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  • 1
    Electronic Resource
    Electronic Resource
    Is the bulge of our Galaxy triaxial? (1991)
    [s.l.] : Nature Publishing Group
    Nature 353 (1991), S. 140-141 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Because of the large interstellar absorption, the galactic bulge cannot be observed at optical wavelengths, except in some optical windows where the extinction is relatively low7. Several infrared observations of stars in the bulge have been made from balloons8'9. Furthermore, Habing et a/.10'11 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/353140a0
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  • 2
    Electronic Resource
    Electronic Resource
    Isophot Mapping Observations of Carbon Stars (1997)
    Springer
    Astrophysics and space science 255 (1997), S. 341-347 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mapping observations have been made toward five carbon stars in the far-infrared using ISOPHOT, an imaging photo-polarimeter on board the Infrared Space Observatory. Cold, very extended dust shells are clearly revealed in two of them. Y CVn is surrounded by a very extended, detached dust shell, which indicates a sudden decline of the mass-loss by two orders of magnitude in the last (1-2) × 104 years on a short time scale. The Hipparcos parallax reinforces our previous conclusion that Y CVn is a J-type carbon star on the asymptotic giant branch. U Ant shows a double shell structure, a compact dust shell surrounded by a very extended one. The outer shell has a brightness comparable to the dust shell of Y CVn. The structure indicates that there were two different high mass-loss phases separated by a period with a much lower mass-loss rate in between the two. The structure is consistent with the double dust shell proposed for this star by Izumiura et al. (1997) based on a detailed investigation of IRAS survey data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001548110477
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  • 3
    Electronic Resource
    Electronic Resource
    ISO-SWS Observations of the Time Variability of Oxygen-righ Mira Variables (1997)
    Springer
    Astrophysics and space science 255 (1997), S. 331-337 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the first observation of variation of the infrared spectrum of circumstellar dust emission around an oxygen-rich Mira variable star, Z Cyg, over an entire light variation cycle, based on the periodic SWS01 observations. The 10 µm and 20 µm ‘silicate features’ become stronger relative to the photospheric emission at maximum that at minimum. In addition, the relative intensity of the 10 µm to the 20 µm features increases at maximum, indicating an increase of the temperature of circumstellar dust grain. A simple model analysis suggests enhanced dust formation near the photosphere around maximum, leading to a scenario that dust nucleation may have occurred near minimum and the dust grains may have subsequently grown till maximum. The strong observed variation suggests that the variability must be taken into account in the interpretation of the infrared spectra of oxygen-rich Mira variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001544025498
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  • 4
    Electronic Resource
    Electronic Resource
    Detection of detached dust envelopes around oxygen-rich AGB stars (1995)
    Springer
    Astrophysics and space science 224 (1995), S. 477-478 
    Details
    ISSN: 1572-946X
    Keywords: circumstellar dust ; stars : AGB ; Mass loss ; stars: individual : R Hya
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Extended emission components are clearly found in the IRAS scan data of optically visible oxygen-rich AGB stars which show no 10µm silicate band feature in the IRAS LRS spectra but a strong infrared excess in the IRAS photometric data. It is most likely that these stars really have their circumstellar dust envelopes, which are detached from the central stars, indicating a halting of mass loss for a significant period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00667913
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  • 5
    Electronic Resource
    Electronic Resource
    Extended dust shells around carbon stars resolved by “HIRAS” (1995)
    Springer
    Astrophysics and space science 224 (1995), S. 495-496 
    Details
    ISSN: 1572-946X
    Keywords: HIRAS ; carbon stars ; dust shells ; thermal pulses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have examined forty-two carbon stars which show excess emission at 60 and/or 100µm by applying maximum-entropy image reconstruction techniques to the IRAS 60µm survey data. Thirteen stars are found to be extended in the reconstructed images. Four of them show a detached ring centered on the stellar position. In particular, U Ant may have a double detached dust shell. The implications of our results are discussed concerning the variation of mass loss on the AGB evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00667922
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  • 6
    Electronic Resource
    Electronic Resource
    Aperture synthesis observations of HCN J=1-0 emission from Y canum venaticorum (1995)
    Springer
    Astrophysics and space science 224 (1995), S. 493-494 
    Details
    ISSN: 1572-946X
    Keywords: carbon stars ; HCN ; abundances ; masers ; Y CVn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have made high resolution observations of HCN (1-0) emission from the carbon star Y Canum Venaticorum using the Nobeyama Millimeter Array. We find that the emission region is not well resolved by the synthesized beam of 3.7” × 4.6” over the entire velocity range (VLSR =10 to 35 km s−1). We find that the true brightness temperature probably exceeds 200 K at many velocity channels as well as at the 26 km s−1 maser spike. The broad emission component may be the result of superimposed maser spikes. The high brightness requires an unreasonably high HCN fractional abundance if LTE is assumed. It is likely that the HCN abundance previously reported for the star is considerably affected by the maser action. A new maser spike has been found at VLSR = 29 km s−1
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00667921
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  • 7
    Electronic Resource
    Electronic Resource
    A Compact Circumstellar Dust Envelope of an Evolved AGB Star IRC-10529 (1997)
    Springer
    Astrophysics and space science 251 (1997), S. 207-210 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have made far-infrared mapping observations around a heavily mass losing evolved star IRC-10529 with ISO. It is found that IRC-10529 shows a very compact circumstellar dust envelope in the 60 and 90 µm images obtained by ISOPHOT. Such a small size of the circumstellar dust envelope indicates very short history of the present strong mass loss. It is very likely that IRC-10529 has just evolved into the final stage of AGB evolution with an extremely high mass-loss rate very recently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000749025676
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  • 8
    Electronic Resource
    Electronic Resource
    Isophot Mapping Observations of a Mira-Type AGB Star R Hya (1997)
    Springer
    Astrophysics and space science 255 (1997), S. 349-350 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Far-infrared mapping observations of a Mira-type AGB star R Hya were carried out with the imaging photo-polarimeter ISOPHOT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001552227316
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