1,371 research outputs found
Persistent starspot signals on M dwarfs: multi-wavelength Doppler observations with the Habitable-zone Planet Finder and Keck/HIRES
Young, rapidly-rotating M dwarfs exhibit prominent starspots, which create
quasiperiodic signals in their photometric and Doppler spectroscopic
measurements. The periodic Doppler signals can mimic radial velocity (RV)
changes expected from orbiting exoplanets. Exoplanets can be distinguished from
activity-induced false positives by the chromaticity and long-term incoherence
of starspot signals, but these qualities are poorly constrained for
fully-convective M stars. Coherent photometric starspot signals on M dwarfs may
persist for hundreds of rotations, and the wavelength dependence of starspot RV
signals may not be consistent between stars due to differences in their
magnetic fields and active regions. We obtained precise multi-wavelength RVs of
four rapidly-rotating M dwarfs (AD Leo, G 227-22, GJ 1245B, GJ 3959) using the
near-infrared (NIR) Habitable-zone Planet Finder, and the optical Keck/HIRES
spectrometer. Our RVs are complemented by photometry from Kepler, TESS, and the
Las Cumbres Observatory (LCO) network of telescopes. We found that all four
stars exhibit large spot-induced Doppler signals at their rotation periods, and
investigated the longevity and optical-to-NIR chromaticity for these signals.
The phase curves remain coherent much longer than is typical for Sunlike stars.
Their chromaticity varies, and one star (GJ 3959) exhibits optical and NIR RV
modulation consistent in both phase and amplitude. In general, though, we find
that the NIR amplitudes are lower than their optical counterparts. We conclude
that starspot modulation for rapidly-rotating M stars frequently remains
coherent for hundreds of stellar rotations, and gives rise to Doppler signals
that, due to this coherence, may be mistaken for exoplanets.Comment: Accepted for publication in the Astrophysical Journa
Potential Added Value of Psychological Capital in Predicting Work Attitudes
Meeting the challenge of effectively managing human resources requires new thinking and approaches. To extend the traditional perspective of economic capital, increasing recognition is being given to human capital and more recently social capital, this article proposes and empirically tests the potential added value that psychological capital may have for employee attitudes of satisfaction and commitment. After first providing the background and theory of PsyCap, this article reports a study of manufacturing employees (N = 74) that found a significant relationship between PsyCap and job satisfaction (r=.373) and organization commitment (r=.313). Importantly, the employees’ PsyCap had a significant added impact over human and social capital on these work attitudes. Future research and practical implications conclude the article
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
Sixty Years of Modern Human Origins in the American Anthropological Association
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65197/1/aa.2003.105.1.89.pd
Persistent Starspot Signals on M Dwarfs: Multiwavelength Doppler Observations with the Habitable-zone Planet Finder and Keck/HIRES
Young, rapidly rotating M dwarfs exhibit prominent starspots, which create quasiperiodic signals in their photometric and Doppler spectroscopic measurements. The periodic Doppler signals can mimic radial velocity (RV) changes expected from orbiting exoplanets. Exoplanets can be distinguished from activity-induced false positives by the chromaticity and long-term incoherence of starspot signals, but these qualities are poorly constrained for fully convective M stars. Coherent photometric starspot signals on M dwarfs may persist for hundreds of rotations, and the wavelength dependence of starspot RV signals may not be consistent between stars due to differences in their magnetic fields and active regions. We obtained precise multiwavelength RVs of four rapidly rotating M dwarfs (AD Leo, G227-22, GJ 1245B, GJ 3959) using the near-infrared (NIR) Habitable-zone Planet Finder and the optical Keck/HIRES spectrometer. Our RVs are complemented by photometry from Kepler, TESS, and the Las Cumbres Observatory network of telescopes. We found that all four stars exhibit large spot-induced Doppler signals at their rotation periods, and investigated the longevity and optical-to-NIR chromaticity for these signals. The phase curves remain coherent much longer than is typical for Sunlike stars. Their chromaticity varies, and one star (GJ 3959) exhibits optical and NIR RV modulation consistent in both phase and amplitude. In general, though, we find that the NIR amplitudes are lower than their optical counterparts. We conclude that starspot modulation for rapidly rotating M stars frequently remains coherent for hundreds of stellar rotations and gives rise to Doppler signals that, due to this coherence, may be mistaken for exoplanets
TOI-1728b: The Habitable-zone Planet Finder confirms a warm super Neptune orbiting an M dwarf host
We confirm the planetary nature of TOI-1728b using a combination of
ground-based photometry, near-infrared Doppler velocimetry and spectroscopy
with the Habitable-zone Planet Finder.TOI-1728 is an old, inactive M0 star with
\teff{} K, which hosts a transiting super Neptune at an
orbital period of 3.49 days. Joint fitting of the radial velocities and
TESS and ground-based transits yields a planetary radius of
R, mass M
and eccentricity . We estimate the stellar properties,
and perform a search for He 10830 \AA absorption during the transit of this
planet and claim a null detection with an upper limit of 1.1 with 90\%
confidence. A deeper level of He 10830 \AA ~ absorption has been detected in
the planet atmosphere of GJ 3470b, a comparable gaseous planet. TOI-1728b is
the largest super Neptune -- the intermediate subclass of planets between
Neptune and the more massive gas-giant planets -- discovered around an M dwarf.
With its relatively large mass and radius, TOI-1728 represents a valuable
datapoint in the M-dwarf exoplanet mass-radius diagram, bridging the gap
between the lighter Neptune-sized planets and the heavier Jovian planets known
to orbit M-dwarfs. With a low bulk density of g/cm,
and orbiting a bright host star (J , V ), TOI-1728b is
also a promising candidate for transmission spectroscopy both from the ground
and from space, which can be used to constrain planet formation and
evolutionary models.Comment: 21 pages, 12 figures, 4 tables: Accepted for publicatio
TOI-1728b: The Habitable-zone Planet Finder Confirms a Warm Super-Neptune Orbiting an M-dwarf Host
We confirm the planetary nature of TOI-1728b using a combination of ground-based photometry, near-infrared Doppler velocimetry and spectroscopy with the Habitable-zone Planet Finder. TOI-1728 is an old, inactive M0 star with T_(eff) = 3980⁺³¹₋₃₂ K, which hosts a transiting super-Neptune at an orbital period of ~3.49 days. Joint fitting of the radial velocities and TESS and ground-based transits yields a planetary radius of 5.05^(+0.16)_(-0.17) R_⊕, mass 26.78^(+5.43)_(-5.13) M_⊕, and eccentricity 0.057^(+0.054)_(-0.039). We estimate the stellar properties, and perform a search for He 10830 Å absorption during the transit of this planet and claim a null detection with an upper limit of 1.1% with 90% confidence. A deeper level of He 10830 Å absorption has been detected in the planet atmosphere of GJ 3470b, a comparable gaseous planet. TOI-1728b is the largest super-Neptune—the intermediate subclass of planets between Neptune and the more massive gas-giant planets—discovered around an M dwarf. With its relatively large mass and radius, TOI-1728 represents a valuable data point in the M-dwarf exoplanet mass–radius diagram, bridging the gap between the lighter Neptune-sized planets and the heavier Jovian planets known to orbit M dwarfs. With a low bulk density of 1.14^(+0.26)_(-0.24) g cm⁻³, and orbiting a bright host star (J ~ 9.6, V ~ 12.4), TOI-1728b is also a promising candidate for transmission spectroscopy both from the ground and from space, which can be used to constrain planet formation and evolutionary models
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