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Multiwavelength study of a young open cluster NGC7419
Using new UBVRIH? CCD photometric observations and the archivalinfrared and X-ray data, we have carried out a multiwavelength study ofa Perseus arm young open star cluster NGC7419. An age of 22.5 +/- 3.0Myrand a distance of 3230+330-430pc are derived forthe cluster. Our photometric data indicate a higher value of colourexcess ratio E(U - B)/E(B - V) than the normal one. There is an evidencefor mass segregation in this dynamically relaxed cluster and in therange 1.4-8.6Msolar, the mass function slope is in agreementwith the Salpeter value. Excess emissions in near-infrared and H?support the existence of a young (<=2Myr) stellar population ofHerbig Ae/Be stars (>=3.0Msolar) indicating a secondepisode of star formation in the cluster region. Using XMM-Newtonobservations, we found several X-ray sources in the cluster region butnone of the Herbig Ae/Be stars is detected in X-rays. We compare thedistribution of upper limits for Herbig Ae/Be stars with the X-raydistribution functions of the T Tauri and the Herbig Ae/Be stars fromprevious studies, and found that the X-ray emission level of theseHerbig Ae/Be stars is not more than LX ~ 5.2 ×1030ergs-1, which is not significantly higher thanfor the T Tauri stars. Therefore, X-ray emission from Herbig Ae/Be starscould be the result of either unresolved companion stars or a processsimilar to T Tauri stars. We report an extended X-ray emission from thecluster region NGC7419, with a total X-ray luminosity estimate of ~1.8× 1031ergs-1arcmin-2. If theextended emission is due to unresolved emission from the point sourcesthen we estimate ~288 T Tauri stars in the cluster region each havingX-ray luminosity ~1.0 × 1030ergs-1.Investigation of dust attenuation and12CO emission map of asquare degree region around the cluster indicates the presence of aforeground dust cloud which is most likely associated with the local armstar-forming region (Sh2-154). This cloud harbours uniformly distributedpre-main-sequence stars (0.1-2.0Msolar), with no obvioustrend of their distribution with either (H - K) excess or AV.This suggests that the star formation in this cloud depend mostly uponthe primordial fragmentation.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| The association of IRAS sources and 12CO emission in the outer Galaxy
We have revisited the question of the association of CO emission withIRAS sources in the outer Galaxy using data from the FCRAO Outer GalaxySurvey (OGS). The availability of a large-scale high-resolution COsurvey allows us to approach the question of IRAS-CO associations from anew direction - namely we examined all of the IRAS sources within theOGS region for associated molecular material. By investigating theassociation of molecular material with random lines of sight in the OGSregion we were able to construct a quantitative means to judge thelikelihood that any given IRAS-CO association is valid and todisentangle multiple emission components along the line of sight. Thepaper presents a list of all of the IRAS-CO associations in the OGSregion. We show that, within the OGS region, there is a significantincrease ( ~ 22%) in the number of probable star forming regions overprevious targeted CO surveys towards IRAS sources. As a demonstration ofthe utility of the IRAS-CO association table we present the results ofthree brief studies on candidate zone-of-avoidance galaxies with IRAScounterparts, far outer Galaxy CO clouds, and very bright CO clouds withno associated IRAS sources. We find that ~ 25% of such candidate ZOAGsare Galactic objects. We have discovered two new far outer Galaxystar-forming regions, and have discovered six bright molecular cloudsthat we believe are ideal targets for the investigation of the earlieststages of sequential star formation around HII regions. Finally, thispaper provides readers with the necessary data to compare othercatalogued data sets with the OGS data.Tables 1, 2 and A1 are only available in electronic form at the CDS viaanonymous ftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/1083
| 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
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| Takýmyýldýz: | Kral-Sefe |
| Sað Açýklýk: | 22h48m52.76s |
| Yükselim: | +61°09'41.1" |
| Görünürdeki Parlaklýk: | 7.935 |
| Uzaklýk: | 243.309 parsek |
| özdevim Sað Açýklýk: | -41.6 |
| özdevim Yükselim: | -9.9 |
| B-T magnitude: | 9.208 |
| V-T magnitude: | 8.041 |
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