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Articles 31 - 60 of 282
Full-Text Articles in Astrophysics and Astronomy
The Heliosphere As Seen In Tev Cosmic Rays, Ming Zhang, Nikolai Pogorelov
The Heliosphere As Seen In Tev Cosmic Rays, Ming Zhang, Nikolai Pogorelov
Aerospace, Physics, and Space Science Faculty Publications
Measurements from several cosmic-ray air shower experiments reveal that the anisotropy of TeV cosmic-ray flux does not agree with a dipole pattern commonly expected from the Compton–Getting effect or from the diffusion of cosmic rays in Galactic magnetic fields. TeV cosmic-ray anisotropy maps often show fine features, some of which are slightly time-dependent. Because the size of the heliosphere is larger than the gyroradius of TeV cosmic rays in the interstellar magnetic field, the electric and magnetic fields of the heliosphere may distort the pattern of cosmic-ray anisotropy that one would see in the local interstellar medium without the presence …
Measurement Of Higher Cumulants Of Net-Charge Multiplicity Distributions In Au + Au Collisions At √Snn =7.7-200 Gev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Klaus Dehmelt, Marcus Hohlmann, Phenix Collaboration
Measurement Of Higher Cumulants Of Net-Charge Multiplicity Distributions In Au + Au Collisions At √Snn =7.7-200 Gev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Klaus Dehmelt, Marcus Hohlmann, Phenix Collaboration
Aerospace, Physics, and Space Science Faculty Publications
We report the measurement of cumulants (Cn,n=1,...,4) of the net-charge distributions measured within pseudorapidity (|η|<0.35) in Au+Au collisions at √sNN=7.7-200GeV with the PHENIX experiment at the Relativistic Heavy Ion Collider. The ratios of cumulants (e.g., C₁/C₂, C₃/C₁) of the net-charge distributions, which can be related to volume independent susceptibility ratios, are studied as a function of centrality and energy. These quantities are important to understand the quantum-chromodynamics phase diagram and possible existence of a critical end point. The measured values are very well described by expectation from negative binomial distributions. We do not observe any nonmonotonic behavior in the ratios of the cumulants as a function of collision energy. The measured values of C₁/C₂ and C₃/C₁ can be directly compared to lattice quantum-chromodynamics calculations and thus allow extraction of both the chemical freeze-out temperature and the baryon chemical potential at each center-of-mass energy. The extracted baryon chemical potentials are in excellent agreement with a thermal-statistical analysis model.
The Puzzling Properties Of The Magnetic O Star Tr16-22, Yaël Nazé, Rodolfo Barbá, Stefano Bagnulo, Nidia Morrell, Roberto Gamen, Véronique Petit, Coralie Neiner
The Puzzling Properties Of The Magnetic O Star Tr16-22, Yaël Nazé, Rodolfo Barbá, Stefano Bagnulo, Nidia Morrell, Roberto Gamen, Véronique Petit, Coralie Neiner
Aerospace, Physics, and Space Science Faculty Publications
Context. The detection of bright, hard, and variable X-ray emission in Tr16-22 prompted spectropolarimetric observations of this star, which in turn led to the discovery of a surface magnetic field. Aims. We want to further constrain the properties of this star, in particular to verify whether X-ray variations are correlated to changes in optical emission lines and magnetic field strength, as expected from the oblique rotator model that is widely accepted for magnetic O stars. Methods. We have obtained new low-resolution spectropolarimetric and long-term high-resolution spectroscopic monitoring of Tr16-22, and we also analyse new, serendipitous X-ray data. Results. The new …
Evidence Of Magnetic Field Decay In Massive Main-Sequence Stars, Luca Fossati, Fabian R.N. Schneider, Norberto Castro, Norbert Langer, Sergio Simón-Díaz, André Luís Müller, Alex De Koter, Thierry Morel, Véronique Petit, Hugues Sana, Gregg A. Wade
Evidence Of Magnetic Field Decay In Massive Main-Sequence Stars, Luca Fossati, Fabian R.N. Schneider, Norberto Castro, Norbert Langer, Sergio Simón-Díaz, André Luís Müller, Alex De Koter, Thierry Morel, Véronique Petit, Hugues Sana, Gregg A. Wade
Aerospace, Physics, and Space Science Faculty Publications
A significant fraction of massive main-sequence stars show strong, large-scale magnetic fields. The origin of these fields, their lifetimes, and their role in shaping the characteristics and evolution of massive stars are currently not well understood. We compile a catalogue of 389 massive main-sequence stars, 61 of which are magnetic, and derive their fundamental parameters and ages. The two samples contain stars brighter than magnitude 9 in the V-band and range in mass between 5 and 100 M⊙. We find that the fractional main-sequence age distribution of all considered stars follows what is expected for a magnitude limited sample, while …
A Search For Brief Optical Flashes Associated With The Seti Target Kic 8462852, A U. Abeysekara, Jamie A. Holder
A Search For Brief Optical Flashes Associated With The Seti Target Kic 8462852, A U. Abeysekara, Jamie A. Holder
Aerospace, Physics, and Space Science Faculty Publications
The F-type star KIC 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC→8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately 1 photon m-2, is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general.
Scaling Properties Of Fractional Momentum Loss Of High- Pt Hadrons In Nucleus-Nucleus Collisions At √Snn From 62.4 Gev To 2.76 Tev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Klaus Dehmelt, Marcus Hohlmann, S. Rembeczki, Phenix Collaboration
Scaling Properties Of Fractional Momentum Loss Of High- Pt Hadrons In Nucleus-Nucleus Collisions At √Snn From 62.4 Gev To 2.76 Tev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Klaus Dehmelt, Marcus Hohlmann, S. Rembeczki, Phenix Collaboration
Aerospace, Physics, and Space Science Faculty Publications
Measurements of the fractional momentum loss (Sloss ≡ δpT/pT) of high-transverse-momentum-identified hadrons in heavy-ion collisions are presented. Using π⁰ in Au+Au and Cu+Cu collisions at √sNN=62.4 and 200 GeV measured by the PHENIX experiment at the Relativistic Heavy Ion Collider and and charged hadrons in Pb+Pb collisions measured by the ALICE experiment at the Large Hadron Collider, we studied the scaling properties of Sloss as a function of a number of variables: the number of participants, Npart, the number of quark participants, Nqp, the charged-particle density, dNch/dη, and the Bjorken energy density times the equilibration time, ᵋᵦjτ₀. We find that …
Transverse Energy Production And Charged-Particle Multiplicity At Midrapidity In Various Systems From √Snn =7.7 To 200 Gev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Klaus Dehmelt, Marcus Hohlmann, S. Rembeczki
Transverse Energy Production And Charged-Particle Multiplicity At Midrapidity In Various Systems From √Snn =7.7 To 200 Gev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Klaus Dehmelt, Marcus Hohlmann, S. Rembeczki
Aerospace, Physics, and Space Science Faculty Publications
Measurements of midrapidity charged-particle multiplicity distributions, dNch/dη, and midrapidity transverse-energy distributions, dET/dη, are presented for a variety of collision systems and energies. Included are distributions for Au+Au collisions at sNN=200, 130, 62.4, 39, 27, 19.6, 14.5, and 7.7 GeV, Cu+Cu collisions at √sNN=200 and 62.4 GeV, Cu+Au collisions at √sNN=200 GeV, U+U collisions at √sNN=193 GeV, d+Au collisions at √sNN=200 GeV, ³He+Au collisions at √sNN=200 GeV, and p+p collisions at √sNN=200 GeV. Centrality-dependent distributions at midrapidity are presented in terms of the number of nucleon participants, Npart, and the number of constituent quark participants, Nqp. For all A+A collisions down …
Transit Timing Observations From Kepler. Ix. Catalog Of The Full Long-Cadence Data Set, Tomer Holczer, Tsevi Mazeh, Gil Nachmani, Daniel Jontof-Hutter, Eric B. Ford, Daniel Fabrycky, Darin Ragozzine, Mackenzie Kane, Jason H. Steffen
Transit Timing Observations From Kepler. Ix. Catalog Of The Full Long-Cadence Data Set, Tomer Holczer, Tsevi Mazeh, Gil Nachmani, Daniel Jontof-Hutter, Eric B. Ford, Daniel Fabrycky, Darin Ragozzine, Mackenzie Kane, Jason H. Steffen
Aerospace, Physics, and Space Science Faculty Publications
We present a new transit timing catalog of 2599 Kepler Objects of Interest (KOIs), using the PDC-MAP long-cadence light curves that include the full 17 quarters of the mission (ftp://wise-ftp.tau.ac.il/pub/tauttv/TTV/ver-112). The goal is to produce an easy-to-use catalog that can stimulate further analyses of interesting systems. For 779 KOIs with high enough S/N, we derived the timing, duration, and depth of 69,914 transits. For 1820 KOIs with lower SNR, we derived only the timing of 225,273 transits. After removal of outlier timings, we derived various statistics for each KOI that were used to indicate significant variations. Including systems found by …
Powerful Activity In The Bright Ages. I. A Visible/Ir Survey Of High Redshift 3c Radio Galaxies And Quasars, Bryan Hilbert, Eric S. Perlman
Powerful Activity In The Bright Ages. I. A Visible/Ir Survey Of High Redshift 3c Radio Galaxies And Quasars, Bryan Hilbert, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We present new rest-frame UV and visible observations of 22 high-z (1 < z < 2.5) 3C radio galaxies and QSOs obtained with the Hubble Space Telescope's Wide Field Camera 3 instrument. Using a custom data reduction strategy in order to assure the removal of cosmic rays, persistence signal, and other data artifacts, we have produced high-quality science-ready images of the targets and their local environments. We observe targets with regions of UV emission suggestive of active star formation. In addition, several targets exhibit highly distorted host galaxy morphologies in the rest frame visible images. Photometric analyses reveal that brighter QSOs generally tend to be redder than their dimmer counterparts. Using emission line fluxes from the literature, we estimate that emission line contamination is relatively small in the rest frame UV images for the QSOs. Using archival VLA data, we have also created radio map overlays for each of our targets, allowing for analysis of the optical and radio axes alignment.
Quiet-Sun Network Bright Point Phenomena With Sigmoidal Signatures, David L. Chesney, Hakeem M. Oluşeyi, Norton Brice Orange, Patrick R. Champey
Quiet-Sun Network Bright Point Phenomena With Sigmoidal Signatures, David L. Chesney, Hakeem M. Oluşeyi, Norton Brice Orange, Patrick R. Champey
Aerospace, Physics, and Space Science Faculty Publications
Ubiquitous solar atmospheric coronal and transition region bright points (BPs) are compact features overlying strong concentrations of magnetic flux. Here, we utilize high-cadence observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to provide the first observations of extreme ultraviolet quietSun (QS) network BP activity associated with sigmoidal structuring. To our knowledge, this previously unresolved fine structure has never been associated with such small-scale QS events. This QS event precedes a bi-directional jet in a compact, low-energy, and low-temperature environment, where evidence is found in support of the typical fan-spine magnetic field topology. As in active regions …
The Rate Of Core Collapse Supernovae To Redshift 2.5 From The Candels And Clash Supernova Surveys, Louis-Gregory Strolger, Tomas Dahlen, Steven A. Rodney, Or Graur, Adam G. Riess, Curtis Mccully, Swara Ravindranath, Bahram Mobasher, A Kristin Shahady
The Rate Of Core Collapse Supernovae To Redshift 2.5 From The Candels And Clash Supernova Surveys, Louis-Gregory Strolger, Tomas Dahlen, Steven A. Rodney, Or Graur, Adam G. Riess, Curtis Mccully, Swara Ravindranath, Bahram Mobasher, A Kristin Shahady
Aerospace, Physics, and Space Science Faculty Publications
The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and Cluster Lensing And Supernova survey with Hubble multi-cycle treasury programs with the Hubble Space Telescope (HST) have provided new opportunities to probe the rate of core-collapse supernovae (CCSNe) at high redshift, now extending to z ≈ 2.5. Here we use a sample of approximately 44 CCSNe to determine volumetric rates, RCC, in six redshift bins in the range 0.1< z < 2.5. Together with rates from our previous HST program, and rates from the literature, we trace a more complete history of RCC (z) , with RCC = 0.72 ± 0.06 yr-1 Mpc-3 10-4 h3 70 at z < 0.08, and increasing to 3.7-1.6 +3.1 yr-1 Mpc-3 10-4 h3 70 to Z ≈ 2.0. The statistical precision in each bin is several factors better than than the systematic error, with significant contributions from host extinction, and average peak absolute magnitudes of the assumed luminosity functions for CCSN types. Assuming negligible time delays from stellar formation to explosion, we find these composite CCSN rates to be in excellent agreement with cosmic star formation rate density (SFRs) derived largely from dust-corrected rest-frame UV emission, with a scaling factor of k = 0.0091 ± 0.0017 M⊙ -1, and inconsistent (to >95% confidence) with SFRs from IR luminous galaxies, or with SFR models that include simple evolution in the initial mass function over time. This scaling factor is expected if the fraction of …
Stochastic Acceleration Of Galactic Cosmic Rays By Compressible Plasma Fluctuations In Supernova Shells, Ming Zhang
Stochastic Acceleration Of Galactic Cosmic Rays By Compressible Plasma Fluctuations In Supernova Shells, Ming Zhang
Aerospace, Physics, and Space Science Faculty Publications
A theory of 2-stage acceleration of Galactic cosmic rays in supernova remnants is proposed. The first stage is accomplished by the supernova shock front, where a power-law spectrum is established up to a certain cutoff energy. It is followed by stochastic acceleration with compressible waves/turbulence in the downstream medium. With a broad ∝k^(-2) spectrum for the compressible plasma fluctuations, the rate of stochastic acceleration is constant over a wide range of particle momentum. In this case, the stochastic acceleration process extends the power-law spectrum cutoff energy of Galactic cosmic rays to the knee without changing the spectral slope. This situation …
Observations Of An Energetically Isolated Quiet Sun Transient: Evidence Of Quasi-Steady Coronal Heating, Norton Brice Orange, David L. Chesney, Hakeem M. Oluseyi
Observations Of An Energetically Isolated Quiet Sun Transient: Evidence Of Quasi-Steady Coronal Heating, Norton Brice Orange, David L. Chesney, Hakeem M. Oluseyi
Aerospace, Physics, and Space Science Faculty Publications
Increasing evidence for coronal heating contributions from cooler solar atmospheric layers, notably quiet Sun (QS) conditions, challenges standard solar atmospheric descriptions of bright transition region (TR) emission. As such, questions about the role of dynamic QS transients in contributing to the total coronal energy budget are raised. Using observations from the Atmospheric Imaging Assembly and Heliosemic Magnetic Imager on board the Solar Dynamics Observatory, and numerical model extrapolations of coronal magnetic fields, we investigate a dynamic QS transient that is energetically isolated to the TR and extrudes from a common footpoint shared with two heated loop arcades. A non-causal relationship …
Chang-Es V: Nuclear Outflow In A Virgo Cluster Spiral After A Tidal Disruption Event, Judith A. Irwin, Richard N. Henriksen, Marita Krause, Daniel Q. Wang, Theresa Wiegert, Eric J. Murphy, George Heald, Eric S. Perlman
Chang-Es V: Nuclear Outflow In A Virgo Cluster Spiral After A Tidal Disruption Event, Judith A. Irwin, Richard N. Henriksen, Marita Krause, Daniel Q. Wang, Theresa Wiegert, Eric J. Murphy, George Heald, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We have observed the Virgo Cluster spiral galaxy, NGC 4845, at 1.6 and 6 GHz using the Karl G. Jansky Very Large Array, as part of the Continuum Halos in Nearby Galaxies—an EVLA Survey (CHANG-ES). The source consists of a bright unresolved core with a surrounding weak central disk (1.8 kpc diameter). The core is variable over the 6 month timescale of the CHANG-ES data and has increased by a factor of ≈6 since 1995. The wide bandwidths of CHANG-ES have allowed us to determine the spectral evolution of this core, which peaks between 1.6 and 6 GHz (it is …
Kepler 453 B - The 10th Kepler Transiting Circumbinary Planet, William F. Welsh, Darin Ragozzine
Kepler 453 B - The 10th Kepler Transiting Circumbinary Planet, William F. Welsh, Darin Ragozzine
Aerospace, Physics, and Space Science Faculty Publications
We present the discovery of Kepler-453 b, a 6.2 RƟ planet in a low-eccentricity, 240.5 day orbit about an eclipsing binary. The binary itself consists of a 0.94 and 0.195 M☉ pair of stars with an orbital period of 27.32 days. The plane of the planetʼs orbit is rapidly precessing, and its inclination only becomes sufficiently aligned with the primary star in the latter portion of the Kepler data. Thus three transits are present in the second half of the light curve, but none of the three conjunctions that occurred during the first half of the light curve produced observable …
A Numerical Simulation Of Cosmic-Ray Modulation Near The Heliopause, Xi Luo, Ming Zhang, Marius S. Potgieter, Xueshang Feng, Nikolai V. Pogorelov
A Numerical Simulation Of Cosmic-Ray Modulation Near The Heliopause, Xi Luo, Ming Zhang, Marius S. Potgieter, Xueshang Feng, Nikolai V. Pogorelov
Aerospace, Physics, and Space Science Faculty Publications
Based on a hybrid galactic cosmic-ray transport model, which incorporated MHD global heliospheric data into Parker's cosmic-ray transport equation, we studied the behavior of the transport of galactic cosmic rays and the corresponding gradients in their flux near the heliopause (HP). We found that, (1) by increasing the ratio of the parallel diffusion coefficient to the perpendicular diffusion coefficient in the interstellar magnetic field of the outer heliosheath, the simulated radial flux near the HP increases as well. As the ratio multiplying factor reached 10^10, the radial flux experienced a sudden jump near the HP, similar to what Voyager 1 …
Optical Detection Of The Pictor A Jet And Tidal Tail: Evidence Against An Ic/Cmb Jet, Eric S. Gentry, Herman L. Marshall, Martin J. Hardcastle, Eric S. Perlman, Mark Birkinshaw, Diana M. Worrall, Emil Lenc, Aneta Siemiginowska, Claudia Megan Urry
Optical Detection Of The Pictor A Jet And Tidal Tail: Evidence Against An Ic/Cmb Jet, Eric S. Gentry, Herman L. Marshall, Martin J. Hardcastle, Eric S. Perlman, Mark Birkinshaw, Diana M. Worrall, Emil Lenc, Aneta Siemiginowska, Claudia Megan Urry
Aerospace, Physics, and Space Science Faculty Publications
New images of the FR II radio galaxy Pictor A from the Hubble Space Telescope reveal a previously undiscovered tidal tail, as well as a number of jet knots coinciding with a known X-ray and radio jet. The tidal tail is approximately 5″ wide (3 kpc projected), starting 18″ (12 kpc) from the center of Pictor A, and extends more than 90″ (60 kpc). The knots are part of a jet observed to be about 4′ (160 kpc) long, extending to a bright hotspot. These images are the first optical detections of this jet, and by extracting knot flux densities …
The Spitzer Survey Of Stellar Structure In Galaxies (S4g): Stellar Masses, Sizes, And Radial Profiles For 2352 Nearby Galaxies, Juan Carlos Muñoz-Mateos, Kartik Sheth, Michael Regan, Trisha Mizusawa
The Spitzer Survey Of Stellar Structure In Galaxies (S4g): Stellar Masses, Sizes, And Radial Profiles For 2352 Nearby Galaxies, Juan Carlos Muñoz-Mateos, Kartik Sheth, Michael Regan, Trisha Mizusawa
Aerospace, Physics, and Space Science Faculty Publications
The Spitzer Survey of Stellar Structure in Galaxies is a volume, magnitude, and size-limited survey of 2352 nearby galaxies with deep imaging at 3.6 and 4.5 μm. In this paper, we describe our surface photometry pipeline and showcase the associated data products that we have released to the community. We also identify the physical mechanisms leading to different levels of central stellar mass concentration for galaxies with the same total stellar mass. Finally, we derive the local stellar mass–size relation at 3.6 μm for galaxies of different morphologies. Our radial profiles reach stellar mass surface densities below ~1 M pc-2 …
Search For Vector-Like T Quarks Decaying To Top Quarks And Higgs Bosons In The All-Hadronic Channel Using Jet Substructure, Cms Collaboration, V. Khachatryan, A. M. Sirunyan, Marc M. Baarmand, Marcus Hohlmann, Himali Kalakhety, Francisco X. Yumiceva
Search For Vector-Like T Quarks Decaying To Top Quarks And Higgs Bosons In The All-Hadronic Channel Using Jet Substructure, Cms Collaboration, V. Khachatryan, A. M. Sirunyan, Marc M. Baarmand, Marcus Hohlmann, Himali Kalakhety, Francisco X. Yumiceva
Aerospace, Physics, and Space Science Faculty Publications
A search is performed for a vector-like heavy T quark that is produced in pairs and that decays to a top quark and a Higgs boson. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector in proton-proton collisions at s=8" role="presentation" style="box-sizing: inherit; display: inline-block; line-height: normal; word-spacing: normal; overflow-wrap: normal; text-wrap: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">�=8 TeV. For T quarks with large mass values the top quarks and Higgs bosons can have significant Lorentz …
Ruling Out Ic/Cmb X-Rays In Pks 0637-752 And The Implications For Tev Emission From Large-Scale Quasar Jets, Eileen T. Meyer, Markos Georganopoulos, William B. Sparks, Leith E.H. Godfrey, James E.J. Lovell, Eric S. Perlman
Ruling Out Ic/Cmb X-Rays In Pks 0637-752 And The Implications For Tev Emission From Large-Scale Quasar Jets, Eileen T. Meyer, Markos Georganopoulos, William B. Sparks, Leith E.H. Godfrey, James E.J. Lovell, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
The Chandra X-ray observatory has discovered dozens of resolved, kiloparsec-scale jets associated with powerful quasars in which the X-ray fluxes are observed to be much higher than the expected level based on the radio-optical synchrotron spectrum. The most popular explanation for the anomalously high and hard X-ray fluxes is that these jets do not decelerate significantly by the kiloparsec scale, but rather remain highly relativistic (Lorentz factors ). By adopting a small angle to the line of sight, the X-rays can thus be explained by inverse Compton upscattering of cosmic microwave background (CMB) photons (IC/CMB), where the observed emission is …
The Event Horizon Of M87, Avery E. Broderick, Ramesh Narayan, John Kormendy, Eric S. Perlman, Marcia J. Rieke, Sheperd S. Doleman
The Event Horizon Of M87, Avery E. Broderick, Ramesh Narayan, John Kormendy, Eric S. Perlman, Marcia J. Rieke, Sheperd S. Doleman
Aerospace, Physics, and Space Science Faculty Publications
The 6 x 10⁹ M⊙ supermassive black hole at the center of the giant elliptical galaxy M87 powers a relativistic jet. Observations at millimeter wavelengths with the Event Horizon Telescope have localized the emission from the base of this jet to angular scales comparable to the putative black hole horizon. The jet might be powered directly by an accretion disk or by electromagnetic extraction of the rotational energy of the black hole. However, even the latter mechanism requires a confining thick accretion disk to maintain the required magnetic flux near the black hole. Therefore, regardless of the jet mechanism, the …
New Constraints On Quantum Gravity From X-Ray And Gamma-Ray Observations, Eric S. Perlman, Saul A. Rappaport, Wayne A. Christiansen, Yeejack Ng, John G. Devore, David A. Pooley
New Constraints On Quantum Gravity From X-Ray And Gamma-Ray Observations, Eric S. Perlman, Saul A. Rappaport, Wayne A. Christiansen, Yeejack Ng, John G. Devore, David A. Pooley
Aerospace, Physics, and Space Science Faculty Publications
One aspect of the quantum nature of spacetime is its “foaminess” at very small scales. Many models for spacetime foam are defined by the accumulation power α, which parameterizes the rate at which Planck-scale spatial uncertainties (and the phase shifts they produce) may accumulate over large path lengths. Here α is defined by the expression for the path-length fluctuations, dℓ, of a source at distance ℓ, wherein dℓ ℓ1-aℓ a P , with ℓP being the Planck length. We reassess previous proposals to use astronomical observations of distant quasars and active galactic nuclei to test models of spacetime foam. …
The Differences In The Torus Geometry Between Hidden And Non-Hidden Broad Line Active Galactic Nuclei, Kohei Ichikawa, Eric S. Perlman
The Differences In The Torus Geometry Between Hidden And Non-Hidden Broad Line Active Galactic Nuclei, Kohei Ichikawa, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We present results from the fitting of infrared (IR) spectral energy distributions of 21 active galactic nuclei (AGNs) with clumpy torus models. We compiled high spatial resolution (∼0.3–0.7 arcsec) mid-IR (MIR) N-band spectroscopy, Q-band imaging, and nuclear near- and MIR photometry from the literature. Combining these nuclear near- and MIR observations, far-IR photometry, and clumpy torus models enables us to put constraints on the torus properties and geometry. We divide the sample into three types according to the broad line region (BLR) properties: type-1s, type-2s with scattered or hidden broad line region (HBLR) previously observed, and type-2s without any published …
The Emergence Of Negative Superhumps In Cataclysmic Variables: Smoothed Particle Hydrodynamics Simulations, David M. Thomas, Matt A. Wood
The Emergence Of Negative Superhumps In Cataclysmic Variables: Smoothed Particle Hydrodynamics Simulations, David M. Thomas, Matt A. Wood
Aerospace, Physics, and Space Science Faculty Publications
Negative superhumps are believed to arise in cataclysmic variable systems when the accretion disk is tilted with respect to the orbital plane. Slow retrograde precession of the line-of-nodes results in a signal—the negative superhump—with a period slightly less than the orbital period. Previous studies have shown that tilted disks exhibit negative superhumps, but a consensus on how a disk initially tilts has not been reached. Analytical work by Lai (1999, ApJ, 524, 1030) suggests that a magnetic field on the primary can lead to a tilt instability in a disk when the dipole moment is offset in angle from the …
A Classical Morphological Analysis Of Galaxies In The Spitzer Survey Of Stellar Structure In Galaxies (S4g), Ronald J. Buta, Trisha Mizusawa
A Classical Morphological Analysis Of Galaxies In The Spitzer Survey Of Stellar Structure In Galaxies (S4g), Ronald J. Buta, Trisha Mizusawa
Aerospace, Physics, and Space Science Faculty Publications
The Spitzer Survey of Stellar Structure in Galaxies (S4G) is the largest available database of deep, homogeneous middle-infrared (mid-IR) images of galaxies of all types. The survey, which includes 2352 nearby galaxies, reveals galaxy morphology only minimally affected by interstellar extinction. This paper presents an atlas and classifications of S4G galaxies in the Comprehensive de Vaucouleurs revised Hubble-Sandage (CVRHS) system. The CVRHS system follows the precepts of classical de Vaucouleurs morphology, modified to include recognition of other features such as inner, outer, and nuclear lenses, nuclear rings, bars, and disks, spheroidal galaxies, X patterns and box/peanut structures, OLR subclass outer …
A Study Of Thunderstorm Microphysical Properties And Lightning Flash Counts Associated With Terrestrial Gamma-Ray Flashes, D. E. Barnes, M. E. Splitt, J. R. Dwyer, S. Lazarus, D. M. Smith, H. K. Rassoul
A Study Of Thunderstorm Microphysical Properties And Lightning Flash Counts Associated With Terrestrial Gamma-Ray Flashes, D. E. Barnes, M. E. Splitt, J. R. Dwyer, S. Lazarus, D. M. Smith, H. K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
The terrestrial gamma ray flash (TGF) is an emission of highly energetic radiation produced by or at least in close association with lightning. Previous investigations attempted to isolate the production mechanisms and production altitude(s) of TGFs as well as macrophysical characteristics, while thunderstorm microphysical characteristics were largely ignored. This investigation into thunderstorms and their hydrometeor and flash characteristics utilize temporal and spatial coincident satellite passes between the Reuven Ramaty High Energy Solar Spectroscopic Imager and the Tropical Rainfall Measuring Mission to determine the bulk (or footprint) microphysical properties of two types of study events, the thunderstorm complexes which are associated …
Spitzer Space Telescope Measurements Of Dust Reverberation Lags In The Seyfert 1 Galaxy Ngc 6418, Billy Vazquez, Dan Batcheldor
Spitzer Space Telescope Measurements Of Dust Reverberation Lags In The Seyfert 1 Galaxy Ngc 6418, Billy Vazquez, Dan Batcheldor
Aerospace, Physics, and Space Science Faculty Publications
We present results from a 15 month campaign of high-cadence (∼3 days) mid-infrared Spitzer and optical (B and V) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 and 4.5 μm flux variations lag behind those of the optical continuum by 37.2 ^+2.4 _-2.2 days and -47.1 ^+3.1 _-3.1 days, respectively. We report a cross-correlation time lag between the 4.5 and 3.6 μm flux of 13.9 ^+0.5 _-0.1 days. The lags indicate that the dust emitting at 3.6 …
An Ancient Extrasolar System With Five Sub-Earth-Size Planets, Tiago L. Campante, Darin Ragozzine
An Ancient Extrasolar System With Five Sub-Earth-Size Planets, Tiago L. Campante, Darin Ragozzine
Aerospace, Physics, and Space Science Faculty Publications
The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of gas-giant hosts, which tend to be metal-rich. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the universe's history when metals were more scarce. We report Kepler spacecraft observations of Kepler-444, a metal-poor Sun-like star from the old population of the Galactic thick disk and the host to a compact system of five transiting planets with sizes between those of Mercury and Venus. We validate this system as a true five-planet …
The Mass Profile And Shape Of Bars In The Spitzer Survey Of Stellar Structure In Galaxies (S⁴G): Search For An Age Indicator For Bars, Taehyun Kim, Trisha Mizusawa
The Mass Profile And Shape Of Bars In The Spitzer Survey Of Stellar Structure In Galaxies (S⁴G): Search For An Age Indicator For Bars, Taehyun Kim, Trisha Mizusawa
Aerospace, Physics, and Space Science Faculty Publications
We have measured the radial light profiles and global shapes of bars using two-dimensional 3.6μm image decompositions for 144 face-on barred galaxies from the Spitzer Survey of Stellar Structure in Galaxies. The bar surface brightness profile is correlated with the stellar mass and bulge-to-total (B/T) ratio of their host galaxies. Bars in massive and bulge-dominated galaxies (B/T > 0.2) show a flat profile, while bars in less massive, disk-dominated galaxies (B/T ∼ 0) show an exponential, disk-like profile with a wider spread in the radial profile than in the bulge-dominated galaxies. The global two-dimensional shapes of bars, however, are rectangular/boxy, independent …
Koi-3158: The Oldest Known System Of Terrestrial-Size Planets, Tiago L. Campante, Darin A. Ragozzine
Koi-3158: The Oldest Known System Of Terrestrial-Size Planets, Tiago L. Campante, Darin A. Ragozzine
Aerospace, Physics, and Space Science Faculty Publications
The first discoveries of exoplanets around Sun-like stars have fueled efforts to find ever smaller worlds evocative of Earth and other terrestrial planets in the Solar System. While gas-giant planets appear to form preferentially around metal-rich stars, small planets (with radii less than four Earth radii) can form under a wide range of metallicities. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the Universe's history when metals were far less abundant. We report Kepler spacecraft observations of KOI-3158, a metal-poor Sun-like star from the old population of the Galactic thick disk, which hosts …