Physical Sciences and Mathematics Commons^™

Faint Sources In The Euve Survey: Identification Of White Dwarfs, Active Late‐Type Stars, And Galactic Nuclei, Elisha Polomski, Stephane Vennes, John R. Thorstensen, Mihalis Mathioudakis, Emilio E. Falco

Dartmouth Scholarship

We report the classification of 21 new extreme-ultraviolet sources from the recent catalog of Lampton et al. The optical spectra presented identify the objects as 14 active late-type stars (including two double active stars and a possible T Tauri star), three white dwarfs, and six active galactic nuclei (a Seyfert galaxy, the BL Lac object 1ES 1028+511 [=EUVE J1031+508], and four quasi-stellar objects). We have detected Ca II absorption lines in the BL Lac object and measured its redshift. Two of the white dwarfs are unusually massive (M > 1.1 M_☉). Our sample of late-type stars includes five …

Optically Identified Supernova Remnants In The Nearby Spiral Galaxies Ngc 5204, Ngc 5585, Ngc 6946, M81, And M101, David M. Matonick, Robert A. Fesen

Dartmouth Scholarship

We present the results of an optical search for supernova remnants (SNRs) in the spiral galaxies NGC 5204, NGC 5585, NGC 6946, M81, and M101. Using the criterion that emission nebulae with [S II]/Hα ≥ 0.45 are identified as SNRs, we found three SNRs in NGC 5204, five in NGC 5585, 27 in NGC 6946, 41 in M81, and 93 in M101. Including the 35 SNRs recently detected in NGC 2403 by Matonick et al., we have doubled the current number of galaxies that have been well searched for SNRs and increased the number of known extragalactic SNRs by about …

Interpretation Of Ultraviolet Absorption Lines In Sn 1006, A. J. S. Hamilton, R. A. Fesen, C.-C. Wu, D. M. Crenshaw

Dartmouth Scholarship

We present a theoretical interpretation of the broad silicon and iron ultraviolet absorption features observed with the Hubble Space Telescope (HST) in the spectrum of the Schweizer-Middleditch star behind the remnant of SN 1006. These features are caused by supernova ejecta in SN 1006.

We propose that the redshifted Si II 1260 Å feature consists of both unshocked and shocked Si II. The sharp red edge of the line at 7070 km s^-1 indicates the position of the reverse shock, while its Gaussian blue edge reveals shocked Si with a mean velocity of 5050 km s^{-1 …}

Far-Ultraviolet Absorption Lines In The Remnant Of Sn 1006, Chi-Chao Wu, D. Michael Crenshaw, Andrew J. S. Hamilton, Robert A. Fesen

Dartmouth Scholarship

We have obtained a far-ultraviolet spectrum (1150-1600 Å) of a hot subdwarf star behind the remnant of supernova 1006 with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope. The high-quality spectrum is used to test previous identifications of the strong absorption features discovered with the International Ultraviolet Explorer. These features have FWHM = 4000 (±300) km s^-1 and are not at the rest wavelengths of known interstellar lines, as opposed to the broader (~8000 km s^-1 FWHM) Fe II lines from the remnant centered at 0 km s^-1 in near-UV FOS spectra. We …

Pulsations And Accretion Geometry In Yy Draconis: A Study Based On Hubble Space Telescope Observations, Carole A. Haswell, Joseph Patterson, John R. Thorstensen, Coel Hellier

Dartmouth Scholarship

We present 1 Å resolution fast ultraviolet spectroscopy of YY Dra, coordinated U, B, V, R, and I photometry, and Hα spectroscopy. The UV continuum is strongly pulsed: we found 16% semiamplitude pulses with period 264.7(1) s; there was no evidence for power at twice this period. The UBV pulses are in phase with the UV continuum pulsation. A color temperature of 10⁵ K was found for the pulse spectrum, with a corresponding area 0.5% of the white dwarf surface. We refine the white dwarf spin period, obtaining P_spin = 529.31 ± 0.02 s. Optical pulses at …