Browsing Physics (Scholarly Publications) by Author "HARPER, GRAHAM"
Now showing items 1-15 of 15
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ALMA Observations of Non-uniform Dust Mass-loss in the Inner Circumstellar Environment of the Red Supergiant VY CMa
HARPER, GRAHAM (2015)The processes leading to dust formation and the subsequent role it plays in driving mass loss in cool evolved stars is an area of intense study. Here we present high resolution ALMA Science Verification data of the continuum ... -
ALMA sub-mm maser and dust distribution of VY Canis Majoris
HARPER, GRAHAM (2014)Cool, evolved stars have copious, enriched winds. Observations have so far not fully constrained models for the shaping and acceleration of these winds. We need to understand the dynamics better, from the pulsating stellar ... -
Chandra observations of coronal emission from the early-G supergiants Alpha and Beta Aquarii
HARPER, GRAHAM (University of Colorado, 2005)We report Chandra detections of coronal X-rays from the early-G supergiants ? Aquarii (HD209750: G2 Ib) and ? Aquarii (HD204867: G0 Ib). Previous ROSAT observations of these archetype \hybrid chromosphere" stars were ... -
Far-UV Emissions of the Sun in Time: Probing Solar Magnetic Activity and Effects on Evolution of Paleo-Planetary Atmospheres
HARPER, GRAHAM (American Astronomical Society, 2003)We present and analyze Far Ultraviolet Spectroscopic Explorer (FUSE) observations of six solar analogs. These are single, main-sequenceG0?5 stars selected as proxies for the Sun at several stages of its main-sequence ... -
From radio to X-ray: The quiescent atmosphere of the dMe Flare Star EV Lac
HARPER, GRAHAM (2006)We report on multi-wavelength observations spanning radio to X-ray wavelengths of the M dwarf flare star, EV Lacertae, probing the characteristics of the outer atmospheric plasma from the upper chromosphere to the corona. ... -
Inferring mass loss rates for cool luminous stars from high-resolution GHRS spectra
HARPER, GRAHAM (Kluwer, 2000) -
Mg I emission lines at 12 and 18?m in K giants
HARPER, GRAHAM (EDP Sciences, 2008)Context. The solar mid-infrared metallic emission lines have already been observed and analyzed well, and the formation scenario of the Mg I 12 $\rm\mu$m lines has been known for more than a decade. Detections of stellar ... -
STIS observations of the hybrid-chromosphere star alpha TrA
HARPER, GRAHAM (San Francisco: ASP, 2001) -
TEXES observations of M supergiants: dynamics and thermodynamics of wind acceleration
HARPER, GRAHAM (American Astronomical Society, 2009)We have detected [Fe II] 17.94 ?m and 24.52 ?m emission from a sample of M supergiants (? Cep, ? Sco, ? Ori, CE Tau, AD Per, and ? Her) using the Texas Echelon Cross Echelle Spectrograph on NASA's Infrared Telescope Facility. ... -
Water vapor on Betelgeuse as revealed by TEXES high-resolution 12 micron spectra
HARPER, GRAHAM (American Astronomical Society, 2006)The outer atmosphere of the M supergiant Betelgeuse is puzzling. Published observations of different kinds have shed light on different aspects of the atmosphere, but no unified picture has emerged. They have shown, for ... -
Water vapor on supergiants. The 12 micron TEXES spectra of ? Cephei
HARPER, GRAHAM (American Astronomical Society, 2006)Several recent papers have argued for warm, semidetached, molecular layers surrounding red giant and supergiant stars, a concept known as a MOLsphere. Spectroscopic and interferometric analyses have often corroborated this ...