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Physical Sciences and Mathematics Commons™

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

2017

Florida Institute of Technology

Astrophysics and Astronomy

Articles 1 - 8 of 8

Full-Text Articles in Physical Sciences and Mathematics

Testing The Wind-Shock Paradigm For B-Type Star X-Ray Production With Θ Carinae, Trisha F. Doyle Dec 2017

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 …

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The Effects Of Thunderstorm Static And Quasi-Static Electric Fields On The Lower Ionosphere, Mohammad Ahmad Salem May 2017

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 …

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A Test Of The Interstellar Boundary Explorer Ribbon Formation In The Outer Heliosheath, Konstantin V. Gamayunov, Jacob Heerikhuisen, Hamid K. Rassoul Jan 2017

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 …

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Characterizing The Source Properties Of Terrestrial Gamma Ray Flashes, Joseph R. Dwyer, Ningyu Liu, J. Eric Grove, Hamid K. Rassoul, David M. Smith Jan 2017

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 …

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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 Jan 2017

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 …

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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 Jan 2017

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 …

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Studying The Photometric And Spectroscopic Variability Of The Magnetic Hot Supergiant Ζ Orionis Aa, Bram Buysschaert, Alexandre David-Uraz Jan 2017

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 …

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A Multi-Band Study Of The Remarkable Jet In Quasar 4c+19.44, Daniel E. Harris, Eric S. Perlman Jan 2017

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 …

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