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  • 1
    Publication Date: 2019-06-28
    Description: The galaxy responsible for causing multiple gravitational lens images of QSO Q0957+561 has been reobserved spectroscopically and a more accurate redshift of 0.36 was obtained. In addition, detailed models of the gravitational lens effect were computed. These models, which can explain all optical and radio data for the system, predict delays of up to five years between variations in the A and B images (with A preceding B). It is suggested that the third image is rather faint and located close to the center of the lens galaxy; it is possible that this third image contributes to the observed galaxy core. The possibility that this system can be used to measure the Hubble constant is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 2
    Publication Date: 2019-06-28
    Description: Deep CCD pictures show a rich cluster of galaxies around the double quasar Q0957 + 561 as well as faint extended wings on the image of the southern quasar. Calculations of gravitational imaging by King model mass distributions show that the cluster and the brightest galaxy together, acting as a gravitational lens on the light from a single, more distant QSO, can easily reproduce all of the present observations. It is concluded that the double quasar is almost certainly the multiple image of a single object produced by a gravitational lens.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 3
    Publication Date: 2019-06-27
    Description: Results are presented for broadband three-color (BVR) photometric observations of the peculiar elliptical radio galaxy M87, which were obtained with digital two-dimensional SIT and CCD detector systems on the Palomar 60-in. and 200-in. telescopes. The observations and the reduction procedures for the digital data are outlined, the luminosity profile of M87 is given, and a nuclear luminosity spike is found to be centered within 0.02 arcsec of the center of M87. Attempts are made to fit various theoretical models to the luminosity profile, and a satisfactory fit is obtained between the observed profile and a model involving a massive black hole in the galactic nucleus. A model-independent dynamical analysis of the central regions is performed which indicates that the nucleus of M87 contains a supermassive object of about 5 billion solar masses with a radius of no more than 100 pc and an M/L ratio of at least 60. The possible nature of this object is considered, and it is concluded that M87 is probably the most plausible candidate for a massive black hole in a galactic nucleus.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 221
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