2010AJ....140..266W

We present new Chandra X-ray data of the NGC 1333 embedded cluster and combine these data with existing Chandra data, Spitzer photometry, and ground-based spectroscopy of both the NGC 1333 and Serpens cloud core clusters to perform a detailed study of the X-ray properties of two of the nearest embedded clusters to the Sun. We first present new, deeper observations of NGC 1333 with Chandra ACIS-I and combine these with existing Spitzer observations of the region. In NGC 1333, a total of 95 cluster members are detected in X-rays of which 54 were previously identified in the Spitzer data. Of the Spitzer-identified sources, we detected 23% of the Class I protostars, 53% of the flat-spectrum sources, 52% of the Class II, and 50% of the transition disk young stellar objects (YSOs). Forty-one Class III members of the cluster are identified, bringing the total identified YSO population to 178. The X-ray luminosity functions (XLFs) of the NGC 1333 and Serpens clusters are compared to each other and the Orion Nebula Cluster (ONC). Based on a comparison of the XLFs of the Serpens and NGC 1333 clusters to the previously published ONC, we obtain a new distance for the Serpens cluster of 360⁺²²_–13pc. Using our previously published spectral types, effective temperatures, and bolometric luminosities, we analyze the dependence of the X-ray emission on the measured stellar properties. The X-ray luminosity was found to depend on the calculated bolometric luminosity as in previous studies of other clusters. We examine the dependence of L_X on stellar surface area and effective temperature, and find that L_X depends primarily on the stellar surface area. In the NGC 1333 cluster, the Class III sources have a somewhat higher X-ray luminosity for a given surface area. We also find evidence in NGC 1333 for a jump in the X-ray luminosity between spectral types of M0 and K7, we speculate that this may result from the presence of radiative zones in the K-stars. The gas column density versus extinction in the NGC 1333 parental molecular cloud was examined using the hydrogen column density determined from the X-ray absorption to the embedded stars and the K-band extinction measured to those stars. In NGC 1333, we find N_H= 0.89±0.13x10²² A_K, this is lower than expected of the standard interstellar medium but similar to that found previously in the Serpens cloud core.