9 research outputs found
Constraints on magnetic braking from the G8 dwarf stars 61 UMa and Tau Cet
Stars and planetary system
Asteroseismology and spectropolarimetry of the exoplanet host star Lambda Serpentis
Stars and planetary system
1st Postgraduate Seminar on Agriculture and Forestry 2021
We present velocity-resolved reverberation results for five active galactic
nuclei. We recovered velocity-delay maps using the maximum-entropy method for
four objects: Mrk 335, Mrk 1501, 3C120, and PG2130+099. For the fifth, Mrk 6,
we were only able to measure mean time delays in different velocity bins of the
Hbeta emission line. The four velocity-delay maps show unique dynamical
signatures for each object. For 3C120, the Balmer lines show kinematic
signatures consistent with both an inclined disk and infalling gas, but the
HeII 4686 emission line is suggestive only of inflow. The Balmer lines in Mrk
335, Mrk 1501, and PG 2130+099 show signs of infalling gas, but the HeII
emission in Mrk 335 is consistent with an inclined disk. We also see tentative
evidence of combined virial motion and infalling gas from the velocity-binned
analysis of Mrk 6. The maps for 3C120 and Mrk 335 are two of the most clearly
defined velocity-delay maps to date. These maps constitute a large increase in
the number of objects for which we have resolved velocity-delay maps and
provide evidence supporting the reliability of reverberation-based black hole
mass measurements.Comment: 23 pages, 17 Figures. Accepted for publication in ApJ. For a brief
video explaining the key results of this paper, see
http://www.youtube.com/watch?v=8xAflzp-Yl
A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS
We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 μHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R∗ = 2.943 ± 0.064 Ro), mass (M∗ = 1.212 ± 0.074 Mo), and age (4.9 ± 1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (Rp = 9.17 ± 0.33 R⊕) with an orbital period of ∼14.3 days, irradiance of F = 343 ± 24 F⊕, and moderate mass (Mp = 60.5 ± 5.7 M⊕) and density (ρp = 0.431 ± 0.062 g cm-3). The properties of HD 221416 b show that the host-star metallicity-planet mass correlation found in sub-Saturns (4-8 R⊕) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ∼15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology. © 2019. The American Astronomical Society. All rights reserved.