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Articles 31 - 60 of 317
Full-Text Articles in Astrophysics and Astronomy
X-Rays From Magnetic B-Type Stars, Corinne Fletcher
X-Rays From Magnetic B-Type Stars, Corinne Fletcher
Theses and Dissertations
Recent surveys have found that ∼10% of massive stars host strong, mostly dipolar magnetic fields with strengths on the order of a kilogauss. The prominent idea describing the interaction between the stellar winds and the magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the ionized wind material is forced to move along the closed magnetic field loops and collides at the magnetic equator, creating a shock (Δv ∼ 500−800 km s−1). As the shocked material cools radiatively, it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and probing the wind material …
Orbital Characteristics Of The Subdwarf-B And F V Star Binary Ec 20117-4014 (=V4640 Sgr), Tomomi Otani, T. D. Oswalt, A. E. Lynas-Gray, D. Kilkenny, C. Koen, M. Amaral, R. Jordan
Orbital Characteristics Of The Subdwarf-B And F V Star Binary Ec 20117-4014 (=V4640 Sgr), Tomomi Otani, T. D. Oswalt, A. E. Lynas-Gray, D. Kilkenny, C. Koen, M. Amaral, R. Jordan
Aerospace, Physics, and Space Science Faculty Publications
Among the competing evolution theories for subdwarf-B (sdB) stars is the binary evolution scenario. EC 20117- 4014 (=V4640 Sgr) is a spectroscopic binary system consisting of a pulsating sdB star and a late F main-sequence companion; however, the period and the orbit semimajor axes have not been precisely determined. This paper presents orbital characteristics of the EC 20117-4014 binary system using 20 years of photometric data. Periodic observed minus calculated (O–C) variations were detected in the two highest-amplitude pulsations identified in the EC 20117-4014 power spectrum, indicating the binary system’s precise orbital period (P = 792.3 days) and the light-travel-time …
Effects Of Coronal Magnetic Field Structures On The Transport Of Solar Energetic Particles, Lulu Zhao, Ming Zhang
Effects Of Coronal Magnetic Field Structures On The Transport Of Solar Energetic Particles, Lulu Zhao, Ming Zhang
Aerospace, Physics, and Space Science Faculty Publications
This Letter presents a model calculation of solar energetic particle (SEP) transport to test the sensitivity of the distribution of escaped SEPs in interplanetary space and dependence upon the details of the magnetic field structure in the corona. It is applied to a circumsolar event on 2011 November 3, in which SEPs are observed promptly after the solar event eruption by three spacecraft (the twin Solar TErrestrial RElations Observatories (STEREO-A and STEREO-B) and ACE) separated by more than 100° in longitude from each other. The corona magnetic field reconstructed from photosphseric field measurements using the PFSS method changes substantially before …
Automated Software For The Detection Of Bolide Events, Elena Botella
Automated Software For The Detection Of Bolide Events, Elena Botella
Theses and Dissertations
The proper detection and analysis of bolide events ensures that we will once day be prepared for a big, catastrophic impact by a meteor. The data obtained from the analysis of these detected smaller events will provide important information about the meteor’s journey through our atmosphere and its orbit before it crossed the Earth’s path. SkySentinel is one of the All-Sky networks in charge of looking at the skies every night and detecting these objects as they fall. At the moment, SkySentinel’s detection process relies heavily on manpower to check whether their cameras picked up actual bolide events or false …
Illuminating Low Surface Brightness Galaxies With The Hyper Suprime-Cam Survey, Johnny P. Greco, Jenny E. Greene, Michael A. Strauss, Lauren A. Macarthur, Xzavier Flowers, Andy D. Goulding, Song Huang, Ji Hoon Kim, Yutaka Komiyama, Alexie Leauthaud, Lukas Leisman, Robert H. Lupton, Cristobal Sifon, Shiang-Yu Wang
Illuminating Low Surface Brightness Galaxies With The Hyper Suprime-Cam Survey, Johnny P. Greco, Jenny E. Greene, Michael A. Strauss, Lauren A. Macarthur, Xzavier Flowers, Andy D. Goulding, Song Huang, Ji Hoon Kim, Yutaka Komiyama, Alexie Leauthaud, Lukas Leisman, Robert H. Lupton, Cristobal Sifon, Shiang-Yu Wang
Aerospace, Physics, and Space Science Faculty Publications
We present a catalog of extended low surface brightness galaxies (LSBGs) identified in the Wide layer of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Using the first ∼200 deg2 of the survey, we have uncovered 781 LSBGs, spanning red (g − I >/0.64) and blue (g − i < 0.64) colors and a wide range of morphologies. Since we focus on extended galaxies (reff = 2 5–14″), our sample is likely dominated by low- redshift objects. We define LSBGs to have mean surface brightnesses m¯ eff (g) > 24.3 mag arcsec−2, which allows nucleated galaxies into our sample. As a result, the central surface brightness distribution spans a wide range of μ0(g) = 18–27.4 mag arcsec−2, with 50% and 95% of galaxies fainter than 24.3 and 22 mag arcsec−2, respectively. Furthermore, the surface brightness distribution is a strong function of …
An X-Ray Imaging Survey Of Quasar Jets: The Complete Survey, H. L. Marshall, J. M. Gelbord, D. M. Worrall, M. Birkinshaw, D. A. Schwartz, D. L. Jauncey, G. Griffiths, D. W. Murphy, J. E. J. Lovell, E. S. Perlman, L. Godfrey
An X-Ray Imaging Survey Of Quasar Jets: The Complete Survey, H. L. Marshall, J. M. Gelbord, D. M. Worrall, M. Birkinshaw, D. A. Schwartz, D. L. Jauncey, G. Griffiths, D. W. Murphy, J. E. J. Lovell, E. S. Perlman, L. Godfrey
Aerospace, Physics, and Space Science Faculty Publications
We present Chandra X-ray imaging of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like structure. X-rays are detected from 59% of 56 jets. No counter-jets were detected. The core spectra are fitted by power-law spectra with a photon index Γx, whose distribution is consistent with a normal distribution, with a mean of 1.61+0.04 and dispersion of 0.15+0.04. We show that the distribution of α , the spectral index between the X-ray −0.05 −0.03 rx and radio band jet fluxes, fits a Gaussian with a mean of 0.974 ± 0.012 and dispersion of 0.077 ± 0.008. We test the …
Whole Earth Telescope Discovery Of A Strongly Distorted Quadrupole Pulsation In The Largest Amplitude Rapidly Oscillating Ap Star, Daniel L. Holdsworth, Donald W. Kurtz, Hideyuki Saio, Judith L. Provençal, Bruno Letarte, Ramotholo R. Sefako, Véronique Petit, Barry Smalley, H. Thomsen, C. L. Fletcher
Whole Earth Telescope Discovery Of A Strongly Distorted Quadrupole Pulsation In The Largest Amplitude Rapidly Oscillating Ap Star, Daniel L. Holdsworth, Donald W. Kurtz, Hideyuki Saio, Judith L. Provençal, Bruno Letarte, Ramotholo R. Sefako, Véronique Petit, Barry Smalley, H. Thomsen, C. L. Fletcher
Aerospace, Physics, and Space Science Faculty Publications
We present a new analysis of the rapidly oscillating Ap (roAp) star, 2MASS J19400781 - 4420093 (J1940; V = 13.1). The star was discovered using SuperWASP broad-band photometry to have a frequency of 176.39 d-1 (2041.55 μHz; P = 8.2min; Holdsworth et al. 2014a) and is shown here to have a peak-to-peak amplitude of 34 mmag. J1940 has been observed during three seasons at the South African Astronomical Observatory, and has been the target of a Whole Earth Telescope campaign. The observations reveal that J1940 pulsates in a distorted quadrupole mode with unusual pulsational phase variations. A higher signal-to-noise ratio …
Testing The Wind-Shock Paradigm For B-Type Star X-Ray Production With Θ Carinae, Trisha F. Doyle
Testing The Wind-Shock Paradigm For B-Type Star X-Ray Production With Θ Carinae, Trisha F. Doyle
Theses and Dissertations
We present Chandra X-ray grating spectroscopy of the B0.2V star, θ Carinae. θ Car is in a critical transition region between the latest O-type and earliest B-type stars, where some of these stars are observed to have UV-determined mass-loss rates much lower than theoretically expected. In general, X-ray emission in this low-luminosity regime should be less prominent than in O-star winds, but observations have shown a higher than expected production of X-ray emission from the winds of these stars (e.g., Cohen et al. 2008; Huenemoerder et al. 2012). A hot wind could explain weak UV wind signatures, but this severely …
The Complex, Dusty Narrow-Line Region Of Ngc 4388: Gas–Jet Interactions, Outflows And Extinction Revealed By Near-Ir Spectroscopy, A. Rodriguez-Ardila,, R. E. Mason, L. Martins, C. Ramos Almeida, R. A. Riffel, R. Riffel, P. Lira, O. Gonzalez Martin, N. Z. Dametto, H. Flohic, L. C. Ho, D. Ruschel-Dutra, K. Thanjavur, L. Colina, R. M. Mcdermid, E. Perlman, C. Winge
The Complex, Dusty Narrow-Line Region Of Ngc 4388: Gas–Jet Interactions, Outflows And Extinction Revealed By Near-Ir Spectroscopy, A. Rodriguez-Ardila,, R. E. Mason, L. Martins, C. Ramos Almeida, R. A. Riffel, R. Riffel, P. Lira, O. Gonzalez Martin, N. Z. Dametto, H. Flohic, L. C. Ho, D. Ruschel-Dutra, K. Thanjavur, L. Colina, R. M. Mcdermid, E. Perlman, C. Winge
Aerospace, Physics, and Space Science Faculty Publications
We present Gemini/GNIRS (Gemini Near-Infrared Spectrograph) spectroscopy of the Seyfert 2 galaxy NGC 4388, with simultaneous coverage from 0.85 to 2.5 µm. Several spatially extended emission lines are detected for the first time, both in the obscured and unobscured portion of the optical narrow-line region (NLR), allowing us to assess the combined effects of the central continuum source, outflowing gas and shocks generated by the radio jet on the central 280 pc gas. The H I and [Fe II] lines allow us to map the extinction affecting the NLR. We found that the nuclear region is heavily obscured, with E(B …
Precipitation And Release Of Solar Energetic Particles From The Solar Coronal Magnetic Field, Ming Zhang, Lulu Zhao
Precipitation And Release Of Solar Energetic Particles From The Solar Coronal Magnetic Field, Ming Zhang, Lulu Zhao
Aerospace, Physics, and Space Science Faculty Publications
Most solar energetic particles (SEPs) are produced in the corona. They propagate through complex coronal magnetic fields subject to scattering and diffusion across the averaged field lines by turbulence. We examine the behaviors of particle transport using a stochastic 3D focused transport simulation in a potential field source surface model of coronal magnetic field. The model is applied to an SEP event on 2010 February 7. We study three scenarios of particle injection at (i) the compact solar flare site, (ii) the coronal mass ejection (CME) shock, and (iii) the EUV wave near the surface. The majority of particles injected …
The Effects Of Thunderstorm Static And Quasi-Static Electric Fields On The Lower Ionosphere, Mohammad Ahmad Salem
The Effects Of Thunderstorm Static And Quasi-Static Electric Fields On The Lower Ionosphere, Mohammad Ahmad Salem
Theses and Dissertations
Thunderstorms and their lightning discharges are of great interest to many areas of geophysics and atmospheric electricity. A thunderstorm is an electric generator; it can produce both electrostatic and quasi-electrostatic fields in the overhead atmospheric D region. The D region is the lower part of the ionosphere that extends from about 40-90 km altitude where the electrons and ions are sufficient enough to affect the propagation of radio waves. In contrast to the electrostatic field, the quasi-electrostatic fields can be much stronger in magnitude, but shorter in duration, and can trigger halos. A halo is one type of the transient …
The Effects Of Interplanetary Transport In The Event-Intergrated Solar Energetic Particle Spectra, Lulu Zhao, Ming Zhang, Hamid K. Rassoul
The Effects Of Interplanetary Transport In The Event-Intergrated Solar Energetic Particle Spectra, Lulu Zhao, Ming Zhang, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
Previous investigations on the energy spectra of solar energetic particle (SEP) events revealed that the energy spectra observed at 1 au often show double power laws with break energies from one to tens of MeV/nuc. In order to determine whether the double power-law features result from the SEP source or the interplanetary transport process from the Sun to 1 au, we separately analyze the SEP spectra in the decay phase, during which the transport effect is minimum. In this paper, we reported three events observed by the Interplanetary Monitory Platform 8 spacecraft, which occurred on 1977 September 19, November 22, …
A Multi-Band Study Of The Remarkable Jet In Quasar 4c+19.44, Daniel E. Harris, Eric S. Perlman
A Multi-Band Study Of The Remarkable Jet In Quasar 4c+19.44, Daniel E. Harris, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
We present arcsecond-resolution data in the radio, IR, optical, and X-ray for 4C+19.44 (=PKS 1354+195), the longest and straightest quasar jet with deep X-ray observations. We report results from radio images with half to one arcsecond angular resolution at three frequencies, plus Hubble Space Telescope and Spitzer data. The Chandra data allow us to measure the X-ray spectral index in 10 distinct regions along the 18″ jet and compare with the radio index. The radio and X-ray spectral indices of the jet regions are consistent with a value of throughout the jet, to within uncertainties. The X-ray jet structure to …
Possible Pair-Instability Supernovae At Solar Motallicity From Magnetic Stellar Progenitors, Cyril Georgy, Georges Meynet, Sylvia Ekström, Gregg A. Wade, Véronique Petit, Zsolt Keszthelyi, Raphael Hirschi
Possible Pair-Instability Supernovae At Solar Motallicity From Magnetic Stellar Progenitors, Cyril Georgy, Georges Meynet, Sylvia Ekström, Gregg A. Wade, Véronique Petit, Zsolt Keszthelyi, Raphael Hirschi
Aerospace, Physics, and Space Science Faculty Publications
Near-solar metallicity (and low-redshift) pair-instability supernova (PISN) candidates challenge stellar evolution models. Indeed, at such a metallicity, even an initially very massive star generally loses so much mass by stellar winds that it will avoid the electron-positron pair-creation instability. We use recent results showing that a magnetic field at the surface of a massive star can significantly reduce its effective mass-loss rate to compute magnetic models of very massive stars (VMSs) at solar metallicity and explore the possibility that such stars end as PISNe. We implement the quenching of the mass loss produced by a surface dipolar magnetic field into …
Studying The Photometric And Spectroscopic Variability Of The Magnetic Hot Supergiant Ζ Orionis Aa, Bram Buysschaert, Alexandre David-Uraz
Studying The Photometric And Spectroscopic Variability Of The Magnetic Hot Supergiant Ζ Orionis Aa, Bram Buysschaert, Alexandre David-Uraz
Aerospace, Physics, and Space Science Faculty Publications
Massive stars play a significant role in the chemical and dynamical evolution of galaxies. However, much of their variability, particularly during their evolved supergiant stage, is poorly understood. To understand the variability of evolved massive stars in more detail, we present a study of the O9.2Ib supergiant ζ Ori Aa, the only currently confirmed supergiant to host a magnetic field. We have obtained two-color space-based BRIght Target Explorer photometry (BRITE) for ζ Ori Aa during two observing campaigns, as well as simultaneous ground-based, high-resolution optical CHIRON spectroscopy. We perform a detailed frequency analysis to detect and characterize the star's periodic …
The Puzzling Case Of The Radio-Loud Qso 3c 186: A Gravitational Wave Recoiling Black Hole In A Young Radio Source?, Marco Chiaberge, Eric S. Perlman
The Puzzling Case Of The Radio-Loud Qso 3c 186: A Gravitational Wave Recoiling Black Hole In A Young Radio Source?, Marco Chiaberge, Eric S. Perlman
Aerospace, Physics, and Space Science Faculty Publications
Context. Radio-loud active galactic nuclei with powerful relativistic jets are thought to be associated with rapidly spinning black holes (BHs). BH spin-up may result from a number of processes, including accretion of matter onto the BH itself, and catastrophic events such as BH-BH mergers. Aims. We study the intriguing properties of the powerful (Lbol ∼ 1047 erg s-1) radio-loud quasar 3C 186. This object shows peculiar features both in the images and in the spectra. Methods. We utilize near-IR Hubble Space Telescope (HST) images to study the properties of the host galaxy, and HST UV and Sloan Digital Sky Survey …
Characterizing The Source Properties Of Terrestrial Gamma Ray Flashes, Joseph R. Dwyer, Ningyu Liu, J. Eric Grove, Hamid K. Rassoul, David M. Smith
Characterizing The Source Properties Of Terrestrial Gamma Ray Flashes, Joseph R. Dwyer, Ningyu Liu, J. Eric Grove, Hamid K. Rassoul, David M. Smith
Aerospace, Physics, and Space Science Faculty Publications
Monte Carlo simulations are used to determine source properties of terrestrial gamma ray flashes (TGFs) as a function of atmospheric column depth and beaming geometry. The total mass per unit area traversed by all the runaway electrons (i.e., the total grammage) during a TGF, Ξ, is introduced, defined to be the total distance traveled by all the runaway electrons along the electric field lines multiplied by the local air mass density along their paths. It is shown that key properties of TGFs may be directly calculated from Ξ and its time derivative, including the gamma ray emission rate, the current …
A Test Of The Interstellar Boundary Explorer Ribbon Formation In The Outer Heliosheath, Konstantin V. Gamayunov, Jacob Heerikhuisen, Hamid K. Rassoul
A Test Of The Interstellar Boundary Explorer Ribbon Formation In The Outer Heliosheath, Konstantin V. Gamayunov, Jacob Heerikhuisen, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
NASA's Interstellar Boundary EXplorer (IBEX) mission is imaging energetic neutral atoms (ENAs) propagating to Earth from the outer heliosphere and local interstellar medium (LISM). A dominant feature in all ENA maps is a ribbon of enhanced fluxes that was not predicted before IBEX. While more than a dozen models of the ribbon formation have been proposed, consensus has gathered around the so-called secondary ENA model. Two classes of secondary ENA models have been proposed; the first class assumes weak scattering of the energetic pickup protons in the LISM, and the second class assumes strong but spatially localized scattering. Here we …
Magnetic Massive Stars As Progenitors Of ‘Heavy’ Stellar-Mass Black Holes, V. Petit, Z. Keszthelyi, R. Macinnis, D. H. Cohen, R. H. D. Townsend, G. A. Wade, S. L. Thomas, S. P. Owocki, J. Puls, A. Ud-Doula
Magnetic Massive Stars As Progenitors Of ‘Heavy’ Stellar-Mass Black Holes, V. Petit, Z. Keszthelyi, R. Macinnis, D. H. Cohen, R. H. D. Townsend, G. A. Wade, S. L. Thomas, S. P. Owocki, J. Puls, A. Ud-Doula
Aerospace, Physics, and Space Science Faculty Publications
The groundbreaking detection of gravitational waves produced by the inspiralling and coales- cence of the black hole (BH) binary GW150914 confirms the existence of ‘heavy’ stellar-mass BHs with masses >25 M . Initial characterization of the system by Abbott et al. supposes that the formation of BHs with such large masses from the evolution of single massive stars is only feasible if the wind mass-loss rates of the progenitors were greatly reduced relative to the mass-loss rates of massive stars in the Galaxy, concluding that heavy BHs must form in low-metallicity (Z ,:S 0.25 0.5 Z ) environments. However, strong …
Hd 164492c: A Rapidly Rotating, Hα-Bright, Magnetic Early B Star Associated With A 12.5 D Spectroscopic Binary, G. A. Wade, M. Shultz, J. Sikora, M.-E. Bernier, Th. Rivinius, E. Alecian, V. Petit, J. H. Grunhut, Binamics Collaboration
Hd 164492c: A Rapidly Rotating, Hα-Bright, Magnetic Early B Star Associated With A 12.5 D Spectroscopic Binary, G. A. Wade, M. Shultz, J. Sikora, M.-E. Bernier, Th. Rivinius, E. Alecian, V. Petit, J. H. Grunhut, Binamics Collaboration
Aerospace, Physics, and Space Science Faculty Publications
We employ high-resolution spectroscopy and spectropolarimetry to derive the physical proper- ties and magnetic characteristics of the multiple system HD 164492C, located in the young open cluster M20. The spectrum reveals evidence of three components: a broad-lined early B star (HD 164492C1), a narrow-lined early B star (HD 164492C2) and a late B star (HD 164492C3). Components C2 and C3 exhibit significant (>100 km s−1) bulk radial velocity variations with a period of 12.5351(7) d that we attribute to eccentric binary motion around a common centre- of-mass. Component C1 exhibits no detectable radial velocity variations. Using constraints derived from …
A Dynamical Analysis Of The Kepler-80 System Of Five Transiting Planets, Mariah G. Macdonald, Darin A. Ragozzine
A Dynamical Analysis Of The Kepler-80 System Of Five Transiting Planets, Mariah G. Macdonald, Darin A. Ragozzine
Aerospace, Physics, and Space Science Faculty Publications
Kepler has discovered hundreds of systems with multiple transiting exoplanets which hold tremendous potential both individually and collectively for understanding the formation and evolution of planetary systems. Many of these systems consist of multiple small planets with periods less than ~50 days known as Systems with Tightly spaced Inner Planets, or STIPs. One especially intriguing STIP, Kepler-80 (KOI-500), contains five transiting planets: f, d, e, b, and c with periods of 1.0, 3.1, 4.6, 7.1, and 9.5 days, respectively. We provide measurements of transit times and a transit timing variation (TTV) dynamical analysis. We find that TTVs cannot reliably detect …
Infrared Polarimetry Of Mrk 231: Scattering Off Hot Dust Grains In The Central Core, E. Lopez-Rodriguez, C. Packham, T. J. Jones, R. Siebenmorgen, P. F. Roche, N. A. Levenson, A. Alonso-Herrero, E. Perlman, K. Ichikawa, C. Ramos Almeida, O. Gonzalez-Martin, R. Nikutta, M. Martinez-Paredez, D. Shenoy, M. S. Gordon, C. M. Telesco
Infrared Polarimetry Of Mrk 231: Scattering Off Hot Dust Grains In The Central Core, E. Lopez-Rodriguez, C. Packham, T. J. Jones, R. Siebenmorgen, P. F. Roche, N. A. Levenson, A. Alonso-Herrero, E. Perlman, K. Ichikawa, C. Ramos Almeida, O. Gonzalez-Martin, R. Nikutta, M. Martinez-Paredez, D. Shenoy, M. S. Gordon, C. M. Telesco
Aerospace, Physics, and Space Science Faculty Publications
We present high-angular (0.17–0.35 arcsec) resolution imaging polarimetric observations of Mrk 231 in the 3.1 μm filter using MMT-Pol on the 6.5-m MMT, and in the 8.7, 10.3, and 11.6 μm filters using CanariCam on the 10.4-m Gran Telescopio CANARIAS. In combination with already published observations, we compile the 1–12 μm total and polarized nuclear spectral energy distribution (SED). The total flux SED in the central 400 pc is explained as the combination of (1) a hot (731 4 K) dusty structure, directly irradiated by the central engine, which is at 1.6 0.1 pc away and attributed to be in …
A Deep Search For Additional Satellites Around The Dwarf Planet Haumea, Luke D. Burkhart, Darin Ragozzine, Michael E. Brown
A Deep Search For Additional Satellites Around The Dwarf Planet Haumea, Luke D. Burkhart, Darin Ragozzine, Michael E. Brown
Aerospace, Physics, and Space Science Faculty Publications
Haumea is a dwarf planet with two known satellites, an unusually high spin rate, and a large collisional family, making it one of the most interesting objects in the outer solar system. A fully self-consistent formation scenario responsible for the satellite and family formation is still elusive, but some processes predict the initial formation of many small moons, similar to the small moons recently discovered around Pluto. Deep searches for regular satellites around Kuiper belt objects are difficult due to observational limitations, but Haumea is one of the few for which sufficient data exist. We analyze Hubble Space Telescope (HST) …
Dynamic Flaring Non-Potential Fields On Quiet Sun Networks Scales, David L. Chesney, Hakeem M. Oluseyi, Norton B. Orange
Dynamic Flaring Non-Potential Fields On Quiet Sun Networks Scales, David L. Chesney, Hakeem M. Oluseyi, Norton B. Orange
Aerospace, Physics, and Space Science Faculty Publications
We report on the identification of dynamic flaring non-potential structures on quiet Sun (QS) supergranular network scales. Data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory allow for the high spatial and temporal resolution of this diverse class of compact structures. The rapidly evolving nonpotential events presented here, with lifetimes <10 minutes, are on the order of 10″ in length. Thus, they contrast significantly with well-known active region (AR) non-potential structures such as high-temperature X-ray and EUV sigmoids (>100″) and micro-sigmoids (>10″) with lifetimes on the order of hours to days. The photospheric magnetic field environment derived from the Helioseismic and Magnetic Imager shows a lack of evidence for these flaring non-potential fields being associated with significant concentrations of bipolar magnetic elements. Of much …
Geological Conditions Required For The Fluvial Erosion Of Titan’S Impact Craters, Rebeca M. Kinser
Geological Conditions Required For The Fluvial Erosion Of Titan’S Impact Craters, Rebeca M. Kinser
Theses and Dissertations
In comparison to other icy satellites, Titan has a small number of impact craters on its surface. Its dense atmosphere screens smaller impactors from the surface, but this alone does not account for the lack of impact craters, especially at large diameters. This suggests that Titan has a relatively young surface and/or erosional processes have effectively removed craters from its surface. For example, fluvial erosion could degrade craters such that they would be unrecognizable from an orbiting spacecraft such as Cassini. The amount of erosion, however, will depend on a number of factors including the geological and meteorological conditions of …
Efficient Geometric Probabilities Of Multi-Transiting Exoplanetary Systems From Corbits, Joshua Brakensiek, Darin Ragozzine
Efficient Geometric Probabilities Of Multi-Transiting Exoplanetary Systems From Corbits, Joshua Brakensiek, Darin Ragozzine
Aerospace, Physics, and Space Science Faculty Publications
NASA’s Kepler Space Telescope has successfully discovered thousands of exoplanet candidates using the transit method, including hundreds of stars with multiple transiting planets. In order to estimate the frequency of these valuable systems, it is essential to account for the unique geometric probabilities of detecting multiple transiting extrasolar planets around the same parent star. In order to improve on previous studies that used numerical methods, we have constructed an efficient, semi-analytical algorithm called the Computed Occurrence of Revolving Bodies for the Investigation of Transiting Systems (CORBITS), which, given a collection of conjectured exoplanets orbiting a star, computes the probability that …
Double Power Laws In The Event-Integrated Solar Energetic Particle Spectrum, Lulu Zhao, Ming Zhang, Hamid K. Rassoul
Double Power Laws In The Event-Integrated Solar Energetic Particle Spectrum, Lulu Zhao, Ming Zhang, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
A double power law or a power law with exponential rollover at a few to tens of MeV nucleon−1 of the eventintegrated differential spectra has been reported in many solar energetic particle (SEP) events. The rollover energies per nucleon of different elements correlate with a particleʼs charge-to-mass ratio (Q/A). The probable causes are suggested as residing in shock finite lifetimes, shock finite sizes, shock geometry, and an adiabatic cooling effect. In this work, we conduct a numerical simulation to investigate a particleʼs transport process in the inner heliosphere. We solve the focused transport equation using a time-backward Markov stochastic approach. …
Reverberation Mapping Of The Dusty Torus In Active Galactic Nuclei, Erich Franz Geisert
Reverberation Mapping Of The Dusty Torus In Active Galactic Nuclei, Erich Franz Geisert
Theses and Dissertations
The Dusty Torus is a structure that is believed to exist in Active Galactic Nuclei. The Torus is physically too small to be spatially resolved, so Reverberation Mapping can be performed in order to replace spatial resolution with temporal resolution, yielding observations that can unravel the mystery of the Dusty Torus. One of the unknowns about the Torus is how the dust is distributed. The two competing theories are that either the dust resides in discrete clouds or that there is a solid wall of dust. This thesis presents the results of a year long observation program, starting in August …
Kepler Eclipsing Binary Stars. Vii. The Catalog Of Eclipsing Binaries Found In The Entire Kepler Data Set, Brian Kirk, Darin Ragozzine
Kepler Eclipsing Binary Stars. Vii. The Catalog Of Eclipsing Binaries Found In The Entire Kepler Data Set, Brian Kirk, Darin Ragozzine
Aerospace, Physics, and Space Science Faculty Publications
The primary Kepler Mission provided nearly continuous monitoring of ∼200,000 objects with unprecedented photometric precision. We present the final catalog of eclipsing binary systems within the 105 deg2 Kepler field of view. This release incorporates the full extent of the data from the primary mission (Q0-Q17 Data Release). As a result, new systems have been added, additional false positives have been removed, ephemerides and principal parameters have been recomputed, classifications have been revised to rely on analytical models, and eclipse timing variations have been computed for each system. We identify several classes of systems including those that exhibit tertiary eclipse …
A Normal Supermassive Black Hole In Ngc 1277, Alister W. Graham, Mark Durré, Giulia A.D. Savorgnan, Anne M. Medling, Dan Batcheldor, Nicholas Scott, Beverly Watson, Alessandro Marconi
A Normal Supermassive Black Hole In Ngc 1277, Alister W. Graham, Mark Durré, Giulia A.D. Savorgnan, Anne M. Medling, Dan Batcheldor, Nicholas Scott, Beverly Watson, Alessandro Marconi
Aerospace, Physics, and Space Science Faculty Publications
The identification of galaxies with “overly massive” black holes requires two measurements: a black hole mass (Mbh) and a host spheroid mass (Msph,*). Here we provide our measurements for NGC 1277. Our structural decomposition reveals that NGC 1277 is dominated by a “classical” spheroid with a Sérsic index n = 5.3, a half-light radius Rₑmajor: You have a new taskSpace: You have a new task,major = 2.1 kpc, and a stellar mass of 2.7 10^11 11 M⊙ (using M*/ LV = 11.65, Martín-Navarro et al.). This mass is an order of magnitude greater than originally reported. Using the latest Mbh–n, …