Blaue Objekte in der Umgebung von M31 II. Häufigkeitsverteilung und Statistik

This paper presents a statistical investigation of 999 blue objects [U(–B) 0.00, limiting magnitude U = 20, B = 21], the majority of which is newly discovered on M31-plates (predominantly taken by F. Börngen ) of the large Schmidt telescope of the Karl Schwarzschild Observatory Tautenburg. A list of the objects is given elsewhere [G. A. RICHTER (1973)].For “very blue objects” [(U – B) -0.40] the number per square degree brighter than magnitude B is as follows: log N_B = 0.72 B -13.1 (starlike objects), log N_B = 0.63 B -12.0 (diffuse and probably diffuse objects). This confirms the results of other authors: log N_B increases more rapidly than in the case of constant density (0.6); there are about 10 QSOs brighter than B = 20 per square degree. A detailed discussion concerning the optical identification of discrete radio sources will soon be given.     

The Edinburgh-Cape blue object survey

The Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B 18 in the southern sky. It is covering an area of sky of 10,000 square degrees with |b| > 30° and < 0°. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric accuracy, the spectroscopic classification, and the completeness of the survey.     

Schmidt plate survey in the galactic centre direction. 1. Investigation of open clusters in the Sagittarius-Carina spiral arm

A study of four open clusters on Tautenburg Schmidt plates in the direction to the Galactic Centre (l = 17.0°, b = +0.8°) is presented. In a field of 8.95 square degrees proper motions and B, V magnitudes were determined for about 36 500 stars up to the limiting magnitudes B = 17^m.9, V = 16^m.8. For stars brighter than B = 16^m an accuracy of about 3 mas/year has been estimated for proper motions. The rms errors of stellar magnitudes and (B—V) colours is about 0.1 mag. There are two open clusters already known in this sky area: Trumpler 32 (C 1814-133) and NGC 6611 (C 1816-138). By the inspection of the plates two additional anonymous clusters were identified near the double star ADS 11285 or BD −14°5014 (C 1819-146) and near the star BD −14°5016 (C 1820-146). The cluster membership determination was carried out using information on spatial and proper motion distributions of stars in the field. The colour-magnitude diagrams up to the limiting stellar magnitude were constructed. For each cluster interstellar extinction A_V, diameters of the core and corona, ages and spatial velocity components (V, W) relative to the LSR in the Y, Z-galactic directions were derived. The distances to the clusters were obtained to 1720 pc, 2260 pc, 2130 pc and 2130 pc for Trumpler 32, NGC 6611, C 1819-146 and C 1820-146, respectively. All clusters are situated in the Sagittarius-Carina spiral arm. Their spatial location confirms the assumption that galactic spiral arms are close to logarithmic spirals with a characteristic angle of about 20 degrees.     

Search for Optical Identifications in the 5C1 Radio Survey

Identifications of 5CI radio sources with optical objects are given. The identification rates amount to 44 and 30 per cent up to the limiting magnitude of about 21^m in R and B, respectively. The objects are to about equal parts galaxies, blue starlike objects, and “unclassified objects” (presumably mostly faint galaxies and less pronounced blue objects). For every proposed identification a reliability and for the identification samples the reliability and the completeness are given. Some inaccuracies in the use of a statistical method, proposed in a previous paper, have been removed; two additional means of statistical treatment have been applied to discuss the data.     

Search and Photographic Photometry of Ultraviolet Excess Objects in the Region of the 5C1 Radio Survey

A sample of ultraviolet excess objects in a 12.56 square degree field near α = 9^h40^m, δ = +50° (5C1-radio survey) is presented. In addition to starlike or and nearly starlike objects a sample of more diffuse ones is listed, presumably containing many Markarjan-type galaxies. UBV-photometry and first spectroscopic results are communicated; the number magnitude relation and the projected number-density of the objects are shortly discussed.     

Total-to-selective extinction ratio in nearby and distant objects

In an area of nearly 23.1 square degrees centered at α(1950) = 23^h57^m and δ(1950) = + 59δ48' magnitudes, colors, and spectral classes were determined for 1419 stars brighter than m_pg = 13^m.00. Star counts were made in this area for all objects brighter than m_pg = m_pv = 15^m.5. Altogether 50585 stars were included in the pv counts. The original photographic data have been transformed to the B, V system. From star counts the ratio of total-to-selective extinction was derived to be R ≉ 4.0 ± 0.2. It depends on the distance to the stars under consideration as well as on the surface density of the objects inside the considered region. In einem Gebiet von annähernd 23.1 Quadratgrad mit den Mittelpunktskoordinaten α(1950) = 23^h57^m und δ(1950) = 59°48' werden für 1419 Sterne heller als m_pg = 13^m.00 Helligkeiten, Farben und Spektraltypen bestimmt. Sternzählungen in Helligkeitsintervallen m_pg und m_pv wurden für alle Objekte heller als m_pg = m_pv = 15^m.5 durchgeführt. Für diese 50585 Sterne wurden die gemessenen photographischen und photovisuellen Helligkeiten in das B, V-System transformiert. Im Ergebnis dieser Sternzählungen wurde ein Wert von R ≉ 4.0 ± 0.2 abgeleitet. Er hängt sowohl von der Entfernung der betrachteten Objektgruppen als auch von der Flächendichte der Sterne innerhalb der Region ab.     

Voyager photometry of Rhea,Dione, Tethys,Enceladus and Mimas

Voyager imaging observations provide new photometric data on Saturn's satellites at large phase angles (up to 133° in the case of Mimas) not observable from Earth. Significant new results include the determination of phase integrals ranging from 0.7 in the case of Rhea to 0.9 for Enceladus. For Enceladus we find an average geometric albedo p_v = 1.04 ± 0.15 and Bond albedo of 0.9 ± 0.1. The data indicate an orbital lightcurve with an amplitude of 0.2 mag, the trailing side being the brighter. For Mimas, the lightcurve amplitude is probably less than 0.1 mag. The value of the geometric albedo of Mimas reported here, p_v = 0.77 ± 0.15 (corresponding to a mean opposition magnitude V₀ = +12.5) is definitely higher than the currently accepted value of about 0.5. For Dione, the Voyager data show a well-defined orbital lightcurve of amplitude about 0.6 mag, with the leading hemisphere brighter than the trailing one.     

A comparison of the measuring machines APM and MAMA for astrometric application

Measurements of two Tautenburg plates were used for a comparison of the astrometric accuracy of the automatic measuring machines PAM and MAMA. From plate-to plate solutions a positional accuracy of about 1 μm was achieved for stars with 7 < B < 17 for MAMA and with 11 < B < 17 for APM measurements. A rapid decrease in positional accuracy of fainter stars is caused rather by random effects of the photographic emulsion. A magnitude equation between the plates was obtained to be less than 1 μm over the whole magnitude range. Systematic errors with a small period of 2 cm in the APM measurements as well as a non-orthogonality and systematic differences between the MAMA and APM coordinate grids were found. A procedure of classifying all real objects measured into stars, galaxies and merged objets is presented for the MAMA measurements and the results are compared with the routine APM classification. Except for merged objects the MAMA and APM classification show a very good agreement for stars brighter than B = 18.5.     

Selection,Statistics and Photometry of Compact Galaxies with Different Instrumental Equipment. Part I

On plates taken with 2 different photographic telescopes compact galaxies in 3 fields near M₃ and M₉₂ were selected. The integral magnitudes and maximum angular diameters of the compacts were determined. The RITCHEY -CHRéTIEN telescope of the FIGL Observatory for Astrophysics (FOA) with a focal ratio of 1:8.3 has a scale of 1 mm = 16.3, while the Tautenburg SCHMIDT with 1:3.2 has a scale of 1 mm ≌ 52°. From the selection statistics for both telescopes results nearly the same number of objects (50) up to 18^m.5 in V in a field of 1.5□°.60% of these objects are identical. An integral photometry on B plates of the same limiting magnitude from both telescopes leads to nearly the same brightness of objects, while they are o^m.5 fainter on FOA V plates. Because of its smaller focal ratio this telescope does not record the halo parts of the compacts. This is clearly demonstrated by the maximum equidensitometric diameters which on FAO plates are on the average only half of those determined on Tautenburg plates. A diameter magnitude diagram is shown.     

The Physical Nature of the Blue Objects in the Field of BD + 15° 2469 (Virgo Cluster)

The physical nature of 277 ultraviolet excess objects of the third Asiago field (22 square degrees, 15 ≦ m_pg ≦ 18, U–B ≦≦ -0.2) is investigated on the basis of objective prism plates. Most of them are stars, 8% are quasar candidates and 7% compact galaxies. The proportions of different kinds of objects changes with the magnitude and U–B colour index. The surface density of quasars is estimated to be between 0.5 Q/sq. deg. and 1.0 Q/sq. deg. for the UVX A₃ objects. The results of the A₃ field (located in the Virgo cluster of galaxies) statistically agree with the ones of the A₁ field, outside clusters of galaxies.     

Observations of distant solar system bodies

Multicolour VRI photometry and astrometry of one Centaur and seven Edgeworth-Kuiper objects were obtained. One object, 1994 JQ₁ may be as red as 5145 Pholus, the reddest minor planet previously known. The Centaur 1995 DW₂ has more moderate colour indices, similar to main-belt asteroids. Seven R-magnitudes were obtained for 1994 JS, 1995 FB₂₁, and 1995 GY₇. No light variation above the expected noise is evident, apart from a few outliers. A total of 47 astrometric positions were obtained for the eight objects. The four nights of observations with the ESO New Technology Telescope covered 0.52 square degrees. Two previosuly unknown object, 1995 FB₂₁ and 1995 GY₇, were discovered. We estimate the density of Edgeworth-Kuiper objects brighter than R = 24 to 5.3 per square degree of sky near the ecliptic.     

First Byurakan Spectral Sky Survey. Blue Stellar Objects. XII. The Region -3° ≤ δ ≤ +1°

The twelfth list of blue stellar objects in the second part of the First Byurakan Spectral Sky Survey (FBS) is presented. This list contains 143 objects in the region -3° +1° at high latitudes with an area of approximately 992 square degrees (62 fields). The objects have magnitudes V of 11.8-18.1 and B-V colors ranging from -0.82 to +0.81. Of the 143 objects, 51 have been discovered for the first time. Equatorial coordinates, V magnitudes, color indices, and preliminary classifications of the objects are given. DSS identification charts are given for the newly discovered objects.     

Quasars in the field of 88 Leonis

We present spectroscopically confirmed quasars in the 25 sq. degrees A1-field to a limiting magnitude of m_B = 18.0. Our estimate of the quasar density of 0.28 ± 0.11 objects per sq. degree based on the “complete” sample of A1-qusars is in agreement with the observed integral number-magnitude relation. However, we consider this value as still a lower limit of the quasar density in the A1-field due to the uncertainties during the colour based selection of objects, especially their brightness dependence, resulting in serious selection effects. Thus, the quasar density of the A1 survey may be underestimated up to 30% and does not contradict the recently estimated incompletness of the BQS survey.     

Schmidt survey in the Galactic anticentre direction. 1. Investigation of open clusters

A study of four open clusters in the direction of the Galactic anticentre (l = 186°, b = +2°) is presented. In a field of 8.32 square degrees proper motions and B magnitudes for about 79 000 stars down to 19.5 were determined on Tautenburg Schmidt plates. For more than 15 500 of them U magnitudes down to 17.3 could be obtained. Additionally, OCA Schmidt plates were used to determine V, R magnitudes in a larger field of 24.45 square degrees for 271 000 stars down to V = 18.2. For stars brighter than V = 15.5 an accuracy of about 1.5 mas/yr has been estimated for proper motions. The rms errors of stellar magnitudes and colour indices are 0.09 – 0.12 mag. Several open clusters have been already known in this direction of the sky, e.g. NGC 2168 or M 35 (C 0605+243), NGC 2158 (C 0604+241) and IC 2157 (C 0601+240). Inspecting the plates and analysing the colour-magnitude diagrams and published data, we could identify an additional anonymous cluster C 0605+242 with a projection on the sky near the centre of M 35 but at a larger distance from the Sun. The cluster membership determination was carried out using information on spatial and proper motion distributions of stars in the field. The colour-magnitude diagrams were derived down to the limiting stellar magnitude. For each cluster the interstellar extinction A_v, the diameters of the core and corona, the ages and spatial velocity components (V,W) relative to the LSR in the Y,Z – Galactic directions were determined. The distances to the clusters of 960 pc, 2 600 pc, 2 520 pc and 3 700 pc were obtained for M 35, IC 2157, C 0605+242 and NGC 2158. They show the loci of the clusters in the Local and Perseus spiral arms and at external border of Perseus arm, respectively.     

CCD‐Δa and BV R photometry of NGC 7296

The first CCD photometric investigation of the open cluster NGC 7296 up to now was performed within the narrow band Δa photometric system, which enables us to detect peculiar objects. A deeper investigation of that cluster followed, using the standard BV R ‐Bessel filter set. The age and E (B – V ) was determined independently to log t = 8.0 ± 0.1 and 0.15 ± 0.02, respectively by using Δa and broadband photometry. In total five Be/Ae objects and two metal‐weak stars showing significant negative Δa ‐values as well as one classical chemically peculiar star could be identified within that intermediate age open cluster. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

New photometry and astrometry of the isolated neutron star RX J0720.4–3125 using recent VLT/FORS observations

Since the first optical detection of RX J0720.4–3125 various observations have been performed to determine astrometric and photometric data. We present the first detection of the isolated neutron star in the V Bessel filter to study the spectral energy distribution and derive a new astrometric position. At ESO Paranal we obtained very deep images with FORS 1 (three hours exposure time) of RX J0720.4–3125 in the V Bessel filter in January 2008. We derive the visual magnitude by standard star aperture photometry. Using sophisticated resampling software we correct the images for field distortions. Then we derive an updated position and proper motion value by comparing its position with FORS 1 observations of December 2000. We calculate a visual magnitude of V = 26.81 ± 0.09 mag, which is seven times in excess of what is expected from X‐ray data, but consistent with the extant U, B, and R data. Over about a seven year epoch difference we measured a proper motion of μ = 105.1 ± 7.4 mas yr^–1 towards θ = 296.951° ± 0.0063° (NW), consistent with previous data (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analysis of the properties of galaxy clusters in the Leo supercluster region

We analyze the properties of galaxy clusters in the region of the Leo supercluster using observational data from the SDSS and 2MASS catalogs. We have selected 14 galaxy clusters with a total dynamical mass of 1.77 × 10¹⁵ M _⊙ in the supercluster region 130 by 60 Mpc in the plane of the sky (z ≃ 0.037). The composite luminosity function of the supercluster is described by a Schechter function with parameters that, within the error limits, correspond to field galaxies and does not differ from the luminosity function of the richer Ursa Major (UMa) supercluster for the same luminosity range (the bright end). The luminosity functions of early-type and late-type galaxies in Leo at the faint end are characterized by a sharp decrease (α = −0.60±0.08) and a steep increase (α = −1.44± 0.10) in the number of galaxies, respectively. In the virialized cluster regions, the fraction of early-type galaxies selected by the u-r color, bulge contribution, and concentration index among the galaxies brighter than M _K ^* + 1 is, on average, 62%. This fraction is smaller than that in the UMa supercluster at a 2–3σ level. The near-infrared luminosities of galaxy clusters down to a fixed absolute magnitude correlate with their masses almost in the same way as for other samples of galaxy clusters (L _200,K ∝ M ₂₀₀^0.63±0.11)).     

Spot activity on HD 89546 (FG UMa) from long‐term photometry

We present the analysis of 20 years of time‐series BV photometry of the SB1 RS CVn binary HD 89546. The system's yearly mean V brightness, the B – V color index, the photometric period, and the light curve amplitude all show clear cyclic variability with an ≈9‐year time scale. We also find some evidence for brightness variability on a time scale longer than the 20‐year time span of our observations, perhaps indicating a longer cycle analogous to the solar Gleissberg cycle. We estimate the unspotted V magnitude of HD 89546 to be 7.^m154, which is ≈0.^m2 brighter than the observed maximum brightness. Spot modelling of the system shows that spot temperature variations affect the observed B – V color as well as the V brightness. Two active longitudes are observed, centered around 180° and 360° longitude on the G9 III primary, each covering a longitude range of 120°. Furthermore, two inactive longitude zones are seen spanning only 60° between the two active longitudes. The longitudinal distribution of the spots exhibits no strong cyclic variability but does show rapid jumps of 120° that look like the flip‐flop phenomenon. We estimate the differential rotation coefficient of the star as k = 0.086 by considering the range of observed photometric period variations and assumed latitudinal spot variations over 45° (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Torun catalogue of 6.7 GHz methanol masers

We report the observations of 289 methanol maser sources at 6.7 GHz obtained over a two month period with the Torun 32 m telescope. The data form a catalogue of all objects north of δ = –22° brighter than 7.5 Jy in the peak emission. The positions of sub‐arcsecond accuracy are updated for 76 % of the objects. We find that about one third of the sources show changes in the peak fluxes by a factor of two or more on time scales of 8.5–9.5 years (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic field of the young star RW Aur

Results of ourmeasurements of the longitudinal magnetic field B _z for the young star RWAur A are presented. B _z measured from the so-called narrow component of the He I 5876 line varies in the range from −1.47 ± 0.15 to +1.10 ± 0.15 kG. Our data are consistent with a stellar rotation period of }~5.6 days and the model of two hot spots with opposite magnetic field polarities spaced about 180° apart in longitude. Relative to the Earth, the spot with B _z < 0 lies in the hemisphere above the midplane of the accretion disk, while the spot with B _z > 0 is below the midplane. The upper limit for B _z (at the 3σ level) obtained by averaging all observations is 180 G for the photosphere and 220 and 230 G for the Hα and [OI] 6300 line formation regions, respectively. We have also failed to detect a field in the formation region of broad emission line components: the upper limit for B _z is 600 G. In two of 11 cases, we have detected a magnetic field in the formation region of the blue absorption wing of the Na I D doublet lines, i.e., in the wind from RW Aur A: B _z = −180 ± 50 and −810 ± 80 G. The radial velocity of the photospheric lines in RW Aur A averaged over all our observations is }~+10.5 km s⁻¹, i.e., a value lower than that obtained by Petrov et al. (2001) ten years earlier by 5.5 km s⁻¹. Therefore, we discuss the possibility that RW Aur is not a binary but a triple system.