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: -------------------------------------------------------- RA (2000) DE Designation(s) -------------------------------------------------------- 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) -------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Note on tableb2.dat: A distance of 1 kpc is assumed for these sources. -------------------------------------------------------------------------------- See also: J/A+A/506/711 : Canis Major R1 X-ray sources (Gregorio-Hetem+, 2009) Byte-by-byte Description of file: tableb1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Byte-by-byte Description of file: tableb2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Note (1): *: Counterpart candidate not considered owing to distance incompatible with the cloud (see Sect. 4.1). -------------------------------------------------------------------------------- Global notes: Note (G1): Sources identified in the four fields, CNNN, ENNN, SNNN and WNNN. -------------------------------------------------------------------------------- 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
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