THE IDENTIFICATION OF PROBABLE SiS EMISSION AT 13–14 μm IN SPECTRA OF GALACTIC S STARS

A sample of 90 Galactic S stars observed by the Spitzer Space Telescope includes two sources with unusual low-contrast spectral structure between 7 and 14 μm. The most likely estimate of the spectral continuum leads to the identification of molecular emission features from SiS at 7 and 13–14 μm. The spectra also show what is best described as featureless excess emission, most likely from iron dust but possibly from amorphous carbon, as well as an emission feature from amorphous alumina dust peaking at 11–12 μm. The spectra show long-wavelength excesses from cool dust grains in an extended envelope and additional emission features of unknown origin.

[1]  J. Bernard-Salas,et al.  CARBON-RICH DUST PRODUCTION IN METAL-POOR GALAXIES IN THE LOCAL GROUP , 2012, 1204.5754.

[2]  S. Srinivasan,et al.  THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. IV. CONSTRUCTION AND VALIDATION OF A GRID OF MODELS FOR OXYGEN-RICH AGB STARS, RED SUPERGIANTS, AND EXTREME AGB STARS , 2014, 1407.8452.

[3]  J. Bernard-Salas,et al.  RUSTY OLD STARS: A SOURCE OF THE MISSING INTERSTELLAR IRON? , 2010, 1005.3489.

[4]  Munetaka Ueno,et al.  The AKARI/IRC mid-infrared all-sky survey , 2010, 1003.0270.

[5]  Joana M. Oliveira,et al.  DUST PRODUCTION AND MASS LOSS IN THE GALACTIC GLOBULAR CLUSTER NGC 362 , 2009, 0909.5154.

[6]  A. J. Markwick-Kemper,et al.  THE DETECTION OF INFRARED SiS BANDS IN SPECTRA OF S STARS , 2009 .

[7]  I. Negueruela,et al.  Stellar tracers of the Cygnus Arm II. A young open cluster in Camelopardalis OB3 , 2008, 0810.2560.

[8]  J. Bernard-Salas,et al.  The Magellanic Zoo: Mid-Infrared Spitzer Spectroscopy of Evolved Stars and Circumstellar Dust in the Magellanic Clouds , 2008, 0807.2998.

[9]  F. V. Leeuwen,et al.  AGB variables and the Mira period–luminosity relation , 2008, 0801.4465.

[10]  Xiao-Hong Yang,et al.  Two Micron All Sky Survey, Infrared Astronomical Satellite, and Midcourse Space Experiment Color Properties of Intrinsic and Extrinsic S Stars , 2006 .

[11]  Stephan D. Price,et al.  Spectral Irradiance Calibration in the Infrared. XVI. Improved Accuracy in the Infrared Spectra of the Secondary and Tertiary Standard Calibration Stars , 2006 .

[12]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[13]  Beverly J. Smith,et al.  Phase Lags in the Optical-Infrared Light Curves of Asymptotic Giant Branch Stars , 2005, astro-ph/0509204.

[14]  M. Templeton,et al.  Secular Evolution in Mira Variable Pulsations , 2005, astro-ph/0504527.

[15]  E. Wright,et al.  The Spitzer Space Telescope Mission , 2004, astro-ph/0406223.

[16]  J. Goebel,et al.  Guilt by Association: The 13 Micron Dust Emission Feature and Its Correlation to Other Gas and Dust Features , 2003 .

[17]  H. Walker,et al.  Classification of 2.4-45.2 Micron Spectra from the Infrared Space Observatory Short Wavelength Spectrometer , 2002, astro-ph/0201507.

[18]  Franz Kerschbaum,et al.  Infrared optical properties of spinels A study of the carrier of the 13, 17 and 32m emission features observed in ISO-SWS spectra of oxygen-rich AGB stars ? , 2001 .

[19]  S. D. Price,et al.  The Infrared Spectral Classification of Oxygen-rich Dust Shells , 1998 .

[20]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[21]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.

[22]  Th. Henning,et al.  Aluminum Oxide and the Opacity of Oxygen-rich Circumstellar Dust in the 12-17 Micron Range , 1997 .

[23]  L. Colangeli,et al.  Optical constants of cosmic carbon analogue grains — I. Simulation of clustering by a modified continuous distribution of ellipsoids , 1996 .

[24]  H. J. Habing,et al.  Circumstellar envelopes and Asymptotic Giant Branch stars , 1996 .

[25]  G. Sloan,et al.  Sources of the 13 Microns Feature Associated with Oxygen-Rich Circumstellar Dust , 1996 .

[26]  H. Shibai,et al.  Extinction spectra of corundum in the wavelengths from UV to FIR. , 1995 .

[27]  R. J. Boyle,et al.  Observations of 13.5 micron rotation-vibration lines of SiS in IRC +10216 , 1994 .

[28]  C. Engelke.  Analytic approximations to the 2-60 microns infrared continua for standard calibration stars - With application to the calibration of spectroscopy and photometry, and the determination of effective temperature and angular size from IR measurements , 1992 .

[29]  J. Nuth,et al.  The formation and annealing of circumstellar dust, as gauged by IRAS low-resolution spectra and the microwave maser chronology , 1990 .

[30]  M. M. Moshir,et al.  IRAS Faint Source Catalogue, version 2.0. , 1990 .

[31]  R. J. Bell,et al.  Optical properties of Al, Fe, Ti, Ta, W, and Mo at submillimeter wavelengths. , 1988, Applied optics.

[32]  S. H. Moseley,et al.  MgS grain component in circumstellar shells , 1985 .

[33]  G. Rieke,et al.  The interstellar extinction law from 1 to 13 microns. , 1985 .

[34]  I. Iben,et al.  Asymptotic Giant Branch Evolution and Beyond , 1983 .

[35]  R. Sahai,et al.  SiS in Circumstellar Shells , 1982 .

[36]  P. C. Keenan,et al.  Spectral types of S and SC stars on the revised MK system. , 1980 .

[37]  T. Ake.  A revised spectral classification system in the red for S stars. , 1979 .

[38]  H. Aumann,et al.  Infrared Astronomical Satellite , 1977 .

[39]  Owen B. Toon,et al.  The optical constants of several atmospheric aerosol species: Ammonium sulfate, aluminum oxide, and sodium chloride , 1976 .

[40]  B. Zuckerman,et al.  Detection of interstellar SiS and a study of the IRC + 10216 molecular envelope , 1975 .

[41]  W. Bidelman.  The Spectrum of GP Orionis. , 1950 .

[42]  P. C. Keenan.  On the Occurrence of Lanthanum Oxide in S-Type Stars. , 1948 .

[43]  P. Merrill.  ZIRCONIUM BANDS IN STELLAR SPECTRA OF CLASS S , 1923 .

[44]  P. Merrill.  Stellar spectra of class S. , 1922 .