that the disk was inclined 27.{sup 0}6 {+-} 6.{sup 0}0 from the plane of the sky, had a half-light radius of 0.49 mas (2.2 stellar radii), and consistently contributed 71.4% {+-} 2.7% of the total flux in the H band from night to night, suggesting no ongoing transfer of material into the disk during the periastron. The new estimation of the periastron passage is UT 2011 July 3 07:00 {+-} 4:30. Re-analysis of archival VLTI-AMBER interferometry data allowed us to determine the rotation direction of the primary disk, constraining it to be inclined either {approx}119 Degree-Sign or {approx}171 Degree-Sign relative to the orbital plane of the binary system. We also detect inner disk asymmetries that could be explained by spot-like emission with a few percent of the disk total flux moving in Keplerian orbits, although we lack sufficient angular resolution to be sure of this interpretation and cannot yet rule out spiral density waves or other more complicated geometries.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Pressure-induced bonding and compound formation in xenon-hydrogen solids

Closed electron shell systems, such as hydrogen, nitrogen or group 18 elements, can form weakly bound stoichiometric compounds at high pressures. An understanding of the stability of these van der Waals compounds is lacking, as is information on the nature of their interatomic interactions. We describe the formation of a stable compound in the Xe-H{sub 2} binary system, revealed by a suite of X-ray diffraction and optical spectroscopy measurements. At 4.8 GPa, a unique hydrogen-rich structure forms that can be viewed as a tripled solid hydrogen lattice modulated by layers of xenon, consisting of xenon dimers. Varying the applied pressure tunes the Xe-Xe distances in the solid over a broad range from that of an expanded xenon lattice to the distances observed in metallic xenon at megabar pressures. Infrared and Raman spectra indicate a weakening of the intramolecular covalent bond as well as persistence of semiconducting behaviour in the compound to at least 255 GPa.

08 HYDROGEN↗
DOE OSTI2020

Diffractive optical elements for multiplexing structured laser beams

We consider methods for obtaining a multitude of structured laser beams (multiplexing) from an illuminating beam (both structured and unstructured) with the help of diffractive optical elements (DOEs). An approach of ‘intelligent multiplexing’ is proposed to describe and develop the methods. A DOE is calculated that forms a set of five diffraction orders located in a line. An example of focusing a set of doughnut-shaped azimuthally polarised laser beams using a diffraction beam splitter is presented. Efficient multiplexing of first-order vortex beams in a two-dimensional region is implemented by a two-dimensional diffraction grating. An approach is proposed and realised in which the transmission functions of a two-dimensional diffraction beam splitter and the elements forming structured laser beams with specified parameters are combined into the transmission function of one element. Such DOEs can be used in optical communication systems for encoding and decoding data. The possibility of using binary curved fork-shaped gratings for the formation of doughnut-shaped three-dimensional vortex beams, which are detected outside the focal plane, is demonstrated. This approach provides additional advantages for safe data transmission; it can be used in laser processing of materials and in laser manipulation applications. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

SPECKLE CAMERA OBSERVATIONS FOR THE NASA KEPLER MISSION FOLLOW-UP PROGRAM

We present the first results from a speckle imaging survey of stars classified as candidate exoplanet host stars discovered by the Kepler mission. We use speckle imaging to search for faint companions or closely aligned background stars that could contribute flux to the Kepler light curves of their brighter neighbors. Background stars are expected to contribute significantly to the pool of false positive candidate transiting exoplanets discovered by the Kepler mission, especially in the case that the faint neighbors are eclipsing binary stars. Here, we describe our Kepler follow-up observing program, the speckle imaging camera used, our data reduction, and astrometric and photometric performance. Kepler stars range from R = 8 to 16 and our observations attempt to provide background non-detection limits 5-6 mag fainter and binary separations of {approx}0.05-2.0 arcsec. We present data describing the relative brightness, separation, and position angles for secondary sources, as well as relative plate limits for non-detection of faint nearby stars around each of 156 target stars. Faint neighbors were found near 10 of the stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

DEBRIS DISKS OF MEMBERS OF THE BLANCO 1 OPEN CLUSTER

We have used the Spitzer Space Telescope to obtain Multiband Imaging Photometer for Spitzer (MIPS) 24 {mu}m photometry for 37 members of the {approx}100 Myr old open cluster Blanco 1. For the brightest 25 of these stars (where we have 3{sigma} uncertainties less than 15%), we find significant mid-IR excesses for eight stars, corresponding to a debris disk detection frequency of about 32%. The stars with excesses include two A stars, four F dwarfs, and two G dwarfs. The most significant linkage between 24 {mu}m excess and any other stellar property for our Blanco 1 sample of stars is with binarity. Blanco 1 members that are photometric binaries show few or no detected 24 {mu}m excesses whereas a quarter of the apparently single Blanco 1 members do have excesses. We have examined the MIPS data for two other clusters of similar age to Blanco 1-NGC 2547 and the Pleiades. The AFGK photometric binary star members of both of these clusters also show a much lower frequency of 24 {mu}m excesses compared to stars that lie near the single-star main sequence. We provide a new determination of the relation between the V - K {sub s} color and K {sub s} - [24] color for main sequence photospheres based on Hyades members observed with MIPS. As a result of our analysis of the Hyades data, we identify three low mass Hyades members as candidates for having debris disks near the MIPS detection limit.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

PSR J1903+0327: A UNIQUE MILLISECOND PULSAR WITH A MAIN-SEQUENCE COMPANION STAR

PSR J1903+0327 is a millisecond pulsar with a mass of 1.67 M{sub Sun} in a highly eccentric orbit (e = 0.44) around a main-sequence star. This unique system cannot be reconciled with current observations where millisecond pulsars are generally seen to orbit white dwarfs in almost exactly circular orbits. Current theoretical models of binary and stellar formation and evolution cannot explain the high eccentricity of this system either. In this work, we present three new epochs of optical spectroscopy for the companion to PSR J1903+0327, obtained to confirm the association of the main-sequence star with the pulsar. These three new epochs, together with the two previous ones, firmly establish the high eccentricity of the companion's orbit as predicted by pulsar timing. Using all five epochs of optical data, we have provided an independent estimate of the mass ratio, R = 1.56 {+-} 0.15, as well as the systemic radial velocity of the binary, {gamma} = 42.1 {+-} 2.5 km s{sup -1}. We constrain the spectral type of the pulsar companion to lie between F5 V and G0 V (a slightly earlier type than suggested previously) by measuring the equivalent widths of two of the three Ca-triplet lines (8498 A, 8542 A) and the Paschen line at 8598 A (P14); we also broadly constrain the metallicity of the companion. Additionally, we have placed a somewhat better limit on the rotational velocity of the pulsar companion of v{sub rot}sin i {<=} 66 km s{sup -1}, which is still not sufficient to allow a test of general relativity using this system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

X-RAY EMISSION FROM AN ASYMMETRIC BLAST WAVE AND A MASSIVE WHITE DWARF IN THE GAMMA-RAY EMITTING NOVA V407 Cyg

Classical nova events in symbiotic stars, although rare, offer a unique opportunity to probe the interaction between ejecta and a dense environment in stellar explosions. In this work, we use X-ray data obtained with Swift and Suzaku during the recent classical nova outburst in V407 Cyg to explore such an interaction. We find evidence of both equilibrium and non-equilibrium ionization plasmas at the time of peak X-ray brightness, indicating a strong asymmetry in the density of the emitting region. Comparing a simple model to the data, we find that the X-ray evolution is broadly consistent with nova ejecta driving a forward shock into the dense wind of the Mira companion. We detect a highly absorbed soft X-ray component in the spectrum during the first 50 days of the outburst that is consistent with supersoft emission from the nuclear burning white dwarf. The high temperature and short turnoff time of this emission component, in addition to the observed breaks in the optical and UV light curves, indicate that the white dwarf in the binary is extremely massive. Finally, we explore the connections between the X-ray and GeV {gamma}-ray evolution, and propose that the gamma-ray turnoff is due to the stalling of the forward shock as the ejecta reach the red giant surface.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

THE CHANDRA LOCAL VOLUME SURVEY: THE X-RAY POINT-SOURCE POPULATION OF NGC 404

We present a comprehensive X-ray point-source catalog of NGC 404 obtained as part of the Chandra Local Volume Survey. A new 97 ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of {approx}123 ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of {approx}6 Multiplication-Sign 10{sup 35} erg s{sup -1} in the 0.35-8 keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections, but find only two X-ray sources with candidate optical counterparts. We find 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei. The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented. The XLFs in the soft band (0.5-2 keV) and the hard band (2-8 keV) have a limiting luminosity at the 90% completeness limit of 10{sup 35} erg s{sup -1} and 10{sup 36} erg s{sup -1}, respectively, significantly lower than previous X-ray studies of NGC 404. We find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10{sup 37} erg s{sup -1}) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation {approx}0.5 Gyr ago.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

THE NOT-SO-MASSIVE BLACK HOLE IN THE MICROQUASAR GRS1915+105

We present a new dynamical study of the black hole X-ray transient GRS1915+105 making use of near-infrared spectroscopy obtained with X-shooter at the Very Large Telescope. We detect a large number of donor star absorption features across a wide range of wavelengths spanning the H and K bands. Our 24 epochs covering a baseline of over 1 yr permit us to determine a new binary ephemeris including a refined orbital period of P = 33.85 {+-} 0.16 days. The donor star radial velocity curves deliver a significantly improved determination of the donor semi-amplitude which is both accurate (K{sub 2} = 126 {+-} 1 km s{sup -1}) and robust against choice of donor star template and spectral features used. We furthermore constrain the donor star's rotational broadening to vsin i = 21 {+-} 4 km s{sup -1}, delivering a binary mass ratio of q = 0.042 {+-} 0.024. If we combine these new constraints with distance and inclination estimates derived from modeling the radio emission, a black hole mass of M{sub BH} = 10.1 {+-} 0.6 M{sub Sun} is inferred, paired with an evolved mass donor of M{sub 2} = 0.47 {+-} 0.27 M{sub Sun }. Our analysis suggests a more typical black hole mass for GRS1915+105 rather than the unusually high values derived in the pioneering dynamical study by Greiner et al. Our data demonstrate that high-resolution infrared spectroscopy of obscured accreting binaries can deliver dynamical mass determinations with a precision on par with optical studies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Active galactic nucleus and quasar science with aperture masking interferometry on the James Webb Space Telescope

Due to feedback from accretion onto supermassive black holes (SMBHs), active galactic nuclei (AGNs) are believed to play a key role in ΛCDM cosmology and galaxy formation. However, AGNs extreme luminosities and the small angular size of their accretion flows create a challenging imaging problem. We show that the James Webb Space Telescope's Near Infrared Imager and Slitless Spectrograph (JWST-NIRISS) Aperture Masking Interferometry (AMI) mode will enable true imaging (i.e., without any requirement of prior assumptions on source geometry) at ∼65 mas angular resolution at the centers of AGNs. This is advantageous for studying complex extended accretion flows around SMBHs and in other areas of angular-resolution-limited astrophysics. By simulating data sequences incorporating expected sources of noise, we demonstrate that JWST-NIRISS AMI mode can map extended structure at a pixel-to-pixel contrast of ∼10{sup –2} around an L = 7.5 point source, using short exposure times (minutes). Such images will test models of AGN feedback, fueling, and structure (complementary with ALMA observations), and are not currently supported by any ground-based IR interferometer or telescope. Binary point source contrast with NIRISS is ∼10{sup –4} (for observing binary nuclei in merging galaxies), significantly better than current ground-based optical or IR interferometry. JWST-NIRISS's seven-hole non-redundant mask has a throughput of 15%, and utilizes NIRISS's F277W (2.77 μm), F380M (3.8 μm), F430M (4.3 μm), and F480M (4.8 μm) filters. NIRISS's square pixels are 65 mas per side, with a field of view ∼2' × 2'. We also extrapolate our results to AGN science enabled by non-redundant masking on future 2.4 m and 16 m space telescopes working at long-UV to near-IR wavelengths.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Beam test performance studies of CMS Phase-2 Outer Tracker module prototypes

A new tracking detector will be installed as part of thePhase-2 upgrade of the CMS detector for the high-luminosity LHC era.This tracking detector includes the Inner Tracker, equipped withsilicon pixel sensor modules, and the Outer Tracker, consisting ofmodules with two parallel stacked silicon sensors. The Outer Trackerfront-end ASICs will be able to correlate hits from chargedparticles in these two sensors to perform on-module discriminationof transverse momenta (p$_{T}$). The p$_{T}$information is generated at a frequency of 40 MHz and will be usedin the Level-1 trigger decision of CMS. Prototypes of theso-called 2S modules were tested at the Test Beam Facility at DESYHamburg between 2019 and 2020. These modules use the finalfront-end ASIC, the CMS Binary Chip (CBC), and for the firsttime the Concentrator Integrated Circuit (CIC), optical readoutand on-module power conversion. In total, seven modules were tested,one of which was assembled with sensors irradiated with protons. Animportant aspect was to show that it is possible to read out modulessynchronously. A cluster hit efficiency of about 99.75 % wasachieved for all modules. The CBC p$_{T}$ discriminationmechanism has been verified to work together with the CIC andoptical readout. The measured module performance meets therequirements for operation in the upgraded CMS tracking detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

MO-FG-303-05: A Feasibility Study of Using a Cherenkov Detector Material with the Prompt Gamma Range Verification Technique in Proton Therapy

Purpose: To simulate the feasibility of a Cherenkov glass material for the determination of the penetration depth of therapeutic proton beams in water. Methods: Proton pencil beams of various energies incident onto a water phantom with dimensions of 5 x 5 x 30 cm{sup 3} were used for simulation with the Geant4 toolkit. The model used standard electromagnetic packages, packages based on binary-cascade nuclear model, several decay modules (G4Decay, G4DecayPhysics, and G4RadioactiveDecayPhysics), and optical photon components (G4OpticalPhysics). A Cherenkov glass material was modeled as the detector medium (7.2 g of In2O3 + 90 g cladding, density of 2.82 g/cm{sup 3}, Zeff = 33.7, index of refraction n(600 nm) = 1.56, and energy threshold of production Eth = 156 keV ). The emitted secondary particles are analyzed characterizing their timing, energy, and angular distributions. A feasibility analysis was conducted for a simplistic detector system using this material to locate the position of the Bragg Peak. Results: The escaping neutrons have energies ranging from thermal to the incident proton energy and the escaping photons have energies >10 MeV. Photon peaks between 4 and 6 MeV were attributed to originate from direct proton interactions with {sup 12}C (∼ 4.4 MeV) and {sup 16}O (∼ 6 MeV), respectively. The escaping photons are emitted isotropically, while low (≤10 MeV) and high (>10 MeV) neutrons are isotropic and forward-directional, respectively. The emissions of photons are categorized into prompt (∼ns) and delayed (∼min) where the prompt photons include the 4.4 and 6 MeV. The Cherenkov material had on average <2% of neutron interactions while LYSO and BGO scintillators had a minimum of ∼50%. Our simplistic detector system was capable of discerning Bragg Peak locations using a timing discrimination of ∼50 ns. Conclusion: We investigate the viability of using the Cherenkov material for MeV photon detection medium for the prompt gamma technique.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Interpretation of a Variable Reflection Nebula Associated with HBC 340 and HBC 341 in NGC 1333

We present multi-epoch, R -band imaging obtained from the Palomar Transient Factory of a small, fan-shaped reflection nebula in NGC 1333 that experiences prominent brightness fluctuations. Photometry of HBC 340 (K7e) and HBC 341 (M5e), a visual pair of late-type, young stellar objects lying near the apex of the nebula, demonstrates that while both are variable, the former has brightened by more than two magnitudes following a deep local minimum in 2014 September. Keck high-dispersion ( R ∼ 45,000–66,000), optical spectroscopy of HBC 340 suggests that the protostar is a spectroscopic binary (HBC 340Aa + HBC 340Ab). Both HBC 340 and HBC 341 exhibit strong H α and forbidden line emission, consistent with accretion and outflow. We conclude that the brightness fluctuations in the reflection nebula represent light echos produced by varying incident radiation emanating from HBC 340. The short-term variability observed in the protostar is attributed to irregular accretion activity, while correlated, dipping behavior on a several hundred day timescale may be due to eclipse-like events caused by orbiting circumstellar material. Archival Hubble Space Telescope imaging of the region reveals a second, faint (F814W ∼ 20.3 mag) companion to HBC 340 that lies 1.″02 (∼235 au) east of the protostar. If associated, this probable substellar mass object (20–50 Jupiter masses), HBC 340B, is likely unrelated to the observed brightness variations. The sustained brightening of HBC 340 since late 2014 can be explained by an EXor-like outburst, the recovery from a long duration eclipse event caused by obscuring circumstellar dust, or by the gradual removal of extincting material from along the line of sight. Our analysis here favors one of the extinction scenarios.

79 ASTRONOMY AND ASTROPHYSICS↗