J/A+A/609/A127 X-ray sources in CMa OB1 (Santos-Silva+, 2018)
Star formation history of Canis Major OB1.
II. A bimodal X-ray population revealed by XMM-Newton.
Santos-Silva T., Gregorio-Hetem J., Montmerle T., Fernandes B., Stelzer B.
<Astron. Astrophys., 609, A127 (2018)>
=2018A&A...609A.127S 2018A&A...609A.127S (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; X-ray sources ; Photometry, infrared ;
Stars, masses ; Stars, ages
Keywords: X-rays: stars - stars: formation - stars: pre-main sequence -
stars: low-mass
Abstract:
The Canis Major OB1 association has an intriguing scenario of star
formation, especially in the region called Canis Major R1 (CMa R1)
traditionally assigned to a reflection nebula, but in reality an
ionized region. This work is focussed on the young stellar population
associated with CMa R1, for which our previous results from ROSAT,
optical, and near-infrared data had revealed two stellar groups with
different ages, suggesting a possible mixing of populations originated
from distinct star formation episodes.
The X-ray data allow the detected sources to be characterized
according to hardness ratios, light curves, and spectra. Estimates of
mass and age were obtained from the 2MASS catalogue and used to define
a complete subsample of stellar counterparts for statistical purposes.
A catalogue of 387 XMM-Newton sources is provided, of which 78% are
confirmed as members or probable members of the CMa R1 association.
Flares (or similar events) were observed for 13 sources and the
spectra of 21 bright sources could be fitted by a thermal plasma
model. Mean values of fits parameters were used to estimate X-ray
luminosities. We found a minimum value of log(LX[erg/s])=29.43,
indicating that our sample of low-mass stars (M*≤0.5 M☉), which
are faint X-ray emitters, is incomplete. Among the 250 objects
selected as our complete subsample (defining our "best sample"), 171
are found to the east of the cloud, near Z CMa and dense molecular
gas, of which 50% of them are young (<5Myr) and 30% are older
(>10Myr). The opposite happens to the west, near GU CMa, in areas
lacking molecular gas: among 79 objects, 30% are young and 50% are
older. These findings confirm that a first episode of distributed star
formation occurred in the whole studied region ∼10Myr ago and
dispersed the molecular gas, while a second, localized episode (<5Myr)
took place in the regions where molecular gas is still present.
Description:
For this work, four fields (each about 30 arcmin diameter with some
overlap) were observed with the XMM-Newton satellite. These fields are
located (Fig. 1) inside the arc-shaped ionized nebula, next to
Z CMa - Field E (east); around GU CMa - Field W (west); and between
both - Field C (centre) and Field S (south).
These observations were performed with the EPIC cameras (MOS1, MOS2,
and PN) in full frame mode with a medium filter. The C, W, and S
fields had an exposure time without background corrections of about
30ks while field E had 40ks.
Objects:
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RA (2000) DE Designation(s)
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07 04 18.3 -11 27 24.0 CMa cluster east (Field E)
07 02 58.4 -11 34 44.7 CMa cluster centre (Field C)
07 02 29.5 -11 47 12.4 CMa cluster south (Field S)
07 01 23.0 -11 19 56.6 CMa cluster west (Field W)
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb1.dat 115 387 X-ray sources detected in the combined images
of the EPIC cameras PN, MOS1 and MOS2
tableb2.dat 102 497 *Infrared 2MASS photometry, mass, age, and
infrared classification of members of CMa R1
region and counterparts to X-ray sources
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Note on tableb2.dat: A distance of 1 kpc is assumed for these sources.
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See also:
J/A+A/506/711 : Canis Major R1 X-ray sources (Gregorio-Hetem+, 2009)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- CMaX X-ray source identification (G1)
6- 7 I2 h RAh right ascension (J2000)
9- 10 I2 min RAm right ascension (J2000)
12- 16 F5.2 s RAs right ascension (J2000)
17 A1 --- DE- Declination sign (J2000)
18- 19 I2 deg DEd Declination (J2000)
21- 22 I2 arcmin DEm Declination (J2000)
24- 28 F5.2 arcsec DEs Declination (J2000)
30- 36 F7.3 --- ML Maximum likelihood
38- 42 F5.1 ct/ks CR-PN ?=- Count rate detected in EPIC camera PN
44- 46 F3.1 ct/ks e_CR-PN ?=- rms uncertainty on CR-PN
48- 52 F5.1 ct/ks CR-MOS1 ?=- Count rate detected in EPIC camera MOS1
54- 56 F3.1 ct/ks e_CR-MOS1 ?=- rms uncertainty on CR-MOS1
60- 64 F5.1 ct/ks CR-MOS2 ?=- Count rate detected in EPIC camera MOS2
66- 68 F3.1 ct/ks e_CR-MOS2 ?=- rms uncertainty on CR-MOS2
70- 74 F5.2 --- HR11 ?=- PN Hardness ratio (0.5-1.0-2.0keV)
76- 81 F6.2 --- e_HR11 ?=- rms uncertainty on HR11
83- 87 F5.2 --- HR21 ?=- PN Hardness ratio (1.0-2.0-7.3keV)
89- 93 F5.2 --- e_HR21 ?=- rms uncertainty on HR21
95- 99 F5.2 --- HR12 ?=- PN Hardness ratio (0.2-0.5-2.0keV)
101-104 F4.2 --- e_HR12 ?=- rms uncertainty on HR12
106-110 F5.2 --- HR22 ?=- PN Hardness ratio (0.5-2.0-4.5keV)
112-115 F4.2 --- e_HR22 ?=- rms uncertainty on HR22
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Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- CMaX X-ray source identification (G1)
5 A1 --- m_CMaX [abcde] Multiplicity index on CMaX
6 A1 --- n_CMaX [*] Note on CMaX (1)
7- 10 F4.1 arcsec Dist ? Distance from X-ray source centre
12- 27 A16 --- 2MASS 2MASS ID
29- 34 F6.3 mag Jmag ?=- 2MASS J magnitude
36- 40 F5.3 mag e_Jmag ?=- rms uncertainty on Jmag
42- 47 F6.3 mag Hmag ?=- 2MASS H magnitude
49- 53 F5.3 mag e_Hmag ?=- rms uncertainty on Hmag
55- 60 F6.3 mag Kmag ?=- 2MASS K magnitude
62- 66 F5.3 mag e_Kmag ?=- rms uncertainty on Kmag
68- 73 A6 --- Qflag 2MASS quality flag
75- 80 F6.3 Msun Mass ?=- Mass
81 A1 --- u_Mass [?] Uncertainty flag on Mass
83- 88 F6.3 Myr Age ?=- Age
89 A1 --- u_Age [?] Uncertainty lfag on Age
91-102 A12 --- WClass WISE classification
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Note (1): *: Counterpart candidate not considered owing to distance
incompatible with the cloud (see Sect. 4.1).
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Global notes:
Note (G1): Sources identified in the four fields, CNNN, ENNN, SNNN and WNNN.
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History:
From electronic version of the journal
References:
Gregorio-hetem et al., Paper I 2009A&A...506..711G 2009A&A...506..711G, Cat. J/A+A/506/711
(End) Patricia Vannier [CDS] 27-Mar-2018