Open Access. Powered by Scholars. Published by Universities.®

Astrophysics and Astronomy Commons™

Open Access. Powered by Scholars. Published by Universities.®

Discipline
Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 4861 - 4890 of 8860

Full-Text Articles in Astrophysics and Astronomy

Absolute Properties Of The Eclipsing Binary Vv Corvi, Francis C. Fekel, Gregory W. Henry, James R. Sowell Oct 2013

Absolute Properties Of The Eclipsing Binary Vv Corvi, Francis C. Fekel, Gregory W. Henry, James R. Sowell

Information Systems and Engineering Management Research Publications

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 52. 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 M1 = 1.978 ± 0.010 M☉ and M2 = 1.513 ± 0.008 M☉, and …

Go to article

Finding Rare Agn: Xmm-Newton And Chandra Observations Of Sdss Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Nico Cappelluti, Francesca Civano Oct 2013

Finding Rare Agn: Xmm-Newton And Chandra Observations Of Sdss Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Nico Cappelluti, Francesca Civano

Dartmouth Scholarship

We have analysed the XMM–Newton and Chandra data overlapping ∼16.5 deg2 of Sloan Digital Sky Survey Stripe 82, including ∼4.6 deg2 of proprietary XMM–Newton data that we present here. In total, 3362 unique X-ray sources are detected at high significance. We derive the XMM–Newton number counts and compare them with our previously reported Chandra logN–logS relations and other X-ray surveys. The Stripe 82 X-ray source lists have been matched to multiwavelength catalogues using a maximum likelihood estimator algorithm. We discovered the highest redshift (z = 5.86) quasar yet identified in an X-ray survey. We …

Go to article

Using Open Datasets And Simulations In Laboratories, Jim Crumley Oct 2013

Using Open Datasets And Simulations In Laboratories, Jim Crumley

Physics Faculty Publications

While advances in instrumentation physics have made many areas more accessible to undergraduate physics laboratories, other areas are still beyond reach. Open data sets and simulations can open up some other frontiers of physics, such as Space Physics and Astronomy. In this talk, I will give an overview of some resources for open data and simulations, and then describe my experiences using these tools in both introductory and advanced labs in our curriculum.

Go to article

Hubble Space Telescope Hot Jupiter Transmission Spectral Survey: A Detection Of Na And Strong Optical Absorption In Hat-P-1b, Nikolay Nikolov, David K. Sing, Frederic Pont, Adam S. Burrows, Jonathan J. Fortney, Gilda E. Ballester, Thomas M. Evans, Catherine M. Huitson, Hannah R. Wakeford, Paul A. Wilson, Suzanne Aigrain, Drake Deming, Neale P. Gibson, Gregory W. Henry, Heather Knutson, Alain Lecavelier Des Etangs, Adam P. Showman, Alfred Vidal-Madjar, Kevin J. Zahnle Oct 2013

Hubble Space Telescope Hot Jupiter Transmission Spectral Survey: A Detection Of Na And Strong Optical Absorption In Hat-P-1b, Nikolay Nikolov, David K. Sing, Frederic Pont, Adam S. Burrows, Jonathan J. Fortney, Gilda E. Ballester, Thomas M. Evans, Catherine M. Huitson, Hannah R. Wakeford, Paul A. Wilson, Suzanne Aigrain, Drake Deming, Neale P. Gibson, Gregory W. Henry, Heather Knutson, Alain Lecavelier Des Etangs, Adam P. Showman, Alfred Vidal-Madjar, Kevin J. Zahnle

Information Systems and Engineering Management Research Publications

We present an optical to near-infrared transmission spectrum of the hot Jupiter HAT-P-1b, based on Hubble Space Telescope observations, covering the spectral regime from 0.29 to 1.027 μm with Space Telescope Imaging Spectrograph (STIS), which is coupled with a recent Wide Field Camera 3 (WFC3) transit (1.087 to 1.687 μm). We derive refined physical parameters of the HAT-P-1 system, including an improved orbital ephemeris. The transmission spectrum shows a strong absorption signature shortward of 0.55 μm, with a strong blueward slope into the near-ultraviolet. We detect atmospheric sodium absorption at a 3.3σ significance level, but find no evidence for the …

Go to article

Discovery Of A New Tev Gamma-Ray Source: Ver J0521+211, P. T. Reynolds, Veritas Oct 2013

Discovery Of A New Tev Gamma-Ray Source: Ver J0521+211, P. T. Reynolds, Veritas

Physical Sciences Publications

We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with the VERITAS imaging atmospheric Cherenkov Telescope Array. These observations were motivated by the discovery of a cluster of >30 GeV photons in the first year of Fermi Large Area Telescope observations. VER J0521+211 is relatively bright at TeV energies, with a mean photon flux of (1.93 ± 0.13stat ± 0.78sys) × 10–11 cm–2 s–1 above 0.2 TeV during the period of the VERITAS observations. The source is strongly variable on a daily timescale across all wavebands, from optical to TeV, with a peak …

Go to article

The Role Of Cross-Shock Potential On Pickup Ion Shock Acceleration In The Framework Of Focused Transport Theory, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul Oct 2013

The Role Of Cross-Shock Potential On Pickup Ion Shock Acceleration In The Framework Of Focused Transport Theory, Pingbing Zuo, Ming Zhang, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

The focused transport theory is appropriate to describe the injection and acceleration of low-energy particles at shocks as an extension of diffusive shock acceleration (DSA). In this investigation, we aim to characterize the role of cross-shock potential (CSP) originated in the charge separation across the shock ramp on pickup ion (PUI) acceleration at various types of shocks with a focused transport model. The simulation results of energy spectrum and spatial density distribution for the cases with and without CSP added in the model are compared.With sufficient acceleration time, the focused transport acceleration finally falls into the DSA regime with the …

Go to article

Gaussian Representation Of Active Galactic Nuclei, Jeffrey W. Klimes, Matthew Lister Oct 2013

Gaussian Representation Of Active Galactic Nuclei, Jeffrey W. Klimes, Matthew Lister

The Summer Undergraduate Research Fellowship (SURF) Symposium

Active galactic nuclei (AGN) are the areas around the centers of galaxies with high luminosity in much of the electromagnetic spectrum. The existing model of AGN describes the high luminosity as the result of accretion of matter around a black hole at the galaxy’s center. Many AGN generate superluminal jets of density higher than the surrounding interstellar medium. The cause for and mechanics driving the relativistic jets are not well understood. In addition, the jets often change direction decaparsecs away from their associated cores, the cause of which has not been well explained. In order to better understand the mechanics …

Go to article

Hst Hot-Jupiter Transmission Spectral Survey: Evidence For Aerosols And Lack Of Tio In The Atmosphere Of Wasp-12b, David K. Sing, Alain Lecavelier Des Etangs, Jonathan J. Fortney, Adam Burrows, Frederic Pont, Hannah R. Wakeford, Gilda E. Ballester, Nikolay Nikolov, Gregory W. Henry, Suzanne Aigrain, Drake Deming, Thomas M. Evans, Neale P. Gibson, Catherine M. Huitson, Heather Knutson, Adam P. Showman, Alfred Vidal-Madjar, Paul A. Wilson, Michael H. Williamson, Kevin J. Zahnle Oct 2013

Hst Hot-Jupiter Transmission Spectral Survey: Evidence For Aerosols And Lack Of Tio In The Atmosphere Of Wasp-12b, David K. Sing, Alain Lecavelier Des Etangs, Jonathan J. Fortney, Adam Burrows, Frederic Pont, Hannah R. Wakeford, Gilda E. Ballester, Nikolay Nikolov, Gregory W. Henry, Suzanne Aigrain, Drake Deming, Thomas M. Evans, Neale P. Gibson, Catherine M. Huitson, Heather Knutson, Adam P. Showman, Alfred Vidal-Madjar, Paul A. Wilson, Michael H. Williamson, Kevin J. Zahnle

Information Systems and Engineering Management Research Publications

We present Hubble Space Telescope (HST) optical transmission spectra of the transiting hot-Jupiter WASP-12b, taken with the Space Telescope Imaging Spectrograph instrument. The resulting spectra cover the range 2900–10 300 Å which we combined with archival Wide Field Camera 3 spectra and Spitzer photometry to cover the full optical to infrared wavelength regions. With high spatial resolution, we are able to resolve WASP-12A's stellar companion in both our images and spectra, revealing that the companion is in fact a close binary M0V pair, with the three stars forming a triple-star configuration. We derive refined physical parameters of the WASP-12 system, …

Go to article

Broadband Monitoring Tracing The Evolution Of The Jet And Disk In The Black Hole Candidate X-Ray Binary Maxi J1659-152, A. J. Horst, P. A. Curran, J. C. A. Miller-Jones, J. D. Linford, J. Gorosabel, D. M. Russell, A. De Ugarte Postigo, A. A. Lundgren, G. B. Taylor, D Maitra, S Guziy, T M. Belloni, C Kouveliotou, P G. Jonker, A Kamble, Z Paragi, J Homan, E Kuulkers, J Granot, D Altamirano, M M. Buxton, A Castro-Tirado, R P. Fender, M A. Garrett, N Gehrels, Dieter H. Hartmann, J A. Kennea, H A. Krimm, V Mangano, E Ramirez-Ruiz, P Romano, R.A.M.J. Wijers, R Wijnands, Y J. Yang Oct 2013

Broadband Monitoring Tracing The Evolution Of The Jet And Disk In The Black Hole Candidate X-Ray Binary Maxi J1659-152, A. J. Horst, P. A. Curran, J. C. A. Miller-Jones, J. D. Linford, J. Gorosabel, D. M. Russell, A. De Ugarte Postigo, A. A. Lundgren, G. B. Taylor, D Maitra, S Guziy, T M. Belloni, C Kouveliotou, P G. Jonker, A Kamble, Z Paragi, J Homan, E Kuulkers, J Granot, D Altamirano, M M. Buxton, A Castro-Tirado, R P. Fender, M A. Garrett, N Gehrels, Dieter H. Hartmann, J A. Kennea, H A. Krimm, V Mangano, E Ramirez-Ruiz, P Romano, R.A.M.J. Wijers, R Wijnands, Y J. Yang

Publications

MAXI J1659−152 was discovered on 2010 September 25 as a new X-ray transient, initially identified as a gamma-ray burst, but was later shown to be a new X-ray binary with a blackhole as the most likely compact object. Dips in the X-ray light curves have revealed that MAXI J1659−152 is the shortest period black hole candidate identified to date. Here we present the results of a large observing campaign at radio, submillimetre, near-infrared (nIR), optical and ultraviolet (UV) wavelengths. We have combined this very rich data set with the available X-ray observations to compile a broad-band picture of the evolution …

Go to article

Wesleyan's Mark Evans Observatory Designated Official Site, Kim Hill Oct 2013

Wesleyan's Mark Evans Observatory Designated Official Site, Kim Hill

News and Events (Discontinued Series)

No abstract provided.

Go to article

Bound Orbits And Virial Theorem In A Dark Energy Universe, Kristen Lackeos Oct 2013

Bound Orbits And Virial Theorem In A Dark Energy Universe, Kristen Lackeos

Von Braun Symposium Student Posters

No abstract provided.

Go to article

New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Viii. Hr 1528, Hr 6993, 2 Sagittae, And 18 Vulpeculae, Francis C. Fekel, Jocelyn Tomkin, Michael H. Williamson Oct 2013

New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Viii. Hr 1528, Hr 6993, 2 Sagittae, And 18 Vulpeculae, Francis C. Fekel, Jocelyn Tomkin, Michael H. Williamson

Information Systems and Engineering Management Research Publications

Improved orbital elements for four A-star double-lined spectroscopic binaries have been determined with numerous new radial velocities. Three of the four systems, HR 1528, 2 Sge, and 18 Vul, have moderately short orbital periods of 7.05, 7.39, and 9.31 days, respectively, and also have circular or nearly circular orbits. Only HR 6993 with a period of 14.68 days has a significantly eccentric orbit. The close visual companion of 2 Sge has been detected spectroscopically, and its velocity measured. The orbital dimensions (a1 sin i and a2 sin i) and minimum masses (m1 sin3 i and m2 sin3 i) of the …

Go to article

Current-Sheet-Like Structures In Solar Winds And Their Effects On The Solar Wind Mhd Turbulence, Junxiang Hu, Allison Bratcher Oct 2013

Current-Sheet-Like Structures In Solar Winds And Their Effects On The Solar Wind Mhd Turbulence, Junxiang Hu, Allison Bratcher

Von Braun Symposium Student Posters

No abstract provided.

Go to article

Design Reference Space Radiation Environments For Spacecraft Design And Mission Planning, Z Robinson Oct 2013

Design Reference Space Radiation Environments For Spacecraft Design And Mission Planning, Z Robinson

Von Braun Symposium Student Posters

No abstract provided.

Go to article

Turbulence Transport Modelling Of The Temporal Outer Heliosphere, Laxman Adhikari Oct 2013

Turbulence Transport Modelling Of The Temporal Outer Heliosphere, Laxman Adhikari

Von Braun Symposium Student Posters

No abstract provided.

Go to article

The Alignment Of The Marshall Grazing Incidence X-Ray Spectrometer (Magixs), Mark Sterrett Oct 2013

The Alignment Of The Marshall Grazing Incidence X-Ray Spectrometer (Magixs), Mark Sterrett

Von Braun Symposium Student Posters

No abstract provided.

Go to article

Particle Acceleration At Shock Pair, Lulu Zhao Oct 2013

Particle Acceleration At Shock Pair, Lulu Zhao

Von Braun Symposium Student Posters

No abstract provided.

Go to article

X-Ray Nuclear Activity In S4g Barred Galaxies: No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling, Mauricio Cristernas, Trisha Mizusawa Oct 2013

X-Ray Nuclear Activity In S4g Barred Galaxies: No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling, Mauricio Cristernas, Trisha Mizusawa

Aerospace, Physics, and Space Science Faculty Publications

Stellar bars can lead to gas inflow toward the center of a galaxy and stimulate nuclear star formation. However, there is no compelling evidence on whether they also feed a central supermassive black hole: by measuring the fractions of barred active and inactive galaxies, previous studies have yielded conflicting results. In this paper, we aim to understand the lack of observational evidence for bar-driven active galactic nucleus (AGN) activity by studying a sample of 41 nearby (d < 35 Mpc) barred galaxies from the Spitzer Survey for Stellar Structure in Galaxies. We use Chandra observations to measure nuclear 2–10 keV X-ray luminosities and estimate Eddington ratios, together with Spitzer 3.6 μm imaging to quantify the strength of the stellar bar in two independent ways: (1) from its structure, as traced by its ellipticity and boxiness, and (2) from its gravitational torque Qb, taken as the maximum ratio of the tangential force to the mean background radial force. In this way, rather than discretizing the presence of both stellar bars and nuclear activity, we are able to account for the continuum of bar strengths and degrees of AGN activity. We find nuclear X-ray sources in 31 out of 41 galaxies with median X-ray luminosity and Eddington ratio of LX = 4.3×1038 erg s−1 and Lbol/LEdd = 6.9×10−6, respectively, consistent with low-luminosity AGN activity. Including upper limits for those galaxies without nuclear detections, we find no significant correlation between any of the bar strength indicators and the degree of nuclear activity, irrespective of galaxy luminosity, stellar mass, Hubble type, or bulge size. Strong bars do not favor brighter or more efficient nuclear activity, implying that at least for the low-luminosity regime, supermassive black hole fueling is not closely connected to large-scale features.

Go to article

Detection Of Ch4 In The Gv Tau N Protoplanetary Disk, David Horne, Erika Gibb Oct 2013

Detection Of Ch4 In The Gv Tau N Protoplanetary Disk, David Horne, Erika Gibb

Physics Faculty Works

T Tauri stars are low mass young stars that may serve as analogs to the early solar system. Observations of organic molecules in the protoplanetary disks surrounding T Tauri stars are important for characterizing the chemical and physical processes that lead to planet formation. Searches for undetected molecules, particularly in the inner, planet forming regions of these disks are important for testing protoplanetary disk chemical models and for understanding the evolution of volatiles through the star and planet formation process. We used NIRSPEC on Keck 2 to perform a high resolution (λ/Δλ ~ 25,000) L-band survey of T Tauri star …

Go to article

Rainich-Type Conditions For Null Electrovacuum Spacetimes Ii, Charles G. Torre Oct 2013

Rainich-Type Conditions For Null Electrovacuum Spacetimes Ii, Charles G. Torre

Research Vignettes

In this second of two worksheets I continue describing local Rainich-type conditions which are necessary and sufficient for the metric to define a null electrovacuum. In other words, these conditions, which I will call the null electrovacuum conditions, guarantee the existence of a null electromagnetic field such that the metric and electromagnetic field satisfy the Einstein-Maxwell equations. When it exists, the electromagnetic field is easily constructed from the metric. In this worksheet I consider the null electrovacuum conditions which apply when a certain null geodesic congruence determined by the metric is twisting. I shall illustrate the these conditions using a …

Go to article

Astr 407 Oct 2013

Astr 407

Department of Physics and Astronomy: Syllabi

No abstract provided.

Go to article

Astr 407: Physics Of The Interstellar Medium, Edward Schmidt Oct 2013

Astr 407: Physics Of The Interstellar Medium, Edward Schmidt

Department of Physics and Astronomy: Syllabi

Syllabus for ASTR 407: Physics of the Interstellar Medium syllabus for Fall 2013 semester.

Go to article

Gamma-Ray Observations Of X-Ray Binaries, Angelo Varlotta Oct 2013

Gamma-Ray Observations Of X-Ray Binaries, Angelo Varlotta

Open Access Dissertations

The detection of GeV/TeV emission from X-ray binaries (XRBs) has established a new class of high-energy (HE, >0.1 GeV) and very-high-energy (VHE, >100 GeV) gamma-ray emitters. XRBs are formed by a compact object, either a neutron star or a black hole, and by an optical companion star. Some XRBs are known to possess collimated relativistic jets, and are called microquasars. VERITAS has conducted observations of the high-mass X-ray binary (HMXB) 1A 0535+262 and of the microquasar Cygnus X-3. Many theoretical models predict VHE emission when these sources manifest persistent relativistic jets or transient ejections. In light of these considerations, VERITAS …

Go to article

Exploring The Variable Sky With Linear. Iii. Classification Of Periodic Light Curves, Lovro Palaversa, Hakeem Oluseyi Oct 2013

Exploring The Variable Sky With Linear. Iii. Classification Of Periodic Light Curves, Lovro Palaversa, Hakeem Oluseyi

Aerospace, Physics, and Space Science Faculty Publications

We describe the construction of a highly reliable sample of ∼7000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10,000 deg2 of the northern sky. The majority of these variables have not been cataloged yet. The sample flux limit is severalmagnitudes fainter than most other wide-angle surveys; the photometric errors range from ∼0.03 mag at r = 15 to ∼0.20 mag at r = 18. Light curves include on average 250 data points, collected over about a decade. Using Sloan Digital Sky Survey (SDSS) based photometric recalibration of the LINEAR data for about …

Go to article

X-Ray Nuclear Activity In S4g Barred Galaxies : No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling., Mauricio Cisternas, Dimitri A. Gadotti, Johan H. Knapen, Taehyun Kim, Simon Diaz-Garcia, Eija Laurikainen, Heikki Salo, Omaira Gonzalez-Martin, Luis C. Ho, Bruce G. Elmegreen, Dennis Zaritsky, Kartik Sheth, E. Athanassoula, Albert Bosma, Sebastien Comeron, Santiago Erroz-Ferrer, Armando Gil De Paz, Joannah L. Hinz, Benne W. Holwerda, Jarkko Laine, Sharon Meidt, Karin Menendez-Delmestre, Trisha Mizusawa, Juan Carlos Munoz-Mateos, Michael W. Regan, Mark Seibert Oct 2013

X-Ray Nuclear Activity In S4g Barred Galaxies : No Link Between Bar Strength And Co-Occurrent Supermassive Black Hole Fueling., Mauricio Cisternas, Dimitri A. Gadotti, Johan H. Knapen, Taehyun Kim, Simon Diaz-Garcia, Eija Laurikainen, Heikki Salo, Omaira Gonzalez-Martin, Luis C. Ho, Bruce G. Elmegreen, Dennis Zaritsky, Kartik Sheth, E. Athanassoula, Albert Bosma, Sebastien Comeron, Santiago Erroz-Ferrer, Armando Gil De Paz, Joannah L. Hinz, Benne W. Holwerda, Jarkko Laine, Sharon Meidt, Karin Menendez-Delmestre, Trisha Mizusawa, Juan Carlos Munoz-Mateos, Michael W. Regan, Mark Seibert

Faculty and Staff Scholarship

Stellar bars can lead to gas inflow toward the center of a galaxy and stimulate nuclear star formation. However, there is no compelling evidence on whether they also feed a central supermassive black hole: by measuring the fractions of barred active and inactive galaxies, previous studies have yielded conflicting results. In this paper, we aim to understand the lack of observational evidence for bar-driven active galactic nucleus (AGN) activity by studying a sample of 41 nearby (d < 35 Mpc) barred galaxies from the Spitzer Survey for Stellar Structure in Galaxies. We use Chandra observations to measure nuclear 2–10 keV X-ray luminosities and estimate Eddington ratios, together with Spitzer 3.6 μm imaging to quantify the strength of the stellar bar in two independent ways: (1) from its structure, as traced by its ellipticity and boxiness, and (2) from its gravitational torque Qb, taken as the maximum ratio of the tangential force to the mean background radial force. In this way, rather than discretizing the presence of both stellar bars and nuclear activity, we are able to account for the continuum of bar strengths and degrees of AGN activity. We find nuclear X-ray sources in 31 out of 41 galaxies with median X-ray luminosity and Eddington ratio of LX = 4.3×1038 erg s−1 and Lbol/LEdd = 6.9×10−6, respectively, consistent with low-luminosity AGN activity. Including upper limits for those galaxies without nuclear detections, we find no significant correlation between any of the bar strength indicators and the degree of nuclear activity, irrespective of galaxy luminosity, stellar mass, Hubble type, or bulge size. Strong bars do not favor brighter or more efficient nuclear activity, implying that at least for the low-luminosity regime, supermassive black hole fueling is not closely connected to large-scale features.

Go to article

Quantified H I Morphology – Vii. Star Formation And Tidal Influence On Local Dwarf H I Morphology., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, S. -L. Blyth Oct 2013

Quantified H I Morphology – Vii. Star Formation And Tidal Influence On Local Dwarf H I Morphology., Benne W. Holwerda, N. Pirzkal, W. J. G. De Blok, S. -L. Blyth

Faculty and Staff Scholarship

Scale-invariant morphology parameters applied to atomic hydrogen maps (H i) of galaxies can be used to quantify the effects of tidal interaction or star formation on the interstellar matter (ISM). Here we apply these parameters, concentration, asymmetry, smoothness, Gini, M20, and the GM parameter, to two public surveys of nearby dwarf galaxies, the Very Large Array-ANGST and Local Irregulars That Trace Luminosity Extremes-The H i Nearby Galaxy Survey, to explore whether tidal interaction or the ongoing or past star formation is a dominant force shaping the H i disc of these dwarfs. Previously, H i morphological criteria were identified for …

Go to article

A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk Sep 2013

A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk

Publications

We apply a self-consistent and robust Bayesian statistical approach to determine the ages, distances, and zero-age main sequence (ZAMS) masses of 28 field DA white dwarfs (WDs) with ages of approximately 4–8 Gyr. Our technique requires only quality optical and near-infrared photometry to derive ages with <15% uncertainties, generally with little sensitivity to our choice of modern initial–final mass relation. We find that age, distance, and ZAMS mass are correlated in a manner that is too complex to be captured by traditional error propagation techniques. We further find that the posterior distributions of age are often asymmetric, indicating that the …

Go to article

Near-Infrared Spectroscopic Study Of V1647 Ori, Sean D. Brittain, T W. Rettig, Theodore Simon, Erika L. Gibb, Joseph Liskowsky Sep 2013

Near-Infrared Spectroscopic Study Of V1647 Ori, Sean D. Brittain, T W. Rettig, Theodore Simon, Erika L. Gibb, Joseph Liskowsky

Publications

We present new high-resolution infrared echelle spectra of V1647 Ori, the young star that illuminates McNeil's nebula. From the start, V1647 Ori has been an enigmatic source that has defied classification, in some ways resembling eruptive stars of the FUor class and in other respects the EXor variables. V1647 Ori underwent an outburst in 2003 before fading back to its pre-outburst brightness in 2006. In 2008, it underwent a new outburst. In this paper we present high-resolution K-band and M-band spectra from the W. M. Keck Observatory that were acquired during the 2008 outburst. We compare the spectra to spectra …

Go to article

Plans For The Next Grape Balloon Flight, Mark L. Mcconnell, Peter F. Bloser, T P. Connor, Camden Ertley, Jason S. Legere, James M. Ryan, Sambid K. Wasti Sep 2013

Plans For The Next Grape Balloon Flight, Mark L. Mcconnell, Peter F. Bloser, T P. Connor, Camden Ertley, Jason S. Legere, James M. Ryan, Sambid K. Wasti

Space Science Center

The Gamma RAy Polarimeter Experiment (GRAPE) was first flown on a 26-hour balloon flight in the fall of 2011. GRAPE consists of an array of Compton polarimeter modules (based on traditional scintillation technologies) designed to operate in the energy range from 50 keV up to 500 keV. The ultimate goal is to operate GRAPE in a wide FoV configuration for the study of gamma-ray bursts. For the first (demonstration) balloon flight, GRAPE was configured in a collimated mode to facilitate observations of known point sources. The Crab nebula/pulsar, the active Sun, and Cygnus X-1 were the primary targets for the …

Go to article

Scintillator Gamma-Ray Detectors With Silicon Photomultiplier Readouts For High-Energy Astronomy, Peter F. Bloser, Jason S. Legere, Chris Bancroft, Mark L. Mcconnell, James M. Ryan, Nathan Schwadron Sep 2013

Scintillator Gamma-Ray Detectors With Silicon Photomultiplier Readouts For High-Energy Astronomy, Peter F. Bloser, Jason S. Legere, Chris Bancroft, Mark L. Mcconnell, James M. Ryan, Nathan Schwadron

Space Science Center

Space-based gamma-ray detectors for high-energy astronomy face strict constraints of mass, volume, and power, and must endure harsh operating environments. Scintillator materials have a long history of successful operation under these conditions, and new materials offer greatly improved performance in terms of efficiency, time response, and energy resolution. The use of scintillators in space remains constrained, however, by the mass, volume, and fragility of the associated light readout device, typically a vacuum photomultiplier tube (PMT). Recently developed silicon photomultipliers (SiPMs) offer gains and efficiencies similar to those of PMTs, but with greatly reduced mass and volume, high ruggedness, and no …

Go to article

First Prev Next Last