17 research outputs found
Caustic Structures and Detectability of Circumbinary Planets in Microlensing
Recent discoveries of circumbinary planets in Kepler data show that there is
a viable channel of planet formation around binary main sequence stars.
Motivated by these discoveries, we have investigated the caustic structures and
detectability of circumbinary planets in microlensing events. We have produced
a suite of animations of caustics as a function of the projected separation and
angle of the binary host to efficiently explore caustic structures over the
entire circumbinary parameter space. Aided by these animations, we have derived
a semi-empirical analytic expression for the location of planetary caustics,
which are displaced in circumbinary lenses relative to those of planets with a
single host. We have used this expression to show that the dominant source of
caustic motion will be due to the planet's orbital motion and not that of the
binary star. Finally, we estimate the fraction of circumbinary microlensing
events that are recognizable as such to be significant (5-50 percent) for
binary projected separations in the range 0.1-0.5 in units of Einstein radii.Comment: 15 pages, 1 table, 18 figures. Accepted for publication in Ap
Astrophysical Insights into Radial Velocity Jitter from an Analysis of 600 Planet-search Stars
Radial velocity (RV) detection of planets is hampered by astrophysical processes on the surfaces of stars that induce a stochastic signal, or "jitter," which can drown out or even mimic planetary signals. Here, we empirically and carefully measure the RV jitter of more than 600 stars from the California Planet Search sample on a star by star basis. As part of this process, we explore the activity–RV correlation of stellar cycles and include appendices listing every ostensibly companion-induced signal we removed and every activity cycle we noted. We then use precise stellar properties from Brewer et al. to separate the sample into bins of stellar mass and examine trends with activity and with evolutionary state. We find that RV jitter tracks stellar evolution and that in general, stars evolve through different stages of RV jitter: the jitter in younger stars is driven by magnetic activity, while the jitter in older stars is convectively driven and dominated by granulation and oscillations. We identify the "jitter minimum"—where activity-driven and convectively driven jitter have similar amplitudes—for stars between 0.7 and 1.7 M⊙ and find that more-massive stars reach this jitter minimum later in their lifetime, in the subgiant or even giant phases. Finally, we comment on how these results can inform future RV efforts, from prioritization of follow-up targets from transit surveys like TESS to target selection of future RV surveys
Astrophysical Insights into Radial Velocity Jitter from an Analysis of 600 Planet-search Stars
Radial velocity (RV) detection of planets is hampered by astrophysical processes on the surfaces of stars that induce a stochastic signal, or "jitter," which can drown out or even mimic planetary signals. Here, we empirically and carefully measure the RV jitter of more than 600 stars from the California Planet Search sample on a star by star basis. As part of this process, we explore the activity–RV correlation of stellar cycles and include appendices listing every ostensibly companion-induced signal we removed and every activity cycle we noted. We then use precise stellar properties from Brewer et al. to separate the sample into bins of stellar mass and examine trends with activity and with evolutionary state. We find that RV jitter tracks stellar evolution and that in general, stars evolve through different stages of RV jitter: the jitter in younger stars is driven by magnetic activity, while the jitter in older stars is convectively driven and dominated by granulation and oscillations. We identify the "jitter minimum"—where activity-driven and convectively driven jitter have similar amplitudes—for stars between 0.7 and 1.7 M⊙ and find that more-massive stars reach this jitter minimum later in their lifetime, in the subgiant or even giant phases. Finally, we comment on how these results can inform future RV efforts, from prioritization of follow-up targets from transit surveys like TESS to target selection of future RV surveys
Retired A Stars and Their Companions VIII: 15 New Planetary Signals Around Subgiants and Transit Parameters for California Planet Search Planets with Subgiant Hosts
We present the discovery of seven new planets and eight planet candidates around subgiant stars, as additions to the known sample of planets around "retired A stars." Among these are the possible first three-planet systems around subgiant stars, HD 163607 and HD 4917. Additionally, we present calculations of possible transit times, durations, depths, and probabilities for all known planets around subgiant (3 9%
Retired A Stars and Their Companions VIII: 15 New Planetary Signals Around Subgiants and Transit Parameters for California Planet Search Planets with Subgiant Hosts
We present the discovery of seven new planets and eight planet candidates around subgiant stars, as additions to the known sample of planets around "retired A stars." Among these are the possible first three-planet systems around subgiant stars, HD 163607 and HD 4917. Additionally, we present calculations of possible transit times, durations, depths, and probabilities for all known planets around subgiant (3 9%
Detection of p-mode Oscillations in HD 35833 with NEID and TESS
We report the results of observations of p-mode oscillations in the G0
subgiant star HD 35833 in both radial velocities and photometry with NEID and
TESS, respectively. We achieve separate, robust detections of the oscillation
signal with both instruments (radial velocity amplitude m s, photometric amplitude
ppm, frequency of maximum power Hz, and
mode spacing Hz) as well as a non-detection in
a TESS sector concurrent with the NEID observations. These data shed light on
our ability to mitigate the correlated noise impact of oscillations with radial
velocities alone, and on the robustness of commonly used asteroseismic scaling
relations. The NEID data are used to validate models for the attenuation of
oscillation signals for exposure times , and we compare
our results to predictions from theoretical scaling relations and find that the
observed amplitudes are weaker than expected by , hinting at gaps in
the underlying physical models.Comment: 19 Pages, 14 Figures, Appendi
NEID Reveals that The Young Warm Neptune TOI-2076 b Has a Low Obliquity
TOI-2076 b is a sub-Neptune-sized planet () that transits a young () bright
() K-dwarf hosting a system of three transiting planets. Using
spectroscopic observations with the NEID spectrograph on the WIYN 3.5 m
Telescope, we model the Rossiter-McLaughlin effect of TOI-2076 b, and derive a
sky-projected obliquity of . Using the size of
the star (), and the stellar rotation period
( days), we estimate a true obliquity of
( at 95% confidence),
demonstrating that TOI-2076 b is on a well-aligned orbit. Simultaneous
diffuser-assisted photometry from the 3.5 m Telescope at Apache Point
Observatory rules out flares during the transit. TOI-2076 b joins a small but
growing sample of young planets in compact multi-planet systems with
well-aligned orbits, and is the fourth planet with an age Myr in
a multi-transiting system with an obliquity measurement. The low obliquity of
TOI-2076 b and the presence of transit timing variations in the system suggest
the TOI-2076 system likely formed via convergent disk migration in an initially
well-aligned disk.Comment: Submitted to ApJL, 13 pages, 4 figures, 3 table