Search Publications
Bridging the Gap between Protoplanetary and Debris Disks: Separate Evolution of Millimeter and Micrometer-sized Dust
Matthews, Brenda C.; van der Marel, Nienke; Michel, Arnaud
The connection between the nature of a protoplanetary disk and that of a debris disk is not well understood. Dust evolution, planet formation, and disk dissipation likely play a role in the processes involved. We aim to reconcile both manifestations of dusty circumstellar disks through a study of optically thin Class III disks and how they correla…
The GALAH survey: a census of lithium-rich giant stars
Lewis, Geraint F.; Ting, Yuan-Sen; Buder, Sven +20 more
We investigate the properties of 1262 red giant stars with high photospheric abundances of lithium observed by the GALAH and K2-HERMES surveys, and discuss them in the context of proposed mechanisms for lithium enrichment and redepletion in giant stars. We confirm that Li-rich giants are rare, making up only 1.2 per cent of our giant star sample. …
Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space
Fragkoudi, Francesca; White, Simon D. M.; Mackereth, J. Ted +2 more
Action space synthesizes the orbital information of stars and is well suited to analyse the rich kinematic substructure of the disc in the second Gaia data release's radial velocity sample. We revisit the strong perturbation induced in the Milky Way disc by an m = 2 bar, using test particle simulations and the actions (JR, Lz…
Detection of an Atmosphere on a Rocky Exoplanet
Sotin, Christophe; West, Robert; Zellem, Robert T. +7 more
We report the detection of an atmosphere on a rocky exoplanet, GJ 1132 b, which is similar to Earth in terms of size and density. The atmospheric transmission spectrum was detected using Hubble WFC3 measurements and shows spectral signatures of aerosol scattering, HCN, and CH4 in a low mean molecular weight atmosphere. We model the atmo…
What sustained multi-disciplinary research can achieve: The space weather modeling framework
Liemohn, Michael W.; van der Holst, Bart; Sokolov, Igor V. +15 more
Magnetohydrodynamics (MHD)-based global space weather models have mostly been developed and maintained at academic institutions. While the "free spirit" approach of academia enables the rapid emergence and testing of new ideas and methods, the lack of long-term stability and support makes this arrangement very challenging. This paper describes a s…
Speckle Observations of TESS Exoplanet Host Stars. II. Stellar Companions at 1-1000 au and Implications for Small Planet Detection
Lester, Kathryn V.; Howell, Steve B.; Hirsch, Lea A. +7 more
We present high-angular-resolution imaging observations of 517 host stars of TESS exoplanet candidates using the 'Alopeke and Zorro speckle cameras at Gemini North and South. The sample consists mainly of bright F, G, K stars at distances of less than 500 pc. Our speckle observations span angular resolutions of ~20 mas out to 1"2, yielding spatial…
Identification of a Local Sample of Gamma-Ray Bursts Consistent with a Magnetar Giant Flare Origin
Cenko, S. B.; Hurley, K.; Ridnaia, A. +23 more
Cosmological gamma-ray bursts (GRBs) are known to arise from distinct progenitor channels: short GRBs mostly from neutron star mergers and long GRBs from a rare type of core-collapse supernova (CCSN) called collapsars. Highly magnetized neutron stars called magnetars also generate energetic, short-duration gamma-ray transients called magnetar gian…
R-process enhancements of Gaia-Enceladus in GALAH DR3
Helmi, Amina; Matsuno, Tadafumi; Hirai, Yutaka +3 more
Context. The dominant site of production of r-process elements remains unclear despite recent observations of a neutron star merger. Observational constraints on the properties of the sites can be obtained by comparing r-process abundances in different environments. The recent Gaia data releases and large samples from high-resolution optical spect…
22Ne Phase Separation as a Solution to the Ultramassive White Dwarf Cooling Anomaly
Blouin, Simon; Saumon, Didier; Daligault, Jérôme
The precise astrometric measurements of the Gaia Data Release 2 have opened the door to detailed tests of the predictions of white dwarf cooling models. Significant discrepancies between theory and observations have been identified, the most striking affecting ultramassive white dwarfs. Cheng et al. found that a small fraction of white dwarfs on t…
3D Morphology of Open Clusters in the Solar Neighborhood with Gaia EDR 3: Its Relation to Cluster Dynamics
Tang, Shih-Yun; Pang, Xiaoying; Kroupa, Pavel +5 more
We analyze the 3D morphology and kinematics of 13 open clusters (OCs) located within 500 pc of the Sun, using Gaia EDR 3 and kinematic data from the literature. Members of OCs are identified using the unsupervised machine-learning method StarGO, using five parameters (X, Y, Z, ${\mu }_{\alpha }\cos \delta ,{\mu }_{\delta }$ ). The OC sample covers…