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J/AJ/154/195    New binaries in the ε Cha association   (Briceno+, 2017)

New binaries in the ε Cha association. Briceno C., Tokovinin A. <Astron. J., 154, 195 (2017)> =2017AJ....154..195B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, double and multiple ; Photometry, RI ; Stars, distances ; Spectral types ; Stars, pre-main sequence Keywords: binaries: close - open clusters and associations: individual (epsilon Cha) - stars: pre-main sequence - techniques: high angular resolution Abstract: We present Adaptive Optics-aided speckle observations of 47 young stars in the ε Cha association made at the 4 m Southern Astrophysical Research Telescope in the I-band. We resolved 10 new binary pairs, 5 previously known binaries, and 2 triple systems, also previously known. In the separation range between 4 and 300 au, the 30 association members of spectral types G0 and later host 6 binary companions, leading to the raw companion frequency of 0.010±0.04 per decade of separation, comparable to the main sequence dwarfs in the field. On the other hand, all five massive association members of spectral types A and B have companions in this range. We discuss the newly resolved and known binaries in our sample. Observed motions in the triple system ε Cha, composed of three similar B9V stars, can be described by tentative orbits with periods 13 and ∼900 years and a large mutual inclination. Description: For the target selection, we used the list of proposed members of the epsilon Cha association from the Table 1 of Murphy et al. (2013, J/MNRAS/435/1325). The speckle observations reported here were obtained on 2016 January 17. The time was allocated through the NOAO program 2015B-0268, C. Briceno Principal Investigator. The sky was clear, with good seeing and a slow wind. We used the High-Resolution Camera (HRCam) - a fast imager designed to work at the 4.1 m SOAR telescope (Tokovinin & Cantarutti 2008PASP..120..170T). The camera was mounted on the SOAR Adaptive Optics Module (SAM; Tokovinin et al. 2016PASP..128l5003T; Objects: --------------------------------------------------------------------------- RA (ICRS) DE Designation(s) --------------------------------------------------------------------------- 11 59 51 -78 12.4 ε Cha association = NAME eps Cha Cluster --------------------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 92 47 Targets Observed in the epsilon Cha Stellar Group table2.dat 78 31 Measurements of Resolved Multiples in epsilon Cha table3.dat 34 28 Detection Limits for Unresolved Targets
See also: I/239 : The Hipparcos and Tycho Catalogues (ESA 1997) B/wds : The Washington Visual Double Star Catalog (Mason+ 2001-2014) I/337 : Gaia DR1 (Gaia Collaboration, 2016) J/AJ/139/743 : Speckle interferometry in 2008-09 (Tokovinin+, 2010) J/MNRAS/435/1325 : Membership of the ε Cha association (Murphy+, 2013) J/AJ/150/50 : Speckle interferometry at SOAR in 2014 (Tokovinin+, 2015) J/AJ/151/153 : Speckle interferometry at SOAR in 2015 (Tokovinin+, 2016) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 20 A20 --- Name Star name 22- 36 A15 --- Memb Designation from Murphy et al. (2013, J/MNRAS/435/1325) (1) 38- 39 I2 h RAh Hour of Right Ascension (J2000) 41- 42 I2 min RAm Minute of Right Ascension (J2000) 44- 47 F4.1 s RAs Second of Right Ascension (J2000) 49 A1 --- DE- Sign of the Declination (J2000) 50- 51 I2 deg DEd Degree of Declination (J2000) 53- 54 I2 arcmin DEm Arcminute of Declination (J2000) 56- 59 F4.1 arcsec DEs Arcsecond of Declination (J2000) 61- 65 F5.2 mag Imag [5.39/14.0] Cousins I-band magnitude 67- 71 A5 -- SpType MK spectral type 73- 75 I3 pc Dist1 [90/477]? Distance from Gaia DR1 parallax (Cat. I/337) 77- 79 I3 pc e_Dist1 [5/157]? Uncertainty in Dist1 81- 83 I3 pc Dist2 [94/165]? Distance from Murphy et al. (2013, J/MNRAS/435/1325) 85 A1 --- r_Dist2 [H] Reference for Dist2 (2) 87- 90 F4.2 arcsec Sep [0.03/4.2]? Separation between components 92 A1 --- f_Sep [*T] Flag on separation (3)
Note (1): Membership confirmed by Murphy et al. (2013, J/MNRAS/435/1325) have their corresponding Cha-NN numbers indicated. Candidate members are marked as "Cha-cand", while rejected members are labeled as "Cha-rej". For previously known multiples listed in the Washington Double Star catalog (Mason et al. 2001, Cat. B/wds) the "discoverer codes" are also provided. Note (2): Reference as follows: H = The parallax is from Hipparcos (Cat. I/239). Otherwise, parallaxes are kinematic. Note (3): Flag as follows: * = First-time resolution; T = Triple system.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 10 A10 --- WDS Washington Double Star catalog designation (HHMMm+DDMM) 12- 39 A28 --- Name Star name (1) 41- 47 F7.4 yr Epoch [16.0474/17.3719] Besselian epoch of observation (minus 2000) 49 A1 --- Filter [Iy] Filter used 51- 55 F5.1 deg theta [5.5/311.3] Position angle θ 57- 62 F6.4 arcsec rho [0.0306/4.2409] Separation ρ 64- 66 F3.1 mag Dm [0/5.7] Magnitude difference Δm between components 68 A1 --- f_Dm [*:q] Flag on Dm (2) 70- 78 A9 --- Note Short note
Note (1): From Table 1, Murphy et al. (2013, J/MNRAS/435/1325). Note (2): Flag as follows: * = Δm and the true quadrant are determined from the resolved long-exposure image; : = Indicates that the data are noisy and Δm is likely overestimated (see Tokovinin et al. 2010, J/AJ/139/743 for details); q = The quadrant is determined from the SAA image. In cases of multiple stars, the positions and photometry refer to the pairings between individual stars, not the photocenters of subsystems.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 21 A21 -- Name Target name 23- 26 F4.2 arcsec rho(min) [0.04/0.1] Minimum separation ρmin (1) 28- 30 F3.1 mag Dm(0.15) [0.7/2.6] Magnitude difference for 0.15 arcsec separation (2) 32- 34 F3.1 mag Dm(1) [2.2/6.1] Magnitude difference for 1 arcsec separation (2)
Note (1): The minimum separation equals the diffraction limit of 40 mas for all targets except the faintest ones, for which it is 0.1 arcsec. Note (2): The maximum detectable magnitude difference in the Cousins I-band at separations of 0.15 and 1 arcsec respectively, estimated from the autocorrelation function.
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 27-Jul-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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