Revising the ages of planet-hosting stars

Abstract

Aims. This article aims to measure the age of stars with planets (SWP) through stellar tracks and isochrones computed with the PAdova and TRieste Stellar Evolutionary Code (PARSEC). Methods. We developed algorithms based on two different techniques for determining the ages of field stars: isochrone placement and Bayesian estimation. Their application to a synthetic sample of coeval stars shows the intrinsic limits of each method. For instance, the Bayesian computation of the modal age tends to select the extreme age values in the isochrones grid. Therefore, we used the isochrone placement technique to measure the ages of 317 SWP. Results. We found that ∼6% of SWP have ages lower than 0.5 Gyr. The age distribution peaks in the interval [1.5, 2) Gyr, then it decreases. However, ∼7% of the stars are older than 11 Gyr. The Sun turns out to be a common star that hosts planets, when considering its evolutionary stage. Our SWP age distribution is less peaked and slightly shifted towards lower ages if compared with ages in the literature and based on the isochrone fit. In particular, there are no ages below 0.5 Gyr in the literature.

Age consistency between exoplanet hosts and field stars

“…Finally, the stellar luminosity L is given by In Bonfanti et al (2015) we have already pointed out that on the right-hand side of the main sequence (in the lower temperature region) or around the turn-off (TO) very old and very young isochrones are close and can even overlap. According to Fig.…”

“…This technique was already described in Bonfanti et al (2015), but several improvements have been made, such as the new kind of activity checks described above and the possibility of computing the age without any input distance d, if we have stellar density measurements. We also solved some problems linked to numerical stability convergence for which the previous algorithm sometimes gave fictitious young ages.…”

Herschel Observations and Updated Spectral Energy Distributions of Five Sunlike Stars With Debris Disks

“…For 25 μm grains, we find   t 0.2 Gyr 2 Gyr for all of the disks in our sample. The quantity star age/τ for 25 μm grains is between 0.7 and 6.5 for all systems except one; HD50554 has age estimates which differ by a factor of 10 (3.3 Gyr from Bonfanti et al (2015) versus 0.33 Gyr from Chen et al 2014), and so star age/τ is either 1.6 or 16. Since the grains that can contribute significantly to the 160 μm emission have lifetimes against radiative drag of at least 1/4 the star age, they are likely to be destroyed by collisions before migrating significantly.…”

“…Table 1 lists the targets in our sample and their Herschel Science Archive observation IDs. The table also includes luminosity and age estimates from the literature (McDonald et al 2012;Chen et al 2014;Bonfanti et al 2015), and luminosity estimates from this work.…”

“…Interestingly, the disk surrounding HD50554 is a true Kuiper Belt analog in its spatial distribution, with a best-fit radius of 45 AU and ring half-width of 4 AU. Since HD50554 is slightly younger than the Sun (3.3 Gyr; Bonfanti et al 2015), its disk may be similar to the Kuiper Belt at an earlier stage of evolution and may have a Neptune-like planet at its inner edge. In N-body simulations of planetesimal belts with giant planets orbiting just inside their inner edges, Rodigas et al (2014) find that the width of the planetesimal belt increases with both planet mass and planet/ disk semimajor axes.…”