Direct detection of a substellar companion to the young nearby star PZ Telescopii

Mugrauer, M.; Vogt, N.; Neuhäuser, R.; Schmidt, T. O. B.

doi:10.1051/0004-6361/201015523

Cited by 42 publications

(72 citation statements)

References 26 publications

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“…Future observations should confirm this and improve the orbital parameters. We also refer to Neuhäuser et al (2010) and Mugrauer et al (2010) for further detailed discussions and sub-stellar examples of the first indications of orbital curvature. As an alternative explanation of apparently co-moving binaries, we could suppose that we have seen two seperate members of the star-forming region in Chamaeleon, aligned by chance along our line of sight.…”

Section: Discussionmentioning

confidence: 99%

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Vogt

Schmidt

Neuhäuser

et al. 2012

A&A

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Context. The star-forming regions in Chamaeleon (Cha) are one of the nearest (distance ∼ 165 pc) and youngest (age ∼ 2 Myr) conglomerates of recently formed stars and the ideal target for population studies of star formation. Aims. We investigate a total of 16 Cha targets that have been suggested, but not confirmed, to be binaries or multiple systems in previous literature. Methods. We used the adaptive optics instrument Naos-Conica (NACO) at the Very Large Telescope Unit Telescope (UT) 4 / YEPUN of the Paranal Observatory, at 2-5 different epochs, in order to obtain relative and absolute astrometric measurements, as well as differential photometry in the J, H, and K band. On the basis of known proper motions and these observations, we analyse the astrometric results in our proper motion diagram (PMD: angular separation / position angle versus time), to eliminate possible (non-moving) background stars, establish co-moving binaries and multiples, and search for curvature as indications for orbital motion. Results. All previously suggested close components are co-moving and no background stars are found. The angular separations range between 0.07 and 9 arcsec, corresponding to projected distances between the components of 6-845 AU. Thirteen stars are at least binaries and the remaining three (RX J0919.4-7738, RX J0952.7-7933, VW Cha) are confirmed high-order multiple systems with up to four components. In 13 cases, we found significant slopes in the PMDs, which are compatible with orbital motion whose periods (estimated from the observed gradients in the position angles) range from 60 to 550 years. However, in only four cases there are indications of a curved orbit, the ultimate proof of a gravitational bond. Conclusions. A statistical study based on the 2MASS catalogue confirms the high probability of all 16 stellar systems being gravitationally bound. Most of the secondary components are well above the mass limit of hydrogen burning stars (0.08 M ), and have masses twice as high as this value or more. Massive primary components appear to avoid the simultaneous formation of equal-mass secondary components, while extremely low-mass secondary components are hard to find for both high and low mass primaries owing to the much higher dynamic range and the faintness of the secondaries.

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Section: Discussionmentioning

confidence: 99%

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Vogt

Schmidt

Neuhäuser

et al. 2012

A&A

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“…To translate CCD into sky positions, we used the scale of 0.01327 arcsec per pixel given in the fits headers of the reduced images. This agrees to within less than 1% with the pixel scale determined astrometrically during other programs (cf., e.g., Mugrauer et al 2010).…”

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confidence: 99%

Masses and activity of AB Doradus B a/b

Wolter

Czesla

Fuhrmeister

et al. 2014

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We present a multiwavelength study of the close binary AB Dor Ba/b (Rst137B). Our study comprises astrometric orbit measurements, optical spectroscopy, X-ray and radio observations. Using all available adaptive optics images of AB Dor B taken with VLT/NACO from 2004 to 2009, we tightly constrain its orbital period to 360.6 ± 1.5 days. We present the first orbital solution of Rst 137B and estimate the combined mass of AB Dor Ba+b as 0.69 +0.02 −0.24 M , slightly exceeding previous estimates based on IR photometry. Our determined orbital inclination of Rst 137B is close to the axial inclination of AB Dor A inferred from Doppler imaging. Our VLT/UVES spectra yield high rotational velocities of ≥30 km s −1 for both components Ba and Bb, in accord with previous measurements, which corresponds to rotation periods significantly shorter than one day. Our combined spectral model, using PHOENIX spectra, yields an effective temperature of 3310 ± 50 K for the primary and approximately 60 K less for the secondary. The optical spectra presumably cover a chromospheric flare and show that at least one component of Rst 137B is significantly active. Activity and weak variations are also found in our simultaneous XMM-Newton observations, while our ATCA radio data yield constant fluxes at the level of previous measurements. Using evolutionary models, our newly determined stellar parameters confirm that the age of Rst 137B is between 50 and 100 Myr.

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“…Biller et al (2010) find best-fitting parameters of 2702 ± 84 K and log g of 4.20 ± 0.11 dex, hence 36 ± 6 M Jup , while Mugrauer et al (2010) find 2500−2700 K, hence 28 +12 −4 M Jup , both using evolutionary models (Chabrier et al 2000). Neuhäuser & Schmidt (2012) noted that given this lower mass limit, the PZ Tel companion could even be a planetary mass object, considering the planet definition by Schneider et al (2011).…”

Section: Introductionmentioning

confidence: 97%

First spectroscopic observations of the substellar companion of the young debris disk star PZ Telescopii

Schmidt

Mugrauer

Neuhäuser

et al. 2014

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Context. In 2010 a substellar companion to the solar analog pre-main sequence star PZ Tel and member of the approximately 12 Myr old β Pic moving group was found by high-contrast direct imaging independently by two teams. Aims. In order to determine the basic parameters of this companion more precisely and independent of evolutionary models, hence age-independent, we obtained follow-up spectroscopic observations of the primary and companion. Methods. We used the Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) at the Very Large Telescope Unit 4/Yepun of ESO's Paranal Observatory in the H + K band and processed the data using the spectral deconvolution technique. The resulting spectrum of the companion was then compared to a grid of Drift-Phoenix synthetic model spectra, a combination of a general-purpose model atmosphere code with a non-equilibrium, stationary cloud and dust model, using a χ 2 minimization analysis. Results. We find a best fitting spectral type of G6.5 for PZ Tel A. The extracted spectrum of the substellar companion, at a spatial position compatible with earlier orbit estimates, yields a temperature T eff = 2500 +138 −115 K, a visual extinction A V = 0.53 +0.84 −0.53 mag, a surface gravity of log g = 3.50 +0.51 −0.30 dex, and a metallicity at the edge of the grid of [M/H] = 0.30 −0.30 dex. Conclusions. We derive a luminosity of log(L bol /L ) = −2.66 +0.06 −0.08 , a radius of R = 2.42 +0.28 −0.34 R Jup , and a mass of M = 7.5 +16.9 −4.3 M Jup for the PZ Tel companion, which is consistent with most earlier estimates using photometry alone. Combining our results with evolutionary models, we find a best-fitting mass of about 21 Jupiter masses at an age corresponding to the recently determined lithium depletion age of 7 +4 −2 Myr. Hence, the PZ Tel companion is most likely a wide brown dwarf companion in the 12 +8 −4 Myr old β Pic moving group.

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Direct detection of a substellar companion to the young nearby star PZ Telescopii

Cited by 42 publications

References 26 publications

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

Masses and activity of AB Doradus B a/b

First spectroscopic observations of the substellar companion of the young debris disk star PZ Telescopii

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