Evidence for a Planetary Companion around a Nearby Young Star

Setiawan, J.; Weise, P.; Henning, Th.; Launhardt, R.; Müller, André; Rodmann, J.

doi:10.1086/518213

Cited by 58 publications

(45 citation statements)

References 20 publications

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“…FEROS is known to be stable over a fairly long baseline at better than the ∼10 ms −1 level (Setiawan et al 2007) and since we observed each star using the simultaneous ThAr mode we are able to measure accurate radial-velocities that allow us to determine the full kinematic space velocity for each star. In fact we found that the scatter in ThAr lamps themselves did not exceed 300 ms −1 for our entire sampling baseline of three years, highlighting the internal stability of FEROS.…”

Section: Radial-velocitiesmentioning

confidence: 99%

Chromospheric activities and kinematics for solar type dwarfs and subgiants: analysis of the activity distribution and the AVR

Jenkins

Murgas

Rojo

et al. 2011

A&A

111

105

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Aims. In this work we present chromospheric activity indices, kinematics, radial-velocities, and rotational velocities for more than 850 FGK-type dwarfs and subgiant stars in the southern hemisphere and test how best to calibrate and measure S -indices from echelle spectra. Methods. We measured our parameters using the high-resolution and high-S /N FEROS echelle spectra acquired for this purpose. Results. We confirm the bimodal distribution of chromospheric activities for such stars and highlight the role that the more active K-dwarfs play in biasing the number of active stars. We show that the age-activity relationship does appear to continue to ages older than the Sun if we simply compare main sequence stars and subgiant stars with an offset of around 2.5 Gyr between the peaks of both distributions. Also we show evidence of an increased spin-down timescale for cool K dwarfs compared with earlier F and G type stars. We highlight that activities drawn from low-resolution spectra (R < 2500) significantly increase the rms scatter when calibrating onto common systems of measurements like the Mt. Wilson system. Also we show that older and widely used catalogues of activities in the south appear to be offset compared to more recent works at the ∼0.1 dex level in log R HK through calibrator drift. In addition, we show how kinematics can be used to preselect inactive stars for future planet search projects. We see the well known trend between projected rotational velocity and activity, however we also find a correlation between kinematic space velocity and chromospheric activity. It appears that after the Vaughan-Preston gap there is a quick step function in the kinematic space motion towards a significantly broader spread in velocities. We speculate on reasons for this correlation and provide some model scenarios to describe the bimodal activity distribution through magnetic saturation, residual low level gas accretion, or accretion by the star of planets or planetesimals. Finally, we provide a new empirical measurement for the disk-heating law, using the latest age-activity relationships to reconstruct the age-velocity distribution for local disk stars. We find a value of 0.337 ± 0.045 for the exponent of this power law (i.e. σ tot ∝ t 0.337 ), in excellent agreement with those found using isochrone fitting methods and with theoretical disk-heating models.

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Section: Radial-velocitiesmentioning

confidence: 99%

Chromospheric activities and kinematics for solar type dwarfs and subgiants: analysis of the activity distribution and the AVR

Jenkins

Murgas

Rojo

et al. 2011

A&A

111

105

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“…Stellar RV variations are produced by different magneticactivity-related phenomena: convection (Saar 2009), starspots , magnetic plage/network (Saar 2003) and flares (Saar 2009;Reiners 2009). Although bisector analysis may sometimes lead to the confirmation of a planet orbiting a star even when RV jitter is present (Sozzetti et al 2006;Setiawan et al 2007Setiawan et al , 2008, the latter technique is not always successful (Huélamo et al 2008;Figueira et al 2010). Several authors have studied the impact of activity on RV jitter using R HK as a proxy (Saar et al 1998;Santos et al 2000;Paulson et al 2002;Saar et al 2003;Wright 2005;Paulson & Yelda 2006;Santos et al 2010).…”

Section: Predicted Radial Velocity Jittermentioning

confidence: 99%

Chromospheric activity and rotation of FGK stars in the solar vicinity

Martínez-Arnáiz¹,

Maldonado

Montes³

et al. 2010

A&A

113

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Context. Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles, and their perturbations alter the line centroids creating a radial velocity jitter that might "contaminate" the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims. We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d ≤ 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e., Ca ii H & K lines, to others that hold noteworthy advantages.Methods. We used high resolution (∼50 000) echelle optical spectra. Standard data reduction was performed using the IRAF echelle package. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. We measured the equivalent widths of the chromospheric emission lines in the subtracted spectrum and transformed them into fluxes by applying empirical equivalent width and flux relationships. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R HK index. Results. We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity to estimate the expected RV jitter for the active stars in the sample.

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“…In the last few years, several young planet detection surveys have been conducted in PMS stars using different techniques, such as direct imaging (e.g., Lafrenière et al 2010;Kraus & Ireland 2012) or radial velocity (RV) monitoring (e.g., Martín et al 2006;Setiawan et al 2007;Crockett et al 2012). To deploy RV surveys on young low-mass stars (which are considerably faint, distant and affected by extinction) is, in most of cases, an arduous task.…”

Section: Introductionmentioning

confidence: 99%

Evidence of a substellar companion around a very young T Tauri star

Almeida

Gameiro

Петров

et al. 2017

A&A

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We present results from a Near Infrared multi-epoch spectroscopic campaign to detect a young low-mass companion to a T Tauri star. AS 205A is a late-type dwarf (≈K5) of ∼ 1 M⊙ that belongs to a triple system. Independent photometric surveys discovered that AS 205A has two distinct periods (P 1 =6.78 and P 2 =24.78 days) detected in the light curve that persist over several years. Period P 1 seems to be linked to the axial-rotation of the star and is caused by the presence of cool surface spots. Period P 2 is correlated with the modulation in AS 205A brightness (V) and red color (V-R), consistent with a gravitating object within the accretion disk.We here derive precise Near Infrared radial velocities to investigate the origin of period P 2 which is predicted to correspond to a cool source in a Keplerian orbit with a semi-major axis of ∼0.17 AU positioned close to the inner disk radius of 0.14 AU. The radial velocity variations of AS 205A were found to have a period of P ≈ 24.84 days and a semi-amplitude of 1.529 kms −1 . This result closely resembles the P 2 period in past photometric observations (P ≈ 24.78 days). The analysis of the cross-correlation function bisector has shown no correlation with the radial velocity modulations, strongly suggesting that the period is not controlled by stellar rotation. Additional activity indicators should however be explored in future surveys. Taking this into account we found that the presence of a substellar companion is the explanation that best fits the results. We derived an orbital solution for AS 205A and found evidence of a m 2 sini ≃19.25 M Jup object in an orbit with moderate eccentricity of e ≃ 0.34. If confirmed with future observations, preferably using a multiwavelength survey approach, this companion could provide interesting constraints on brown dwarf and planetary formation models.

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Evidence for a Planetary Companion around a Nearby Young Star

Cited by 58 publications

References 20 publications

Chromospheric activities and kinematics for solar type dwarfs and subgiants: analysis of the activity distribution and the AVR

Chromospheric activities and kinematics for solar type dwarfs and subgiants: analysis of the activity distribution and the AVR

Chromospheric activity and rotation of FGK stars in the solar vicinity

Evidence of a substellar companion around a very young T Tauri star

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