Contents
Images
Upload your image
DSS Images Other Images
Related articles
Spectroscopy and photometry of the protoplanetary nebula candidate stHα62 = IRAS 07171+1823
We present the results of spectroscopic and photometric observations forthe B star StHα62 with an IR excess, a post-AGB candidateidentified with the IR source IRAS 07171+1823. High-resolutionspectroscopy has allowed the λ4330 7340 Å spectrum of thestar to be identified: it contains absorption lines of an early B starand emission lines of a gaseous shell. The residual line intensitieshave been measured. The heliocentric radial velocities measured fromabsorption lines of the star and emission lines of the shell are 〈Vr 〉 = +45 ± 1 and +52 ± 1 km s-1, respectively. Theline-of-sight velocities of gas-dust clouds determined from theinterstellar Na I lines are 12 and 33 km s-1. The He I λ5876Å line exhibits a P Cyg profile, which is indicative of an ongoingmass loss by the star. The expansion velocity of the outer shellestimated from forbidden lines is 12 13 km s-1. Quantitativeclassification gives the spectral type B0.51 for the star. Theparameters of the gaseous shell have been determined: N e = 3.1 ×103 cm-3 and T e 21 000 K. Over 4 years of its observations, thestar showed rapid irregular light variations with the amplitudesΔV = &$0(m) .2; , ΔB = &0(m) .2; , and ΔU = &0(m) .3; and no color-magnitude correlation. We estimate the total extinctionfor the star from our photometric observations as A v = &0(m) .4$; . Near-IR observations have revealed dust radiation with a temperatureof 1300 K. We estimate the distance to StHα62 to be r = 5.2± 1.2 kpc by assuming that the star is a low-mass (M = 0.55± 0.05 M ȯ) protoplanetary nebula.
| The Maximum Age of Trapezium Systems
We sought to determine the maximum age of Trapezium systems by studyingpossible trapezium systems that were selected independently of theiroccurrence in H II regions. We started with the unpublished catalog byAllen, Tapia, & Parrao of all the known visual systems having threeor more stars in which the maximum separation is less than 3.0 times theminimum separation. Their catalog has 968 such systems whose mostfrequent primary type is F, which does not describe young systems. Witha CCD on the Kitt Peak 0.9 m telescope we obtained UBV frames for 265systems accessible with our equipment on Kitt Peak. The frames were usedto obtain UBV photometry for about 1500 stars with an accuracy of+/-0.04 mag between V=7 and 14 mag. Also these frames were used toobtain astrometry with an accuracy of +/-0.015d in position angle and+/-0.01" in separation. For the brightest star in each system weobtained a spectral type to determine the distance and reddening to thesystem. The measures were used to determine physical membership fromstars that (1) fit a single color-magnitude diagram, (2) fit a commoncolor-color diagram, and (3) show no astrometric motion compared tovisual measures made (mostly) a century ago. Combining the results withspectroscopic data for 20 additional Allen et al. systems by Abt, wefound that 126 systems had only optical companions to the primaries, 116systems contained only a single physical pair, 13 were hierarchicalsystems with 3-6 members and having separation ratios of more than afactor of 10, two were small clusters, and only 28 fitted the criteriaof Trapezium systems. However, as shown by Ambartsumian, about 9% of thehierarchical systems should appear to be Trapezium systems inprojection. Those, like other hierarchical systems, have a broaddistribution of primary spectral types. We isolated 14 systems that seemto be true Trapezium systems. They have primary types of B3 or earlier,indicating a maximum age of about 5×107 yr. This upperlimit is consistent with the estimate made by Allen & Poveda for anage of several million years for these dynamically unstable systems.These Trapezia are also large with a median radius of 0.2 pc and amaximum radius of 2.6 pc. We asked why the sample of 285 possibleTrapezium systems yielded only 14 true ones, despite the attempt made byAllen et al. to eliminate optical companions with a ``1% filter,'' i.e.,demanding that each companion have less than a 1% chance of being afield star of that magnitude within a circle of its radius from theprimary. The explanation seems to be that the double star catalogs arebased mostly on BD magnitudes that, fainter than V=12 mag, aresystematically too faint by 1 mag.
| New uvbybeta photometry of stars of ``astrophysical interest''
Not Available
| MSC - a catalogue of physical multiple stars
The MSC catalogue contains data on 612 physical multiple stars ofmultiplicity 3 to 7 which are hierarchical with few exceptions. Orbitalperiods, angular separations and mass ratios are estimated for eachsub-system. Orbital elements are given when available. The catalogue canbe accessed through CDS (Strasbourg). Half of the systems are within 100pc from the Sun. The comparison of the periods of close and widesub-systems reveals that there is no preferred period ratio and allpossible combinations of periods are found. The distribution of thelogarithms of short periods is bimodal, probably due to observationalselection. In 82\% of triple stars the close sub-system is related tothe primary of a wide pair. However, the analysis of mass ratiodistribution gives some support to the idea that component masses areindependently selected from the Salpeter mass function. Orbits of wideand close sub-systems are not always coplanar, although thecorresponding orbital angular momentum vectors do show a weak tendencyof alignment. Some observational programs based on the MSC aresuggested. Tables 2 and 3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Photoelectric UBV-photometry of triple-star components
Photoelectric UBV photometry was performed on components of 30 brightand nearby triple stars to identify physically linked triple systems andto determine their distances and dynamic evolution. An analysis of 60catalogs showed only 10 triple systems. For every component, E(B-V) andE(U-B) color excesses are determined and photometric parallaxes arecalculated using available spectral types.
| The Equatorial Coordinates of Components of Triple Stars from the Astrometric Satellite HIPPARCOS Input Catalogue - Part Two - the Results of Statistical Study of Data from Aitken's Catalogue of Double Stars / ADS
Not Available
| The fourth meridian catalog of Besancon Observatory
The catalog presented gives differential meridian positions for 670F-type stars between plus 15 and plus 45 deg declination. The positionsare reduced to the equinox of 1950.0 without proper motions; 333 FK4stars were used as reference stars. A minimum of three and an average offive transits of each program star were observed photoelectrically usinga Gautier transit circle and a Hog grid. The internal accuracy ofindividual measurements is shown to range from 0.013 sec in rightascension and 0.30 arcsec in declination for brighter stars under betterobserving conditions to 0.020 sec in right ascension and 0.38 arcsec indeclination for fainter stars under worse conditions. The standarderrors were applied to compute weighted mean positions, mean epochs, andunweighted means for the program stars. Mean corrections for 283 FK4stars are also provided.
| The proper motions of Struve double stars
The proper motions of the components of 103 Struve double stars fromMuller's list of neglected stars and of 15 other systems were measuredrelative to sets of reference stars, for the primary purpose ofdistinguishing physical from optical pairs. A by-product of thisinvestigation is a list of measured position angles and distances ofthese objects, at two epochs each.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Gemini |
| Right ascension: | 07h26m27.34s |
| Declination: | +18°31'00.9" |
| Apparent magnitude: | 7.239 |
| Distance: | 158.983 parsecs |
| Proper motion RA: | -16.6 |
| Proper motion Dec: | -20.8 |
| B-T magnitude: | 7.646 |
| V-T magnitude: | 7.273 |
Catalogs and designations:
|
INHABITED SKY
