C~(18)O Observations of the Dark Molecular Cloud L134 and Gas Depletion onto Dust

We map the dark molecular cloud core of L134 in the C18O (J = 1 - 0) emission line using the PMO 13.7m telescope, and present a contour map of integrated intensity of C18O (J = 1 - 0) emission. The C18O cloud is inside the distribution of extinction AB, the visual extinction of blue light, as well as inside the 13CO cloud in the L134 region. The depletion factors in this C18O cloud are generally greater than unity, which means there is gas depletion onto dust. Since only a minimum AB = 9.7 mag is available, and our observations measure both undepleted and depleted regions along the line of sight, the depletion factors could very likely be larger in the central core than the calculated value. So we conclude that depletion does occur in the bulk of the C18O cloud through a comparison between the C18O and blue extinction maps in the L134 region. There is no direct evidence as yet for star formation in L134, and so cores on the verge of collapse will not be visible in CO and other gas molecules.     

Rényi Thermodynamics as a Mandatory Basis to Model the Evolution of a Protoplanetary Gas−Dust Disk with a Fractal Structure

Solar System Research - For the purpose of mathematical simulations of the formation processes for planetesimals in the Solar protoplanetary disk, statistical thermodynamics for nonextensive...     

Relations between the IR—UV—X—ray Continuum and Emission Lines for a Large Compostie Sample of Narrow Line and Normal Seyfert 1 Galaxies

We report on our research on the UV, optical line parameters and the infrared through UV to soft X-ray continuum parameters for a composite sample of narrow line and normal Seyfert 1 galaxies. The strong correlations among the line width of Hβ，optical line strength of Fe Ⅱ and the soft X-ray slope are confirmed. We found no correlations between the UV line parameters, the equivalent widths of Lyα and CIV and their ratio on one hand and the optical line parameters on the other. The UV and X-ray luminosities strongly correlate with the line widths of Hβ and the Fe Ⅱ/Hβ ratio. No significant correlation is found between the infrared-soft X-ray continuum slope αix and the line width of Hβ。     

Column densities of Interstellar Gas in the direction of the starε Ori (B0 IA)

We have investigated the star Ori with IUE high resolution SWP spectrum in order to derive curve of growth and column densities of Al II, Si II, S II, Fe II, Ni II and Zn II. It has been possible to fit these ions on one empirical curve of growth with a velocity parameterb = 11 km s^–1 for the star studied.Based on observations made by the International Ultraviolet Explorer (IUE), and collected at the Villafranca Satellite Tracking Station of the European Space Agency.     

Some Features of Comet Hale–Bopp (According to the Observations of 1995–1998)

Solar System Research - “The Great Comet of 1997” was a significant event in cometary physics. Numerous interesting scientific studies are devoted to this comet. Unfortunately, in the...     

HD 45583—a chemically peculiar star with an unusual curve of longitudinal magnetic field variations

The results of a complex study of the chemically peculiar star HD 45583 are reported. Observations were made using the Main Stellar Spectrograph equipped with a circular polarization analyzer and NES echelle spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. Our measurements of Zeeman spectra show that the star exhibits unusual variations of the longitudinal component of magnetic field with a secondary minimum. The period of spectral and magnetic variability coincides with the rotation period, which is equal to 1.^d177000. Two possible causes of the secondary minimum are discussed: spots with higher than ambient content of some chemical elements on the star’s surface or complex structure of the stellar magnetic field. The parameters of the star’s atmosphere are determined (T _eff = 13000 K, log g = 4.0), as well as the abundances of some elements: the star shows a 1–2 dex overabundance of Fe, Si, and Cr, helium is underabundant by about 2 dex with respect to the Sun.     

Particle Acceleration and High-Frequency (X-ray and γ-ray) Emission in the Jets of Active Galactic Nuclei

It is suggested that the outflowing plasma in the jets of active galactic nuclei (AGNs) is inhomogeneous and consists of separate clouds. These clouds are strongly magnetized and move away from the central engine at relativistic speeds. The clouds interact with an ambient medium which is assumed to be at rest. In the process of this interaction, particles of the ambient medium are accelerated to high energies at the cloud front and flow ahead of the front. It is shown that the radiation of the accelerated particles may be responsible for the X-ray and γ-ray emission from AGN jets. TeV γ-ray emission is generated in the inner parts of AGN jets where the Lorentz factor of the cloud fronts is Γ0≥ 30, while GeV γ-ray emission emanates from the outer parts of AGN jets where Γ0 is ∼ 10. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigation of Long-Period Oscillations of Sunspots with Ground-Based (Pulkovo) and SOHO/MDI Data

We applied special data-processing algorithms to the study of long-period oscillations of the magnetic-field strength and the line-of-sight velocity in sunspots. The oscillations were investigated with two independent groups of data. First, we used an eight-hour-long series of solar spectrograms, obtained with the solar telescope at the Pulkovo Observatory. We simultaneously measured Doppler shifts of six spectral lines, formed at different heights in the atmosphere. Second, we had a long time series of full-disk magnetograms (10 – 34 hour) from SOHO/MDI for the line-of-sight magnetic-field component. Both ground- and space-based observations revealed long-period modes of oscillations (40 – 45, 60 – 80, and 160 – 180 minutes) in the power spectrum of the sunspots and surrounding magnetic structures. With the SOHO/MDI data, one can study the longer periodicities. We obtained two new significant periods (> 3σ) in the power spectra of sunspots: around 250 and 480 minutes. The power of the oscillations in the lower frequencies is always higher than in the higher ones. The amplitude of the long-period magnetic-field modes shows magnitudes of about 200 – 250 G. The amplitude of the line-of-sight velocity periodicities is about 60 – 110 m s⁻¹. The absence of low-frequency oscillations in the telluric line proves their solar nature. Moreover, the absence of low-frequency oscillations of the line-of-sight velocity in the quiet photosphere (free of magnetic elements) proves their direct connection to magnetic structures. Long-period modes of oscillation observed in magnetic elements surrounding the sunspot are spread over the meso-granulation scales (10″ – 12″), while the sunspot itself oscillates as a whole. The amplitude of the long-period mode of the line-of-sight velocity in a sunspot decreases rapidly with height: these oscillations are clearly visible in the spectral lines originating at heights of approximately 200 km and fade away in lines originating at 500 km. We found a new interesting property: the low-frequency oscillations of a sunspot are strongly reduced when there is a steady temporal trend (strengthening or weakening) of the sunspot’s magnetic field. Another important result is that the frequency of long-period oscillations evidently depends on the sunspot’s magnetic-field strength.     

A moment method for radiative transfer in an anisotropically-scattering slab medium with space-dependent albedoω(x)

The moment method is used to solve the radiative transfer problem in an anisotropic scattering plane medium with arbitrary space-dependent albedo(x). The results are compared with those obtained recently by Cengel and Özisik.     

The properties of molecular clouds with high redshifts (z=2–3)

This paper deals with molecular clouds discovered in the absorption spectra (z=2–3) of distant quasars. It is argued that these clouds belong to the gaseous subsystems of young galaxies. We estimate the gas concentration to ben<10⁴ cm^–3 in the cloud observed in the direction of the quasar PHL957. It is shown that this cloud is exposed to ultraviolet radiation. The UV-energy flux does not exceed the value typical for our Galaxy by an order of magnitude (F2×10^–6 ergs cm^–2 s^–1 Å^–1 at =2000 Å). The mechanisms maintaining the thermal balance in this cloud are discussed.     

A Low-Frequency (30 – 110 MHz) Antenna System for Observations of Polarized Radio Emission from the Solar Corona

An interferometer antenna system to observe polarized radio emission from the solar corona at different frequencies in the range 30?–?110 MHz has been commissioned recently by the Indian Institute of Astrophysics at the Gauribidanur Radio Observatory (latitude 13°36^′12^′′N and longitude 77°27^′07^′′E), about 100 km north of Bangalore (http://www.iiap.res.in/centres_radio.htm). This paper describes the antenna system, associated analog/digital receiver setup, calibration scheme, and preliminary results.     

Chandra archival study of (U)LIRGs with a double nucleus:binary AGNs?

We present our initial results from a study of 14(U)LIRGs with a doublenucleus(z <0.15)and an AGN signature in the Chandra archive.The goals of our study are to search for more possible cases of binary AGNs and to investigate the X-ray properties and energy sources of these energetic objects,a major effort devoted specifically to searching for binary AGNs from(U)LIRGs.Our studies suggest that Mrk 266 might be a new candidate in hosting binary AGNs supported by X-ray observations.Our analysis shows that most(U)LIRGs are essentially weak X-ray sources and are not dominated by AGNs,due to both the lack of Fe K line detections and weak emission in the hard X-ray band.We find evidence for thermal emission with temperature kT～0.7 keV in seven nuclear regions,and this component is possibly associated with the nuclear or circumnuclear starburst.The soft and hard X-ray to far-infrared ratios also suggest that most(U)LIRGs are not energetically dominated by AGNs.Therefore,this study only provides one additional candidate of binary AGNs.We cannot rule out the existence of low luminosity AGNs and thus binary AGNs in all of them,particulaxly,those highly obscured and spatially unresolved systems.Nine of 14(U)LIRGs,including three previously known binary AGNs and a new candidate Mrk 266,clearly have obvious X-ray counterparts to their double optical/near-IR nuclei,whereas only two out of 14 have one obvious X-ray counterpart detected.Additionally,Arp 220 and Mrk 273 are not spatially resolved owing to their small nuclear separations(～1"),and no significant X-ray detection in the most distant source.     

The Lyman-alpha Solar Telescope(LST) for the ASO-S mission——Ⅱ. design of LST

As one of the three payloads for the Advanced Space-based Solar Observatory(ASO-S) mission,the Lyman-alpha(Lyα) Solar Telescope(LST) is composed of three instruments: a Solar Corona Imager(SCI), a Lyα Solar Disk Imager(SDI) and a full-disk White-light Solar Telescope(WST). When working in-orbit, LST will simultaneously perform high-resolution imaging observations of all regions from the solar disk to the inner corona up to 2.5 R_⊙(R_⊙ stands for the mean solar radius) with a spatial resolution of 4.8′′and 1.2′′for coronal and disk observations, respectively, and a temporal resolution of 30 – 120 s and 1 – 120 s for coronal and disk observations, respectively. The maximum exposure time can be up to20 s due to precise pointing and image stabilization function. Among the three telescopes of LST, SCI is a dual-waveband coronagraph simultaneously and independently observing the inner corona in the HI Lyα(121.6±10 nm) line and white light(WL)(700±40 nm) wavebands by using a narrowband Lyα beam splitter and has a field of view(FOV) from 1.1 to 2.5 R_⊙. The stray-light suppression level can attain10~(-6) B_⊙(B_⊙ is the mean brightness of the solar disk) at 1.1 R_⊙ and ≤5×10~(-8) B_⊙ at 2.5 R_⊙. SDI and WST are solar disk imagers working in the Lyα line and 360.0 nm wavebands, respectively, which adopt an off-axis two-mirror reflective structure with an FOV up to 1.2 R_⊙, covering the inner coronal edge area and relating to coronal imaging. We present the up-to-date design for the LST payload.     

Properties of the Main Phases of the Super Geomagnetic Storms(ΔSYM-H ≤-250 nT) with Different Heliolongitudes

We studied the properties of the main phases of 24 super geomagnetic storms(SGSs)(ΔSYM-H ≤-250 nT)since 1981. We divided the SGSs into two subgroups: SGSs-Ⅰ(-400 nT <Δ SYM-H ≤-250 nT) and SGSs-Ⅱ(ΔSYM-H ≤-400 nT). Of the 24 SGSs, 16 are SGSs-Ⅰ and eight are SGSs-Ⅱ. The source locations of SGSs were distributed in the longitudinal scope of [E37, W66]. 95.8% of the SGSs were distributed in the longitudinal scope of [E37, W20]. East and west hemispheres of the Sun had 14 and 10 SGSs, respectively...     

Imaging of an unknown sector of Mercury (260–350°W) at the Special Astrophysical Observatory of the Russian Academy of Sciences using the short-exposure method

A series of observations of Mercury were performed at the Special Astrophysical Observatory using the short-exposure method to image a hitherto unknown part of the Hermean surface. Several thousand electronic frames of the planet were taken during its morning elongation in the period from November 20–24, 2006. The phase angle of Mercury varied from 103° to 80°, and the interval of planetocentric longitudes observed spanned from 260 to 350°W. Observations were made with a CCD camera attached to the 1-m Zeiss-1000 Ritchey-Chretien telescope operating with a KS-19 filter (short-wavelength border at 700 nm). The Hermean surface is known to be almost impossible to resolve on ordinary images. A reduction of a large number of frames taken with millisecond-long exposures made it possible to obtain a rather sharp image of the observed part of the Hermean surface. One of the primary aims of new observations was to have a general outline of the basin earlier found by one of the authors (L. Ksanfomaliti). We are the first to image this giant feature. The size of its inner part exceeds that of the largest lunar Mare — Mare Imbrium, however, unlike the latter the studied basin is of impact origin. The synthesized images reveal a number of large impact craters of various ages, as well as smaller features. The highest resolution achieved corresponds to the diffraction limit for the instrument employed, or about 100 km on the Hermean surface.     

Frequency domain light curve analysis of partially eclipsing binary systems: With an application to β Persei (Algol)

Kopal's new iterative method for analysing partially eclipsing binary light curves in the frequency domain has been put into a form suitable for applications, and explicit forms for basic expressions developed. To facilitate the computations in practice, the required newS _m -functions, which are expressed in terms ofJ _, ⁰ -integrals, have been extensively tabulated by making use of hypergeometric series. The automated method has been tested successfully on the light curves of Persei (Algol). Short information on the system and the revised sets of elements including a new determination of the limb-darkening coefficient in the ultraviolet have been presented.