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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
Cataclysmic Variables In The Superblink Proper Motion Survey, Julie N. Skinner, John R. Thorstensen, Sébastien Lépine
Cataclysmic Variables In The Superblink Proper Motion Survey, Julie N. Skinner, John R. Thorstensen, Sébastien Lépine
Dartmouth Scholarship
We have discovered a new high proper motion cataclysmic variable (CV) in the SUPERBLINK proper motion survey, which is sensitive to stars with proper motions greater than 40 mas yr−1. This CV was selected for follow-up observations as part of a larger search for CVs selected based on proper motions and their near-UV−V and V−Ks colors. We present spectroscopic observations from the 2.4 m Hiltner Telescope at MDM Observatory. The new CVʼs orbital period is near 96 minutes, its spectrum shows the double-peaked Balmer emission lines characteristic of quiescent dwarf novae, and its V magnitude is …
Electron-Ion Equilibrium And Shock Precursors In The Northeast Limb Of The Cygnus Loop, Amber A. Medina, John C. Raymond, Richard J. Edgar, Nelson Caldwell, Robert A. Fesen, Dan Milisavljevic
Electron-Ion Equilibrium And Shock Precursors In The Northeast Limb Of The Cygnus Loop, Amber A. Medina, John C. Raymond, Richard J. Edgar, Nelson Caldwell, Robert A. Fesen, Dan Milisavljevic
Dartmouth Scholarship
We present an observational study using high-resolution echelle spectroscopy of collisionless shocks in the Cygnus Loop supernova remnant. Measured Hα line profiles constrain pre-shock heating processes, shock speeds, and electron-ion equilibration (Te /Ti ). The shocks produce faint Hα emission line profiles, which are characterized by narrow and broad components. The narrow component is representative of the pre-shock conditions, while the broad component is produced after charge transfer between neutrals entering the shock and protons in the post-shock gas, thus reflecting the properties of the post-shock gas. We observe a diffuse Hα region extending about 25 …
Magnetic Inhibition Of Convection And The Fundamental Properties Of Low-Mass Stars. I. Stars With A Radiative Core, Gregory A. Feiden, Brian Chaboyer
Magnetic Inhibition Of Convection And The Fundamental Properties Of Low-Mass Stars. I. Stars With A Radiative Core, Gregory A. Feiden, Brian Chaboyer
Dartmouth Scholarship
Magnetic fields are hypothesized to inflate the radii of low-mass stars—defined as less massive than 0.8 M ☉—in detached eclipsing binaries (DEBs). We investigate this hypothesis using the recently introduced magnetic Dartmouth stellar evolution code. In particular, we focus on stars thought to have a radiative core and convective outer envelope by studying in detail three individual DEBs: UV Psc, YY Gem, and CU Cnc. Our results suggest that the stabilization of thermal convection by a magnetic field is a plausible explanation for the observed model-radius discrepancies. However, surface magnetic field strengths required by the models are significantly stronger …
Ejecta Knot Flickering, Mass Ablation, And Fragmentation In Cassiopeia A, Robert A. Fesen, Jordan A. Zastrow, Molly C. Hammell, J. Michael Shull, Devin W. Silvia
Ejecta Knot Flickering, Mass Ablation, And Fragmentation In Cassiopeia A, Robert A. Fesen, Jordan A. Zastrow, Molly C. Hammell, J. Michael Shull, Devin W. Silvia
Dartmouth Scholarship
Ejecta knot flickering, ablation tails, and fragmentation are expected signatures associated with the gradual dissolution of high-velocity supernova (SN) ejecta caused by their passage through an inhomogeneous circumstellar medium or interstellar medium (ISM). Such phenomena mark the initial stages of the gradual merger of SN ejecta with and the enrichment of the surrounding ISM. Here we report on an investigation of this process through changes in the optical flux and morphology of several high-velocity ejecta knots located in the outskirts of the young core-collapse SN remnant Cassiopeia A using Hubble Space Telescope images. Examination of WFPC2 F675W and combined ACS …
Polarization Of The Charge-Exchange X-Rays Induced In The Heliosphere, M. Gacesa, H.-R. Müller, R. Côté, V. Kharchenko
Polarization Of The Charge-Exchange X-Rays Induced In The Heliosphere, M. Gacesa, H.-R. Müller, R. Côté, V. Kharchenko
Dartmouth Scholarship
We report results of a theoretical investigation of polarization of the X-ray emissions induced in charge-exchange collisions of fully stripped solar wind ions C6+and O8+ with the heliospheric hydrogen atoms. The polarization of X-ray emissions has been computed for line-of-sight observations within the ecliptic plane as a function of solar wind ion velocities, including a range of velocities corresponding to the slow and fast solar wind, and Coronal Mass Ejections. To determine the variability of polarization of heliospheric X-ray emissions, the polarization has been computed for solar minimum conditions with self-consistent parameters of the solar wind plasma and heliospheric gas …
Optical Discovery Of An Apparent Galactic Supernova Remnant G159.6+7.3, Robert A. Fesen, Dan Milisavljevic
Optical Discovery Of An Apparent Galactic Supernova Remnant G159.6+7.3, Robert A. Fesen, Dan Milisavljevic
Dartmouth Scholarship
Deep Hα images of portions of a faint 3° × 4° Hα shell centered at l = 1596, b = 73 seen on the Virginia Tech Spectral Line Survey images revealed the presence of several thin emission filaments along its eastern limb. Low-dispersion optical spectra of two of these filaments covering the wavelength range of 4500-7500 Å show narrow Hα line emissions with velocities around –170 ± 30 km s–1. Both the morphology and spectra of these filaments are consistent with a Balmer-dominated shock interpretation and we propose that these optical filaments indicate that the large Hα emission …
Dust And The Type Ii-Plateau Supernova 2004et, R. Kotak, W. P. S. Meikle, D. Farrah, C. L. Gerardy, R. J. Foley, S. D. Van Dyk, C. Fransson, P. Lundqvist, J. Sollerman, R. Fesen
Dust And The Type Ii-Plateau Supernova 2004et, R. Kotak, W. P. S. Meikle, D. Farrah, C. L. Gerardy, R. J. Foley, S. D. Van Dyk, C. Fransson, P. Lundqvist, J. Sollerman, R. Fesen
Dartmouth Scholarship
We present mid-infrared (MIR) observations of the Type II-plateau supernova (SN) 2004et, obtained with the Spitzer Space Telescope between 64 and 1406 days past explosion. Late-time optical spectra are also presented. For the period 300-795 days past explosion, we argue that the spectral energy distribution (SED) of SN 2004et comprises (1) a hot component due to emission from optically thick gas, as well as free-bound radiation; (2) a warm component due to newly formed, radioactively heated dust in the ejecta; and (3) a cold component due to an IR echo from the interstellar-medium dust of the host galaxy, NGC 6946. …
A Spitzer Space Telescope Study Of Sn 2002hh: An Infrared Echo From A Type Iip Supernova, W. P. S. Meikle, S. Mattila, C. L. Gerardy, R. Kotak, M. Pozzo, S. D. Van Dyk, D. Farrah, R. A. Fesen
A Spitzer Space Telescope Study Of Sn 2002hh: An Infrared Echo From A Type Iip Supernova, W. P. S. Meikle, S. Mattila, C. L. Gerardy, R. Kotak, M. Pozzo, S. D. Van Dyk, D. Farrah, R. A. Fesen
Dartmouth Scholarship
We present late-time (590-994 days) mid-IR photometry of the normal but highly reddened Type IIP supernova SN 2002hh. Bright, cool, slowly fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star formation region or molecular cloud along the line of sight. We also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly condensed dust and/or an ejecta/CSM impact, …