J/A+A/537/A135 X-ray view of IC348 (Stelzer+, 2012)
X-ray view of IC348 in the light of an updated cluster census.
Stelzer B., Preibisch T., Alexander F., Mucciarelli P., Flaccomio E.,
Micela G., Sciortino S.
<Astron. Astrophys. 537, A135 (2012)>
=2012A&A...537A.135S 2012A&A...537A.135S
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; YSOs ; X-ray sources
Keywords: stars: pre-main sequence - X-rays: stars - stars: activity -
stars: coronae
Abstract:
IC348 is a nearby (∼310pc), young (∼2-3Myr) open cluster with >300
members identified from optical and infrared observations. We study
the properties of the coronae of the young low-mass stars in IC348
combining X-ray and optical/infrared data. The four existing Chandra
observations of IC348 are merged, thus providing a deeper and
spatially more complete X-ray view than previous X-ray studies of the
cluster. We have compiled a comprehensive catalog of IC348 members
taking into account recent updates to the cluster census. Our data
collection comprises fundamental stellar parameters, infrared excess
indicating the presence of disks, Halpha emission as a tracer of
chromospheric emission or accretion and mass accretion rates. We have
detected 290 X-ray sources in four merged Chandra exposures, of which
187 are associated with known cluster members corresponding to a
detection rate of ∼60% for the cluster members of IC348 identified in
optical/infrared studies. According to the most recent spectral
classification of IC348 members only four of the X-ray sources are
brown dwarfs (spectral type M6 and later). The detection rate is
highest for diskless Class III stars and increases with stellar mass.
This may be explained with higher X-ray luminosities for higher mass
and later evolutionary stage that is evident in the X-ray luminosity
functions. In particular, we find that for the lowest examined masses
(0.1-0.25 Msun) there is a difference between the X-ray luminosity
functions of accreting and non-accreting stars (classified on the
basis of their Halpha emission strength) as well as those of
disk-bearing and diskless stars (classified on the basis of the slope
of the spectral energy distribution). These differences disappear for
higher masses. This is related to our finding that the Lx/Lbol ratio
is non-constant across the mass/luminosity sequence of IC348 with a
decrease towards lower luminosity stars. Our analysis of an analogous
stellar sample in the Orion Nebula Cluster suggests that the decline
of Lx/Lbol for young stars at the low-mass end of the stellar
sequence is likely universal.
Description:
X-ray fluxes and upper limits are presented for all known
optical/infrared IC348 members observed by Chandra. The basic source
parameters for all X-ray sources are given.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 39 314 X-ray fluxes and upper limits
table7.dat 112 290 Primary Chandra catalog
--------------------------------------------------------------------------------
See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
J/AJ/131/1574 : Infrared photometry of IC348 members (Lada+, 2006)
J/A+A/324/549 : Deep UVBRI photometry in IC 348 (Trullols+ 1997)
J/ApJ/497/736 : The young cluster IC 348. (Herbig, 1998)
J/ApJ/525/466 : Young low-mass stars & brown dwarfs in IC 348 (Luhman+, 1999)
J/ApJ/541/977 : HST observations of low-mass stars in IC 348 (Najita+, 2000)
J/A+A/409/147 : J magnitude of IC 348 brown dwarfs (Preibisch+, 2003)
J/ApJ/593/1093 : IC 348 membership (Luhman+, 2003)
J/ApJ/597/555 : IR photometry of IC 348 young brown dwarfs (Mainzer+, 2003)
J/AJ/127/1602 : Cousins RI photometry in IC 348 (Cohen+, 2004)
J/MNRAS/358/341 : Ic photometry of IC 348 (Littlefair+, 2005)
J/ApJ/649/862 : IR phot. of IC 348 pre-main-sequence stars (Cieza+, 2006)
J/AJ/134/411 : Properties of IC 348 members (Muench+, 2007)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- CXOUJ Chandra designation (HHMMSS.ss+DDMMSS.s)
22- 26 I5 --- LRL Identifier, Cl* IC 348 LRL NNNNN in Simbad (1)
27 A1 --- m_LRL [AB] Multiplicity index on LRL (1)
28 A1 --- l_logFX Limit flag on logFX
30- 35 F6.2 [mW/m2] logFX Log of X-ray flux
38- 39 A2 --- Note [f2 ] Note (2)
--------------------------------------------------------------------------------
Note (1): Identifier from Luhman et al., 2003, Cat. J/ApJ/593/1093,
Luhman et al., 2005ApJ...618..810L 2005ApJ...618..810L, or
Muench et al., 2007, Cat. J/AJ/134/411.
The multiplicity column (m_LRL) was added on 10-Feb-2012 (see the
"History" section below).
Note (2): f2 if the flux was obtained as FLUX2 from ACIS Extract software
package
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq X-ray catalog sequence number
6- 23 A18 --- CXOUJ Chandra designation, HHMMSS.ss+DDMMSS.s
25- 33 F9.6 deg RAdeg Right Ascension in decimals degrees (J2000)
35- 43 F9.6 deg DEdeg Declination J2000 (in decimals degrees) (J2000)
45- 48 F4.1 arcsec ePos Standard deviation of position error (1)
50- 53 F4.1 arcmin theta Off-axis angle
55- 61 F7.1 ct CTnet Net counts extracted in the total energy band
(0.5-8.0keV)
63- 67 F5.1 ct e_CTnet One sigma uncertainty on Ct,net
69- 73 F5.1 ct BT background counts expected in the source
extraction region (total band)
75- 81 F7.1 ct CHnet Net counts extracted in the hard energy band
(2.0-8.0keV)
83- 86 F4.2 --- PSFf Fraction of PSF enclosed in extraction region
(at 1.497keV) (2)
88- 92 F5.1 --- Signi Source significance
94 A1 --- l_logPb limit flag of logPb
95- 98 F4.1 [-] logPb Probability that extracted counts (total band)
are solely from background (3)
100 A1 --- Anom [g] Source anomalies flag (4)
102 A1 --- Var [abc] Source variability flag (5)
104-108 F5.1 ks texp Source effective exposure time
110-112 F3.1 keV Emed Background-corrected median photon energy
in the total 0.5-8keV energy band
--------------------------------------------------------------------------------
Note (1): The single-axis position errors, sigmax and sigmay, are
estimated from the single-axis standard deviations of the PSF inside
the extraction region and the number of counts extracted.
Note (2): Note that a reduced PSF fraction (significantly below 90%) may
indicate that the source is in a crowded region or on the edge of the
field.
Note (3): Some sources have Pb values above the 1% threshold that defines
the catalog because local background estimates can rise during the
final extraction iteration after sources are removed from the catalog.
Note (4): Source anomalies flags as follows:
g = fractional time that source was on a detector
(FRACEXPO from MKARF) is <0.9
Note (5): Source variability flags based on KS statistic as follows:
a = no evidence for variability (0.05<PKS)
b = possibly variable (0.005<PKS<0.05)
c = definitively variable (PKS<0.005)
No value is reported for sources with fewer than four counts and for
sources in chip gaps or on field edges.
--------------------------------------------------------------------------------
Acknowledgements:
Beate Stelzer, stelzer(at)astropa.unipa.it
History
* 02-Dec-2011: Original version
* 10-Feb-2012: column "m_LRL" added to distinguish the components of
close binaries (following a note from Stephen Drake). In 2 cases
(LRL 60 and 187) there is an ambiguity on which component of the
binary is the X-ray emitter
(End) Beate Stelzer [INAF-OAPa Italy], Patricia Vannier [CDS] 02-Dec-2011