Recursos de colección

Caltech Authors (160.010 recursos)

Repository of works by Caltech published authors.

Group = Owens Valley Radio Observatory

Mostrando recursos 1 - 8 de 8

  1. Optical EVPA rotations in blazars: testing a stochastic variability model with RoboPol data

    Kiehlmann, S.; Blinov, D.; Pearson, T. J.; Liodakis, I.
    We identify rotations of the polarization angle in a sample of blazars observed for three seasons with the RoboPol instrument. A simplistic stochastic variability model is tested against this sample of rotation events. The model is capable of producing samples of rotations with parameters similar to the observed ones, but fails to reproduce the polarization fraction at the same time. Even though we can neither accept nor conclusively reject the model, we point out various aspects of the observations that are fully consistent with a random walk process.

  2. Optical EVPA rotations in blazars: testing a stochastic variability model with RoboPol data

    Kiehlmann, S.; Blinov, D.; Pearson, T. J.; Liodakis, I.
    We identify rotations of the polarization angle in a sample of blazars observed for three seasons with the RoboPol instrument. A simplistic stochastic variability model is tested against this sample of rotation events. The model is capable of producing samples of rotations with parameters similar to the observed ones, but fails to reproduce the polarization fraction at the same time. Even though we can neither accept nor conclusively reject the model, we point out various aspects of the observations that are fully consistent with a random walk process.

  3. A luminous companion to SGR 1806-20

    van Kerkwijk, M. H.; Kulkarni, S. R.; Matthews, K.; Neugebauer, G.
    We have obtained infrared spectra of the star suggested to be the counterpart of the soft gamma-ray repeater (SGR) 1806-20. We found strong emission lines similar to those seen in the spectra of the rare luminous blue variables and B(e) stars. A He I absorption line is also seen, from which we infer a spectral type O9-B2. This classification, in combination with the minimum distance of greater than or approximately = 6 kpc inferred from its extinction, makes the star one of the most luminous in the Galaxy. We infer that it is a companion to SGR 1806-20 and suggest...

  4. Imaging the Small-Scale Circumstellar Gas Around T Tauri Stars

    Koerner, D. W.; Sargent, A. I.
    We have detected circumstellar molecular gas around a small sample of T Tauri stars through aperture synthesis imaging of CO(2→1) emission at ˜2"-3" resolution. RY Tauri, DL Tauri, DO Tauri, and AS 209 show resolved and elongated gaseous emission. For RY Tau, the deconvolved, half-maximum radius along the direction of elongation, P.A. ˜48°, is 110 AU. Corresponding radii and orientations for the other sources are: DL Tau-250 AU at P.A. ˜84°; DO Tau-350 AU at P.A. ˜160°; AS 209-290 AU at P.A. ˜138°. RY Tau, DL Tau, and AS 209 show velocity gradients parallel to the elongation, suggesting that the...

  5. Aperture Synthesis Maps of CO Emission from M51

    Lo, K. Y.; Berge, G.; Claussen, M.; Heiligman, G.; Keene, J.; Masson, C.; Phillips, T.; Sargent, A.; Scoville, N.; Watson, D.; Woody, D.
    7"-resolution maps of CO emission from the central 2' of M51 have been made with the Owens Valley millimeter-wave interferometer. Relative warm gas from giant molecular clouds is seen largely confined to arms coincident with the dust lanes, forming coherent structure on the scale of ~3 Kpc. There is a minimum of CO emission within 400 pc of the center. Integrated CO intensity maps are presented. Non-circular motion of the CO gas is evident from the velocity field.

  6. The Caltech Millimeter Wave Interferometer

    Masson, C. R.; Berge, G. L.; Claussen, Mark J.; Heiligman, G. M.; Leighton, R. B.; Lo, K. Y.; Moffett, A. T.; Phillips, T. G.; Sargent, Anneila I.; Scott, S. L.; Woody, David P.; Young, A.
    The Caltech Millimeter-Wave Interferometer has recently begun observations at a wavelength of 2.6 mm. We describe the instrument and some of the first results from it.

  7. Methane Abundance Variations toward the Massive Protostar NGC 7538 IRS 9

    Boogert, A. C. A.; Blake, G. A.; Öberg, K.
    Absorption and emission lines originating from the ν_3 C–H stretching manifold of gas-phase CH_4 were discovered in the high-resolution (R = 25,000) infrared L-band spectrum along the line of sight toward NGC 7538 IRS 9. These observations provide a diagnostic of the complex dynamics and chemistry in a massive star-forming region. The line shapes resemble P Cygni profiles with the absorption and emission components shifted by ~7 km s^(-1) with respect to the systemic velocity. Similar velocity components were observed in CO at 4.7 μm, but in contrast to CH_4, the CO shows deep absorption due to a high-velocity outflow...

  8. Molecular abundances in OMC-1: The chemical composition of interstellar molecular clouds and the influence of massive star formation

    Blake, Geoffrey A.; Sutton, E. C.; Masson, C. R.; Phillips, T. G.
    We present here an investigation of the chemical composition of the various regions in the core of the Orion molecular cloud (OMC-1) based on results from the Caltech Owens Valley Radio Observatory (OVRO) millimeter-wave spectral line survey (Sutton et al.; Blake et al.). This survey covered a 55 GHz interval in the 1.3 mm (230 GHz) atmospheric window and contained emission from over 800 resolved spectral features. Of the 29 identified species 14 have a sufficient number of detected transitions to be investigated with an LTE "rotation diagram" technique, in which large numbers of lines are used to estimate both the rotational...

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