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 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 2008PASP..120..170T). The camera was mounted on the SOAR Adaptive Optics
Module (SAM; Tokovinin et al. 2016PASP..128l5003T 2016PASP..128l5003T;
http://www.ctio.noao.edu/soar/content/soar-adaptive-optics-module-sam).
Objects:
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RA (ICRS) DE Designation(s)
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11 59 51 -78 12.4 ε Cha association = NAME eps Cha Cluster
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File Summary:
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FileName Lrecl Records Explanations
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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
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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
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Bytes Format Units Label Explanations
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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)
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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.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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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
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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.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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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)
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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.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 27-Jul-2018