ORCID Profile
0000-0002-0216-0994
Current Organisations
Western University
,
Queen's University
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Publisher: Oxford University Press (OUP)
Date: 11-08-2017
Publisher: Informa UK Limited
Date: 19-05-2023
Publisher: EDP Sciences
Date: 05-2017
Publisher: EDP Sciences
Date: 11-2018
DOI: 10.1051/0004-6361/201834251
Abstract: Stellar magnetic fields are poorly understood, but are known to be important for stellar evolution and exoplanet habitability. They drive stellar activity, which is the main observational constraint on theoretical models for magnetic field generation and evolution. Starspots are the main manifestation of the magnetic fields at the stellar surface. In this study we measured the variation in their latitude with time, called a butterfly diagram in the solar case, for the solar analogue HD 173701 (KIC 8006161). To this end, we used Kepler data to combine starspot rotation rates at different epochs and the asteroseismically determined latitudinal variation in the stellar rotation rates. We observe a clear variation in the latitude of the starspots. It is the first time such a diagram has been constructed using asteroseismic data.
Publisher: EDP Sciences
Date: 10-2014
Publisher: Oxford University Press (OUP)
Date: 07-06-2022
Abstract: The Milky Way was shaped by the mergers with several galaxies in the past. We search for remnant stars that were born in these foreign galaxies and assess their ages in an effort to put upper limits on the merger times and thereby better understand the evolutionary history of our Galaxy. Using 5D-phase space information from Gaia eDR3, radial velocities from Gaia DR2 and chemical information from apogee DR16, we kinematically and chemically select 21 red giant stars belonging to former dwarf galaxies that merged with the Milky Way. With added asteroseismology from Kepler and K2 , we determine the ages of the 21 ex situ stars and 49 in situ stars with an average σage/age of ∼31 per cent. We find that all the ex situ stars are consistent with being older than 8 Gyr. While it is not possible to associate all the stars with a specific dwarf galaxy, we classify eight of them as Gaia-Enceladus/Sausage stars, which is one of the most massive mergers in our Galaxy’s history. We determine their mean age to be 9.5 ± 1.3 Gyr consistent with a merger time of 8–10 Gyr ago. The rest of the stars are possibly associated with Kraken, Thamnos, Sequoia, or another extragalactic progenitor. The age determination of ex situ stars paves the way to more accurately pinning down when the merger events occurred and hence provide tight constraints useful for simulating how these events unfolded.
No related grants have been discovered for Maren Goodman.