J/ApJ/567/423 CHANDRA obs. of YSOs in Monoceros R2 (Kohno+, 2002)
Chandra observations of high-mass young stellar objects in the
Monoceros R2 molecular cloud.
Kohno M., Koyama K., Hamaguchi K.
<Astrophys. J. 567, 423 (2002)>
=2002ApJ...567..423K 2002ApJ...567..423K
ADC_Keywords: Stars, pre-main sequence ; X-ray sources
Keywords: stars: early-type - stars: individual (Monoceros R2) -
stars: pre-main-sequence - X-rays: stars
Abstract:
We observed the Monoceros R2 molecular cloud with the ACIS-I array on
board the Chandra X-Ray Observatory. From the central 3.2'x3.2'
region, we detect 154 sources above the detection limit of
∼5x10-16erg/s/cm2 with a 100ks exposure. About 85% of the X-ray
sources are identified with an infrared counterpart, including four
high-mass stars in the zero-age main-sequence (ZAMS) and/or
premain-sequence (PMS) phase. The X-ray spectra of the high-mass ZAMS
and PMS stars are represented by a thin thermal plasma model of a
temperature above ∼2keV. The X-rays are time variable and exhibit
rapid flares. This high-temperature plasma and flaring activity is
similar to that seen in low-mass PMS stars and is contrary to the
behavior observed in high-mass main-sequence stars.The X-ray
luminosity increases as the intrinsic K-band flux increases. However,
the X-ray luminosity saturates at a level of ∼1031erg/s. We conclude
that high-mass ZAMS and PMS stars emit X-rays, possibly because of
magnetic activity such as that of low-mass stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 118 154 CHANDRA X-ray sources in the Monoceros R2 region
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See also:
J/AJ/114/198 : The Monoceros R2 Cluster (Carpenter+ 1997)
J/ApJ/566/974 : CHANDRA obs. of YSOs in OMC-2 and OMC-3 (Tsujimoto+, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [KKH2002] Source number
5- 6 I2 h RAh Hour of Right Ascension (J2000) (1)
8- 9 I2 min RAm Minute of Right Ascension (J2000) (1)
11- 15 F5.2 s RAs Second of Right Ascension (J2000) (1)
17 A1 --- DE- Sign of the Declination (J2000) (1)
18- 19 I2 deg DEd Degree of Declination (J2000) (1)
21- 22 I2 arcmin DEm Arcminute of Declination (J2000) (1)
24- 27 F4.1 arcsec DEs Arcsecond of Declination (J2000) (1)
29- 31 I3 ct Cts CHANDRA counts
33- 37 F5.1 % VarPr Variable probability (2)
39- 42 F4.1 kT Temp ? Temperature
44 A1 --- l_Temp Limit flag on the 90% confidence limit
45- 47 F3.1 kT e_Temp ? The 90% confidence value on Temp or
lower limit if E_Temp is given
49- 52 F4.1 kT E_Temp ? The upper 90% confidence limit on Temp
54 A1 --- f_Temp [fg] Flag on Temp (3)
56- 59 F4.1 [cm-3] LogEM Log of the emission measure
61- 64 F4.1 [cm-3] e_LogEM The lower 90% confidence limit on LogEM
66- 69 F4.1 [cm-3] E_LogEM The upper 90% confidence limit on LogEM
71- 74 F4.1 10+22cm-2 NH Hydrogen column density
76- 79 F4.1 10+22cm-2 e_NH The lower 90% confidence limit on NH
81- 85 F5.1 10+22cm-2 E_NH The upper 90% confidence limit on NH
87- 90 F4.1 10-15mW/m2 Flux Observed 0.5-10.0 keV band flux
in 10-15erg/cm2/s
92- 95 F4.1 [10-7W] LogLX Log of the absorption-corrected
0.5-10.0keV band luminosity in erg/s
97-100 F4.1 [10-7W] e_LogLX The lower 90% confidence limit on LogLX
102-105 F4.1 [10-7W] E_LogLX The upper 90% confidence limit on LogLX
107-109 I3 --- IRNum ? IR counterpart number (4)
111-117 A7 --- IRName IR source name (5)
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Note (1): Mean position error is 0.15".
Note (2): Obtained by Kolmogorov-Smirnov test to 0.5-10keV band.
Note (3): Flags on Temp:
f = fixed;
g = The best-fit values of kT not determined to be below 20keV,
hence we assume the temperatures are 20keV for estimation of the
other parameters.
Note (4): Source numbers are from Carpenter et al. (1997, Cat. J/AJ/114/198).
Note (5): From Beckwith et al. (1976ApJ...208..390B 1976ApJ...208..390B),
Howard et al. (1994ApJ...425..707H 1994ApJ...425..707H) and
Capenter et al. (1997, Cat. J/AJ/114/198).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 25-Apr-2002