ABSTRACT
I report updates to the substellar mass–radius diagram for 11 transiting brown dwarfs (BDs) and low-mass stars published before the third data release from the Gaia mission (Gaia DR3). I ...re-analyse these transiting BD systems whose physical parameters were published between 2008 and 2019 and find that when using the parallax measurements from Gaia DR3, seven BDs show significant differences in their radius estimate or an improvement in the radius uncertainty. This has important implications for how these BDs are used to test substellar evolutionary models in the mass–radius diagram. The remaining four BDs show mass–radius estimates that are consistent with their previous pre-Gaia DR3 measurements. The seven BDs that show significant deviation from the original mass–radius measurements are AD 3116b, CoRoT-3b, CoRoT-15b, EPIC 201702477b, Kepler-39b, KOI-205b, and KOI-415b. Of these, AD 3116b is a known member of the Praesepe cluster at an age of 600 Myr. Additionally, some of the previously smallest known transiting BDs, KOI-205b and KOI-415b, are not as small as once thought, leaving the mass–radius region for the very oldest BDs relatively sparse as a result of this work.
We present the discoveries of a brown dwarf (BD) and a low-mass star from the Kepler and K2 missions. The newly discovered BD is EPIC 212036875b and the low-mass star is KOI-607b. EPIC 212036875b has ...a mass of Mb = 52.3 1.9 MJ, a radius of Rb = 0.874 0.017 RJ, and orbits its host star in P = 5.169885 0.000027 days. Its host star is a late F-type star with M = 1.288 0.065 M , R = 1.498 0.025 R , and Teff = 6238 60 K. KOI-607b has a mass of Mb = 95.1 3.4 MJ, a radius of Rb = 1.089 0.089 RJ, and an orbital period of P = 5.89399148 0.00000060 days. The primary star in the KOI-607 system is a G dwarf with M =0.993 0.052 M , R = 0.915 0.031 R , and Teff = 5418 87 K. We also revisit a BD, CWW 89Ab, that was previously published by Nowak et al. (under the designation EPIC 219388192b). CWW 89Ab is one of two known transiting BDs associated with a star cluster, which illustrates the need for more BDs with accurate masses, radii, and reliable age determinations to test theoretical models. We find that the newly discovered BD, EPIC 212036875b, falls in the middle of the so-called BD desert, indicating that EPIC 212036875b is either a particularly rare object, or the BD desert may not be so dry after all.
We report the discovery of two intermediate-mass transiting brown dwarfs (BDs), TOI-569b and TOI-1406b, from NASA's Transiting Exoplanet Survey Satellite mission. TOI-569b has an orbital period of P ...= 6.55604 0.00016 days, a mass of Mb = 64.1 1.9 , and a radius of Rb = 0.75 0.02 . Its host star, TOI-569, has a mass of M = 1.21 0.05 , a radius of R = 1.47 0.03 , dex, and an effective temperature of Teff = 5768 110 K. TOI-1406b has an orbital period of P = 10.57415 0.00063 days, a mass of Mb = 46.0 2.7 , and a radius of Rb = 0.86 0.03 . The host star for this BD has a mass of M = 1.18 0.09 , a radius of R = 1.35 0.03 , dex, and an effective temperature of Teff = 6290 100 K. Both BDs are in circular orbits around their host stars and are older than 3 Gyr based on stellar isochrone models of the stars. TOI-569 is one of two slightly evolved stars known to host a transiting BD (the other being KOI-415). TOI-1406b is one of three known transiting BDs to occupy the mass range of 40-50 and one of two to have a circular orbit at a period near 10 days (with the first being KOI-205b). Both BDs have reliable ages from stellar isochrones, in addition to their well-constrained masses and radii, making them particularly valuable as tests for substellar isochrones in the BD mass-radius diagram.
We report the discovery of an intermediate-mass transiting brown dwarf (BD), TOI-503b, from the TESS mission. TOI-503b is the first BD discovered by TESS, and it has circular orbit around a ...metallic-line A-type star with a period of P=3.6772±0.0001 days. The light curve from TESS indicates that TOI-503b transits its host star in a grazing manner, which limits the precision with which we measure the BD’s radius R(b) = 1.34(+0.26, -0.15)R(J). We obtained high resolution spectroscopic observations with the FIES, Ondrejov, PARAS, Tautenburg, and TRES spectrographs, and measured the mass of TOI-503b to be M(b)=53.7±1.2 M(J). The host star has a mass of M(*)=1.80±0.06M(ʘ), a radius of R(*)=1.70±0.05R(ʘ), an effective temperature of T(eff)=7650±160 K, and a relatively high metallicity of 0.61±0.07 dex. We used stellar isochrones to derive the age of the system to be ∼180 Myr, which places its age between that of RIK 72b (a ∼10 Myr old BD in the Upper Scorpius stellar association) and AD 3116b (a ∼600 Myr old BD in the Praesepe cluster). Given the difficulty in measuring the tidal interactions between BDs and their host stars, we cannot precisely say whether this BD formed in situ or has had its orbit circularized by its host star over the relatively short age of the system. Instead, we offer an examination of plausible values for the tidal quality factor for the star and BD. TOI-503b joins a growing number of known short-period, intermediate-mass BDs orbiting main sequence stars, and is the second such BD known to transit an A star, after HATS-70b. With the growth in the population in this regime, the driest region in the BD desert (35–55M(J) sin i) is reforesting.
Abstract
Warm Jupiters—defined here as planets larger than 6 Earth radii with orbital periods of 8–200 days—are a key missing piece in our understanding of how planetary systems form and evolve. It ...is currently debated whether Warm Jupiters form in situ, undergo disk or high-eccentricity tidal migration, or have a mixture of origin channels. These different classes of origin channels lead to different expectations for Warm Jupiters’ properties, which are currently difficult to evaluate due to the small sample size. We take advantage of the Transiting Exoplanet Survey Satellite (TESS) survey and systematically search for Warm Jupiter candidates around main-sequence host stars brighter than the TESS-band magnitude of 12 in the full-frame images in Year 1 of the TESS Prime Mission data. We introduce a catalog of 55 Warm Jupiter candidates, including 19 candidates that were not originally released as TESS objects of interest by the TESS team. We fit their TESS light curves, characterize their eccentricities and transit-timing variations, and prioritize a list for ground-based follow-up and TESS Extended Mission observations. Using hierarchical Bayesian modeling, we find the preliminary eccentricity distributions of our Warm-Jupiter-candidate catalog using a beta distribution, a Rayleigh distribution, and a two-component Gaussian distribution as the functional forms of the eccentricity distribution. Additional follow-up observations will be required to clean the sample of false positives for a full statistical study, derive the orbital solutions to break the eccentricity degeneracy, and provide mass measurements.
ABSTRACT
We report the discovery of TOI-2119b, a transiting brown dwarf (BD) that orbits and is completely eclipsed by an active M-dwarf star. Using light-curve data from the Transiting Exoplanet ...Survey Satellite mission and follow-up high-resolution Doppler spectroscopic observations, we find the BD has a radius of Rb = 1.08 ± 0.03RJ, a mass of Mb = 64.4 ± 2.3MJ, an orbital period of P = 7.200865 ± 0.00002 d, and an eccentricity of e = 0.337 ± 0.002. The host star has a mass of M⋆ = 0.53 ± 0.02M⊙, a radius of R⋆ = 0.50 ± 0.01R⊙, an effective temperature of Teff = 3621 ± 48K, and a metallicity of $\rm Fe/H=+0.06\pm 0.08$. TOI-2119b joins an emerging population of transiting BDs around M-dwarf host stars, with TOI-2119 being the ninth such system. These M-dwarf–brown dwarf systems typically occupy mass ratios near q = Mb/M⋆ ≈ 0.1−0.2, which separates them from the typical mass ratios for systems with transiting substellar objects and giant exoplanets that orbit more massive stars. The nature of the secondary eclipse of the BD by the star enables us to estimate the effective temperature of the substellar object to be 2030 ± 84K, which is consistent with predictions by substellar evolutionary models.
Abstract
We report the discovery of two transiting brown dwarfs (BDs), TOI-811b and TOI-852b, from NASA’s Transiting Exoplanet Survey Satellite mission. These two transiting BDs have similar masses ...but very different radii and ages. Their host stars have similar masses, effective temperatures, and metallicities. The younger and larger transiting BD is TOI-811b at a mass of
M
b
= 59.9 ± 13.0
M
J
and radius of
R
b
= 1.26 ± 0.06
R
J
, and it orbits its host star in a period of
P
= 25.16551 ± 0.00004 days. We derive the host star’s age of
Myr from an application of gyrochronology. The youth of this system, rather than external heating from its host star, is why this BD’s radius is relatively large. This constraint on the youth of TOI-811b allows us to test substellar mass–radius evolutionary models at young ages where the radius of BDs changes rapidly. TOI-852b has a similar mass at
M
b
= 53.7 ± 1.4
M
J
but is much older (4 or 8 Gyr, based on bimodal isochrone results of the host star) and is also smaller with a radius of
R
b
= 0.83 ± 0.04
R
J
. TOI-852b’s orbital period is
P
= 4.94561 ± 0.00008 days. TOI-852b joins the likes of other old transiting BDs that trace out the oldest substellar mass–radius evolutionary models where contraction of the BD’s radius slows and approaches a constant value. Both host stars have a mass of
M
⋆
= 1.32
M
⊙
± 0.05 and differ in their radii,
T
eff
, and Fe/H, with TOI-811 having
R
⋆
= 1.27 ± 0.09
R
⊙
,
T
eff
= 6107 ± 77 K, and Fe/H = + 0.40 ± 0.09 and TOI-852 having
R
⋆
= 1.71 ± 0.04
R
⊙
,
T
eff
= 5768 ± 84 K, and Fe/H = + 0.33 ± 0.09. We take this opportunity to examine how TOI-811b and TOI-852b serve as test points for young and old substellar isochrones, respectively.
Abstract
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.
Abstract
We report the discovery of two short-period massive giant planets from NASA’s Transiting Exoplanet Survey Satellite (TESS). Both systems, TOI-558 (TIC 207110080) and TOI-559 (TIC 209459275), ...were identified from the 30 minute cadence full-frame images and confirmed using ground-based photometric and spectroscopic follow-up observations from TESS’s follow-up observing program working group. We find that TOI-558 b, which transits an F-dwarf (
M
*
=
1.349
−
0.065
+
0.064
M
⊙
,
R
*
=
1.496
−
0.040
+
0.042
R
⊙
,
T
eff
=
6466
−
93
+
95
K, age
1.79
−
0.73
+
0.91
Gyr) with an orbital period of 14.574 days, has a mass of 3.61 ± 0.15
M
J
, a radius of
1.086
−
0.038
+
0.041
R
J
, and an eccentric (
e
=
0.300
−
0.020
+
0.022
) orbit. TOI-559 b transits a G dwarf (
M
*
= 1.026 ± 0.057
M
⊙
,
R
*
=
1.233
−
0.026
+
0.028
R
⊙
,
T
eff
=
5925
−
76
+
85
K, age
6.8
−
2.0
+
2.5
Gyr) in an eccentric (
e
= 0.151 ± 0.011) 6.984 days orbit with a mass of
6.01
−
0.23
+
0.24
M
J
and a radius of
1.091
−
0.025
+
0.028
R
J
. Our spectroscopic follow up also reveals a long-term radial velocity trend for TOI-559, indicating a long-period companion. The statistically significant orbital eccentricity measured for each system suggests that these planets migrated to their current location through dynamical interactions. Interestingly, both planets are also massive (>3
M
J
), adding to the population of massive giant planets identified by TESS. Prompted by these new detections of high-mass planets, we analyzed the known mass distribution of hot and warm Jupiters but find no significant evidence for multiple populations. TESS should provide a near magnitude-limited sample of transiting hot Jupiters, allowing for future detailed population studies.
This thesis presents an analysis of transiting brown dwarf (BD) systems and examines their effectivenessas tests to substellar evolutionary models. The radius, mass, and age of transiting BDsystems ...are the parameters most useful in testing these models and in this work, I show how mycollaborators and I have used three facilities to derive these parameters for transiting BD systems.These facilities are: 1) NASA’s Transiting Exoplanet Survey Satellite (TESS) mission, 2) the TillinghastReflector Echelle Spectrograph (TRES), and 3) ESA’s Gaia mission. In this work, I use TESS,TRES, and Gaia in tandem to detect and characterize 10 new transiting BD systems with preciseradius, mass, and age determinations (in most cases). Most of the age determinations in this workcome solely from stellar isochrone models of the host star, but several systems have age constraintsfrom stellar clusters and gyrochronology, which we use to constrain the youth of one transiting BD,TOI-811b, to less than 200 Myr. This is important because it is at these young ages when the radii ofBDs changes most rapidly. In addition, I apply parallax measurements from the Gaia mission’s second data release (GaiaDR2) to improve the radius determinations of 10 transiting BD systems published prior to GaiaDR2 and the launch of the TESS mission. For these 10 previously published systems, new lightcurves from TESS are used, when possible, and the stellar distances, luminosities, and radii areupdated with the parallaxes from Gaia DR2, which improves our constraint on the companionBD’s radius. This work has significantly improved the radius determinations of 7 previously knowntransiting BDs, including CoRoT-15b and AD 3116b, whose radius uncertainties have been improvedfrom 15% to 5-7%, making them much more effective for testing substellar evolutionary models. Using these 20 new and previously known transiting BD systems, I have shown that the substellarevolutionary models ranging from young to old substellar isochrones are generally able toreproduce the observed radius, mass, and age determinations of the known transiting BD population.
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