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Diffraction-limited bispectrum speckle interferometry and speckle polarimetry of the young bipolar outflow source S140 IRS1
We present bispectrum speckle interferometry and speckle polarimetry ofthe deeply embedded infrared bipolar outflow source S140 IRS1, a massiveprotostellar object in the L1204 molecular cloud. Using the SAO 6 mtelescope, we obtained 280 mas resolution polarization maps of S140 IRS1as well as a K-band image with diffraction-limited resolution lambda /Dof 76 mas, which is the highest angular resolution image of a youngoutflow source ever obtained in the infrared. Our data suggest that thecentral source is marginally resolved with a FWHM diameter ofapproximately 20 mas ( ~ 20 AU). The most remarkable feature in ourimage is a bright extended and very clumpy structure pointing away fromthe central source in exactly the same direction as the blue-shifted COoutflow lobe. A centro-symmetric pattern of high polarization in thisfeature suggests that we see scattered light from the central source. Weinterprete this feature as the clumpy inner surface of a partiallyevacuated cavity in the circumstellar envelope around IRS1, which hasbeen excavated by the strong outflow from IRS1.
| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 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
| Mesures de vitesses radiales. VIII. Accompagnement AU sol DU programme d'observation DU satellite HIPPARCOS
We publish 1879 radial velocities of stars distributed in 105 fields of4^{\circ} \times 4^{\circ}. We continue the PPO series \cite[(Fehrenbachet al. 1987;]{Feh87} \cite[Duflot et al. 1990, 1992 and 1995),]{Du90}using the Fehrenbach objective prism method. Table 1 only available inelectronic form at CDS via to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Magnetic structure in cool stars. XVII - Minimum radiative losses from the outer atmosphere
The emissions in several chromospheric and transition region lines andin coronal soft X-rays are analyzed for a sample of cool stars. Thenature of the lower-limit flux densities is explored, and evidence isgiven for the possibility of a basal, nonmagnetic heating mechanismbeing responsible for these emission fluxes up to, and perhapsincluding, the upper transition region. It is argued that the excessflux density, derived by subtraction of the basal flux density from theobserved stellar flux, is the proper measure of magnetic activity. Thelevel of the basal flux density as a function of color is determined tobe 2 x 10 exp 6 erg/sq cm/s for F-type stars and 2 x 10 exp 5 erg/sqcm/s for K-type stars.
| An unbiased survey of field star X-ray emission
To determine the X-ray luminosity function of normal stars, 1700 starsbrighter than 10th magnitude were surveyed by the imaging proportionalcounter aboard the Einstein Observatory. Seventy star positions werefound to contain excess X-ray counting rates. The number of stars persquare degree in a number of magnitude intervals was calculated as afunction of spectral type and luminosity class, and the total number ofstars for each spectral type brighter than magnitude 9.5 derived in thismanner was compared with the 1700-star sample. The agreement is good, asis that between the surface density of soft X-ray sources and the numberof stellar emitters predicted from the field star survey. It isconcluded that stars probably do not contribute significantly to thediffuse soft X-ray background. The findings are consistent with thenotion that stellar age and/or rotation velocity are importantdeterminants of stellar X-ray emission level.
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Membre dels grups següents:
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Dades d'Observació i Astrometria
| Constel·lació: | Cepheus |
| Ascensió Recta: | 22h16m32.30s |
| Declinació: | +63°42'44.8" |
| Magnitud Aparent: | 7.245 |
| Distancia: | 182.149 parsecs |
| Moviment propi RA: | 18.8 |
| Moviment propi Dec: | 14.5 |
| B-T magnitude: | 8.629 |
| V-T magnitude: | 7.36 |
Catàlegs i designacions:
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