Explore the vast range of titles available.

Blanco 1 is an ≈130 Myr open cluster located 240 pc from the Sun, below the Galactic plane. Recent studies have reported the existence of diffuse tidal tails extending 50–60 pc from the cluster center based on the positions and velocities measured by Gaia. To independently assess the reality and extent of this structure, we used light curves generated from TESS full-frame images to search for photometric rotation periods of stars in and around Blanco 1. We detected rotation periods down to a stellar effective temperature of ≈3100 K in 347 of the 603 cluster member candidates for which we have light curves. For cluster members in the core and candidate members in the tidal tails, both within a temperature range of 4400–6200 K, 74% and 72% of the rotation periods, respectively, are consistent with the single-star gyrochronological sequence. In contrast, a comparison sample of field stars yielded gyrochrone-consistent rotation periods for only 8.5% of the stars. The tidal tail candidates’ overall conformance to the core members’ gyrochrone sequence implies that their contamination ratio is consistent with zero and <0.33 at the 2σ level. This result confirms the existence of Blanco 1 tidal tails and doubles the number of Blanco 1 members for which there are both spatio-kinematic and rotation-based cluster membership verification. Extending the strategy of using TESS light curves for gyrochronology to other nearby young open clusters and stellar associations may provide a viable strategy for mapping out their dissolution and broadening the search for young exoplanets.

We present a near-infrared transmission spectrum of the long-period (P = 542 days), temperate (T eq = 294 K) giant planet HIP 41378 f obtained with the Wide-Field Camera 3 instrument aboard the Hubble Space Telescope (HST). With a measured mass of 12 ± 3 M ⊕ and a radius of 9.2 ± 0.1 R ⊕, HIP 41378 f has an extremely low bulk density (0.09 ± 0.02 g cm−3). We measure the transit depth with a median precision of 84 ppm in 30 spectrophotometric channels with uniformly sized widths of 0.018 μm. Within this level of precision, the spectrum shows no evidence of absorption from gaseous molecular features between 1.1 and 1.7 μm. Comparing the observed transmission spectrum to a suite of 1D radiative-convective-thermochemical-equilibrium forward models, we rule out clear, low-metallicity atmospheres and find that the data prefer high-metallicity atmospheres or models with an additional opacity source, such as high-altitude hazes and/or circumplanetary rings. We explore the ringed scenario for HIP 41378 f further by jointly fitting the K2 and HST light curves to constrain the properties of putative rings. We also assess the possibility of distinguishing between hazy, ringed, and high-metallicity scenarios at longer wavelengths with the James Webb Space Telescope. HIP 41378 f provides a rare opportunity to probe the atmospheric composition of a cool giant planet spanning the gap in temperature, orbital separation, and stellar irradiation between the solar system giants, directly imaged planets, and the highly irradiated hot Jupiters traditionally studied via transit spectroscopy.

This article presents the history of the Visual Survey Group (VSG)—a Professional-Amateur (Pro-Am) collaboration within the field of astronomy working on data from several space missions (Kepler, K2 and Transiting Exoplanet Survey Satellite). This paper covers the formation of the VSG, its survey-methods including the most common tools used and its discoveries made over the past decade. So far, the group has visually surveyed nearly 10 million light curves and authored 69 peer-reviewed papers which mainly focus on exoplanets and discoveries involving multistellar systems. The preferred manual search-method carried out by the VSG has revealed its strength by detecting numerous objects which were overlooked or discarded by automated search programs, uncovering some of the most rare stars in our galaxy, and leading to several serendipitous discoveries of unprecedented astrophysical phenomena. The main purpose of the VSG is to assist in the exploration of our local universe, and we therefore advocate continued crowd-sourced examination of time-domain data sets, and invite other research teams to reach out in order to establish collaborating projects.

Young planets with mass measurements are particularly valuable in studying atmospheric mass-loss processes, but these planets are rare and their masses difficult to measure due to stellar activity. We report the discovery of a planetary system around TOI-6109, a young, 75 Myr-old Sun-like star in the Alpha Persei cluster. It hosts at least two transiting Neptune-like planets within 10 day orbital periods. Using three TESS sectors, 30 CHEOPS orbits, and photometric follow-up observations from the ground, we confirm the signals of the two planets. TOI-6109 b has an orbital period of P = 5.6904−0.0004+0.0004 days and a radius of R = 4.87−0.12+0.16 R⊕. The outer planet, TOI-6109 c has an orbital period of P = 8.5388−0.0005+0.0006 days and a radius of R = 4.83−0.06+0.07 R⊕. These planets orbit just outside a 3:2 mean motion resonance. The near-resonant configuration presents the opportunity to measure the planet’s mass via TTV measurements and to bypass difficult RV measurements. Measuring the masses of the planets in this system will allow us to test theoretical models of atmospheric mass loss.

We present the confirmation of TOI-5573 b, a Saturn-sized exoplanet on an 8.79 days orbit around an early M dwarf (3790 K, 0.59 R⊙, 0.61 M⊙, 12.30 Jmag). TOI-5573 b has a mass of 112−19+18 M⊕(0.35 ± 0.06 MJup) and a radius of 9.75 ± 0.47 R⊕(0.87 ± 0.04 RJup), resulting in a density of 0.66−0.13+0.16 g cm−3, akin to that of Saturn. The planet was initially discovered by the Transiting Exoplanet Survey Satellite (TESS) and confirmed using a combination of 11 transits from four TESS Sectors (20, 21, 47, and 74), ground-based photometry from the Red Buttes Observatory, and high-precision radial velocity data from the Habitable-zone Planet Finder and NN-EXPLORE Exoplanet Investigations with Doppler spectrographs, achieving a 5σ precision on the planet’s mass. TOI-5573 b is one of the coolest Saturn-like exoplanets discovered around an M-dwarf, with an equilibrium temperature of only 528 ± 10 K, making it a valuable target for atmospheric characterization. Saturn-like exoplanets around M dwarfs likely form through core accretion, with increased disk opacity slowing gas accretion and limiting their mass. The host star’s supersolar metallicity supports core accretion, but uncertainties in M-dwarf metallicity estimates complicate definitive conclusions. Compared to other GEMS (Giant Exoplanets around M-dwarf Stars) orbiting metal-rich stars, TOI-5573 b aligns with the observed pattern that giant planets preferentially form around M-dwarfs with supersolar metallicity. Further high-resolution spectroscopic observations are needed to explore the role of stellar metallicity in shaping the formation and properties of giant exoplanets like TOI-5573 b.

This article presents the history of the Visual Survey Group (VSG)—a Professional-Amateur (Pro-Am) collaboration within the field of astronomy working on data from several space missions (Kepler, K2 and Transiting Exoplanet Survey Satellite). This paper covers the formation of the VSG, its survey-methods including the most common tools used and its discoveries made over the past decade. So far, the group has visually surveyed nearly 10 million light curves and authored 69 peer-reviewed papers which mainly focus on exoplanets and discoveries involving multistellar systems. The preferred manual search-method carried out by the VSG has revealed its strength by detecting numerous objects which were overlooked or discarded by automated search programs, uncovering some of the most rare stars in our galaxy, and leading to several serendipitous discoveries of unprecedented astrophysical phenomena. The main purpose of the VSG is to assist in the exploration of our local universe, and we therefore advocate continued crowd-sourced examination of time-domain data sets, and invite other research teams to reach out in order to establish collaborating projects.

Studying exoplanets which transit their host stars is a fruitful approach to developing a detailed understanding of their planetary systems. In this thesis, we develop data analysis methods and techniques to study transiting planets, and we use these methods to perform case studies to learn about the past histories, present-day characteristics, and future evolution of these planetary systems.In Chapters 2 and 3, we develop techniques to analyze data from the Kepler space telescope in its new K2 operating mode. After a mechanical failure ended the original Kepler mission, the spacecraft was repurposed to conduct a survey for transiting planets in the ecliptic plane. Data from K2 shows large systematic errors which were not present in the original Kepler mission, and which hinder searches for and studies of transiting exoplanets if they are not taken into account. In these two chapters, we develop techniques to correct these systematics and search the K2 light curves for exoplanets.In Chapters 4 and 5, we conduct a detailed investigation into a single planetary system for which it is possible to place unique constraints on its past formation and migration history. In Chapter 4, we present the discovery in K2 data of two additional transiting planets in the known hot Jupiter system, WASP-47. The existence of these planets shows that the system must have formed in a dynamically quiet enough manner to not disrupt their orbits. In Chapter 5, we continue studying the WASP-47 system using precise radial velocity observations with the HARPS-N spectrograph. We measure the masses of the two smaller planets, determining the composition of the inner planet to be inconsistent with an Earth-like rocky composition, making it likely this planet is the photo-evaporated remnant of a larger Neptune-like exoplanet. We also refine the orbit of a long-period gas giant planet discovered nearly simultaneous with our discovery of the two smaller transiting planets and find that it likely has an inclination very close to the inclination of the inner transiting planets, further suggesting a dynamically quiet formation history for the WASP-47 system.In Chapters 6, 7, and 8, we present the discovery in K2 data (and in one case, follow-up mass measurements) of new systems of planets transiting nearby bright stars. These planets are important because they are amenable to follow-up observations to learn about their masses, compositions, and atmospheres. It will be possible to learn more about the present-day characteristics of these exoplanets as we will continue to study them in detail.In Chapter 9, we present the discovery in K2 data and a study of remains of a minor planet that is transiting a white dwarf star. The star WD 1145+017 is a metal-polluted white dwarf star with infrared excess emission, characteristic of white dwarfs which were recently believed to have disrupted minor planets and accreted the remains onto their surfaces. We discovered that WD 1145+017 is being transited by the debris produced by the disruption of a minor planet, probably the size of Ceres, from the white dwarf progenitor's planetary system. Most of the stars in our galaxy will eventually become white dwarfs when they exhaust their nuclear fuel and evolved off the main sequence, so planetary systems around stellar remnants like WD 1145+017 represent the future fate of most of the exoplanets we know of today.

Blanco 1 is an \\( 130\\,Myr\\) open cluster located 240 pc from the Sun below the Galactic plane. Recent studies have reported the existence of diffuse tidal tails extending 50-60 pc from the cluster center based on the positions and velocities measured by Gaia. To independently assess the reality and extent of this structure, we used light curves generated from TESS full-frame images to search for photometric rotation periods of stars in and around Blanco 1. We detected rotation periods down to a stellar effective temperature of \\( 3100\\,K\\) in 347 of the 603 cluster member candidates for which we have light curves. For cluster members in the core and candidate members in the tidal tails, both within a temperature range of 4400 to 6200 K, 74% and 72% of the rotation periods are consistent with the single-star gyrochronological sequence, respectively. In contrast, a comparison sample of field stars yielded gyrochrone-consistent rotation periods for only 8.5% of stars. The tidal tail candidates' overall conformance to the core members' gyrochrone sequence implies that their contamination ratio is consistent with zero and < 0.33 at the \\(2\\) level. This result confirms the existence of Blanco 1 tidal tails and doubles the number of Blanco 1 members for which there are both spatio-kinematic and rotation-based cluster membership verification. Extending the strategy of using TESS light curves for gyrochronology to other nearby young open clusters and stellar associations may provide a viable strategy for mapping out their dissolution and broadening the search for young exoplanets.

We present the discoveries of a brown dwarf and a low mass star from the Kepler and K2 missions. The newly discovered brown dwarf is EPIC 212036875b and the low mass star is KOI-607b. EPIC 212036875b has a mass of \\( M_b=52.3 1.9M_J\\), a radius of \\( R_b=0.874 0.017R_J\\), 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 0.065M_\\), \\( R_=1.498 0.025R_\\), and \\( T_ eff=6238 60\\)K. KOI-607b has a mass of \\( M_b=95.1 3.4M_J\\), a radius of \\( R_b=1.089 0.089R_J\\), 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 0.052M_\\), \\( R_=0.915 0.031R_\\), and \\( T_ eff = 5418 87\\)K. We also revisit a brown dwarf, CWW 89Ab, that was previously published by Nowak et al. 2017 (under the designation EPIC 219388192b). CWW 89Ab is one of two known transiting brown dwarfs associated with a star cluster, which illustrates the need for more brown dwarfs with accurate masses and radii and reliable age determinations to test theoretical models. We find that the newly discovered brown dwarf, EPIC 212036875b, falls in the middle of the so-called \"brown dwarf desert\", indicating that EPIC 212036875b is either a particularly rare object, or the brown dwarf desert may not be so dry after all.

HIP 67522 b is a 17 Myr old, close-in (\\(P_orb = 6.96\\) d), Jupiter-sized (\\(R = 10\\,R_\\)) transiting planet orbiting a Sun like star in the Sco-Cen OB association. We present our measurement of the system's projected orbital obliquity via two spectroscopic transit observations using the CHIRON spectroscopic facility. We present a global model that accounts for large surface brightness features typical of such young stars during spectroscopic transit observations. With a value of \\(|| = 5.8^+2.8\\,_-5.7\\), it is unlikely that this well-aligned system is the result of a high eccentricity driven migration history. By being the youngest planet with a known obliquity, HIP 67522 b holds a special place in contributing to our understanding of giant planet formation and evolution. Our analysis shows the feasibility of such measurements for young and very active stars.