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American Astronomical Society Meeting Abstracts #213; 01/2009
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E. Dwek,
R. G. Arendt,
P. Bouchet,
D. N. Burrows,
P. Challis,
I. J. Danziger, J. M. De Buizer,
R. D. Gehrz,
R. P. Kirshner,
R. McCray,
S. Park,
E. F. Polomski,
C. E. Woodward
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ABSTRACT: Multiwavelength observations of supernova remnant (SNR) 1987A show that its morphology and luminosity are rapidly changing at X-ray, optical, infrared, and radio wavelengths as the blast wave from the explosion expands into the circumstellar equatorial ring, produced by mass loss from the progenitor star. The observed infrared (IR) radiation arises from the interaction of dust grains that formed in mass outflow with the soft X-ray emitting plasma component of the shocked gas. Spitzer IRS spectra at 5 - 30 microns taken on day 6190 since the explosion show that the emission arises from ~ 1.1E-6 Msun of silicate grains radiating at a temperature of ~180+20-15 K. Subsequent observations on day 7137 show that the IR flux had increased by a factor of 2 while maintaining an almost identical spectral shape. The observed IR-to-X-ray flux ratio (IRX) is consistent with that of a dusty plasma with standard Large Magellanic Cloud dust abundances. IRX has decreased by a factor of ~ 2 between days 6190 and 7137, providing the first direct observation of the ongoing destruction of dust in an expanding SN blast wave on dynamic time scales. Detailed models consistent with the observed dust temperature, the ionization timescale of the soft X-ray emission component, and the evolution of IRX suggest that the radiating silicate grains are immersed in a 3.5E6 K plasma with a density of (0.3-1)E4 cm^{-3}, and have a size distribution that is confined to a narrow range of radii between 0.023 and 0.22 microns. Smaller grains may have been evaporated by the initial UV flash from the supernova. Comment: Accepted for publication in the Astrophysical Journal. Document is 28 pages long and includes 9 figures
12/2007;
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ABSTRACT: The Mira AB system is a nearby (~107 pc) example of a wind accreting binary
star system. In this class of system, the wind from a mass-losing red giant
star (Mira A) is accreted onto a companion (Mira B), as indicated by an
accretion shock signature in spectra at ultraviolet and X-ray wavelengths.
Using novel imaging techniques, we report the detection of emission at
mid-infrared wavelengths between 9.7 and 18.3 $\mu$m from the vicinity of Mira
B but with a peak at a radial position about 10 AU closer to the primary Mira
A. We interpret the mid-infrared emission as the edge of an optically-thick
accretion disk heated by Mira A. The discovery of this new class of accretion
disk fed by M-giant mass loss implies a potential population of young planetary
systems in white-dwarf binaries which has been little explored, despite being
relatively common in the solar neighborhood.
03/2007;
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ABSTRACT: We present high spatial resolution mid-IR images of the nuclear region of Centaurus A. Images were obtained at 8.8 um, N-band (10.5uem), and 18.3um using the mid-IR in- strument T-ReCS on Gemini South, a pro- genitor to CanariCam on the Gran Telescopio Canarias (GTC).
Revista Mexicana de Astronomía y Astrofísica : Universidad Nacional Autónoma de México. Instituto de Astronomía. 01/2007;
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J. T. Radomski,
C. Packham,
E. Perlman,
P. Roche,
R. K. Piña,
C. M. Telesco,
D. Aitken,
A. Alonso-Herrero,
J. Biretta, J. M. De Buizer,
R. S. Fisher,
A. Robinson,
W. Sparks,
C. Tadhunter
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ABSTRACT: This paper represents only a summary of mid-IR observations of four AGN
presented at the Spitzer Space Telescope: New Views of the Cosmos
conference. For more detail please refer to the corresponding
publications.
11/2006; 357:263.
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ABSTRACT: We present here a mid-infrared imaging survey of 26 sites of water maser emission. Observations were obtained at the InfraRed Telescope Facility 3-m telescope with the University of Florida mid-infrared imager/spectrometer OSCIR, and the JPL mid-infrared camera MIRLIN. The main purpose of the survey was to explore the relationship between water masers and the massive star formation process. It is generally believed that water masers predominantly trace outflows and embedded massive stellar objects, but may also exist in circumstellar disks around young stars. We investigate each of these possibilities in light of our mid-infrared imaging. We find that mid-infrared emission seems to be more closely associated with water and OH maser emission than cm radio continuum emission from UC HII regions. We also find from the sample of sources in our survey that, like groups of methanol masers, both water and OH masers have a proclivity for grouping into linear or elongated distributions. We conclude that the vast majority of linearly distributed masers are not tracing circumstellar disks, but outflows and shocks instead. Comment: 49 pages; 23 figures; To appear in February 2005 ApJS; To download a version with better quality figures, go to http://www.ctio.noao.edu/~debuizer/
10/2004;
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ABSTRACT: We present here mid-infrared images of seven sites of water maser emission thought to be associated with the hot molecular core (HMC) phase of massive star formation. Observations were obtained at the NASA InfraRed Telescope Facility 3-m, the Gemini 8-m, and Keck II 10-m telescopes. We have detected mid-infrared sources at the locations of two HMC candidates, G11.94-0.62 and G45.07-0.13. We observed G19.61-0.23 and G34.26+0.15, each of which have HMCs previously detected in the mid-infrared. We did not detect mid-infrared emission from either HMC source, and we place new upper limits on the mid-infrared flux densities for these HMCs that are much lower than their previously reported flux densities. We were able to obtain extremely accurate astrometry for our mid-infrared images of G9.62+0.19, and conclude that the mid-infrared emission thought to be coming from the HMC in this field is in fact coming from a different source altogether. Subject headings: circumstellar matter – infrared: ISM – stars: early type – stars: formation – masers 1. introduction Hot molecular cores (HMCs) are believed to represent an extremely early stage of massive stellar birth. An HMC consists of a massive protostar surrounded by a thick enve-lope of accreting dust and gas. Though there are very few observations of these objects to date, we are beginning to piece together an empirically derived list of the basic ob-servational characteristics of HMCs: 1) they are compact sources seen in radio-wavelength ammonia (or molecular line) images but have little or no radio continuum emission; 2) they lie in massive star forming regions near ultracom-pact HII (UC HII) regions; 3) they are too young and/or embedded to be seen in the optical or near infrared; and 4) they are often coincident with water maser emission. Only a small number of sources exist that have had such a holistic set of observations performed. The work by Cesaroni et al. (1994) remains the most comprehensive work on the subject, even though their work involved radio-wavelength ammonia line imaging to-wards only four fields of massive star formation. In all four cases they found compact (∼0.1 pc) ammonia clumps offset from, but near to, UC HII regions. In all four cases the water masers were directly coincident with the ammo-nia emission rather than the radio continuum emission of the UC HII region. Cesaroni et al. (1994) observed in the high-excitation (4,4) line of NH 3 , which traces gas with kinetic temperatures of 50-200 K, and densities approxi-mating n H2 ∼ 10 7 cm −3 (n N H3 /n H2 > 10 −6) within these HMCs. Cesaroni et al. (1994) also argue that gas and dust would be well mixed in the HMCs and that there would be a high rate of collisions between the dust and gas. When densities in excess of n H2 10 5 cm −3 exist, temperature equilibrium between gas and dust is established (Krugel and Walmsley 1984). Given the high observed densities of HMCs, it can be concluded that the gas kinetic tem-perature is a fair approximation to the dust temperature. The observed gas temperatures for HMCs is typically be-tween 50 and 200 K (Cesaroni et al. 1994). Therefore one should be able to detect new HMCs via their mid-infrared emission, at least for the warmest sources. Recently there was a detection of mid-infrared emission from the HMC of G29.96-0.02 (De Buizer et al. 2002), a source that was first imaged by Cesaroni et al. (1994) in NH 3 emission. This source is also in the survey of Hofner & Churchwell (1996), who studied the relationship between the 2 cm radio continuum emission of UC HII regions and the location of the water masers on the field. They found that G29.96-0.02, like several other sources in their survey, did not have water masers associated with the observed UC HII regions. Instead, the water masers tend to be in groups that lie offset from the radio continuum emission. The hypothesis is that the water masers are excited by embedded massive stellar sources within the HMCs. It is pointed out by Hofner & Churchwell (1996) that several of the UC HII regions in their survey are cometary-shaped, like G29.96-0.02, and have their water masers located in front of the cometary arc of radio continuum emission. Another source in common between the Cesaroni et al. (1994) survey and Hofner & Churchwell (1996) survey is G9.62+0.19. Hofner & Churchwell (1996) showed that both sources display radio continuum regions with water masers offset, and Cesaroni et al. (1994) showed that both have HMCs at the water maser locations as seen in NH 3 .
08/2003;
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ABSTRACT: NGC 6334 I is one of the northern-most sites of massive star formation
in the 20 parsec long train of molecular clouds and HII regions known as
NGC 6334. At the center of NGC 6334 I lies a bright, cometary UCHII
region named NGC 6334 F. Recent observations of NGC 6334 F and its
vicinity at mid-infrared wavelengths have revealed several separate
sources (Persi et al. 1998, Kraemer et al. 1999). Furthermore, a new
source has been detected at 7 mm by Carral et al. (1997) just west of
NGC 6334 F. Here we present new mid-infrared images of the sources in
this area acquired with OSCIR at the CTIO 4-m and the Keck II 10-m
telescopes. These new high-resolution images, coupled with already
existent data on outflow and distribution of molecular material, allow
new insights into the nature of the sources in NGC 6334 I, and the roles
that outflow and masers play in this region.
11/2000; 32:1469.
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ABSTRACT: G339.88-1.26 is considered to be a good candidate for a massive star with a circumstellar disk. This has been supported by the observations of linearly distributed methanol maser spots believed to delineate this disk and mid-infrared observations that have discovered a source at this location that is elongated at the same position angle as the methanol maser distribution. We used the mid-infrared imager/spectrometer OSCIR at Keck Observatory to make high-resolution images of G339.88-1.26. We resolve the mid-infrared emission into three sources within 1".5 of the location of the masers. We determine that the methanol masers are most likely not located in a circumstellar disk. Furthermore, we find that the observed radio continuum emission most likely comes from two sources in close proximity to each other. One source is an unobscured massive star with an extended H II region that is responsible for the peak in the radio continuum emission. A second source is embedded and centered on the elongation in the radio continuum emission that is believed to be tracing an outflow in this region.
Astrophysical Journal, v.564, 327-332 (2002).
