Transit Hunt for Young and Maturing Exoplanets (THYME). VIII. A Pleiades-age Association Harboring Two Transiting Planetary Systems from Kepler

Barber, Madyson G.; Mann, Andrew W.; Bush, Jonathan L.; Tofflemire, Benjamin M.; Kraus, Adam L.; Krolikowski, Daniel M.; Vanderburg, Andrew; Fields, Matthew J.; Newton, Elisabeth R.; Owens, Dylan A.; Thao, Pa Chia

doi:10.3847/1538-3881/ac7b28

“…All but one predicted ages agreed within 1σ to their reported values. The exception, MELANGE-3, had a 3.5σ older variability age (;300 Myr) compared to the age derived from lithium and rotation (105 Myr; Barber et al 2022). This may have been because the group lands at the distance limit of our calibration sample (326 pc) and has a high field contamination rate (;50%; Barber et al 2022).…”

Section: Testing the Ages Of Groupsmentioning

confidence: 74%

Using the Gaia Excess Uncertainty as a Proxy for Stellar Variability and Age

Barber,

Mann

2023

ApJ

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Stars are known to be more active when they are young, resulting in a strong correlation between age and photometric variability. The amplitude variation between stars of a given age is large, but the age–variability relation becomes strong over large groups of stars. We explore this relation using the excess photometric uncertainty in Gaia photometry (VarG, VarBP, and VarRP) as a proxy for variability. The metrics follow a Skumanich-like relation, scaling as ≃t −0.4. By calibrating against a set of associations with known ages, we show how the Var of population members can predict group ages within 10%–20% for associations younger than ≃2.5 Gyr. In practice, age uncertainties are larger, primarily due to the finite group size. The index is most useful at the youngest ages (<100 Myr), where the uncertainties are comparable to or better than those derived from a color–magnitude diagram (CMD). The index is also widely available, easy to calculate, and can be used at intermediate ages where there are few or no pre- or post-main-sequence stars. We further show how Var can be used to find new associations and test if a group of comoving stars is a real coeval population. We apply our methods to Theia groups within 350 pc and find ≳90% are inconsistent with drawing stars from the field and ≃80% have variability ages consistent with those derived from the CMD. Our findings suggest the great majority of these groups contain real populations.

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“…The closest case is MELANGE-1, which is closer in age (∼250 Myr; Tofflemire et al 2021) and hence has similar large V off scatters. Most of the stars in MELANGE-2 (Newton et al 2022) and MELANGE-3 (Barber et al 2022) that agree in RV space are within 1-2 km s −1 in V off .…”

Section: A Potential ∼200 Myr Young Association Candidate In the Phoe...mentioning

confidence: 80%

“…For field-age planets, we use data from the NASA Exoplanet Archive, 11 which are shown as small gray circles in the background. We include a number of planetary systems discovered in the Hyades and Praesepe clusters (∼650 Myr; Mann et al 2016aMann et al , 2017Mann et al , 2018Rizzuto et al 2018), several planets in young associations (Mann et al 2016b;David et al 2019;Plavchan et al 2020;Hedges et al 2021), all the THYME planets (Newton et al 2019(Newton et al , 2021Mann et al 2020Mann et al , 2022Rizzuto et al 2020;Tofflemire et al 2021), three young planets orbiting K2-233 (David et al 2018), and several young planets in the Kepler field (Barber et al 2022;Bouma et al 2022aBouma et al , 2022b. The young planets are in large filled circles (large circles in…”

Section: Summary and Discussionmentioning

confidence: 99%

“…In this work, we present a different approach to identifying stellar siblings and young association candidates where a planet resides, which, in turn, helps to constrain its age. This method has successfully identified the 250 Myr MELANGE-1 (Tofflemire et al 2021), the MELANGE-2 (Newton et al 2022), and the Pleiades-aged MELANGE-3 (Barber et al 2022) association (candidate). The increasing number of planets found in stellar associations would help to answer whether the planet occurrence rate in stellar associations shows any difference from that in the field stars, which is essential for understanding the early planet formation and evolution conditions (Dai et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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A Search for Stellar Siblings of the ∼200 Myr TOI-251 b Planetary System

Sun

¹

,

Wang

²

,

Mann

³

et al. 2023

ApJ

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0

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Young planets (<1 Gyr) are helpful for studying the physical processes occurring at the early stage of planet evolution. TOI-251 b is a recently discovered sub-Neptune orbiting a young G dwarf, which has an imprecise age estimation of 40–320 Myr. We select TOI-251 sibling candidates based on kinematics and spatial proximity to TOI-251 and further use the color–magnitude diagram to refine the list and to compare to multiple open clusters. We report the stellar rotational period for 321 sibling candidates in a 50 pc radius around TOI-251 by analyzing their stellar light curves and find a color–rotational period sequence that lies in between the Group X (300 Myr) and Pleiades (120 Myr) members, suggesting an age ∼ 200 Myr. A quantitative age analysis using gyrochronology relations gives 204 ± 45 Myr, consistent with the average Li age of selected siblings (238 ± 38 Myr) and the Gaia variability age (193 − 54 102 Myr). The detection fraction of comoving candidates that have a short rotational period is 68.1%, much higher than the typical value in the field (14%–16% from Kepler). The overdensity of young stars and consistency in age of stellar siblings suggest a potential young association candidate in the Phoenix–Grus constellation. Though TOI-251 b has a radius larger than most of its field-age counterparts, we are uncertain whether TOI-251 is inflated, due to a lack of knowledge on the planet’s mass.

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“…We followed the method outlined in Barber et al (2022). To briefly summarize, we generated TESS light curves from the FFI cutouts, first creating raw flux light curves from the FFI cutouts centered on each candidate.…”

Section: Measuring Melange-6's Agementioning

confidence: 99%

HIP 33609 b: An Eccentric Brown Dwarf Transiting a V = 7.3 Rapidly Rotating B Star

Vowell

¹

,

Rodriguez

²

,

Quinn

³

et al. 2023

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We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting a late B star, discovered by NASA's Transiting Exoplanet Survey Satellite as TOI-588 b. HIP 33609 b is a large (R b = 1.580 − 0.070 + 0.074 R J) brown dwarf on a highly eccentric (e = 0.560 − 0.031 + 0.029 ) orbit with a 39 days period. The host star is a bright (V = 7.3 mag), T eff = 10,400 − 660 + 800 K star with a mass of M * = 2.383 − 0.095 + 0.10 M ⊙ and radius of R * = 1.863 − 0.082 + 0.087 R ⊙, making it the hottest transiting brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion's mass of M b = 68.0 − 7.1 + 7.4 M J as well as the host star's rotation rate ( v sin i * = 55.6 ± 1.8 km s−1). We also present the discovery of a new comoving group of stars, designated as MELANGE-6, and determine that HIP 33609 is a member. We use a combination of rotation periods and isochrone models fit to the cluster members to estimate an age of 150 ± 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.

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Transit Hunt for Young and Maturing Exoplanets (THYME). VIII. A Pleiades-age Association Harboring Two Transiting Planetary Systems from Kepler

Cited by 17 publications

References 128 publications

Using the Gaia Excess Uncertainty as a Proxy for Stellar Variability and Age

Using the Gaia Excess Uncertainty as a Proxy for Stellar Variability and Age

A Search for Stellar Siblings of the ∼200 Myr TOI-251 b Planetary System

HIP 33609 b: An Eccentric Brown Dwarf Transiting a V = 7.3 Rapidly Rotating B Star

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