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Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
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 …
Interaction Between The Broad-Lined Type Ic Supernova 2012ap And Carriers Of Diffuse Interstellar Bands, Dan Milisavljevic, Raffaella Margutti, Kyle N. Crabtree, Jonathan B. Foster, Alicia M. Soderberg, Robert A. Fesen, Jerod T. Parrent
Interaction Between The Broad-Lined Type Ic Supernova 2012ap And Carriers Of Diffuse Interstellar Bands, Dan Milisavljevic, Raffaella Margutti, Kyle N. Crabtree, Jonathan B. Foster, Alicia M. Soderberg, Robert A. Fesen, Jerod T. Parrent
Dartmouth Scholarship
Diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond to electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short ( 30 days) timescales. The 4428 Å and 6283 Å DIB features get weaker with …
The Fast And Furious Decay Of The Peculiar Type Ic Supernova 2005ek, M. R. Drout, A. M. Soderberg, P. A. Mazzali, J. T. Parrent
The Fast And Furious Decay Of The Peculiar Type Ic Supernova 2005ek, M. R. Drout, A. M. Soderberg, P. A. Mazzali, J. T. Parrent
Dartmouth Scholarship
We present extensive multi-wavelength observations of the extremely rapidly declining Type Ic supernova (SN Ic), SN 2005ek. Reaching a peak magnitude of MR = –17.3 and decaying by ~3 mag in the first 15 days post-maximum, SN 2005ek is among the fastest Type I supernovae observed to date. The spectra of SN 2005ek closely resemble those of normal SN Ic, but with an accelerated evolution. There is evidence for the onset of nebular features at only nine days post-maximum. Spectroscopic modeling reveals an ejecta mass of ~0.3 M ☉ that is dominated by oxygen (~80%), while the pseudo-bolometric light …
Evidence For Particle Acceleration To The Knee Of The Cosmic Ray Spectrum In Tycho’S Supernova Remnant, Kristoffer A. Eriksen, John P. Hughes, Carles Badenes, Robert Fesen
Evidence For Particle Acceleration To The Knee Of The Cosmic Ray Spectrum In Tycho’S Supernova Remnant, Kristoffer A. Eriksen, John P. Hughes, Carles Badenes, Robert Fesen
Dartmouth Scholarship
Supernova remnants (SNRs) have long been assumed to be the source of cosmic rays (CRs) up to the "knee" of the CR spectrum at 10^15 eV, accelerating particles to relativistic energies in their blast waves by the process of diffusive shock acceleration (DSA). Since cosmic ray nuclei do not radiate efficiently, their presence must be inferred indirectly. Previous theoretical calculations and X-ray observations show that CR acceleration modifies significantly the structure of the SNR and greatly amplifies the interstellar magnetic field. We present new, deep X-ray observations of the remnant of Tycho's supernova (SN 1572, henceforth Tycho), which reveal a …
Subaru High-Resolution Spectroscopy Of Star G In The Tycho Supernova Remnant, Wolfgang E. Kerzendorf, Brian P. Schmidt, M. Asplund, Ken'ichi Nomoto, Ph. Podsiadlowski, Anna Frebel, Robert A. Fesen, David Yong
Subaru High-Resolution Spectroscopy Of Star G In The Tycho Supernova Remnant, Wolfgang E. Kerzendorf, Brian P. Schmidt, M. Asplund, Ken'ichi Nomoto, Ph. Podsiadlowski, Anna Frebel, Robert A. Fesen, David Yong
Dartmouth Scholarship
It is widely believed that Type Ia supernovae (SNe Ia) originate in binary systems where a white dwarf accretes material from a companion star until its mass approaches the Chandrasekhar mass and carbon is ignited in the white dwarf's core. This scenario predicts that the donor star should survive the supernova (SNe) explosion, providing an opportunity to understand the progenitors of SNe Ia. In this paper, we argue that rotation is a generic signature expected of most nongiant donor stars that is easily measurable. Ruiz-Lapuente et al. examined stars in the center of the remnant of SN 1572 (Tycho SN) …
De Canum Venaticorum: A Bright, Eclipsing Red Dwarf–White Dwarf Binary, E. J. M. Van Den Besselaar, R. Greimel, L. Morales-Rueda, G. Nelemans, J. R. Thorstensen
De Canum Venaticorum: A Bright, Eclipsing Red Dwarf–White Dwarf Binary, E. J. M. Van Den Besselaar, R. Greimel, L. Morales-Rueda, G. Nelemans, J. R. Thorstensen
Dartmouth Scholarship
Close white dwarf - red dwarf binaries must have gone through a common-envelope phase during their evolution. DE CVn is a detached white dwarf - red dwarf binary with a relatively short (~8.7 hours) orbital period. Its brightness and the presence of eclipses makes this system ideal for a more detailed study. From a study of photometric and spectroscopic observations of DE CVn we derive the system parameters which we discuss in the frame work of common-envelope evolution. Photometric observations of the eclipses are used to determine an accurate ephemeris. From a model fit to an average low-resolution spectrum of …
Hs 2331+3905: The Cataclysmic Variable That Has It All, S. Araujo-Betancor, B. T. Gänsicke, H.-J. Hagen, T. R. Marsh, E T. Harlaftis, J Thorstensen
Hs 2331+3905: The Cataclysmic Variable That Has It All, S. Araujo-Betancor, B. T. Gänsicke, H.-J. Hagen, T. R. Marsh, E T. Harlaftis, J Thorstensen
Dartmouth Scholarship
We report detailed follow-up observations of the cataclysmic variable HS 2331+3905, identified as an emission- line object in the Hamburg Quasar Survey. An orbital period of 81.08 min is unambiguously determined from the detection of eclipses in the light curves of HS 2331+3905. A second photometric period is consistently detected at P ≃ 83.38 min, ∼2.8% longer than Porb, which we tentatively relate to the presence of permanent superhumps. High time resolution photometry exhibits short-timescale variability on time scales of ≃5−6 min which we interpret as non-radial white dwarf pulsations, as well as a coherent signal at 1.12 min, which …