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Multi-wavelength imaging of the peculiar Vela Molecular Ridge nebula BBW 192E
We present the first images of the nebula BBW 192E at near- andmid-infrared wavelengths as well as a 1.3 mm continuum map. The nebulaBBW 192E is associated with the IRAS point source 08513-4201 which has aluminosity of about 1400 L_sun and a strongly rising spectral energydistribution towards mid-infrared wavelengths. The infrared images showa pronounced bipolar nebula, which is offset by about 10arcsec from theknown optical emission, as well as several point sources. We interpretthis morphology as evidence for an inclined disk-like structure andscattered light emerging from the lobes. This is supported by ournear-infrared imaging polarimetry at sub-arcsecond resolution whichfurthermore indicates that the central energy source is seen directly atnear-infrared wavelengths. At 1.3 millimetre, we detected a cometaryshaped source in the dust continuum radiation, 151arcsec x 55arcsec insize, with a total mass of 180 M_sun as well as average hydrogen columnand number densities of 4.5x1022 cm-2 and2.6x105 cm-3, respectively. This dust cloud isalso responsible for the strong spatial variation of the extinctionacross the nebula. We discuss the physical properties of the infraredpoint sources and conclude that some might be young, low-mass pre-mainsequence stars. The main energy source of the nebula is an embeddedintermediate-mass young stellar object. These observations are among thefirst infrared detections of a disk-like system associated with abipolar nebula surrounding an intermediate-mass young stellar object.Based on observations collected at the European Southern Observatory, LaSilla, Chile (Proposal-IDs: 57.B-0392, 52.7-0086, 57.D-0260, 58.D-0213,and 63.I-0173)
| Infrared Photometry of Red Supergiants in Young Clusters in the Magellanic Clouds
We present broadband infrared photometry for 52 late-type supergiants inthe young Magellanic Cloud clusters NGC 330, 1818, 2004, and 2100.Standard models are seen to differ in the temperature they predict forthe red supergiant population by on the order of 300 K. It appears thatthese differences are most probably due to the calibration of themixing-length parameter alpha_P in the outermost layers of the stellarenvelope. Because alpha_P apparently depends on the model used, we donot quantitatively compare alpha_P between models. Qualitatively, wefind that alpha_P decreases with increased stellar mass within standardmodels. We do not find evidence that alpha_P depends on metallicity.
| Obscured Asymptotic Giant Branch stars in the Magellanic Clouds. III. New IRAS counterparts.
We have searched for near-infrared stellar counterparts of IRAS pointsources in the Large Magellanic Cloud (LMC), in J- and K-bands. Thisresulted in the detection of 21 counterparts, of which 19 are newdiscoveries. Using colour-magnitude and colour-colour diagrams, weidentify 13 Asymptotic Giant Branch (AGB) stars with thick circumstellardust envelopes, 7 possible early post-AGB stars or stars recovering froma thermal pulse, and 1 red supergiant or foreground star. For 10 of theIRAS targets we do not succeed in detecting and/or identifying anear-infrared counterpart. We serendipitously detect 14 other redsources, of which 2 are known Long Period Variables, and a few galaxies.The near-infrared and optical colours of the galaxies may indicateconsiderable interstellar extinction through the LMC, as much asA_V_~2-4mag. The relative number of AGB carbon stars over oxygen starsis shown to decrease as the luminosity increases. Yet amongst thefaintest mass-losing AGB stars oxygen-rich stars still exist, which putsconstraints on current convection theories that predict the occurrenceof third dredge-up and Hot Bottom Burning. We investigate the nature ofsome LMC stars that have infrared properties very similar to suspectedGalactic post-AGB stars.
| Infrared Images and Millimeter Data from Cold Southern IRAS Sources
We present near-infrared (H, K'), CO (2--1), CS (2--1), and 1.3 mmcontinuum data for 31 southern objects [ delta (1950) <= 10 deg]known to have extremely red IRAS colors [F nu (100 mu m) > F nu (60mu m) > F nu (25 mu m) > 20 x F nu (12 mu m)]. The data are meantto help reveal new, very young stellar objects. K'-band near-infraredcounterparts to the IRAS point sources are detected in 22 of 25 good K'images. Most K' counterparts are multiples. Eighteen of 21 objects weredetected in CS, implying the presence of dense gas. Completing the setof CS (2--1) spectra by including the data of Bronfman, Nyman, &Ray, we still find only three nondetections among all 31 objects; thesethree were also not detected in K'. Wings indicative of outflows arefound in a large fraction (20/30) of CO spectra. Twenty-six of 31observations in the millimeter continuum were detections and point tothe presence of large amounts of circumstellar matter. Most of theobjects have 103--105 times solar luminosity; we speculate that mostcontain at least one massive star capable of producing acompact/ultracompact H II region.
| Carbon monoxide in supernova 1995ad
Infrared spectroscopy of the type II supernova 1995ad 105d after itsdiscovery has been performed at the Anglo-Australian Telescope. Thespectra exhibit strong emission longwards of 2.3 mum, consistent withemission from carbon monoxide from within the ejecta of the supernova. Alocal thermodynamic equilibrium (LTE) analysis of the spectrum gives10^-4 M_solar of CO emitting at a temperature of 3000K. The similarityof these observations to those of SN 1987A allow for the possibilitythat due to non-LTE and optical depth effects the mass of CO present inthe ejecta of SN 1995ad may be as high as 5x10^-2M_solar.
| Fainter Southern JHK Standards Suitable for Infrared Arrays
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995MNRAS.276..734C&db_key=AST
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Pozíciós és asztrometriai adatok
| Csillagkép: | Hajófar |
| Rektaszcenzió: | 06h59m19.71s |
| Deklináció: | -42°14'15.4" |
| Vizuális fényesség: | 8.424 |
| Távolság: | 476.19 parszek |
| RA sajátmozgás: | -4.7 |
| Dec sajátmozgás: | 8 |
| B-T magnitude: | 8.323 |
| V-T magnitude: | 8.416 |
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