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LAMORIXMM - Lambda Orionis Cluster XMM-Newton X-Ray Point Source Catalog

HEASARC
Archive

Overview

The authors studied the X-ray properties of the young (~1-8M yr) open cluster around the hot (O8 III) star Lambda Ori and compared them with those of the similarly-aged Sigma Ori cluster in order to investigate the possible effects of the different ambient environments. They analysed an XMM-Newton observation of the cluster using EPIC imaging and low-resolution spectral data. They studied the variability of the detected sources, and performed a spectral analysis of the brightest sources in the field using multi-temperature models.

The authors detected 167 X-ray sources above a 5-sigma detection threshold the properties of which are listed in this table, of which 58 are identified with known cluster members and candidates, from massive stars down to low-mass stars with spectral types of ~ M5.5. Another 23 sources were identified with new possible photometric candidates. Late-type stars have a median log LX/Lbol ~ -3.3, close to the saturation limit. Variability was observed in ~ 35% of late-type members or candidates, including six flaring sources. The emission from the central hot star Lambda Ori is dominated by plasma at 0.2 - 0.3 keV, with a weaker component at 0.7 keV, consistent with a wind origin. The coronae of late-type stars can be described by two plasma components with temperatures T1 ~ 0.3-0.8 keV and T2 ~ 0.8-3 keV, and subsolar abundances Z ~ 0.1-0.3 Zsun, similar to what is found in other star-forming regions and associations. No significant difference was observed between stars with and without circumstellar discs, although the smallness of the sample of stars with discs and accretion does not definitive conclusions to be drawn. The authors concluded that the X-ray properties of Lambda Ori late-type stars are comparable to those of the coeval Sigma Ori cluster, suggesting that stellar activity in Lambda Ori has not been significantly affected by the different ambient environment.

The lambda Ori cluster was observed by XMM-Newton from 20:46 UT on September 28, 2006 to 12:23 UT on September 29, 2006 (Obs. ID 0402050101), for a total duration of 56ks, using both the EPIC MOS and PN cameras and the RGS instruments. The EPIC cameras were operated in full frame mode with the thick filter.


Catalog Bibcode

2011A&A...530A.150F

References

XMM-Newton observations of the young open cluster around {lambda} Orionis.
    Franciosini E., Sacco G.G.
   <Astron. Astrophys., 530, A150 (2011)>
   =2011A&A...530A.150F    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in November 2011 based on CDS Catalog J/A+A/530/A150 files tablea1.dat ('X-ray sources detected in the Lambda Ori Cluster'), table1,dat ('X-ray and optical properties of sources identified with known cluster members and candidates') and table2.dat ('X-ray sources identified with possible new cluster candidates'). It does not include the objects listed in tablea2.dat ('3-sigma upper limits and optical properties of undetected cluster members and candidates').

HEASARC Implementation

The HEASARC has added the supporting data given in Tables 1 (58 sources identified with known cluster members and candidates) and 2 (23 sources identified with possible new cluster candidates) of the reference paper to the list of 167 detected XMM-Newton X-ray sources (Table A1) to construct the present table. The original as-published version of Table A1 had 169 entries, since there were 2 entries for the sources 70 and 150 corresponding to their two potential optical/IR counterparts. The HEASARC has merged the information on the counterparts for these two X-ray sources into single entries, so that there are 1 entry per X-ray source in this HEASARC version of the table.

Parameters

Source_Number
A unique source number for each X-ray source in order of increasing J2000.0 Right Ascension.

Name
The primary X-ray source designation for these sources, using the 'LOX' prefix for 'Lambda Ori X-ray' and the source number.

RA
The corrected Right Ascension of the XMM-Newton source in the selected equinox. This was given in J2000.0 equatorial ccordinates to a precision of 0.01 seconds of time in the original table. The original X-ray sources were cross-correlated against the 2MASS Catalog using an identification radius of 6 arcseconds, and a median offset of -1.8 arcsecs in RA was found. This correction was then applied to all positions.

Dec
The corrected Declination of the XMM-Newton source in the selected equinox. This was given in J2000.0 equatorial ccordinates to a precision of 0.1 arcseconds in the original table. The original X-ray sources were cross-correlated against the 2MASS Catalog using an identification radius of 6 arcseconds, and a median offset of -0.2 arcsecs in Dec was found. This correction was then applied to all positions.

LII
The Galactic Longitude of the XMM-Newton source.

BII
The Galactic Latitude of the XMM-Newton source.

Off_Axis
The offaxis offset of the X-ray source from the nominal XMM-Newton pointing direction, in arcminutes.

SNR
The detection significance of the X-ray source in the 0.3 to 7.8 keV energy band in the merged MOS1 + MOS2 + PN dataset using the Palermo wavelet detection algorithm.

Count_Rate
The MOS-equivalent count rate of the X-ray source in the 0.3-7.8 keV energy band, in counts per seconds.

Count_Rate_Error
The RMS uncertainty in the MOS-equivalent count rate of the X-ray source in the 0.3-7.8 keV energy band, in counts per seconds.

Alt_Name
The optical or infared identification of the X-ray source. The authors cross-correlated their X-ray source psoitions with an optical catalog of known objects in the XMM-Newton field of view, using a search radius of 4 arcsecs. With this value, they expected to have at most 3 spurious identifications. Identifications labelled DM are from Dolan & Mathieu (1999, AJ, 118, 2409: the CDS recommends a '[DM99]' prefix for these objects), while LOri objects are from Barrado y Navascues et al. (2004, ApJ, 610,1064: the CDS recommends a '[LOri-CFHT]' prefix for these objects), and Lori-SOC objects are from Bouy et al. (2009A&A, 504, 199B: the CDS recommends a '[LOri-SOC]' prefix for these objects). The sources with alt_names of '2MASS J05340691+1001005' (LOX 1) and '2MASS J05351974+0947476' (LOX 99) are stars X2 and X4 from Stone & Taam (1985, ApJ, 291, 183). The two stars with TYC identification are stars b and f in Murdin & Penston (1977, MNRAS, 181, 657).

Note_Alt_Name
The source flagged by 'e' has a fainter visual companion (2MASS J05340664+1001034, J = 13.10 mag) at a distance of ~5 arcsecs, which however falls outside the authors' identification radius (offset=4.2 arcsec). Indicates Individual Note Concerning Identification

Offset
The angular offset between the X-ray source position and its optical/infrared identification, in arcseconds.

Notes
Notes on the probability that the object identified with the XMM-Newton source is a member of the cluster, as follows:

             Member = previously known members and candidates
             NM = previously known non-members. Reason for membership exclusion
                    in parenthesis
             New? = possible new candidates
  

Alt_Name_2
An alternative optical/infrared identification of the X-ray source within the 4 arcsecs search radius.

Offset_2
The angular offset between the X-ray source position and the alternative optical/infrared identification, in arcseconds.

Notes_2
Notes on the probability that the alternative object identified with the XMM-Newton source is a member of the cluster, as follows:

             Member = previously known members and candidates
             NM = previously known non-members. Reason for membership exclusion
                    in parenthesis
             New? = possible new candidates
  

Log_Lx
The logarithm of the X-ray luminosity log Lx of the source in the 0.3 - 7.8 keV band, in erg s-1, assuming it is at the 400 pc distance of the Lambda Ori Cluster. For most sources, the results of the best-fit spectral models for the brighter sources (shown in Tables 3 and 4 of the reference paper) were used to derive a count rate to flux conversion factor based on the median value of 8.7 x 10-12 erg cm-2 ct-1 which was found for the latter. This parameter is provided only for the 81 sources identified with known cluster members and candidates listed in Tables 1 and 2 of the reference paper.

Log_Lx_Flag
This flag is set to 'S' to indicates that the quoted value for log Lx is directly derived from a flux obtained from a spectral fit rather than from a flux derived using the median count rate to flux conversion factor, and set to 'd' in the case of LOX 150 for which the X-ray luminosity has been equally divided between the two stars which are possible counterparts to the X-ray source (see Section 2.4 of the reference paper for more details).

Log_Lx_Lbol
The logarithm of the X-ray-to-bolometric luminosity ratio log Lx/Lbol, of the source, using the quoted log Lx value (0.3 - 7.8 keV band) and the calculated stellar bolometric luminosity. For stars with optical photometry, Lbol and stellar masses were derived from the optical colors; for the others, they were computed from the J or Ks magnitudes for an age of 5 Myr. This parameter is provided only for the 81 sources identified with known cluster members and candidates listed in Tables 1 and 2 of the reference paper.

Vmag
The V magnitude of the identified counterpart to the X-ray source.

Rmag
The R magnitude of the identified counterpart to the X-ray source. Optical photometry is from Dolan & Mathieu (2002, AJ, 123, 387), except for the values for which the corresponding flag value is 'S': these are photographic magnitudes from the USNO-B1.0 or GSC2.3 catalogs.

Rmag_Flag
This flag parameter is set to 'S' to indicate that the corresponding magnitude is a photographic magnitude from the USNO-B1.0 or GSC2.3 catalogs.

Imag
I Magnitude of the identified counterpart to the X-ray source. Optical photometry is from Dolan & Mathieu (2002, AJ, 123, 387), except for the values for which the corresponding flag value is 'S': these are photographic magnitudes from the USNO-B1.0 or GSC2.3 catalogs.

Imag_Flag
This flag parameter is set to 'S' to indicate that the corresponding magnitude is a photographic magnitude from the USNO-B1.0 or GSC2.3 catalogs.

Jmag
The J magnitude of the identified counterpart to the X-ray source.

Hmag
The H magnitude of the identified counterpart to the X-ray source.

Ks_Mag
The K_s magnitude of the identified counterpart to the X-ray source.

Mass
The mass of the identified counterpart to the X-ray source, in solar masses. For stars with optical photometry, Lbol and stellar masses were derived from the optical colors; for the others, they were computed from the J or Ks magnitudes for an age of 5 Myr. This parameter is provided only for the 81 sources identified with known cluster members and candidates listed in Tables 1 and 2 of the reference paper.

Hmag_2
The H magnitude of the alternative optical/infrared identification for the X-ray source within the 4 arcsecs search radius.

Ks_Mag_2
The Ks magnitude of the alternative optical/infrared identification for the X-ray source within the 4 arcsecs search radius.

Log_Lx_2
The logarithm of the X-ray luminosity log Lx(alt) of the source in the 0.3-7.8 keV energy band, in erg s-1, assuming that it is associated with the alternative identification for the X-ray source, and calculated in the same way as log Lx.

Log_Lx_Lbol_2
The logarithm of the X-ray-to-bolometric luminosity ratio log Lx/Lbol (alt), assuming that it is associated with the alternative identification for the X-ray source, and calculated in the same way as log Lx /Lbol.

Mass_2
The mass of the identified alternative counterpart to the X-ray source, in solar masses, calculated in the same way as the mass for the the primary proposed counterpart.

Spect_Type
THe MK spectral type of the identified counterpart to the X-ray source.

Disk_Type
The disk classification for the identified counterpart to the X-ray source. The disk classification information is taken from Barrado y Navascues et al. (2007, ApJ, 664, 481) and Hernandez et al. (2009, ApJ, 707, 705); for Class II or EV stars (stars with evolved, optically thin disks), the authors also indicate whether there is spectroscopic evidence for accretion or not by appending an 'a' or 'n' to the classification.

Membership_Flag
This parameter flags with 's' those 46 sources with counterparts which are spectroscopically-confirmed members, i.e., objects with spectroscopic youth features and radial velocities which are consistent with their membership. This parameter was provided only for the 58 known cluster members and candidates which were listed in Table 1 of the reference paper. The HEASARC has added a value of 'P' to flag (1) the 12 remaining objects in Table 1 of the reference paper which are believed to be cluster members but have not been spectroscopically confirmed and (2) the 23 possible new cluster candidates which were listed in Table 2 of the reference paper that also lack spectroscopic confirmation.

Class
The HEASARC Browse object classification, based on the value of the disk_type parameter, when available.


Contact Person

Questions regarding the LAMORIXMM database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 21-Nov-2011