%R 1998A&AS..132..155H
%J-171
%A Huensch M., Schmitt J.H.M.M., Voges W.
%T The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars.
%M ds1539
%F 1998.10.13
%B We present X-ray data for all main-sequence and subgiant stars of spectral types A, F, G, and K and luminosity classes IV and V listed in the Bright Star Catalogue that have been detected as X-ray sources in the ROSAT all-sky survey; several stars without luminosity class are also included. The catalogue contains 980 entries yielding an average detection rate of 32 percent. In addition to count rates, source detection parameters, hardness ratios, and X-ray fluxes we also
list X-ray luminosities derived from Hipparcos parallaxes.
%K stars: activity - stars: coronae - stars: late-type - X-rays: stars - catalogs

%R 1998A&AS..132..173L
%J-179
%A Li J.Z., Hu J.Y.
%T Newly discovered candidate weak-line T Tauri stars in the surrounding area of the Taurus-Auriga region.
%M ds1403
%F 1998.10.13
%B We present results of an extensive search for weak-line T Tauri stars (WTTS) in the outskirts of the Taurus-Auriga molecular cloud on the basis of the ROSAT All-Sky Survey Bright Source Catalog. Our surveyed region extends from 2^h^40^m^ to 5^h^40^m^ in right ascension and from 10{deg} to 40{deg} in declination, with the central part of Taurus-Auriga (4^h^<{alpha}< 5^h^, 15{deg}<{delta}< 34{deg}), accomplished by Wichmann et al. (1996A&A...312..439W), excluded. Within a sky coverage of about
10^3^ square degrees, 219 X-ray sources fulfil the criteria for selecting program sources suggested by Neuhaeuser et al. (1995A&A...295L...5N), and 164 of these X-ray sources were found to have at least one optical counterpart with E magnitude brighter than 16. Low-resolution spectroscopic observation has been carried out in order to discard early type stars and galaxies from the sample, additional intermediate-resolution spectra of a sub-sample of 156 late type optical counterparts
were obtained for spectral classification and for the calculation of the equivalent width of H_{alpha}_ emission and LiI line absorption at 6707{AA}. Excluding 2 previously identified WTTS, a total of 75 new candidate WTTS and one possible classical T Tauri star have been discovered in our study. The majority of the newly found Li-rich optical counterparts are believed to be PMS stars rather than ZAMS stars as those of the Pleiades.
%K stars: formation - stars: pre-main sequence - X-ray: stars - surveys

%R 1998A&AS..132..181W
%J-193
%A Wu H., Zou Z.L., Xia X.Y., Deng Z.G.
%T A statistical study of the spectra of very luminous IRAS galaxies. II. Spectral and environmental analysis.
%M ds1477
%F 1998.10.13
%B Spectroscopic observations of a sample of 73 very luminous IRAS galaxies (log(L_IR_/L_{sun}_)>=11.5 for H_0_=50km/s/Mpc, q_0_=0.5) from the 2Jy redshift survey catalogue were carried out using the 2.16 m telescope at the Beijing Astronomical Observatory. The observational data, including the optical images (extracted from Digital Sky Survey) and spectra for these galaxies, are presented in Paper I (Wu et al., 1998A&AS..127..521W). In this paper, we give the spectral and
morphological classifications for these very luminous IRAS galaxies (VLIRGs). We show that about 60% of VLIRGs exhibit AGN-like spectra (Seyfert 1s, Seyfert 2s, LINER-like galaxies). This fraction goes up to 82% for the ultraluminous IRAS galaxies (ULIRGs) subsample (Log(L_IR_/L_{sun}_)>=12.0). 56% of the VLIRGs show strong interaction or merging signatures; this fraction rises to 91% for the ULIRGs. These statistical results strongly suggest that interaction triggers
nuclear activities and enhances the infrared luminosity. We find that LINER and a mixture type which have optical properties of both HII galaxies and LINERs could be at the transition stage from infrared luminous HII galaxies to AGNs; their main energy production is from starbursts as well as AGNs.
Both infrared luminosities and H{alpha} equivalent widths increase dramatically as nuclear separations between VLIRGs and their nearest neighbors decrease. There is little doubt that strong starbursts happen in the nuclei of VLIRGs. Assuming class 0 as advanced merger, we construct a simple merger sequence, from morphological classes 1 to 4 (with near or far companions), to class 5 and 6 (interacting pairs and mergers) and then to class 0 (isolated galaxies). Along this
sequence, VLIRGs evolve from HII galaxies to AGNs.
%K infrared: galaxies - galaxies: active; starburst; interaction

%R 1998A&AS..132..195N
%J-196
%A Noeel F.
%T Observations of the Sun with the astrolabe of Santiago: 1995-1997.
%M ds7557
%F 1998.10.13
%B Observations of the Sun with a modified Danjon astrolabe at 30{deg} and 60{deg} zenith distances are beeing carried out since 1990 at Santiago, Chile. Here are presented the results in right ascension, parameter Y and apparent semidiameter obtained during the period 1995-1997. These results and those obtained in former years are available in electronic form. The differences astrolabe minus ephemeris in {alpha} and semidiameter are briefly discussed.
%K astrometry - Sun: general

%R 1998A&AS..132..197K
%J-210
%A Kotilainen J.K.
%T Optical colour maps of Seyfert galaxies. II. More Seyfert 2s.
%M ds1525
%F 1998.10.13
%B We present optical broad band B-I colour maps of a further sample of 10 Seyfert 2 galaxies. In these bands, the contribution from emission lines to the total flux is small, and hence the images predominantly trace the continuum distribution. As in our earlier colour maps of a sample of Seyferts type 1 and 2, we detect extended blue continuum components in the circumnuclear region of several galaxies. These components are either elongated (in Mkn 533, Mkn 607, Mkn 1066, NGC
5347, NGC 5953 and NGC 7319) or form a double structure across the nucleus (in NGC 5929). They are closely aligned with the radio and emission line axes of these galaxies and probably arise from scattering of nuclear continuum light by extranuclear mirrors. Similar blue elongations (in Mkn 1 and NGC 7212) and double structures (in NGC 788) are less well aligned with the radio and line emission, and their relationship with scattering regions must be considered uncertain. The
colours of the blue maxima are consistent with those expected from scattering off dust or electrons, a conclusion strengthened by the combined sample of the two papers in this series. Our findings thus strongly support the current unified models of AGN.
%K galaxies: active - galaxies: nuclei - galaxies: seyfert - galaxies: stellar content - galaxies: structure

%R 1998A&AS..132..211H
%J-231
%A Harju J., Lehtinen K., Booth R.S., Zinchenko I.
%T A survey of SiO emission towards interstellar masers. I. SiO line characteristics.
%M h0592
%F 1998.10.13
%B We have conducted a survey of SiO emission towards galactic H_2_O and OH masers and ultracompact HII regions using the 15-m SEST and the 20-m Onsala telescope. With the SEST the transitions (v=0,J=2-1) and (v=0,J=3-2) of SiO at 3 and 2mm were measured simultaneously. With Onsala only the (v=0,J=2-1) line was accessible. Altogether 369 objects were observed and SiO was detected towards 137 of them. The detection rate is highest towards the most intense H_2_O masers, which
probably require powerful shocks to be excited. The SiO detection rate correlates also with the integrated far-infrared flux density and the FIR luminosity of the associated IRAS point source, indicating that the occurrence of shocks is related to the amount of radiation from the central stellar source(s). For flux and luminosity limited samples the SiO detection rate is higher in the inner 7kpc from the galactic centre than elsewhere. This suggests that dense cores
belonging to the so called ``molecular ring" provide particularly favourable conditions for the production of gaseous SiO. The full widths above 2{sigma} of the SiO(J=2-1) lines, which are likely to be related to the associated shock velocities, range from 2 to 60km/s except for the line in Ori KL which has a full width of about 100km/s. The median of our sample is 19km/s. The SiO lines are single-peaked and the peak velocities are always close to the ambient
cloud velocity as determined from published CS observations. These line characteristics are compared with the predictions of kinematical bow-shock models. The SiO line shapes correspond with the model of Raga & Cabrit (1993A&A...278..267R) where the emission arises from turbulent wakes behind bow-shocks. However, the number of symmetric, relatively narrow profiles indicates that at least in some of the observed sources SiO emission arises also from the quiescent gas component. We suggest
that this is due to evaporation of silicon compounds from grain mantles and their reprocessing to SiO in dense quiescent gas according to the model of McKay (1995MNRAS.274..694M, 1996MNRAS.278...62M). These reactions may be initiated and sustained by ionizing radiation from shocks, in the same way as the enhancement of HCO^+^ near Herbig-Haro objects has been explained in the model of Wolfire & Koenigl (1993ApJ...415..204W). The excitation temperatures of SiO(J=2-1) and (J=3-2) transitions were determined towards
three strong sources using measurements in isotopically substituted SiO. In all three sources the transitions are clearly subthermally excited, implying moderate densities (<3x10^6^cm^-3^) in the SiO emission regions.
%K stars: formation - ISM: clouds - ISM: jets and outflows - ISM: molecules - radio lines: interstellar

%R 1998A&AS..132..233X
%J-236
%A Xu Jiayan , Li D., Liu J., Chen H., Zhang Z., Raschotin S.I., Emeliyanov V.A., Kaplenko V.V., Zalutsky V.T.
%T Continuous declination system set up by observations of photoelectric astrolabe Mark I In Irkutsk. The first results of international cooperation between CSAO and VS NIIFTRI.
%M ds6693
%F 1998.10.13
%B The Photoelectric Astrolabe Mark I (PHA I) has been revised with a new combined prism which could work as an almucantar with zenith distance of 45{deg}, to measure continuous declinations at the latitude of Irkutsk, Russia ({phi}= 52.2deg). The PHA I has been working at the astronomical base of VS NIIFTRI in Irkutsk since Nov. 1995 based on an international cooperation agreement of near 4 years for star catalogue and EOP measurements. The first observing program was ended in
June 1997, giving corrections in both right ascension and declination to 200 stars with no blind zone in declination determination, which most astrolabe catalogues in the world usually would have.
%K astrolabe - star catalogue

%R 1998A&AS..132..237A
%J-252
%A Alzner A.
%T Measurements of double stars 1993.67 - 1998.13.
%M ds1549
%F 1998.10.13
%B 624 Micrometer Measurements of 224 pairs with a 32.5 cm Cassegrain, 719 Measurements of 310 double stars with a 360 mm Newtonian are given.
%K astrometry - stars: binaries: visual

%R 1998A&AS..132..253A
%J-254
%A Alzner A.
%T Orbital elements of 9 visual double stars.
%M ds1571
%F 1998.10.13
%B Orbital elements and ephemerides for 9 visual double stars are given.
%K binaries: visual - astrometry

%R 1998A&AS..132..255G
%J-260
%A Golev V., Prugniel P.
%T A catalogue of Mg_2_ indices of galaxies and globular clusters.
%M ds1545
%F 1998.10.13
%B We present a catalogue of published absorption-line Mg_2_ indices of galaxies and globular clusters. The catalogue is maintained up-to-date in the HYPERCAT database. The measurements are listed together with the references to the articles where the data were published. A coded description of the observations is provided. The catalogue gathers 3541 measurements for 1491 objects (galaxies or globular clusters) from 55 datasets. Compiled raw data for 1060 galaxies are
zero-point corrected and transformed to a homogeneous system.
%K galaxies: galaxies: general - galaxies: star clusters - galaxies: stellar content

%R 1998A&AS..132..261L
%J-273
%A Lobanov A.P.
%T Spectral distributions in compact radio sources. I. Imaging with VLBI data.
%M ds7109
%F 1998.10.13
%B We discuss a technique for mapping the synchrotron turnover frequency distribution using nearly simultaneous, multi-frequency VLBI observations. The limitations of the technique arising from limited spatial sampling and frequency coverage are investigated. The errors caused by uneven spatial sampling of typical multi-frequency VLBA datasets are estimated through numerical simulations, and are shown to be of the order of 10%, for pixels with the deconvolution SNR ~7. The
fitted spectral parameters are corrected for the errors due to limited frequency coverage of VLBI data. First results from mapping the turnover frequency distribution in \object{3C 345} are presented.
%K methods: data analysis - methods: observational - quasars: individual: \object{3C 345} - techniques: interferometric

%R 1998A&AS..132..275A
%J-279
%A Abad C., Vieira K., Zambrano A.
%T Reduction of the Astrographic Catalogue, zone of S. Fernando.
%M ds1559
%F 1998.10.13
%B The San Fernando Zone of the Astrographic Catalogue is reduced to the HIPPARCOS system in order to test a reduction model previously presented by Abad (1993A&AS...98....1A). A new method for the determination of field distortion and magnitude or color dependent systematic errors on photographic plates is discussed.
%K astrometry - catalogs

%R 1998A&AS..132..281B
%J-289
%A Brandi E., Barba R., Garcia L.G., Beltran N.
%T A spectrographic study of the symbiotic system Hen 1761.
%M ds7041
%F 1998.10.13
%B This work presents the results of a spectroscopic study in the optical and near infrared region of the symbiotic star Hen 1761. Relative fluxes and radial velocities of emission and absorption lines are obtained on the basis of low, intermediate and high resolution spectra. Our observations show that this scarcely studied object underwent very important spectroscopic variations in the interval 1990-1995. The observed variations are quite similar to those of symbiotic stars
where accretion events on a hot dwarf are responsible for an eruptive behavior. Some of the physical parameters of the system are derived.
%K stars: emission-lines - symbiotic stars - stars: variable stars - stars: individual: \objS{Hen 3-1761}{Hen 1761}

%R 1998A&AS..132..291P
%J-299
%A Piana M., Brown J.C.
%T Optimal inversion of hard X-ray bremsstrahlung spectra. I. SVD analysis.
%M ds7537
%F 1998.10.13
%B The instability properties of bremsstrahlung spectrum inversion to yield source electron spectra in flares are examined in terms of singular value decomposition (SVD) for the cases of thin- and thick-target models for different bremsstrahlung cross-sections. It is shown that, for the Kramers and Bethe-Heitler cross-sections, analytic expressions can be obtained for evaluation of the Gram matrix. These allow quantitative comparison of the instability of inversion for each
case and hence assessment of the accuracy and resolution of the electron source function recovery. Based on this analysis we find that: (a) the solution instability is worse for the Bethe-Heitler than for the Kramers approximation; care must therefore be taken in real data analysis to use the most accurate possible cross-section to avoid over- or under-estimating the maximum precision and resolution achievable in the recovered electron spectrum; (b) instability is worse in
recovering thick-target injection spectra than thin-target mean source spectra, as expected because of the double deconvolution involved in the former; (c) such SVD analysis should form an important part of future analysis of high resolution flare data such as from the HESSI Mission.
%K X-rays: general - methods: analytical; data analysis

%R 1998A&AS..132..301Q
%J-304
%A Qin Y.-P., Xie G.Z., Zheng X.-T., Wu S.-M.
%T A statistical method for testing assumed distributions of sources.
%M ds7271
%F 1998.10.13
%B For a known distribution of sources, the variance of the distribution function of samples can be obtained by applying mathematical statistics. A statistical method, called the 1{sigma} distribution function deviation test, is defined and introduced to test this kind of distributions. We find that, when random variables vary continuously, a sample passing the test also passes any other statistical test which depends on the deviation of a statistic from its expected value at
the 1{sigma} confidence level. In particular, the sample passes the Kolmogorov-Smirnov test at the same confidence level. This new method is suitable for testing the distribution of gamma-ray bursts as well as the luminosity function of quasars. An example of application of the new test is also presented in this paper.
%K galaxies: luminosity function, mass function - galaxies: statistic - methods: statistical