Kinematic parameters of the galactic spiral pattern from data on open star clusters and OB stars     

M. É. Popova  A. V. Loktin 《Astronomy Letters》2005,31(10):663-667

Data on the positions, radial velocities, and proper motions of open star clusters and OB stars are used to obtain the rotation curve of the Galaxy fitted by a polynomial in inverse powers of the distances from the Galactic rotation axis. We determine the locations of the corotation region and the inner and outer Lindblad resonances using a previously estimated pattern speed. Based on data for objects of the Carina-Sagittarius and Orion arms, we have determined the distortion amplitudes of the velocity field of the Galactic disk, ?_R = ?3.97±4.79 km s^?1 and f_θ=+13.27±2.57 km s^?1.  相似文献   

Very high energy γ-rays from galactic sources     

P. R. Vishwanath 《Journal of Astrophysics and Astronomy》2002,23(1-2):45-51

The field of Very High Energy (VHE) gamma ray astronomy using the Atmospheric Cerenkov Technique has entered an interesting phase with detection of various galactic and extragalactic sources. Among galactic sources, only the Crab nebula has been established as a standard candle. Most observations on pulsars are in agreement as to the necessity for the GeV spectra to steepen at < 200 GeV. While the Imaging method for increase of sensitivity has been successful with many results, an alternate technique —Wavefront Sampling Technique- is also being used by an increasing number of experiments. The recently commissioned experiment at Pachmarhi (PACT) in India is presented as an example of this technique. Preliminary results from this experiment show detection of VHE γ-ray emission from (a) the Crab nebula at a high significance and (b) Crab and Geminga pulsars at > 1.5 TeV which could be the second component of the Outer Gap pulsar models.  相似文献   

Hidden broad line regions and anisotropy in AGN     

David J. Axon  J. H. Hough  S. Young  M. Inglis 《Astrophysics and Space Science》1994,216(1-2):379-398

We discuss the recent advances made in the search for hidden broad line regions in Seyfert and Narrow Line Radio Galaxies (NLRG) using both spectropolarimetry and infrared spectroscopy/spectropolarimetry. Two important results which support the Grand Unification Theory are presented. In the first of these we report that the famous Seyfert 1 NGC 4151 has a scattered component to its broad line region, and is most likely an object where we view obliquely into its occulting torus. In the second, we show high signal to noise observations of scattered broad lines in the NLRG of 3C 234.  相似文献   

Upper-ocean hydrography of the Nordic Seas during the International Polar Year (2007–2008) as observed by instrumented seals and Argo floats     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Following indications of recent warming trends in the Nordic Seas, we have studied the hydrography of these marginal seas from the summer of 2007 until the fall of 2008, using observations gathered by instrumented seals and Argo floats. The combined dataset shows that the upper ocean was indeed both warmer and saltier over much of the Nordic Seas in 2007–2008 compared to the average ocean state for the period 1956–2006 (based on the World Ocean Atlas 2009). There are also indications that the surface Polar Waters of the East Greenland Current were colder and fresher than the climatology, though the quality of the climatology is questionable for this region given the low number of historical observations. Dynamic height calculations suggest that the observed hydrographic changes were associated with enhanced northward upper-ocean thermal wind transport in the east and possibly also enhanced southward transport in the west.  相似文献   

Extragalactic cosmic rays and their signatures     

《Astroparticle Physics》2014

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On the Sun’s distance from the center and the shape of the inner halo in the Galaxy: Gaia EDR3, HST and literature globular clusters     

《New Astronomy》2022

A statistical method is used to derive both the Sun’s distance $r_0$ from the Galactic Center (GC) and the 3D geometry of the inner ($<$ 25 kpc) halo. The spatial distribution of the 138 Gaia EDR3 globular clusters (GCs) with distances established on a combination of HST and literature data of Baumgardt and Vasiliev (2021) is explored. An estimate by using these ancient objects of the pressure-supported subsystem of the Galaxy with newly derived distances leads to the mean $r_0=7.81\pm 0.14$ kpc. The distribution of GCs within 25 kpc is almost spherically symmetric, and has the shape of an ellipsoid with a major axis of its symmetry slightly elongated toward the Sun and two minor axes of almost the same length. The obtained scale-length ratio of the major axis to the minor axis in the plane and to the vertical axis of the ellipsoid is $\approx$ 1:0.8:0.7. Based on the papers of a series, for practical use we argue to employ the following Sun’s distances from the GC and the plane: $r_0=8.15\pm 0.15$ kpc and $z_0=15\pm 5$ pc.  相似文献