SIGORIXMM - Sigma Orionis Cluster XMM-Newton X-Ray Point Source Catalog
This table contains some of the results of an analysis of the
full EPIC field in an XMM-Newton observation of the young (~2 - 4 Myr) cluster
around the hot star sigma Orionis.The authors have detected 175 X-ray sources,
88 of which have been identified with cluster members, including very low-mass
stars down to the substellar limit. They detected eleven new possible
candidate members from the 2MASS (CDS Cat. <II/246>) catalog. The authors find
that late-type stars have a median log L_X/L_bol ~ -3.3, i.e. very close to
the saturation limit. They detected significant variability in ~ 40% of
late-type members or candidates, including 10 flaring sources; rotational
modulation was detected in one K-type star and possibly in another 3 or 4
stars. Spectral analysis of the brightest sources shows typical quiescent
temperatures in the range T_1 ~ 0.3 - 0.8 keV and T_2 ~ 1 - 3 keV, with
subsolar abundances Z ~ 0.1 - 0.3 solar, similar to what is found in other
star-forming regions and associations. The authors find no significant
difference in the spectral properties of classical and weak-lined T Tauri
stars, although classical T Tauri stars tend to be less X-ray luminous than
weak-lined T Tauri stars.
XMM-Newton observations of the sigma Ori cluster, centered on the
hot star sigma Ori AB, were carried out as part of the Guaranteed
Time of Roberto Pallavicini using both the EPIC MOS and PN cameras and
the RGS instrument. The observation (ID 0101440301) started at 21:47
UT on March 23, 2002 and ended at 9:58 UT on March 24, 2002, for a
total duration of 43 ks. The EPIC cameras were operated in Full Frame
mode using the thick filter.
This table contains the combined list of 88 X-ray sources positionally
(<= 5") associated with
confirmed or candidate cluster members, and 66 X-ray sources with no
such positional associations, detected above a significance thereshold
of 5 sigma. The two X-ray sources (source numbers 67 and
167) with 2 posssible positional associations are listed twice, once for
each positional association, with the X-ray information repeated. Thus,
there are 156 entries in this HEASARC table.
XMM-Newton observations of the sigma Orionis cluster.
II. Spatial and spectral analysis of the full EPIC field.
Franciosini E., Pallavicini R., Sanz-Forcada J.
<Astron. Astrophys., 446, 501-513 (2006)>
This table was created by the HEASARC in May 2007 based on CDS
catalog J/A+A/446/501 files tablea1.dat and tableb.dat.
A running source number (called NX in the reference paper)
in order of increasing J2000.0 Right Ascension, which uniquely identifies the
The name of the X-ray source using the '[FPS2006] NX' prefix (where
FPS2006 refers to Franciosini, Pallavicini, Sanz-Forcada 2006, and NX is the
name of the source number parameter in the reference paper), togther with the
X-ray source number, as recommended by the CDS Dictionary of Nomenclature of
This flag is set to 'Y' to indicate the 2 X-ray sources
(source numbers 59 and 130) which have been detected only on one MOS, else is
set to 'N'.
To create this Browse table, the HEASARC has combined
rows from two tables in the reference paper, Table A.1 which listed 88
X-ray sources which had at least one cluster member or candidate member
within 5" (2 of the 88 X-ray sources have 2 counterparts each, and are listed
twice, once for each counterpart), and Table B which listed 66 X-ray sources
which have no optical counterparts. To distinguish these two groups, the
HEASARC has created this flag parameter, which is set to 'Y' for the entries
from Table A.1 and to 'N' for the entries from Table B.
The Right Ascension of the X-ray source in the selected equinox. This was
given in J2000.0 coordinates to a precision of 0.01 seconds of time in the
The Declination of the X-ray source in the selected equinox. This was
given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original
The Galactic Longitude of the X-ray source.
The Galactic Latitude of the X-ray source.
The statiscal significance of the X-ray source detection.
The MOS-equivalent count rate of the X-ray source, in ct/s,
derived from the source detection algorithm run on the summed MOS1+MOS2+PN
dataset in the 0.3-7.8 keV energy band.
The rms uncertainty in the X-ray source count rate,
The name of the optical counterpart to the X-ray source.
Optical identifications are from the following sources:
-- 4772- 1 r05..., p05... = Wolk (1996, Ph.D. Thesis,
Univ. New York at Stony Brook)
-- rHHMMSS-DDMMa = [W96] rJHHMMSS+DDMMa in Simbad
-- pHHMMSS-DDMMa = [W96] pJHHMMSS+DDMMa in Simbad
-- 4771-NNNN = [W96] 4771-NNNN in Simbad
-- SE NNN = Scholz & Eisloffel (2004, CDS Cat. <J/A+A/419/249>)
[SE2004] NNN in Simbad
-- SWW NNN = Sherry et al. (2004, CDS Cat. <J/AJ/128/2316>) where
NNN is the "recno" of J/AJ/128/2316/table4 in VizieR
-- S Ori, J05... = Bejar et al. (2004, CDS Cat. <J/other/AN/325/705>,
Caballero et al. (2004A&A...424..857C)
Zapatero Osorio et al. (2002A&A...384..937Z): note that the
authors have dropped the S Ori prefix in front of the J05...
S Ori J05... = [BMZ2001] S Ori J05... in Simbad
S Ori NN = [BZR99] S Ori NN in Simbad
-- K = Kenyon et al. (2005, CDS Cat. <J/MNRAS/356/89>)
[KJN2005] NN in simbad
-- B = Burningham et al. (2005, CDS Cat. <J/MNRAS/356/1583>)
[BNL2005] F.FF NNNN in Simbad
This parameter flags the following notes about specific
c = Source #3 in Paper I (Sanz-Forcada et al., 2004A&A...421..715S)
d = Source #4 in Paper I (Sanz-Forcada et al., 2004A&A...421..715S)
e = Source detected on the PN only. The reported count rates are PN
count rates. L_X was derived using the conversion factor for PN
(see Sect. 3.1 of the reference paper).
The offset between the X-ray source and its optical counterpart's
position, in arcseconds.
The I magnitude of the optical/near-IR counterpart to the X-ray source.
The R-I color index of the optical/near-IR counterpart to the
The I-J color index of the optical/near-IR counterpart to the
The spectral type of the optical/near-IR counterpart to the
X-ray source. Spectroscopically-determined spectral types from the literature
are marked by having a value of 'L' for the spect_type_flag parameter. The
other spectral types have been estimated from the R-I, V-I or I-J colours
using the relations by Kenyon & Hartmann (1995, CDS Cat. <J/ApJS101/117>) and
Leggett et al. (2001ApJ...548..908L).
This flag parameter is set to 'L' if the spectral type
was taken from the literature.
The logarithm of the unabsorbed X-ray luminosity of the cluster member or
candidate, in the 0.3 - 8 keV energy band, in erg/s. This was computed
using a conversion factor in based on the results of the PN and MOS1
spectral fits of late-type stars (see Sect. 4 of the reference paper). The
conversion factor was determined by comparing the count rates obtained from
the Wavelet algorithm on the summed dataset with the unabsorbed X-ray flux
derived from the best-fit models, excluding the few sources with absorption
higher than the mean value of N_H = 2.7 x 10^20 cm^-2, derived from the
mean reddening E(B-V) = 0.05, and then taking the median value. The derived
conversion factor, valid for the summed and MOS datasets, is CF =6.6 x
10^-12 erg cm^-2 ct^-1, with an uncertainty of ~ 15% (1-sigma standard
deviation). For the source detected only in the PN the authors derived in
the same way a median conversion factor CF = 2.1 x 10^-12 erg cm^-2 ct^-1
for the PN count rates. They applied these factors to all stars for which
no spectral analysis can be performed, assuming that all of them have the
mean absorption, since individual absorption measures are generally not
available. For stars having N_H ~ 1 - 2 x 10^21 cm^-2, as found for some
sources, this will underestimate the X-ray luminosity by a factor of ~
1.5. For the stars with spectral fits the authors used instead the fluxes
determined from the PN or MOS1 (if PN is not available) best-fit models.
reported in Table 3 of the reference paper and in Sanz-Forcada et al.
(2004A&A...421..715S). Finally, X-ray luminosities have been derived using
the Hipparcos cluster distance of 352 pc.
The sensitivity in the center of the field (from 3-sigma upper limits) is L_X
~ 2 x 10^28 erg s^-1, and decreases to ~ 4 x 10^28 erg s^-1 at 13' offaxis,
and to ~ 7 x 10^28 erg s^-1 when only a MOS source is present.
This flag parameter is set to 'F' to mark values of the X-ray
luminosity which have been derived from the PN or MOS1 spectral fits reported
in Table 3 of the reference paper and in Sanz-Forcada et al.
This flag parameter indicates the type of T Tauri star that the
optical counterpart is believed to be, using the following categories:
C = probable Classical T Tauri Stars (CTTS)
C? = possible Classical T Tauri Stars (CTTS)
W = probable Weak-lined T Tauri Stars (WTTS)
W? = possible Weak-lined T Tauri Stars (WTTS)
The HEASARC Browse object classification based on the value of
the spect_type parameter, if available.
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