J/A+A/475/959 X-ray properties of young stellar objects (Forbrich+, 2007)
Coronae in the Coronet: a very deep X-ray look into a stellar nursery.
Forbrich J., Preibisch T.
<Astron. Astrophys., 475, 959-972 (2007)>
=2007A&A...475..959F 2007A&A...475..959F
ADC_Keywords: Stars, pre-main sequence ; X-ray sources
Keywords: stars: pre-main sequence - stars: activity - stars: magnetic fields -
X-rays: stars
Abstract:
To study the X-ray properties of young stellar objects (YSOs), we
analyze an exceptionally sensitive Chandra dataset of the Coronet
cluster in the CrA star-forming region, achieving a limiting
luminosity of LX,min∼5x1026erg/s for lightly absorbed sources.
This dataset represents one of the most sensitive X-ray observations
ever obtained of a star-forming region.
The X-ray data are used to investigate the membership status of
tentative members of the region, to derive plasma temperatures and
X-ray luminosities of the YSOs, and to investigate variability on the
timescale of several years.
46 of the 92 X-ray sources in the merged Chandra image can be
identified with optical or near/mid-infrared counterparts. X-ray
emission is detected from all of the previously known optically
visible late-type (spectral types G to M) stellar cluster members,
from five of the eight brown dwarf candidates, and from nine embedded
objects ("protostars") with class 0, class I, or flat-spectrum
spectral-energy distributions (SEDs) in the field of view. While the
Herbig Ae/Be stars TY CrA and R CrA, a close companion of the B9e star
HD 176386, and the F0e star T CrA are detected, no X-ray emission is
found from any of the Herbig-Haro (HH) objects or the protostellar
cores without infrared source. We find indications for diffuse X-ray
emission near R CrA/IRS 7.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 86 46 Identification of Chandra X-ray sources with
optical or infrared counterparts in the CrA
star-forming region
tablea1.dat 122 92 Complete source list with parameters determined
by acis_extract for the energy range of 0.5-8keV
tablea2.dat 129 32 X-ray spectral fitting results for one- and
two-temperature models
--------------------------------------------------------------------------------
See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- CXOJ CXOJ designation (HHMMSS.ss+DDMMSS.s)
20 A1 --- n_CXOJ [a] Note for IRS 5a/b CXOJ (1)
22 A1 --- Opt [y/n] Counterparts to the X-ray source in the
optical DSS images ? (2)
24 A1 --- NIR [y/n] Counterparts to the X-ray source in the
infrared 2MASS images ? (2)
26 A1 --- MIR [y/n] Counterparts to the X-ray source in the
infrared Spitzer images ? (2)
28- 33 A6 --- SED SED class derived from the Spitzer photometry
36- 63 A28 --- Name Name(s) (3)
66- 78 A13 --- SpType MK spectral type(s)
82- 85 F4.2 solLum Lbol ? Stellar bolometric luminosity
86 A1 --- u_Lbol [?] Uncertain Lbol (1)
--------------------------------------------------------------------------------
Note (1):
a = The X-ray emission of the 0.9" binary IRS 5a/b (Chen & Graham
1993ApJ...409..319C 1993ApJ...409..319C; Nisini et al. 2005A&A...429..543N 2005A&A...429..543N) is
marginally resolved in the Chandra imag
Note (2):
y means that a counterpart exists;
n means that no counterpart can be seen
Note (3): Data collected from Casey et al. (1998AJ....115.1617C 1998AJ....115.1617C);
+ Olofsson et al. (1999, Cat. J/A+A/350/883);
+ Walter et al. (1997AJ....114.1544W 1997AJ....114.1544W);
+ Neuhauser et al. (2000, cat. J/A+AS/146/323);
+ Wilking et al. (1992, Cat. J/ApJ/397/52);
+ Prato et al. (2003ApJ...584..853P 2003ApJ...584..853P) and
+ Nisini et al. (2005A&A...429..543N 2005A&A...429..543N);
additional references are given in the discussion of the individual
objects in Sects. 3 and 4.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- CXOJ CXOJ designation (HHMMSS.ss+DDMMSS.s)
19 A1 --- n_CXOJ [*] *: manually added source
21- 27 F7.1 ct Counts Net (background-subtracted) counts
29- 33 F5.1 ct E_Counts Error on Counts (upper limit)
35- 39 F5.1 ct e_Counts Error on Counts (lower limit)
41- 43 F3.1 keV MedE Median photon energy
45- 49 F5.1 --- Signi Source significance (photometric S/N ratio)
51- 55 F5.2 --- HR1 Hardness ratio HR1 (1)
57- 60 F4.2 --- E_HR1 Error on HR1 (upper limit)
62- 65 F4.2 --- e_HR1 Error on HR1 (lower limit)
67- 71 F5.2 --- HR2 Hardness ratio HR2 (1)
73- 76 F4.2 --- E_HR2 Error on HR2 (upper limit)
78- 81 F4.2 --- e_HR2 Error on HR2 (lower limit)
83- 87 F5.2 --- HR3 Hardness ratio HR3 (1)
89- 92 F4.2 --- E_HR3 ?=- Error on HR3 (upper limit)
94- 97 F4.2 --- e_HR3 Error on HR3 (lower limit)
99-106 E8.3 ct/cm2/s Flux1 axis_extract estimate of the observed flux,
which is done channel-wise
108-115 E8.3 ct/cm2/s Flux2 axis_extract estimate of the observed flux,
which is done using an averaged value
117-120 F4.2 --- RelExp Ratio of the summed exposure map values at the
source position relative to the maximum
value (2)
122 I1 --- Nobs Number of observations in which a source was
detected (3)
--------------------------------------------------------------------------------
Note (1): Hardness ratios as:
HR1 = (H-S)/(H+S) where S=0.5-2.0keV and H=2.0-8.0keV
HR2 = (H-S)/(H+S) where S=0.5-1.7keV and H=1.7-2.8keV
HR3 = (H-S)/(H+S) where S=1.7-2.8keV and H=2.8-8.0keV
Note (2): i.e. information on the effective exposure time
Note (3): This number can be lower than eight in the outer parts of the map.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- CXOJ CXOJ designation (HHMMSS.ss+DDMMSS.s)
19 A1 --- n_CXOJ [ab] Note on CXOJ (1)
21- 26 F6.3 10+22cm-2 NH Hydrogen column density
28- 32 F5.3 10+22cm-2 E_NH Error on NH (upper limit)
34- 38 F5.3 10+22cm-2 e_NH ? Error on NH (lower limit)
40 A1 --- l_T1 Limit flag on T1
41- 46 F6.2 MK T1 Plasma temperature T1
48- 52 F5.2 MK E_T1 ? Error on T1 (upper limit)
54- 58 F5.2 MK e_T1 ? Error on T1 (lower limit)
60- 63 F4.1 MK T2 ? Second plasma temperature for
two-temperature model
65- 67 F3.1 MK E_T2 ? Error on T2 (upper limit)
69- 71 F3.1 MK e_T2 ? Error on T2 (lower limit)
73- 79 E7.3 --- Norm1 Normalization factor from XSPEC (2)
81- 87 E7.3 --- E_Norm1 Error on Norm1 (upper limit)
89- 95 E7.3 --- e_Norm1 Error on Norm1 (lower limit)
97-103 E7.3 --- Norm2 ? Second normalization factor from XSPEC
for two-temperature model (2)
105-111 E7.3 --- e_Norm2 ? rms uncertainty on Norm2
113-120 E8.3 10-7W LX Extinction-corrected (unabsorbed) X-ray
luminosity integrated over the 0.2-8keV band)
derived from the model parameters
122-125 F4.2 --- chi2 Goodness-of-fit measure chi2red value
127-129 I3 --- DOF Degree of freedom
--------------------------------------------------------------------------------
Note (1): Note as follows:
a = Iron abundance adjusted to fit the 6.7keV line.
b = Fit including fluorescent iron line at 6.4keV
Note (2): Defined as 10-14/(4πD2)∫(ne*nHdV).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 21-Jan-2008