KAPORIXMM - Kappa Orionis XMM-Newton X-Ray Point Source Catalog

Overview

X-rays are a powerful probe of activity in the early stages of star formation. They allow us to identify young stars even after they have lost the IR signatures of circumstellar disks and provide constraints on their distance. Here, the authors report on XMM-Newton observations that detected 121 young stellar objects (YSOs) in two fields between the filamentary dark cloud complex Lynds 1641S and the star Kappa Ori. These observations extend the Survey of Orion A with XMM and Spitzer (SOXS). The YSOs are contained in a ring of gas and dust apparent at millimeter wavelengths, and in far-IR and near-IR surveys. The X-ray luminosity function of the YSOs detected in the two fields indicates a distance of 250-280 pc, much closer than the Orion A cloud and similar to the distance estimates for Kappa Ori. The authors propose that the ring is a 5-8 pc diameter shell that has been swept up by Kappa Ori. This ring contains several groups of stars detected by Spitzer and WISE including one surrounding the Herbig Ae/Be star V1818 Ori. In this interpretation, the Kappa Ori ring is one of several shells swept up by massive stars within the Orion Eridanus Superbubble and is unrelated to the southern portion of Orion A/L 1641S.

The XMM-Newton observations consist of two fields, north (Field N = KN) and south (Field S = KS), and were obtained in 2015 March 10 and 15 using EPIC as the primary instrument. Table 1 in the reference paper shows the details of the exposures, each one with a duration of about 50 ks and taken with the Medium filter. The authors used SAS version 14.0 to reduce the observation data files (ODFs) and to obtain calibrated lists of events for the MOS and pn instruments. They filtered the events in the 0.3-0.8 keV energy band and used only events with FLAG = 0 and PATTERN < 12 as prescribed by the SAS manual. With SAS, the authors obtained exposure maps in the 0.3-8.0 keV band and performed source detection with a code based on wavelet convolution that operated simultaneously on MOS and pn data. They used a threshold of significance of 4.5 sigma of the local background to discriminate real sources from spurious background fluctuations. However, they added few sources to the final list with significance S in 4.0 < S < 4.5 for the cases of positional match with objects in SIMBAD or PPMX catalogs. The final list was also checked for spurious sources that could appear at the border of the CCDs. In sum, the authors detected 238 X-ray sources with significance > 4 sigma of the local background; 104 sources are in KN and 134 in KS.

The authors cross-correlated the positions of the X-ray sources with the coordinates of the IR catalog of Megeath et al. (2012, AJ, 144, 192). This IR catalog is the result of a survey of Orion with Spitzer that produced a classification of protostars and stars with disks. Of the 238 X-ray sources, 191 are identified within 8 arcseconds of one of 206 IR objects, 99 sources in KS, 92 sources in KN. Some X-ray sources were multiple matches within 8 arcsec of IR objects. For these cases, the authors assigned the most likely counterparts based on IR photometry and visual inspection of X-rays and IR images. However, nine X-ray sources were left associated with two or three IR objects. Among the IR matches, the authors found 15 stars with disks in KN and 35 in KS with X-ray detection. One protostar in KN and three in KS were detected in X-rays.

The authors used X-ray detection of sources without IR excess as criteria to identify disk-less stars (hereafter Class III stars). They classified as Class III stars those IR objects with X-ray detections, with [4.5um]-[8.0um] colors < 0.3 mag and brighter than [4.5um] magnitude < 14. At the distance of the ONC (400 pc), the [4.5um] magnitude ~ 14 threshold at an age of 4-5 Myrs roughly identifies M3-M4 spectral types and masses around 0.3 solar masses. With this selection scheme, the authors identified 48 objects in KN and 19 in KS as Class III candidates.

Catalog Bibcode

2016ApJ...820L..28P

References

A star-forming ring around Kappa Ori 250 pc from the Sun.
    Pillitteri I., Wolk S.J., Megeath S.T.
   <Astrophys. J., 820, L28 (2016)>
   =2016ApJ...820L..28P    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in August 2016 based on the electronic version of Table 2 from the reference paper which was obtained from the CDS (their catalog J/ApJ/820/L28 file table2.dat).

Parameters

Source_Number
A unique identification number for each X-ray source in the catalog in order of increasing Declination.

Name
The conventional XMM-Newton source name using the standard 'XMMU' prefix, e.g., 'XMMU JHHMMSS.s+DDMMSS'. This was created by the HEASARC based on the J2000.0 equatorial coordinates of the source.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 seconds of time in the original table.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 1 arcsecond in the original table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Count_Rate
The count rate of the X-ray source in the 0.3-8 keV band, in counts per second (converted by the HEASARC from the ct/ks used in the original table). The wavelet code returns the count rate scaled by a reference instrument. In this table, the count rates are referred to the MOS.

Count_Rate_Error
The error in the 0.3-8 keV count rate of the X-ray source, in counts per second (converted by the HEASARC from the ct/ks used in the original table).

Flux
The unabsorbed 0.3-8 keV band flux of the X-ray source, in erg cm^-2 s^-1. The fluxes were derived using PIMMS software and adopting a WABS+APEC model. For 36 sources with more than 500 total counts, the authors performed a best-fit modeling to X-ray spectra using the XSPEC software. For faint sources, they used median energies of count events and N_H values from a distance-weighted average of N_H of bright sources as inputs for PIMMS.

Protostar_Flag
This Boolean flag parameter based on the infrared properties of the source indicates a protostar classification if set to 1. If it does not satisfy this criterion, it is set to 0.

Disk_Flag
This Boolean flag parameter based on the infrared properties of the source indicates the presence of a disk if set to 1. If it does not satisfy this criterion, it is set to 0.

Class_III_Flag
This Boolean flag parameter is set to 1 if the source satisfies the authors' criteria for a candidate class III (disk-less) pre-main sequence star (see Overview above for more details). If it does not satisfy these criteria, it is set to 0.

W1_Mag
For sources with WISE counterparts, the WISE [3.6-micron] band magnitude.

W1W3_Color
For sources with WISE counterparts, the WISE [3.6um-12um] color index.

Contact Person

Questions regarding the KAPORIXMM database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:29:43 EDT