Chandra Announcement: Chandra Source Catalog 2.0.1 Variability Update

[Tara Gokas]

CSC 2.0.1 VARIABILITY UPDATE
 

Release 2.0.1 of the Chandra Source Catalog updates intra-observation and inter-observation variability properties to resolve two issues detected in release 2.0. These issues resulted in an underestimation of the variability probabilities in release 2.0 for some CSC sources at the Stacked Observation Detection and Master Source levels. When computing the variability properties, CSC 2.0.1 now uses all observations that contribute to a particular stacked observation detection and/or master source, whereas release 2.0 incorrectly used only the observations in the best Bayesian block. In addition, an error that caused incorrect calculations of the inter-observation variability properties when one or more per-observation detections included upper limits for the fluxes, and/or lower or upper limits for the hardness ratios, was fixed. The updated catalog properties have been thoroughly tested and corrected variability probabilities are verified for detections and/or sources for which the values were previously underestimated, and for statistical consistency with CSC 2.0. At the Stacked Observation Detection and Master Source levels, properties affected by this change are: var_inter_hard_prob_{hs,ms,hm}, var_inter_hard_sigma_{hs,ms,hm}, var_inter_prob_{b,h,m,s,u,w}, var_inter_index_{b,h,m,s,u,w}, var_inter_sigma_{b,h,m,s,u,w}, ks_intra_prob_{b,h,m,s,u,w}, kp_intra_prob_{b,h,m,s,u,w}, var_intra_prob_{b,h,m,s,u,w}, var_intra_index_{b,h,m,s,u,w}, var_inter_hard_flag, and var_flag.