5.4 Determination of physical parameter
5.4.1 Primary mass and age
The method presented in this section is based on the work by Dr. Janos Schmidt, which is also published in Schmidt et al. (2014). The procedure therein was adopted for this work to get an estimate of the primary mass and age using the most recent version of the MATLAB program (MATLAB 2010) developed and kindly provided by Dr. Schmidt.
With the observational parameter for each investigated object, i.e. BVJHK s photometry,
5 D a ta An a ly si s
Table 13. Measured brightness differences, apparent and absolute magnitudes for the visual companions identified in this study.
Object Distance Observation Band ∆ma msystem mprim mcomp Mprim Mcomp
(pc) date (mag) (mag) (mag) (mag) (mag) (mag)
Binaries
2548 81.0+3.8−3.5 2005-12-06 K s 1.1620±0.0044 5.637±0.019 5.96±0.02 7.119±0.022 1.415+0.103−0.095 2.577+0.104−0.095 2007-09-16 K s 1.1400±0.0054 5.637±0.019 5.96±0.02 7.103±0.023 1.421+0.103−0.095 2.561+0.104−0.095 15627 156.0+20.1−16.0 2006-10-16 H 2.166±0.049 5.439±0.017 5.578±0.025 7.743±0.075 −0.44+0.28−0.22 1.73+0.29−0.23 16511 107.4+4.6−4.2 2005-01-06 K s 2.547±0.025 5.881±0.017 5.980±0.019 8.53±0.04 0.824+0.094−0.087 3.371+0.101−0.094
2005-11-26 K s 2.710±0.025 5.881±0.017 5.967±0.019 8.68±0.04 0.811+0.094−0.087 3.521+0.101−0.094 2011-08-25 K s 2.353±0.029 5.881±0.017 6.00±0.02 8.351±0.043 0.843+0.095−0.087 3.195+0.102−0.095 16803 149.3+12.3−10.6 2005-01-09 K s 0.884±0.012 5.526±0.024 5.924±0.028 6.808±0.032 0.07+0.18−0.16 0.96+0.18−0.16
2007-09-20 K s 0.812±0.026 5.526±0.024 5.947±0.032 6.759±0.042 0.09+0.18−0.16 0.91+0.18−0.16 2007-09-30 K s 0.798±0.013 5.526±0.024 5.951±0.028 6.749±0.033 0.10+0.18−0.16 0.90+0.18−0.16 17563 163.7+8.2−7.4 2005-01-10 K s 5.88±0.13 5.592±0.02 5.597±0.021 11.48±0.16 −0.5+0.1−0.1 5.38+0.19−0.18
: : : : : : : : : :
Higher-order multiple systems
24925AB 281.7+158.8−74.7 2005-01-09 K s 2.27637±0.00077 6.433±0.019 6.62±0.02 8.899±0.021 −0.65+1.22−0.58 1.62+1.22−0.58 2012-09-19 K s 2.2885±0.0043 6.433±0.019 6.618±0.021 8.906±0.024 −0.66+1.22−0.58 1.63+1.22−0.58 2013-01-04 K s 2.258±0.001 6.433±0.019 6.62±0.02 8.878±0.021 −0.66+1.22−0.58 1.60+1.22−0.58 24925AC 2005-01-09 K s 2.920±0.015 6.433±0.019 6.62±0.02 9.542±0.034 −0.65+1.22−0.58 2.27+1.22−0.58 2012-09-19 K s 2.988±0.022 6.433±0.019 6.618±0.021 9.605±0.041 −0.66+1.22−0.58 2.33+1.23−0.58 2013-01-04 K s 3.001±0.012 6.433±0.019 6.62±0.02 9.62±0.03 −0.66+1.22−0.58 2.35+1.22−0.58 26237AB 271.0+130.6−66.5 2005-04-09 K s 0.9890±0.0089 5.056±0.017 5.536±0.025 6.525±0.029 −1.67+1.05−0.53 −0.68+1.05−0.53
2012-09-19 K s 1.0510±0.0058 5.056±0.017 5.516±0.018 6.567±0.021 −1.69+1.05−0.53 −0.63+1.05−0.53
26237AC 2005-04-09 K s 2.036±0.054 5.056±0.017 5.536±0.025 7.572±0.068 −1.67+1.05−0.53 0.37+1.05−0.54 2012-09-19 K s 2.07312±0.00018 5.056±0.017 5.516±0.018 7.589±0.019 −1.69+1.05−0.53 0.39+1.05−0.53
: : : : : : : : : :
Notes. The given companion identification AB, AC, etc. for visual higher-order multiples indicates the sequences of detection by increasing magnitude difference. The full list is presented in Table A4.
aMeasured magnitude difference in the given band.
parallax, spectral type and luminosity class, the effective temperature Teff, the interstellar extinction in the V band AV and the bolometric luminosity Lbol were derived, and then the mass and age were estimated comparing the results with theoretical models. The most important steps of the procedure are described in the following.
The given spectral type from literature was employed to calculate the effective temperature using data from Lang (1992)12 and Kenyon and Hartmann (1995) for main sequence stars.
The temperature was then linear interpolated between neighbouring grid-points for a deci-mal spectral type. To get an estimate on the error of the temperature an uncertainty of the spectral type of ±1 subclass was assumed. This rather conservative assumption was made to take into account that the source of the given spectral type is mostly unknown, i.e. it is not clear whether the given spectral type was determined by photometric or spectroscopic analysis.
The interstellar reddening in the V band AV due to interstellar extinction was compiled from the measured colours (X − V )m and the model colours (X − V )0 by Bessell et al.
V applied for the different available bands X (X = BVJHK ) are listed in Table 12. However, the model data by Bessell et al. (1998) depend on log g and the temperature, hence on the spectral classification. The investigated sample does not contain objects with negative parallax values. Therefore, no correction of the parallaxes according to Smith and Eichhorn (1996) was applied. The bolometric luminosity was then derived by Lbol = 100.4·(5 log d−5+4.74−BCV−mV+AV), (5.29) where d is the distance in pc, BCV the bolometric correction in the V band, mV the apparent V band magnitude, and AV the corresponding interstellar extinction. The BCV
obtained from Bessell et al. (1998) was calibrated to the bolometric magnitude of the Sun Mbol,⊙ = 4.74 mag and is consistent with the apparent magnitude of the Sun V⊙ =
−26.76 mag given in their paper. This test is suggested by Torres (2010), because the zero point of BCV is arbitrary, while the bolometric magnitude of the Sun Mbol,⊙ cannot be chosen arbitrary.
Mass and age were estimated by comparing the calculated bolometric luminosities and effective temperatures with theoretical models for solar metallicity by Schaller et al. (1992), Bertelli et al. (1994) and Claret (2004). The metallicity is only well known for few stars and affect the mass estimation only by a few percent. The differences in mass between the models with the same metallicity are comparable to this (Hohle et al. 2010). The results were averaged from the error-weighted closest grip points per model.
The results of the parameter estimation for the 315 primary stars (blue dots), without the post-RGB star HIP 3678, contained in this sample are shown in the left-hand panel of
12Originally from Schmidt-Kaler (1982)
data those tables were selected where the metallicity Z is about 0.02 and the fraction of helium Y is roughly 0.26. The main characteristics of the used models are summarised in Table 14. The evolutionary models slightly differ in their assumed metallicity. This also effects the obtained masses. However, the variation between these models is very low, and therefore the variation of the results is also expected to be at a negligible level of percent-age. The mass range covered by the evolutionary tracks varies from 0.02 M⊙ to more than 20 M⊙, and the available isochrones range from a few thousand year up to several Gyr.
For each model a three-dimensional grid was constructed with the input parameter age
Table 14. Parameter ranges covered by the utilised evolutionary models.
Model Y Z Mass Age
M⊙ log10([yr ]) Baraffe et al. (1998; 2002) 0.275 -a 0.02–1.4 6.0–9.9 Siess et al. (2000) 0.279 0.02 0.1–7.0 ∼3.0–10.4 Girardi et al. (2000) 0.273 0.019 0.1–7.0 7.8–10.25 Bertelli et al. (2009) 0.26 0.017 0.15–20.0 8.95–10.15 Bressan et al. (2012) 0.275 0.0152 0.1–350 6.0–10.1
aBaraffe et al. (1998) only gives the total metal abundance [M/H]=0.
and magnitude in the x-y plane and the resulting physical parameter in z direction. Points between the model grid points were estimated by linear interpolation. Given the input pa-rameter, magnitude and age, and their associated uncertainties (3×3 values in total), the mass and the other parameter were determined as median and standard deviation of this set of 9 result data points. Finally, the results of the different models were averaged to obtain mass, luminosity and effective temperature of any found companion. The uncertainty of the results was determined from the average error of each model.
In order to analyse the binary properties of the sample statistically, the mass ratio q for each system and each model was calculated from the estimated mass of the primary and the companion. The mass ratio as a function of the primary is given by
q = MS
MP
,
where MS donates the mass of the companion and MP the mass of the primary. The obtained mass ratios from each model were also averaged. The physical parameter derived for each sample stars and their identified companion(s) as well as the calculated average masses and mass ratios are summarised in Table 15 and Table A5.
5 D a ta An a ly si s
Table 15. Estimated masses for the visual companions resolved in this study. The full list is presented in Table A5.
Mcomp
Object log(Age[yr ]) Observation Band MX,comp Mprim (1) (2) (3) (4) (5) (6) Mcomp q
date (mag) (M⊙) (M⊙) (M⊙) (M⊙) (M⊙) (M⊙) (M⊙) (M⊙)
Binaries
2548 9.06+0.03−0.04 2005-12-06 K s 2.577+0.104−0.095 2.00±0.01 1.26±0.02 1.24±0.03 1.28±0.03 1.28±0.03 1.29±0.03 1.27±0.03 0.64±0.01 2007-09-16 K s 2.561+0.104−0.095 1.27±0.03 1.24±0.03 1.28±0.03 1.28±0.03 1.30±0.03 1.28±0.03 0.64±0.01 15627 7.64+0.08−0.09 2006-10-16 H 1.73+0.29−0.23 4.4±0.1 2.1±0.3 2.0±0.2 2.1±0.2 2.1±0.2 0.46±0.06 16511 8.1+0.1−0.2 2005-01-06 K s 3.371+0.101−0.094 2.65±0.07 1.06±0.02 1.03±0.02 1.07±0.02 1.06±0.02 1.07±0.03 1.06±0.02 0.40±0.01 2005-11-26 K s 3.521+0.101−0.094 1.02±0.02 0.99±0.02 1.03±0.02 1.02±0.02 1.03±0.02 1.02±0.02 0.38±0.01 2011-08-25 K s 3.195+0.102−0.095 1.12±0.02 1.08±0.02 1.12±0.03 1.11±0.03 1.13±0.03 1.11±0.03 0.42±0.01 16803 8.47+0.03−0.03 2005-01-09 K s 0.96+0.18−0.16 3.13±0.04 2.34±0.09 2.5±0.1 2.5±0.1 2.5±0.1 2.4±0.1 0.78±0.03
2007-09-20 K s 0.91+0.18−0.16 2.4±0.1 2.5±0.1 2.5±0.1 2.5±0.1 2.5±0.1 0.79±0.03
2007-09-30 K s 0.90+0.18−0.16 2.38±0.09 2.5±0.1 2.5±0.1 2.5±0.1 2.5±0.1 0.79±0.03
17563 7.1+0.3−0.7 2005-01-10 K s 5.38+0.19−0.18 5.9±0.3 0.58±0.03 0.2±0.1 0.2±0.1 0.56±0.03 0.3±0.1 0.39±0.09 0.07±0.02 20020 8.26+0.03−0.04 2004-12-08 K s 2.04+0.12−0.11 2.79±0.06 1.61±0.07 1.69±0.07 1.65±0.08 1.67±0.08 1.66±0.08 0.59±0.03 2007-09-20 K s 2.06+0.13−0.12 1.58±0.08 1.68±0.07 1.64±0.08 1.66±0.08 1.64±0.08 0.59±0.03 2007-09-30 K s 2.0+0.1−0.1 1.61±0.07 1.69±0.07 1.65±0.08 1.67±0.07 1.66±0.07 0.59±0.03 20042 7.4+0.2−0.3 2005-11-16 K s 6.48+0.32−0.32 3.9807±0.0005 0.37±0.04 0.17±0.05 0.15±0.05 0.35±0.05 0.19±0.05 0.25±0.05 0.06±0.01 2012-09-19 K s 7.24+0.35−0.35 0.26±0.04 0.10±0.03 0.10±0.01 0.24±0.03 0.13±0.03 0.17±0.03 0.042±0.007
: : : : : : : : : : : : : :
Higher-order multiple systems
24925AB 8.12+0.04−0.05 2005-01-09 K s 1.62+1.22−0.58 3.8±0.1 2.0±0.7 2.1±0.8 2.3±0.7 2.3±0.7 2.2±0.7 0.6±0.2
2012-09-19 K s 1.63+1.22−0.58 2.0±0.7 2.1±0.8 2.3±0.7 2.3±0.7 2.2±0.7 0.6±0.2
2013-01-04 K s 1.60+1.22−0.58 2.0±0.7 2.1±0.8 2.3±0.7 2.3±0.7 2.2±0.7 0.6±0.2
24925AC 2005-01-09 K s 2.27+1.22−0.58 1.5±0.6 1.1874±0.0008 1.6±0.7 1.8±0.6 1.8±0.6 1.6±0.5 0.4±0.1 2012-09-19 K s 2.33+1.23−0.58 1.4±0.6 1.1654±0.0005 1.5±0.6 1.7±0.6 1.8±0.6 1.5±0.5 0.4±0.1 2013-01-04 K s 2.35+1.22−0.58 1.4±0.6 1.1601±0.0005 1.5±0.6 1.7±0.6 1.7±0.6 1.5±0.5 0.4±0.1 26237AB 6.98+0.05−0.06 2005-04-09 K s −0.68+1.05−0.53 10.9±0.4 7.0±0.7 7.3±2.0 7.3±2.0 7.2±2.0 0.7±0.2
2012-09-19 K s −0.63+1.05−0.53 6.9±0.7 7.2±2.0 7.2±2.0 7.1±2.0 0.6±0.2
26237AC 2005-04-09 K s 0.37+1.05−0.54 4.4±2.0 4.6±1.0 4.6±1.0 4.5±2.0 0.4±0.1
2012-09-19 K s 0.39+1.05−0.53 4.3±2.0 4.6±1.0 4.6±1.0 4.5±2.0 0.4±0.1
39331AB 7.34+0.04−0.05 2007-01-20 K s 7.25+1.36−0.61 9.2±0.5 0.3±0.1 0.13±0.08 0.3±0.1 0.19±0.08 0.2±0.1 0.02±0.01
39331AC 2007-01-20 K s 7.49+1.37−0.61 0.3±0.1 0.11±0.07 0.3±0.1 0.2±0.1 0.02±0.01
42504AB 7.2+0.2−0.4 2006-01-07 K s 2.6+0.1−0.1 5.0±1.0 1.23±0.04 1.30±0.06 1.31±0.04 1.30±0.06 1.28±0.05 0.26±0.01
42504AC 2006-01-07 K s 4.75+0.12−0.11 0.71±0.02 0.5±0.1 0.5±0.1 0.69±0.02 0.5±0.1 0.6±0.1 0.11±0.02
: : : : : : : : : : : : : :
Note. Mcomp is the average mass obtained from available models. q is the mass ratio as function of the primary mass; q = Mcomp/MP. References. (1) Delfosse et al. (2000); empirical mass-luminosity relation for M . 1.0 M⊙. (2) Girardi et al. (2000). (3) Baraffe et al. (2002).
(4) Siess et al. (2000). (5) Bertelli et al. (2009). (6) Bressan et al. (2012)
6 Detection limits and completeness
In order to minimize the bias in the characterisation of the multiplicity status of all target objects, and consequently in the resulting distribution of the companion properties, the quantitative detection limits were estimated in the course of the analysis of each target star. These limits depend on a variety of parameter such as the atmospheric conditions, i.e.
seeing and coherence time, in the observing night, the total exposure time, but also on the angular separation and magnitude difference from the bright primary star. The achieved contrast level for each target star were used to create a completeness map of the survey in order to be able to estimate reasonable limits for the statistical analysis.
Detection limits
To measure the detection limits as a function of the angular separation, a one-dimensional sensitivity curve was created using the following procedure. First, for each pixel i on the detector the distance ri to the previously determined position of the central star was calculated, and the corresponding measured flux Fj stored. Then, n annuli of equal width w were selected depending on the central wavelength λ of the used filter by
w = 0.61 · λ D,
the half diffraction limit available in the observation. D is the size of the mirror at the VLT, with D = 8.2 m. For a typical observation investigated in this study, taken in the K s band (λ = 2.18 µm) with the S13 objective, the width of an annulus w is ≈ 2.5 Px.
The flux values Fj from all rj ∈ (Ri, Ri+1], with i = 0, 1, ... n − 1, were than sorted, the upper and lower 10 % excluded and those values rejected which deviate by more than 3σ13 from the median in order to remove the contribution of the stars contained in the annulus from the calculation. The standard deviation of the remaining values σ(R) was than used as estimate of the background noise. The resulting 3 σ contrast level as a function of the angular separation is then estimated to be
Σ(R) = 2.5 · log Fpeak
3σ(R)
mag. (6.1)
The procedure described above was also applied to the PSF-subtracted image. However, the differences between the two resulting curves is only marginal. The main reason for this is that the main source of the noise is the photon-noise which is superimposed with the measured signal. The removal of the signal by subtraction of the PSF does not significantly change the measured residual noise, and thus the computed sensitivity remains almost equal.
13The choice of the 3 σ noise level was confirmed by inserting and retrieving simulated companions at this contrast level by Haase (2009).
brown dwarf limit (M . 75 MJup) is indicated by the blue dotted lines. In case of HIP 20042, located at a distance of about 55 pc from Earth and with an estimated age of ≈ 27 Myr, sub-stellar objects could have been detected at separations larger than ≈ 0.6 arcsec or
≈ 33 au, respectively. The diffraction limit in the observed band and the closest image boundary are plotted for completeness by the vertical dash-dotted lines.
0.1 1 10
Angular separation (arcsec) 0
2
4
6
8
10
Magnitude difference (mag)
Figure 20. Plot of the average sensitivity, i.e. the achieved magnitude difference as function of the angular separation of all NaCo observations investigated in this study, including stars without detection of candidate companions in the FoV of the NaCo image.
Companion candidates with more than one NaCo observation are plotted as filled circles, those with only one NaCo observation are indicated by open circles. The used filter band is illustrated by the colour of the observed objects and the average sensitivity curves (H-red; K s-black), respectively, while the used objectives (S13-solid; S27-dashed; SDI-dotted) are represented by the shape of the lines. Duplicate observations of the same companion have not been removed in this picture.
The average sensitivity curve for each used NaCo objective and filter band is shown in Figure 20. Companion candidates with more than one VLT/NaCo observation within this study are shown as filled circles, while companion candidates with only one available obser-vation are plotted as open circles. The used NaCo objectives are indicated by the shape of the lines, whereas the colour of the lines and the circles represent the filter band in which the images were taken. Note that duplicate observations of the same companion have not been removed in the picture.
The detection limits in the different bands and observed with SDI, S13 or S27 are com-parable for separations smaller than about 0.3′′ and typical average contrasts achieved are 5 mag, 7.5 mag and 8 mag at 0.2′′, 0.5′′ and >0.8′′ from the primary star, respectively.
The best average contrast of ∆m ≈ 9 mag, however, was achieved in the K s band images obtained with the NaCo S13 and S27 objective for separations ρ& 2 arcsec. Towards larger angular distances the survey is limited by the field of view of the S27 objective, and thus objects with ρ& 15′′ cannot be measured. At closer separations this survey is limited by the PSF wings of the corresponding primary star which hinder the detection of even relatively
respectively.
The completeness distribution appears smoother in terms of the angular separation ρ and the magnitude difference ∆m compared to the right-hand panel due to the relatively small uncertainties in the astrometric and photometric measurements. In this plane a complete-ness of more than 90 % was achieved at a K band magnitude difference of about 7 mag for separations between 1 to 9 arcsec. Beyond this separation the completeness drops rapidly due to the FoV of the S 13 objective and its superimposition with the FoV of the S 27 objective. The completeness in the plane of the deduced parameter, on the other hand, appears less smooth due to the uncertainties in a variety of parameter such as distance to the star, spectral type or magnitude of the primary, respectively, which were employed for the calculations. The uncertainties are reflected in the calculated ages, and consequently in the derived masses, as well as in the projected separations. This leads to the reduced completeness observed in the sample.
Also visible is the mentioned deficiency of low mass-ratio companions (q . 0.1) at close separations smaller than about 100 au, due to the PSF wings of the corresponding primary star, while numerous possible companions are observed with q < 0.1 at projected distances between about 100 and 2000 au.
As pointed out in section 5.2, the probability of finding a background source in the vicinity of a target star is a function of the distance to the star and the brightness of the candidate companion, and in particular distant, very faint companion candidates therefore show an increased probability of being a background source. While this is no problem for those targets with more than one observation, where background sources are identified through the CPM analysis, it is well possible that the sample of remaining companion candidates, with an inconclusive companion status, includes a few background sources. However, given the low number of objects with only one observation the number of background sources is expected to be negligible.
The following limits were specified for the statistical analysis as reasonable compromise between the minimum number of background objects included by mistake in the sample, the number of missed possible companions due to incompleteness, but also to ensure a fair, quantitative comparison of the results with other surveys, respectively.
(1) A main sample containing the companions confirmed by the CPM analysis, which is not affected by background objects. To minimise the detection bias in q at small separations the mass ratio was limited to q ≥ 0.05.
(2) A combined sample including the confirmed companions as well as the remaining candidate companions with q ≥ 0.1 to minimise the number of possible background sources.
(3) A second sub-sample, constructed for completeness, including the confirmed com-panions as well as the remaining candidate comcom-panions with q ≥ 0.05, which marginally increases the chance of included background sources.
(4) All sample were also restricted to detections at separations between 20 and 2000 au, following the completeness limit of 68 % (dashed line), because at smaller and larger distances the detection bias in q becomes too important.
From the inspection of the completeness, achieved in this thesis, it is evident that a future extension of this work requires a combination of different observation techniques to minimise observational and target selection biases, inherited in the analysed archive data. While larger separations can be mapped using wide-field adaptive optic observations and may include also historical photographic plate observations, next-generation extreme AO systems, such as VLT/SPHERE, and advanced imaging and analysis techniques, are required to map the regions between about 10 to 100 au and mass ratios q < 0.1. Below the resolution limit of current AO systems, only radial velocity measurements provide a sufficient sensitivity to low-mass companions with q = 0.1 compared to interferometric observation techniques which are currently limited by their dynamic range.
7 Results and Discussion
7.1 Identified companions
General results
In this thesis, a total of 317 stars were investigated, containing 316 B-type stars and the central star of the planetary nebula NGC 246 (HIP 3678 A), which was found by chance in the selected volume-limited sample.
In the vicinity of 148 B-type stars, about 47 % of the whole analysed sample, in total 194 sources were resolved. The physical association of 86 objects, in the vicinity of 79 primary stars, could be confirmed using the common proper motion analysis technique, and hence these sources are considered to be co-moving companions, hereafter. The status of 75 com-panion candidate sources, detected in the proximity of 55 primary stars, remains uncertain.
This is mainly due to inconclusive results obtained in the common proper motion analysis which can be introduced by, for instance, only two available observational data-sets that are insufficiently separated in time, discrepancies in separation or position angle due to different calibration methods, used in observations by other authors, different instrumentation, or an underestimation in the assumed maximum possible orbital motion which was estimated for a circular orbit not taking into account the likely eccentricity of the orbit, for instance.
Because a second-epoch observation was not available for 34 of the 75 inconclusive sources their companion status is based on the statistical assessment being a chance projection, described in section 5.2. 25 of these sources, satisfying the probability criterion of less than 5 %, are considered to be likely physical associated companion candidates whereas 9 sources are presumable background. However, all these 75 objects are subject to further investigation and will be observed at least one more time in the near future to be able to derive robust conclusions on their companion status. Furthermore 33 sources, detected in the surrounding area of 21 B-type primaries, were identified as background and are therefore not included in the analysis.
A study of the available literature for each sample star ended up with 106 already known objects found among the 194 detected sources, while 25 objects, resolved in the vicinity of 23 stars, were identified as known sources for which the companion status, either co-moving, inconclusive/undefined or background objects, respectively, could be confirmed for the first time within this thesis. In addition to that no published data were found for 63 objects in the direct surrounding of 45 sample stars. A more detailed overview on these new companions and companion candidates is presented in the adjacent section.
The observed and computed properties for systems with physical or visual companions are summarized in extracts in Table 16. The full result table for all sample stars is presented in Table A6. For those objects identified as background, the derived properties such as the mass or the mass ratio were left blank to avoid confusion.
In addition to these properties auxiliary infos such as the assigned WDS component desig-nation and the evaluated companion status are given. These data as well as information about other known, physically associated companions, such as spectroscopic, interferomet-ric companions or objects outside the field of view of NaCo are of particular interest for a robust estimation of the multiplicity- and companion star fraction.
The known additional companions identified via VizieR and the catalogues therein, for in-stance through the Ninth Catalogue of Spectroscopic Binary Orbits (SB9; Pourbaix et al.
2004) or the Washington Double Star Catalogue (WDS; Mason et al. 2001), are listed in Table A7. The table shows the observed sample star, the separation data of any known companion and the corresponding reference, where the data have been taken from. The separation data listed are either recorded as period, in days, for e.g., spectroscopic compan-ions or as apparent angular distance, in arc-second, for instance, for wide visual systems, outside the field of view of the VLT/NaCo instrument.
The companion status codes presented in Table 16 and Table A6 are as follows:
C – for co-moving (physical) companion;
B – for definite background object (optical companion);
U – for undefined analysis results, i.e. a final assessment of the companion status was not possible based on the available and analysed data.
n – for newly resolved sources, presented for the first time in this thesis.
lt s a n d D iscu ssi o n
75HIP CC# WDS MJD Θ PA Band ∆m aproj. log(Age[yr ]) M1 Mcomp q Chance proj. prob. Comp.
desig. (days) (arcsec) (deg) (mag) (au) (M⊙) (M⊙) (%) statusb
Visual binaries and multiples with only one observation and without additional data points from literature
17563 1 – 53380.085 4.325±0.007 277.2±0.1 Ks 5.88±0.13 707.8+35.3−32.1 7.1+0.3−0.7 5.9±0.3 0.39±0.09 0.07±0.02 4.43 × 10−2 nU 18213 1 – 53266.307 0.259±0.004 239.0±0.9 Ks 4.78±0.12 27.5+0.8−0.7 7.6+0.1−0.2 3.7±0.1 0.56±0.06 0.15±0.02 4.27 × 10−5 nU 25657 1 – 54097.209 1.070±0.006 74.1±0.5 H 4.4793±0.0091 184.5+24.9−19.6 7.9+0.1−0.1 2.5117±0.0002 0.52±0.04 0.21±0.02 1.35 × 10−2 nU 26549 4 – 53289.404 17.44±0.05 116.2±0.2 Ks 6.7±0.1 5737.9+8704.5−4279.5 7.02+0.02−0.03 13.3±0.5 1.2±1.0 0.09±0.09 2.66 × 100 nU 26549 5 – 53289.404 3.35±0.01 17.0±0.2 Ks 7.32±0.14 1102.1+1671.9−822.0 7.02+0.02−0.03 13.3±0.5 0.9±0.9 0.07±0.07 1.52 × 10−1 nU 26549 6 – 53289.404 17.20±0.04 116.4±0.2 Ks 7.59±0.16 5657.0+8581.8−4219.1 7.02+0.02−0.03 13.3±0.5 0.7±0.7 0.06±0.06 4.70 × 100 nU 27810 1 – 53454.001 1.037±0.007 198.2±0.4 Ks 5.1701±0.0031 106.4+2.5−2.4 7.5+0.1−0.2 3.9807±0.0004 0.48±0.05 0.12±0.01 1.70 × 10−3 U 32823 1 – 54458.281 1.194±0.007 250.9±0.5 H 5.277±0.021 918.5+28932.7−452.1 7.4+0.2−0.3 3.981±0.001 0.4±2.0 0.1±0.4 1.73 × 10−1 nU 34041 1 – 54497.142 0.149±0.006 134.3±0.7 H 2.095±0.064 75.4+20.1−13.4 7.40+0.06−0.07 6.77±0.09 3.0±0.6 0.45±0.08 6.09 × 10−5 nU
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Visual binaries and multiples with more than one observation, including data points from literature
Visual binaries and multiples with more than one observation, including data points from literature