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  • ASTROPHYSICS  (9)
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  • 1
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    Two UV colours of the central part of M 31 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Two photographs of the galaxy M 31 have been obtained in the far UV with a Faust rocket experiment and in the near UV with the S 183 experiment aboard Skylab. Only the central part of the galaxy is detected. Reductions provide both the energy received and the angular area over M 31 from which it is emitted. The UV flux is brighter than expected from extrapolation of the visible spectrum. The distribution below 300 A is rather flat and different from previous OAO-2 observations. These results, combined with Lyman continuum flux evaluation, are used to discuss the temperature and the age of the stars which may be responsible for this anomalous UV distribution.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 50; 3, Au; Aug. 197
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  • 2
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    High resolution imaging of galaxy cores (1993)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Surface photometry data obtained with the Faint Object Camera of the Hubble Space Telescope in the cores of ten galaxies is presented. The major results are: (1) none of the galaxies show truly 'isothermal' cores, (2) galaxies with nuclear activity show very similar light profiles, (3) all objects show central mass densities above 10 exp 3 solar masses/cu pc3, and (4) four of the galaxies (M87, NGC 3862, NGC 4594, NGC 6251) show evidence for exceptional nuclear mass concentrations.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 106; 4; p. 1371-1393, 1707,
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  • 3
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    Imaging of four planetary nebulae in the Magellanic Clouds using the Hubble Space Telescope Faint Object Camera (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Using the Faint Object Camera on-board the Hubble Space Telescope, we have obtained images of four planetary nebulae (PNe) in the Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the LMC. Each nebula was imaged through two narrow-band filters isolating forbidden O III 5007 and H-beta, for a nominal exposure time of 1000 s in each filter. In forbidden O III, SMC N5 shows a circular ring structure, with a peak-to-peak diameter of 0.26 arcsec and a FWHM of 0.35 arcsec while SMC N2 shows an elliptical ring structure with a peak-to-peak diameter of 0.26 x 0.21. The expansion ages corresponding to the observed structures in SMC N2 and N5 are of the order of 3000 yr. LMC N201 is very compact, with a FWHM of 0.2 arcsec in H-beta. The Type I PN LMC N66 is a multipolar nebula, with the brightest part having an extent of about 2 arcsec and with fainter structures extending over 4 arcsec.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 398; 1; p. L41-L44.
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  • 4
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    Faint Object Camera observations of M87 - The jet and nucleus (1992)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: UV and optical images of the central region and jet of the nearby elliptical galaxy M87 have been obtained with about 0.1 arcsec resolution in several spectral bands with the Faint Object Camera (FOC) on the HST, including polarization images. Deconvolution enhances the contrast of the complex structure and filamentary patterns in the jet already evident in the aberrated images. Morphologically there is close similarity between the FOC images of the extended jet and the best 2-cm radio maps obtained at similar resolution, and the magnetic field vectors from the UV and radio polarimetric data also correspond well. We observe structure in the inner jet within a few tenths arcsec of the nucleus which also has been well studied at radio wavelengths. Our UV and optical photometry of regions along the jet shows little variation in spectral index from the value 1.0 between markedly different regions and no trend to a steepening spectrum with distance along the jet.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 261; 2; p. 393-404.
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  • 5
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    Detection of an ultraviolet and visible counterpart of the NGC 6624 X-ray burster (1993)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We have detected, in images taken with the HST FOC, the UV and optical counterpart of the X-ray source 4U 1820-30 in the globular cluster NGC 6624. Astrometric measurements place this object 2 sigma from the X-ray position of 4U 1820-30. The source dominates a far-UV FOC image and has the same flux at 1400 A as was seen through the large IUE aperture by Rich et al. (1993). It has a B magnitude of 18.7 but is not detected in V. It is 0.66 arcsec from the center of NGC 6624, a fact that may change the interpretation of the P-average of the 11 minute binary orbit. The flux drops between 1400 and 4300 A at a rate that is nearly as steep as that of a Rayleigh-Jeans curve. The flux is far too large to come from the neutron star directly but could accord with radiation from a heated accretion disk and/or the heated side of the companion star.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 413; 2; p. L117-L120.
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  • 6
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    First results from the faint object camera - High-resolution observations of the central object R136 in the 30 Doradus nebula (1991)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: R136 is the luminous central object of the giant H II region 30 Doradus in the LMC. The first high-resolution observations of R136 with the Faint Object Camera on board the Hubble Space Telescope are reported. The physical nature of the brightest component R136a has been a matter of some controversy over the last few years. The UV images obtained show that R136a is a very compact star cluster consisting of more than eight stars within 0.7 arcsec diameter. From these high-resolution images a mass upper limit can be derived for the most luminous stars observed in R136.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 378; L21-L23
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  • 7
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    Preliminary analysis of an ultraviolet Hubble Space Telescope faint object camera image of the center of M31 (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A 5161 s exposure was taken with the FOC on the central 44 arcsec of M31, through a filter centered at 1750 A. Much of the light is redleak from visible wavelengths, but nearly half of it is genuine UV. The image shows the same central peak found earlier by Stratoscope, with a somewhat steeper dropoff outside that peak. More than 100 individual objects are seen, some pointlike and some slightly extended. We identify them as post-asymptotic giant branch stars, some of them surrounded by a contribution from their accompanying planetary nebulae. These objects contribute almost a fifth of the total UV light, but fall far short of accounting for all of it. We suggest that the remainder may result from the corresponding evolutionary tracks in a population more metal-rich than solar.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 397; 1; p. L35-L38.
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  • 8
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    Search for ultraviolet emission lines from a hot gaseous halo in the edge-on galaxy NGC 4244 (1986)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Short and long wavelength IUE spectra of the halo region in the edge-on galaxy NGC 4244 are analyzed in order to identify evidence of line emission at the level of 0.000001 ergs per cu cm sr/s. Features are found at 1245 A and 1402 A, having peaks four times greater than the rms intensity fluctuations of nearby spectra. The spectral features are identified with semi-forbidden N V, semi-forbidden S IV at 1240 A, and Si IV and semi-forbidden O IV multiplets at 1400 A, respectively. The appearance of high-peak features and the lack of astrophysically important lines in the sample are evidence of a gas near T = 10 exp 5.2 and emission measure (EM) equal to about 0.000001 pc. However, the case for the existence of such a gas is weakened due to the existence of two other similarly sized features with no identifiable astrophysical origin and the extremely faint nature of the candidate features. The assumed upper limit for the line intensities in NGC 4244 leads to the conclusion that at T less than 100,000 K any emitting gas is either highly clumped or has a p/k value of less than 1000 per cu cm K. It is suggested that if the observed low level features in the short wavelength spectrum are real, the temperature and emission measures allow for a single component gas in the halo of NGC 4244, and are in agreement with those derived by Paresce et al. (1983).
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 154; 1-2
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  • 9
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    Discovery of an optical synchrotron jet in 3C 264 (1993)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: Observations with the Faint Object Camera on board the Hubble Space Telescope have revealed a new optical jet in the core of the elliptical galaxy NGC 3862 (3C 264). Morphologically, this jet is similar to the synchrotron jets seen in other galaxies, as it shows knots and bifurcations. The optical spectral index is also similar to that found in other jets. Thus, the nucleus of NGC 3862 appears to contain the fifth known example of an optical synchrotron jet. Since NGC 3862 is a typical radio-loud elliptical galaxy, it seems likely that many nonthermal jets found in the radio continuum may also have optical counterparts.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 402; 2; p. L37-L40.
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