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A deep wide-field optical survey in the young open cluster Collinder 359
We present the first deep, optical, wide-field imaging survey of theyoung open cluster Collinder 359, complemented by near-infraredfollow-up observations. This study is part of a large programme aimed atexamining the dependence of the mass function on environment and time.We have surveyed 1.6 square degrees in the cluster, in the I and zfilters, with the CFH12K camera on the Canada-France-Hawaii 3.6-mtelescope down to completeness and detection limits in both filters of22.0 and 24.0 mag, respectively. Based on their location in the optical(I-z, I) colour-magnitude diagram, we have extracted new cluster membercandidates in Collinder 359 spanning 1.3-0.03 Mȯ,assuming an age of 60 Myr and a distance of 450 pc for the cluster. Wehave used the 2MASS database as well as our own near-infrared photometryto examine the membership status of the optically-selected clustercandidates. Comparison of the location of the most massive members inCollinder 359 in a (B-V, V) diagram with theoretical isochrones suggeststhat Collinder 359 is older than α Per but younger than thePleiades. We discuss the possible relationship between Collinder 359 andIC 4665 as both clusters harbour similar parameters, including propermotion, distance, and age.
| Near-Infrared Adaptive Optics Spectroscopy of Binary Brown Dwarfs HD 130948B and HD 130948C
We present near-infrared spectroscopy of low-mass companions in a nearbytriple system HD 130948 (Gliese 564, HR 5534). Adaptive optics on theSubaru Telescope allowed spectroscopy of the individual components ofthe 0.13" binary system. Based on a direct comparison with a series oftemplate spectra, we determined the spectral types of HD 130948B and Cto be L4 +/- 1. If we take the young age of the primary star intoaccount (0.3-0.8 Gyr), HD 130948B and 130948C most likely are a binarybrown dwarf system. Based on data collected at the Subaru Telescope,which is operated by the National Astronomical Observatory of Japan.
| An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
| UBVRI photometry of the open cluster Collinder 359, alleged to contain W Ursae Majoris systems
The question of the existence of Cr 359 is addressed. UBV(RI)cphotometry for all 13 stars suggests that nine stars of the originalcluster may form a common main sequence. This may be an indication ofthe physical association of these stars.
| A note on the existence of W UMa-type systems in the cluster CR 359
Arguments are presented that supposedly numerous W UMa-type systems inCr 359 might in fact be field objects with the expected frequency ofoccurrence; in addition four out of the listed nine objects might beeither non-variable or of the RR Lyr-type. The physical association ofstars forming Cr 359 is also questioned but the present data do not makeit possible to disprove it entirely. The far reaching conclusion ofvan't Veer regarding the presence of W UMa systems in very youngclusters finds no support from these results.
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Observation and Astrometry data
| Constellation: | Ophiucus |
| Right ascension: | 18h00m41.77s |
| Declination: | +03°08'57.5" |
| Apparent magnitude: | 9.394 |
| Proper motion RA: | 1.6 |
| Proper motion Dec: | -10.7 |
| B-T magnitude: | 9.328 |
| V-T magnitude: | 9.389 |
Catalogs and designations:
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INHABITED SKY
