Author
K. M. Merrill
Bio: K. M. Merrill is an academic researcher. The author has contributed to research in topics: Photometry (astronomy) & Photosphere. The author has an hindex of 1, co-authored 1 publications receiving 39 citations.
Topics: Photometry (astronomy), Photosphere, Stars, Infrared, Circumstellar dust
Papers
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TL;DR: In this paper, a large number of 2 m Sky Suwey objects were used for infrared photometry and spectrophotometry with resolution 4A -0.015 over the wavelength range 2.
Abstract: Broad-band infrared photometry and spectrophotometry with resolution 4A --0.015 over the wavelength range 2- is presented for a large number of 2 m Sky Suwey objects. All of these sources within the present sample except IRC +40091 (Lk Ha 101) are shown to have characteristics similar to stars of the conventional spectral sequence or perhaps a slight extension to cooler surface temperature. A progression of increasing optical depth of circumstellar dust surrounding the stars is demonstrated. No evidence for a cool stellar photosphere is observed for IRC +40091. Key words: infrared objects - infrared spectrophotometry - circumstellar dust
39 citations
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TL;DR: In this paper, low-resolution spectra were extracted for 11,224 IRAS sources and classified into astrophysical classes, based on the presence of emission and absorption features and on the shape of the continuum.
Abstract: IRAS low-resolution spectra were extracted for 11,224 IRAS sources. These spectra were classified into astrophysical classes, based on the presence of emission and absorption features and on the shape of the continuum. Counterparts of these IRAS sources in existing optical and infrared catalogs are identified, and their optical spectral types are listed if they are known. The correlations between the photospheric/optical and circumstellar/infrared classification are discussed.
218 citations
TL;DR: In this article, high-resolution 4.6 mu m CO spectra of the circumstellar environments of two RSGs that are potential supernova (SN) progenitors, Betelgeuse and VY Canis Majoris, were presented.
Abstract: We present high-resolution 4.6 mu m CO spectra of the circumstellar environments of two red supergiants (RSGs) that are potential supernova (SN) progenitors: Betelgeuse and VY Canis Majoris (VY CMa). Around Betelgeuse, (CO)-C-12 emission within +/-3 '' (+/-12 km s(-1)) follows a mildly clumpy but otherwise spherical shell, smaller than its similar to 55 '' shell in KI lambda 7699. In stark contrast, 4.6 mu m CO emission around VY CMa is coincident with bright KI in its clumpy asymmetric reflection nebula, within +/-5 '' (+/-40 km s(-1)) of the star. Our CO data reveal redshifted features not seen in KI spectra of VY CMa, indicating a more isotropic distribution of gas punctuated by randomly distributed asymmetric clumps. The relative CO and KI distribution in Betelgeuse arises from ionization effects within a steady wind, whereas in VY CMa, KI is emitted from skins of CO cloudlets resulting from episodic mass ejections 500-1000 yr ago. In both cases, CO and KI trace potential pre-SN circumstellar matter: we conclude that an extreme RSG like VY CMa might produce a Type IIn event like SN 1988Z if it were to explode in its current state, but Betelgeuse will not. VY CMa demonstrates that luminous blue variables are not necessarily the only progenitors of SNe IIn, but it underscores the requirement that SNe IIn suffer enhanced episodic mass loss shortly before exploding.
195 citations
University of Manchester1, Keele University2, Space Telescope Science Institute3, University College London4, Cornell University5, European Southern Observatory6, California Institute of Technology7, Air Force Research Laboratory8, Katholieke Universiteit Leuven9, Johns Hopkins University10, University of Virginia11, National Radio Astronomy Observatory12, Iowa State University13, Hoffmann-La Roche14, University of California, Berkeley15, Paris Diderot University16, University of Arizona17, Harvard University18, Nagoya University19, University of Missouri20, Imperial College London21, Max Planck Society22, University of Warsaw23, Institut d'Astrophysique de Paris24, University of Toledo25
TL;DR: In this article, a decision-tree method of object classification based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership and variability information was used to classify the SAGE-Spec sample of point sources.
Abstract: We present the classification of 197 point sources observed with the Infrared Spectrograph in the SAGE-Spec Legacy programme on the Spitzer Space Telescope. We introduce a decision-tree method of object classification based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership and variability information, which is used to classify the SAGE-Spec sample of point sources. The decision tree has a broad application to mid-infrared spectroscopic surveys, where supporting photometry and variability information are available. We use these classifications to make deductions about the stellar populations of the Large Magellanic Cloud and the success of photometric classification methods. We find 90 asymptotic giant branch (AGB) stars, 29 young stellar objects, 23 post-AGB objects, 19 red supergiants, eight stellar photospheres, seven background galaxies, seven planetary nebulae, two H_(II) regions and 12 other objects, seven of which remain unclassified.
128 citations
TL;DR: In this article, the carbon and silicon isotropic compositions of 246 anomalous SiC grains measured in low-position residues were reported, and residues were prepared from nine chondrites, namely, 6 unequilibrated ordinary chondites (UOCs), Qingzhen (EH3), Leoville (CV3), and Murchison (CM2).
113 citations