A young massive planet in a star–disk system

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

doi:10.1038/nature06426

Cited by 162 publications

(145 citation statements)

References 25 publications

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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

116

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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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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

116

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“…The detectability limit of an embedded giant planet by radial velocity measurements is ∼10 M J or ∼2 M J (M J is the mass of Jupiter) orbiting at 1 AU or 0.5 AU, respectively, due to heavy variability in the optical spectra of young (<10 Myr) stars (e.g., Paulson & Yelda 2006;Prato et al 2008). Note that although there were attempts to detect planets by radial velocity measurements in young systems, no firm detection has yet been repeated see, e.g., Setiawan et al (2008) for TW Hya b, debated later by Huélamo et al (2008). The discovery of planetary systems by direct imaging nowadays is restricted to large separations >10−100 AU (Veras et al 2009) and favors higher mass planets.…”

Section: Introductionmentioning

confidence: 99%

Detectability of giant planets in protoplanetary disks by CO emission lines

Regály

Sándor

Dullemond

et al. 2010

A&A

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Context. Planets are thought to form in protoplanetary accretion disks around young stars. Detecting a giant planet still embedded in a protoplanetary disk would be very important and give observational constraints on the planet-formation process. However, detecting these planets with the radial velocity technique is problematic owing to the strong stellar activity of these young objects. Aims. We intend to provide an indirect method to detect Jovian planets by studying near infrared emission spectra originating in the protoplanetary disks around T Tauri stars. Our idea is to investigate whether a massive planet could induce any observable effect on the spectral lines emerging in the disks atmosphere. As a tracer molecule we propose CO, which is excited in the ro-vibrational fundamental band in the disk atmosphere to a distance of ∼2−3 AU (depending on the stellar mass) where terrestrial planets are thought to form. Methods. We developed a semi-analytical model to calculate synthetic molecular spectral line profiles in a protoplanetary disk using a double layer disk model heated on the outside by irradiation by the central star and in the midplane by viscous dissipation due to accretion. 2D gas dynamics were incorporated in the calculation of synthetic spectral lines. The motions of gas parcels were calculated by the publicly available hydrodynamical code FARGO which was developed to study planet-disk interactions. Results. We demonstrate that a massive planet embedded in a protoplanetary disk strongly influences the originally circular Keplerian gas dynamics. The perturbed motion of the gas can be detected by comparing the CO line profiles in emission, which emerge from planet-bearing to those of planet-free disk models. The planet signal has two major characteristics: a permanent line profile asymmetry, and short timescale variability correlated with the orbital phase of the giant planet. We have found that the strength of the asymmetry depends on the physical parameters of the star-planet-disk system, such as the disk inclination angle, the planetary and stellar masses, the orbital distance, and the size of the disk inner cavity. The permanent line profile asymmetry is caused by a disk in an eccentric state in the gap opened by the giant planet. However, the variable component is a consequence of the local dynamical perturbation by the orbiting giant planet. We show that a forming giant planet, still embedded in the protoplanetary disk, can be detected using contemporary or future high-resolution near-IR spectrographs like VLT/CRIRES and ELT/METIS.

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“…A number of controversial cases have been reported in the literature (e.g. Setiawan et al 2008;Huélamo et al 2008;Hernán-Obispo et al 2010;Figueira et al 2010). Simultaneous monitoring of activity indicators, spectral line profile changes, and photometric variations may allow one to recognize the true origin of the radial velocity variations and to at least partially account for them (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Astrophysical false positives in direct imaging for exoplanets: a white dwarf close to a rejuvenated star

Zurlo

Vigan

Hagelberg

et al. 2013

A&A

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Context. As is the case for all techniques involved in the research for exoplanets, direct imaging has to take into account the probability of so-called astrophysical false positives, which are phenomena that mimic the signature of the objects we are seeking. Aims. In this work we present the case of a false positive found during a direct-imaging survey conducted with VLT/NACO. A promising exoplanet candidate was detected around the K2-type star HD 8049 in July 2010. Its contrast of ∆H = 7.05 at 1.57 arcsec allowed us to assume a 35 M Jup companion at 50 projected AU, for the nominal system age and heliocentric distance. Methods. To check whether it was gravitationally bound to the host star, as opposed to an unrelated background object, we re-observed the system one year later and concluded a high probability of a bound system. We also used radial velocity measurements of the host star, spanning a time range of ∼30 yr, to constrain the companion's mass and orbital properties, as well as to probe the host star's spectral age indicators and general spectral energy distribution. We also obtained U-band imaging with EFOSC and near-infrared spectroscopy for the companion. Results. Combining all these information we conclude that the companion of HD 8049 is a white dwarf (WD) with temperature T eff = 18 800 ± 2100 K and mass M WD = 0.56 ± 0.08 M . The significant radial velocity trend combined with the imaging data indicates that the most probable orbit has a semi-major axis of about 50 AU. The discrepancy between the age indicators speaks against a bona-fide young star. The moderately high level of chromospheric activity and fast rotation, mimicking the properties of a young star, might be induced by the exchange of mass with the progenitor of the WD. This example demonstrates some of the challenges in determining accurate age estimates and identifications of faint companions.

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A young massive planet in a star–disk system

Cited by 162 publications

References 25 publications

Chromospheric activity and rotation of FGK stars in the solar vicinity

Chromospheric activity and rotation of FGK stars in the solar vicinity

Detectability of giant planets in protoplanetary disks by CO emission lines

Astrophysical false positives in direct imaging for exoplanets: a white dwarf close to a rejuvenated star

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