Multiwavelength study of a young open cluster NGC 7419

Abstract

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. Our photometric data indicate a higher value of colour excess ratio E(U − B)/E(B − V) 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 × 10³⁰ s−¹ erg , 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 × 10³¹ erg s−¹ arcmin−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 × 10³⁰ erg s−¹ . Investigation of dust attenuation and ¹²co 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 suggests that the star formation in this cloud depend mostly upon the primordial fragmentation.