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Kimeswenger 《Monthly notices of the Royal Astronomical Society》1998,294(2):312-314
In 1977, Weinberger published a list of 12 new extended possible planetary nebulae (PNe). Whereas, because of their characteristic morphology and/or the presence of a blue central star, almost all of them could easily be suspected to be genuine planetary nebulae, one object (No. 12) captivated because of its unusually bright central star. This find prompted Kaler & Feibelman to question the PN nature of this object (We 1–12) on the basis of IUE spectra. A definite conclusion could, however, not be drawn by them; thus, until now, the real nature of We 1–12 remained unsolved. For the first time, a spectral investigation of both the central star and the nebula is presented in this paper. It definitely shows that this intriguing object is an (isolated) H ii region and its central star, as previously assumed, is an early B star which serves as the ionizing source. We 1–12, a part of which is coincident with a weak IRAS point source, is at a distance of 2–2.6 kpc and is reddened by E ( B − V )=0.6–0.8 mag. 相似文献
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We present near-infrared polarimetric images of the dusty circumstellar envelope (CSE) of IRAS 19306+1407, acquired at the United Kingdom Infrared Telescope (UKIRT) using the UKIRT 1–5 μm Imager Spectrometer (UIST) in conjunction with the half-waveplate module IRPOL2. We present additional 450- and 850-μm photometry data obtained with the Submillimetre Common-User Bolometer Array (SCUBA) at the James Clerk Maxwell Telescope (JCMT), as well as archived Hubble Space Telescope ( HST ) F606W - and F814W -filter images. The CSE structure in polarized flux at J and K bands shows an elongation north of north-east and south of south-west with two bright scattering shoulders north-west and south-east. These features are not perpendicular to each other and could signify a recent 'twist' in the outflow axis. We model the CSE using an axisymmetric light scattering ( als ) code to investigate the polarization produced by the CSE, and an axisymmetric radiation transport ( dart ) code to fit the spectral energy distribution. A good fit was achieved with the als and dart models using silicate grains, 0.1–0.4 μm with a power-law size distribution of a −3.5 , and an axisymmetric shell geometry with an equator-to-pole ratio of 7:1. The spectral type of the central star is determined to be B1 i supporting previous suggestions that the object is an early planetary nebula. We have constrained the CSE and interstellar extinction as 2.0 and 4.2 mag, respectively, and have estimated a distance of 2.7 kpc. At this distance, the stellar luminosity is ∼4500 L⊙ and the mass of the CSE is ∼0.2 M⊙ . We also determine that the mass loss lasted for ∼5300 yr with a mass-loss rate of ∼3.4 × 10−5 M⊙ yr−1 . 相似文献
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A. M. Mickaelian 《Astrophysics》2004,47(3):361-377
Results of spectral observations of 66 objects from the BIG (Byurakan IRAS Galaxies) sample made with the 1.93 m telescope at the Observatoire de Haute Provence (OHP, France) are presented. Emission lines are observed from 64 of the galaxies. The red shifts are determined, the radial velocities, distances, and absolute stellar magnitudes are calculated, the spectrum line parameters are determined, diagnostic diagrams are constructed, the objects are classified according to activity type, and their IR and far-IR luminosities are calculated. Of the 66 objects (corresponding to 61 IRAS sources), 6 are Sy2, 2 are LINERs, 8 are AGN (Sy2 or LINER), 10 are composite, 34 are HII, and 4 are Em of undetermined type. It is calculated that IRAS 07479+7832= BIG d141a is a ultraluminous IR galaxy (ULIG), and 21 are LIG. Spectra of several of the galaxies being studied are presented. 相似文献
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具有硅酸盐尘埃特征碳星的新的候选者 总被引：1，自引：1，他引：0
本文根据红外天文卫星的宽波段测光及低分辨率光谱资料，给出了两颗新的可能具有硅酸尘埃特征的碳星及４颗可能的候选者。 相似文献
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Rui-Qing Mao Qin Zeng Purple Mountain Observatory Chinese Academy of Sciences Nanjing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2004,4(5):440-454
The massive star forming region S 233 IR is observed in the molecular lines CO J = 2-1, 3-2, NH3 (1,1), (2,2) and the 870#m dust continuum. Four submillimeter continuum sources, labelled SMM 1-4, are revealed in the 870μm dust emission. The main core, SMM1, is found to be associated with a deeply embedded near infrared cluster in the northeast; while the weaker source SMM2 coincides with a more evolved cluster in the southwest. The best fit spectral energy distribution of SMM1 gives an emissivity of β = 1.6, and temperatures of 32 K and 92 K for the cold- and hot-dust components. An SMM1 core mass of 246 M⊙ and a total mass of 445 M⊙ are estimated from the 870μm dust continuum emission.SMM1 is found to have a temperature gradient decreasing from inside out, indicative of the presence of interior heating sources. The total outflow gas mass as traced by the CO J = 3-2 emission is estimated to be 35 M⊙. Low velocity outflows are also found in the NH3 (1,1) emission. The non-thermal dominant NH3 line width as well as the substantial core mass suggest that the SMM1 core is a “turbulent,massive dense core”, in the process of forming a group or a cluster of stars. The much higher star formation efficiency found in the southwest cluster supports the suggestion that this cluster is more evolved than the northeast one. Large near infrared photometric variations found in the source PCS-IR93, a previously found highly polarized nebulosity, indicate an underlying star showing the FU Orionis type of behavior. 相似文献
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We have carried out systematic surveys for small bright-rimmed clouds associated with IRAS point sources in/around HII regions. They are candidate sites for star formation due to radiation-driven implosion. 相似文献