Physical Sciences and Mathematics Commons^™

Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch

Professor David Lynch

Reflectance difference (RD) spectra for the a–b plane of the single crystals of Gd5Si2Ge2and b–c planes of Gd5Si2Ge2 and Tb5Si2.2Ge1.8 were obtained in the photon energy range of 1.5–5.5 eV. Several peaks were observed for these crystals in the measured spectrum range. Similar features were observed in the RD spectra for the b–c planes ofGd5Si2Ge2 and Tb5Si2.2Ge1.8, while different features were observed for the a–b plane and b–c plane of Gd5Si2Ge2. The RD spectra for the crystals arise not only from the surface anisotropy but also from the bulk anisotropy due to the monoclinic structure of the bulk crystal.

The Xmm-Newton Epic X-Ray Light Curve Analysis Of Wr 6., Richard Ignace, K. Gayley, W.-R. Hamann, D. Huenemoerder, L. Oskinova, A. Pollock, M. Mcfall

ETSU Faculty Works

We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the results of spectral analysis, this follow-up highlights the X-ray variability clearly detected in all four pointings. However, phased light curves fail to confirm obvious cyclic behavior on the well-established 3.766 d period widely found at longer wavelengths. The data are of such quality that we were able to conduct a search for "event clustering" in the arrival times of X-ray photons. However, we fail to detect any such clustering. One possibility is that X-rays …

Faraday Rotation Distributions From Stellar Magnetism In Wind-Blown Bubbles., Richard Ignace, N. Pingel

ETSU Faculty Works

Faraday rotation is a valuable tool for detecting magnetic fields. Here, the technique is considered in relation to wind-blown bubbles. In the context of spherical winds with azimuthal or split monopole stellar magnetic field geometries, we derive maps of the distribution of position angle (P.A.) rotation of linearly polarized radiation across projected bubbles. We show that the morphology of maps for split monopole fields are distinct from those produced by the toroidal field topology; however, the toroidal case is the one most likely to be detectable because of its slower decline in field strength with distance from the star. We …

A Report On The X-Ray Properties Of The Τ Sco Class Of Stars., Richard Ignace, L. Oskinova, D. Massa

ETSU Faculty Works

An increasing number of OB stars have been shown to possess magnetic fields. Although the sample remains small, it is surprising that the magnetic and X-ray properties of these stars appear to be far less correlated than expected. This contradicts model predictions, which generally indicate that the X-rays from magnetic stars are harder and more luminous than their non-magnetic counterparts. Instead, the X-ray properties of magnetic OB stars are quite diverse. τ Sco is one example where the expectations are better met. This bright main-sequence, early B star has been studied extensively in a variety of wavebands. It has a …

Investigating The Spectroscopic, Magnetic And Circumstellar Variability Of The O9 Subgiant Star Hd 57682., J. Grunhut, G. Wade, J. Sundqvist, A. Ud-Doula, C. Neiner, Richard Ignace, W. Marcolino, Th. Rivinius, A. Fullerton, L. Kaper, B. Mauclaire, C. Buil, T. Garrel, J. Ribeiro, S. Ubaud

ETSU Faculty Works

The O9IV star HD 57682, discovered to be magnetic within the context of the Magnetism in Massive Stars (MiMeS) survey in 2009, is one of only eight convincingly detected magnetic O-type stars. Among this select group, it stands out due to its sharp-lined photospheric spectrum. Since its discovery, the MiMeS Collaboration has continued to obtain spectroscopic and magnetic observations in order to refine our knowledge of its magnetic field strength and geometry, rotational period and spectral properties and variability. In this paper we report new Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) spectropolarimetric observations of HD 57682, which …

Discovery Of A Magnetic Field In The Rapidly-Rotating O-Type Secondary Of The Colliding-Wind Binary Hd 47129 (Plaskett’S Star)., J. Grunhut, G. Wade, M. Leutenegger, V. Petit, G. Rauw, C. Neiner, F. Martins, D. Cohen, M. Gagné, Richard Ignace, S. Mathis, S. De Mink, A. Moffat, S. Owocki, M. Shultz, J. Sundqvist, Mimes Collaboration

ETSU Faculty Works

We report the detection of a strong, organized magnetic field in the secondary component of the massive O8III/I+O7.5V/III double-lined spectroscopic binary system HD 47129 (Plaskett's star) in the context of the Magnetism in Massive Stars survey. Eight independent Stokes V observations were acquired using the Echelle SpectroPolarimetric Device for the Observations of Stars (ESPaDOnS) spectropolarimeter at the Canada–France–Hawaii Telescope and the Narval spectropolarimeter at the Télescope Bernard Lyot. Using least-squares deconvolution we obtain definite detections of signal in Stokes V in three observations. No significant signal is detected in the diagnostic null (N) spectra. The Zeeman signatures are broad and …

Celestial Paleontology: The Legacy Of Dying Stars, Alexa Hodgson Hart

Electronic Theses and Dissertations

In their death throes, stars dole out their atmospheric material to the interstellar medium in dramatic stellar winds and spectacular explosions. The details of this profound metamorphosis, from star to remnant, play a key role in the next generation of star formation as well as the energetic and chemical evolution of galaxies and the universe as a whole. Dying stars are thought to be the source of all of the nuclei heavier than iron in the universe, as well as more complex molecules, such as carbon chains, which form the backbone of life as we know it.

High mass Wolf-Rayet …

The X-Ray And Spectropolarimetric View Of Mass Loss And Transfer In Massive Binary Stars, Jamie Renae Lomax

Electronic Theses and Dissertations

The majority of massive stars are members of binary systems. In order to have a better understanding of their evolutionary pathways, the mass and angular momentum loss from massive binaries needs to be well understood. Self consistent explanations for their behavior need to be valid across many wavelength regimes in order to illuminate key phases of mass loss to completely determine how it affects their evolution. In this dissertation I present the results of X-ray and specropolarimetric studies on one Roche-lobe overflow binary (β Lyr) and two colliding wind binaries (V444 Cyg and WR 140).

In β Lyr a …

Oxide Semiconductors For Organic Opto-Electronic Devices, Ajaya Kanta Sigdel

Electronic Theses and Dissertations

Development of transparent oxide semiconductors (TOS) from Earth-abundant materials is of great interest for cost-effective thin film device applications, such as solar cells, light emitting diodes (LEDs), touch-sensitive displays, electronic paper, and transparent thin film transistors. The need of inexpensive or high performance electrode might be even greater for organic photovoltaic (OPV), with the goal to harvest renewable energy with inexpensive, lightweight, and cost competitive materials. The natural abundance of zinc and the wide bandgap (~3.3 eV) of its oxide make it an ideal candidate.

In this dissertation, I have introduced various concepts on the modulations of various surface, interface …