Journal Article

Multiwavelength study of a young open cluster NGC 7419

Himali Joshi, Brijesh Kumar, K. P. Singh, Ram Sagar, Saurabh Sharma and J. C. Pandey

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 391, issue 3, pages 1279-1300
Published in print December 2008 | ISSN: 0035-8711
Published online November 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13936.x
Multiwavelength study of a young open cluster NGC 7419

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Using new UBVRI Hα CCD photometric observations and the archival infrared and X-ray data, we have carried out a multiwavelength study of a Perseus arm young open star cluster NGC 7419. An age of 22.5 ± 3.0 Myr and a distance of 3230+330−430 pc are derived for the cluster. Our photometric data indicate a higher value of colour excess ratio E(UB)/E(BV) than the normal one. There is an evidence for mass segregation in this dynamically relaxed cluster and in the range 1.4–8.6 M, the mass function slope is in agreement with the Salpeter value. Excess emissions in near-infrared and Hα support the existence of a young (≤2 Myr) stellar population of Herbig Ae/Be stars (≥3.0 M) indicating a second episode of star formation in the cluster region. Using XMM–Newton observations, we found several X-ray sources in the cluster region but none of the Herbig Ae/Be stars is detected in X-rays. We compare the distribution of upper limits for Herbig Ae/Be stars with the X-ray distribution functions of the T Tauri and the Herbig Ae/Be stars from previous studies, and found that the X-ray emission level of these Herbig Ae/Be stars is not more than LX∼ 5.2 × 1030erg s−1, which is not significantly higher than for the T Tauri stars. Therefore, X-ray emission from Herbig Ae/Be stars could be the result of either unresolved companion stars or a process similar to T Tauri stars. We report an extended X-ray emission from the cluster region NGC 7419, with a total X-ray luminosity estimate of ∼1.8 × 1031erg s−1arcmin−2. If the extended emission is due to unresolved emission from the point sources then we estimate ∼288 T Tauri stars in the cluster region each having X-ray luminosity ∼1.0 × 1030erg s−1. Investigation of dust attenuation and12CO emission map of a square degree region around the cluster indicates the presence of a foreground dust cloud which is most likely associated with the local arm star-forming region (Sh2−154). This cloud harbours uniformly distributed pre-main-sequence stars (0.1–2.0 M), with no obvious trend of their distribution with either (HK) excess or AV. This suggests that the star formation in this cloud depend mostly upon the primordial fragmentation.

Keywords: stars: emission-line, Be; stars: formation; stars: pre-main-sequence; X-rays: galaxies: clusters; X-rays: stars

Journal Article.  14405 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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