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Stars, Interstellar Medium and the Galaxy

Dartmouth Scholarship

2004

Articles 1 - 6 of 6

Full-Text Articles in Physical Sciences and Mathematics

Signature Of Electron Capture In Iron‐Rich Ejecta Of Sn 2003du, Peter Hoflich, Christopher L. Gerardy, Ken-Ichi Nomoto, Kentaro Motohara, Robert A. Fesen Dec 2004

Signature Of Electron Capture In Iron‐Rich Ejecta Of Sn 2003du, Peter Hoflich, Christopher L. Gerardy, Ken-Ichi Nomoto, Kentaro Motohara, Robert A. Fesen

Dartmouth Scholarship

Late-time near-infrared and optical spectra of the normal-bright Type Ia supernova 2003du about 300 days after the explosion are presented. At this late epoch, the emission profiles of well-isolated [Fe II] lines (in particular that of the strong 1.644 μm feature) trace out the global kinematic distribution of radioactive material in the expanding supernova ejecta. In SN 2003du, the 1.644 μm [Fe II] line seems to show a flat-topped profile, indicative of a thick but hollow-centered expanding shell, rather than a strongly peaked profile that would be expected from a "center-filled" distribution. Based on detailed models for exploding Chandrasekhar-mass white …

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A Million Secondchandraview Of Cassiopeia A, Una Hwang, J. Martin Laming, Carles Badenes, Fred Berendse, John Blondin, Denis Cioffi, Tracey Delaney, Daniel Dewey, Robert Fesen Nov 2004

A Million Secondchandraview Of Cassiopeia A, Una Hwang, J. Martin Laming, Carles Badenes, Fred Berendse, John Blondin, Denis Cioffi, Tracey Delaney, Daniel Dewey, Robert Fesen

Dartmouth Scholarship

We introduce a million second observation of the supernova remnant Cassiopeia A with the Chandra X-Ray Observatory. The bipolar structure of the Si-rich ejecta (northeast jet and southwest counterpart) is clearly evident in the new images, and their chemical similarity is confirmed by their spectra. These are most likely due to jets of ejecta as opposed to cavities in the circumstellar medium, since we can reject simple models for the latter. The properties of these jets and the Fe-rich ejecta will provide clues to the explosion of Cas A.

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Location Of The Optical Reverse Shock In The Cassiopeia A Supernova Remnant, Jon A. Morse, Robert A. Fesen, Roger A. Chevalier, Kazimierz J. Borkowski Oct 2004

Location Of The Optical Reverse Shock In The Cassiopeia A Supernova Remnant, Jon A. Morse, Robert A. Fesen, Roger A. Chevalier, Kazimierz J. Borkowski

Dartmouth Scholarship

We use two epochs of Hubble Space Telescope WFPC2 images separated by 2 yr to determine the location and propagation of the reverse shock (RS) in the young supernova remnant Cassiopeia A (Cas A). The images trace optical line emission from fast-moving knots and filaments of highly processed ejecta as they cross the RS, become heated and compressed, and radiatively cool. At numerous positions around the optical shell, new emission features are seen in the 2002 images that were not yet visible in the 2000 exposures. In a few instances emission features seen in the first epoch have completely disappeared …

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Kinematics Of X‐Ray–Emitting Components In Cassiopeia A, Tracey Delaney, Lawrence Rudnick, Robert A. Fesen, T. W. Jones Sep 2004

Kinematics Of X‐Ray–Emitting Components In Cassiopeia A, Tracey Delaney, Lawrence Rudnick, Robert A. Fesen, T. W. Jones

Dartmouth Scholarship

We present high-resolution X-ray proper-motion measurements of Cassiopeia A using Chandra X-Ray Observatory observations from 2000 and 2002. We separate the emission into four spectrally distinct classes: Si-dominated, Fe-dominated, low-energy-enhanced, and continuum-dominated. These classes also represent distinct spatial and kinematic components. The Si- and Fe-dominated classes are ejecta and have a mean expansion rate of 0.2% yr-1. This is the same as for the forward shock filaments but less than the 0.3% yr-1 characteristic of optical ejecta. The low-energy-enhanced spectral class possibly illuminates a clumpy circumstellar component and has a mean expansion rate of 0.05% yr-1. The continuum-dominated emission likely …

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Sn 2003du: Signatures Of The Circumstellar Environment In A Normal Type Ia Supernova?, Christopher L. Gerardy, Peter Hoflich, Robert A. Fesen, G. H. Marion May 2004

Sn 2003du: Signatures Of The Circumstellar Environment In A Normal Type Ia Supernova?, Christopher L. Gerardy, Peter Hoflich, Robert A. Fesen, G. H. Marion

Dartmouth Scholarship

We present observations of the Type Ia supernova 2003du obtained with the Hobby-Eberly Telescope and report the detection of a high-velocity component in the Ca II infrared triplet near 8000 Å, similar to features previously observed in SN 2000cx and SN 2001el. This feature exhibits a large expansion velocity (≈18,000 km s-1), which is nearly constant between -7 and +2 days relative to maximum light and disappears shortly thereafter. Other than this feature, the spectral evolution and light curve of SN 2003du resemble those of a normal SN Ia. We consider a possible origin for this high-velocity Ca II line …

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Observations Of White Dwarfs In The Solar Neighborhood, Adela Kawka, Stphane Vennes, John R. Thorstensen Mar 2004

Observations Of White Dwarfs In The Solar Neighborhood, Adela Kawka, Stphane Vennes, John R. Thorstensen

Dartmouth Scholarship

High proper motion surveys are still adding much to our understanding of the local white dwarf population and, possibly, to the Galactic halo membership of some objects. As part of our study of white dwarfs in the solar neighborhood we have observed seven white dwarfs from the revised New Luyten Two Tenths (NLTT) catalog of Salim & Gould. We found four DA white dwarfs (NLTT 529, 49985, 53468, 55932), one DZ white dwarf (NLTT 40607) that shows a close resemblance to the unusual DZ white dwarf G165-7, and two DC white dwarfs (NLTT 19138, NLTT 52404). The white dwarf candidates …

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