Eric Gaidos - Hawaii

Eric Gaidos
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Eric Gaidos
United States

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Earth and Planetary Astrophysics (39)
Solar and Stellar Astrophysics (27)
Astrophysics (2)
Astrophysics of Galaxies (2)
Instrumentation and Methods for Astrophysics (2)
Physics - Geophysics (1)
Physics - Atmospheric and Oceanic Physics (1)
High Energy Astrophysical Phenomena (1)
Cosmology and Nongalactic Astrophysics (1)

Publications Authored By Eric Gaidos

All water-covered rocky planets in the inner habitable zones of solar-type stars will inevitably experience a catastrophic runaway climate due to increasing stellar luminosity and limits to outgoing infrared radiation from wet greenhouse atmospheres. Reflectors or scatterers placed near Earth's inner Lagrange point (L1) have been proposed as a 'geo-engineering" solution to anthropogenic climate change and an advanced version of this could modulate incident irradiation over many Gyr or "rescue" a planet from the interior of the habitable zone. The distance of the starshade from the planet that minimizes its mass is 1. Read More

The star EPIC 210894022 has been identified from a light curve acquired through the K2 space mission as possibly orbited by a transiting planet. Our aim is to confirm the planetary nature of the object and derive its fundamental parameters. We combine the K2 photometry with reconnaissance spectroscopy and radial velocity (RV) measurements obtained using three separate telescope and spectrograph combinations. Read More

One of the most well-studied young stellar associations, Taurus-Auriga, will be observed by the extended Kepler mission, K2, in the spring of 2017. K2 Campaign 13 (C13) will be a unique opportunity to study many stars in this young association at high photometric precision and cadence. Using observations from the Kilodegree Extremely Little Telescope (KELT) survey, we identify "dippers", stochastic variables, and periodic variables among K2 C13 target stars. Read More

Observations of free-free continuum radio emission of four young main-sequence solar-type stars (EK Dra, Pi1 UMa, Chi1 Ori; and Kappa1 Cet) are studied to detect stellar winds or at least to place upper limits on their thermal radio emission, which is dominated by the ionized wind. These stars are excellent proxies for representing the young Sun. Upper limits on mass loss rates are calculated using their observational radio emission. Read More

We used the Robo-AO laser adaptive optics system to image 99 main sequence and subgiant stars that have Kepler-detected asteroseismic signals. Robo-AO allows us to resolve blended secondary sources at separations as close as 0.15" that may contribute to the measured Kepler light curves and affect asteroseismic analysis and interpretation. Read More

Open clusters and young stellar associations are attractive sites to search for planets and to test theories of planet formation, migration, and evolution. We present our search for, and characterization of, transiting planets in the ~800 Myr old Praesepe (Beehive, M44) Cluster from K2 light curves. We identify seven planet candidates, six of which we statistically validate to be real planets, the last of which requires more data. Read More

We provide estimates of atmospheric pressure and surface composition on short-period rocky exoplanets with dayside magma pools and silicate vapor atmospheres. Atmospheric pressure tends toward vapor-pressure equilibrium with surface magma, and magma-surface composition is set by the competing effects of fractional vaporization and surface-interior exchange. We use basic models to show how surface-interior exchange is controlled by the planet's temperature, mass, and initial composition. Read More

Strongly irradiated giant planets are observed to have radii larger than thermal evolution models predict. Although these inflated planets have been known for over fifteen years, it is unclear whether their inflation is caused by deposition of energy from the host star, or inhibited cooling of the planet. These processes can be distinguished if the planet becomes highly irradiated only when the host star evolves onto the red giant branch. Read More

Studying the properties of young planetary systems can shed light on how the dynamics and structure of planets evolve during their most formative years. Recent K2 observations of nearby young clusters (10-800 Myr) have enabled the discovery of such planetary systems. Here we report the discovery of a Neptune-sized planet transiting an M4. Read More

We confirm a 0.995 d periodic planetary transit-like signal, KOI 6705.01, in the Kepler lightcurve of the star KIC 6423922. Read More

Authors: Warren Skidmore, Ian Dell'Antonio, Misato Fukugawa, Aruna Goswami, Lei Hao, David Jewitt, Greg Laughlin, Charles Steidel, Paul Hickson, Luc Simard, Matthias Schöck, Tommaso Treu, Judith Cohen, G. C. Anupama, Mark Dickinson, Fiona Harrison, Tadayuki Kodama, Jessica R. Lu, Bruce Macintosh, Matt Malkan, Shude Mao, Norio Narita, Tomohiko Sekiguchi, Annapurni Subramaniam, Masaomi Tanaka, Feng Tian, Michael A'Hearn, Masayuki Akiyama, Babar Ali, Wako Aoki, Manjari Bagchi, Aaron Barth, Varun Bhalerao, Marusa Bradac, James Bullock, Adam J. Burgasser, Scott Chapman, Ranga-Ram Chary, Masashi Chiba, Michael Cooper, Asantha Cooray, Ian Crossfield, Thayne Currie, Mousumi Das, G. C. Dewangan, Richard de Grijs, Tuan Do, Subo Dong, Jarah Evslin, Taotao Fang, Xuan Fang, Christopher Fassnacht, Leigh Fletcher, Eric Gaidos, Roy Gal, Andrea Ghez, Mauro Giavalisco, Carol A. Grady, Thomas Greathouse, Rupjyoti Gogoi, Puragra Guhathakurta, Luis Ho, Priya Hasan, Gregory J. Herczeg, Mitsuhiko Honda, Masa Imanishi, Hanae Inami, Masanori Iye, Jason Kalirai, U. S. Kamath, Stephen Kane, Nobunari Kashikawa, Mansi Kasliwal, Vishal Kasliwal, Evan Kirby, Quinn M. Konopacky, Sebastien Lepine, Di Li, Jianyang Li, Junjun Liu, Michael C. Liu, Enrigue Lopez-Rodriguez, Jennifer Lotz, Philip Lubin, Lucas Macri, Keiichi Maeda, Franck Marchis, Christian Marois, Alan Marscher, Crystal Martin, Taro Matsuo, Claire Max, Alan McConnachie, Stacy McGough, Carl Melis, Leo Meyer, Michael Mumma, Takayuki Muto, Tohru Nagao, Joan R. Najita, Julio Navarro, Michael Pierce, Jason X. Prochaska, Masamune Oguri, Devendra K. Ojha, Yoshiko K. Okamoto, Glenn Orton, Angel Otarola, Masami Ouchi, Chris Packham, Deborah L. Padgett, Shashi Bhushan Pandey, Catherine Pilachowsky, Klaus M. Pontoppidan, Joel Primack, Shalima Puthiyaveettil, Enrico Ramirez-Ruiz, Naveen Reddy, Michael Rich, Matthew J. Richter, James Schombert, Anjan Ananda Sen, Jianrong Shi, Kartik Sheth, R. Srianand, Jonathan C. Tan, Masayuki Tanaka, Angelle Tanner, Nozomu Tominaga, David Tytler, Vivian U, Lingzhi Wang, Xiaofeng Wang, Yiping Wang, Gillian Wilson, Shelley Wright, Chao Wu, Xufeng Wu, Renxin Xu, Toru Yamada, Bin Yang, Gongbo Zhao, Hongsheng Zhao

The TMT Detailed Science Case describes the transformational science that the Thirty Meter Telescope will enable. Planned to begin science operations in 2024, TMT will open up opportunities for revolutionary discoveries in essentially every field of astronomy, astrophysics and cosmology, seeing much fainter objects much more clearly than existing telescopes. Per this capability, TMT's science agenda fills all of space and time, from nearby comets and asteroids, to exoplanets, to the most distant galaxies, and all the way back to the very first sources of light in the Universe. Read More

If the photospheres of solar-type stars represent the composition of circumstellar disks from which any planets formed, spectroscopic determinations of stellar elemental abundances offer information on the composition of those planets, including smaller, rocky planets. In particular, the C/O ratio is proposed to be a key determinant of the composition of solids that condense from disk gas and are incorporated into planets. Also, planets may leave chemical signatures on the photospheres of their host stars by sequestering heavy elements, or by being accreted by the stars. Read More

Precise and accurate parameters for late-type (late K and M) dwarf stars are important for characterization of any orbiting planets, but such determinations have been hampered by these stars' complex spectra and dissimilarity to the Sun. We exploit an empirically calibrated method to estimate spectroscopic effective temperature ($T_{\rm{eff}}$) and the Stefan-Boltzmann law to determine radii of 183 nearby K7-M7 single stars with a precision of 2-5%. Our improved stellar parameters enable us to develop model-independent relations between $T_{\rm{eff}}$ or absolute magnitude and radius, as well as between color and $T_{\rm{eff}}$. Read More

We confirm and characterize the exoplanetary systems Kepler-445 and Kepler-446: two mid-M dwarf stars, each with multiple, small, short-period transiting planets. Kepler-445 is a metal-rich ([Fe/H]=+0.25 $\pm$ 0. Read More

We present a summary of the splinter session on "touchstone stars" -- stars with directly measured parameters -- that was organized as part of the Cool Stars 18 conference. We discuss several methods to precisely determine cool star properties such as masses and radii from eclipsing binaries, and radii and effective temperatures from interferometry. We highlight recent results in identifying and measuring parameters for touchstone stars, and ongoing efforts to use touchstone stars to determine parameters for other stars. Read More

Planets orbiting within the close-in habitable zones of M dwarf stars will be exposed to elevated high-energy radiation driven by strong magneto-hydrodynamic dynamos during stellar youth. Near-ultraviolet (NUV) irradiation can erode and alter the chemistry of planetary atmospheres, and a quantitative description of the evolution of NUV emission from M dwarfs is needed when modeling these effects. We investigated the NUV luminosity evolution of early M-type dwarfs by cross-correlating the Lepine & Gaidos (2011) catalog of bright M dwarfs with the GALEX catalog of NUV (1771-2831A) sources. Read More

Using the cumulative catalog of planets detected by the NASA Kepler mission, we reconstruct the intrinsic occurrence of Earth- to Neptune-size (1 - 4$R_{\oplus}$) planets and their distributions with radius and orbital period. We analyze 76,711 solar-type ($0.8Read More

Comparisons between the planet populations around solar-type stars and those orbiting M dwarfs shed light on the possible dependence of planet formation and evolution on stellar mass. However, such analyses must control for other factors, i.e. Read More

Metallicity is a fundamental parameter that contributes to the physical characteristics of a star. However, the low temperatures and complex molecules present in M dwarf atmospheres make it difficult to measure their metallicities using techniques that have been commonly used for Sun-like stars. Although there has been significant progress in developing empirical methods to measure M dwarf metallicities over the last few years, these techniques have been developed primarily for early- to mid-M dwarfs. Read More

We present revised properties for 196,468 stars observed by the NASA Kepler Mission and used in the analysis of Quarter 1-16 (Q1-Q16) data to detect and characterize transiting exoplanets. The catalog is based on a compilation of literature values for atmospheric properties (temperature, surface gravity, and metallicity) derived from different observational techniques (photometry, spectroscopy, asteroseismology, and exoplanet transits), which were then homogeneously fitted to a grid of Dartmouth stellar isochrones. We use broadband photometry and asteroseismology to characterize 11,532 Kepler targets which were previously unclassified in the Kepler Input Catalog (KIC). Read More

We use moderate-resolution spectra of nearby late K and M dwarf stars with parallaxes and interferometrically determined radii to refine their effective temperatures, luminosities, and metallicities. We use these revised values to calibrate spectroscopic techniques to infer the fundamental parameters of more distant late-type dwarf stars. We demonstrate that, after masking out poorly modeled regions, the newest version of the PHOENIX atmosphere models accurately reproduce temperatures derived bolometrically. Read More

GJ 1214 is a nearby M dwarf star that hosts a transiting super-Earth-size planet, making this system an excellent target for atmospheric studies. Most studies find that the transmission spectrum of GJ 1214b is flat, which favors either a high mean molecular weight or cloudy/hazy hydrogen (H) rich atmosphere model. Photometry at short wavelengths (< 0. Read More

Analyses of exoplanet statistics suggest a trend of giant planet occurrence with host star mass, a clue to how planets like Jupiter form. One missing piece of the puzzle is the occurrence around late K dwarf stars (masses of 0.5-0. Read More

It has been shown that F, G, and early K dwarf hosts of Neptune-sized planets are not preferentially metal-rich. However, it is less clear whether the same holds for late K and M dwarf planet hosts. We report metallicities of Kepler targets and candidate transiting planet hosts with effective temperatures below 4500 K. Read More

We used a thermal model of an iron core to calculate magnetodynamo evolution in Earth-mass rocky planets to determine the sensitivity of dynamo lifetime and intensity to planets with different mantle tectonic regimes, surface temperatures, and core properties. The heat flow at the core-mantle boundary (CMB) is derived from numerical models of mantle convection with a viscous/pseudo-plastic rheology that captures the phenomenology of plate-like tectonics. Our thermal evolution models predict a long-lived (~8 Gyr) field for Earth and similar dynamo evolution for Earth-mass exoplanets with plate tectonics. Read More

A key goal of the Kepler mission is the discovery of Earth-size transiting planets in "habitable zones" where stellar irradiance maintains a temperate climate on an Earth-like planet. Robust estimates of planet radius and irradiance require accurate stellar parameters, but most Kepler systems are faint, making spectroscopy difficult and prioritization of targets desirable. The parameters of 2035 host stars were estimated by Bayesian analysis and the probabilities p(HZ) that 2738 candidate or confirmed planets orbit in the habitable zone were calculated. Read More

Knowledge of late K and M dwarf metallicities can be used to guide planet searches and constrain planet formation models. However, the determination of metallicities of late-type stars is difficult because visible wavelength spectra of their cool atmospheres contain many overlapping absorption lines, preventing the measurement of equivalent widths. We present new methods, and improved calibrations of existing methods, to determine metallicities of late-K and M dwarfs from moderate resolution (1300 < R < 2000) visible and infrared spectra. Read More

Statistical analyses of large surveys for transiting planets such as the Kepler mission must account for systematic errors and biases. Transit detection depends not only on the planet's radius and orbital period, but also on host star properties. Thus, a sample of stars with transiting planets may not accurately represent the target population. Read More

We review current observational and theoretical constraints on the Galactic chemical evolution (GCE) of oxygen isotopes in order to explore whether GCE plays a role in explaining the lower 17O/18O ratio of the Sun, relative to the present-day interstellar medium, or the existence of distinct 16O-rich and 16O-poor reservoirs in the Solar System. Although the production of both 17O and 18O are related to the metallicity of progenitor stars, 17O is most likely produced in stars that evolve on longer timescales than those that produce 18O. Therefore the 17O/18O ratio need not have remained constant over time, contrary to preconceptions and the simplest models of GCE. Read More

We present a spectroscopic catalog of the 1,564 brightest (J<9) M dwarf candidates in the northern sky, as selected from the SUPERBLINK proper motion catalog. Observations confirm 1,408 of the candidates to be late-K and M dwarfs with spectral subtypes K7-M6. From the low \mu>40 mas/yr proper motion limit and high level of completeness of the SUPERBLINK catalog in that magnitude range, we estimate that our spectroscopic census most likely includes >90% of all existing, northern-sky M dwarfs with apparent magnitude J<9. Read More

We estimate the stellar parameters of late K and early M type Kepler target stars. We obtain medium resolution visible spectra of 382 stars with Kp-J>2 (~K5 and later spectral type). We determine luminosity class by comparing the strength of gravity-sensitive indices (CaH, K I, Ca II, and Na I) to their strength in a sample of stars of known luminosity class. Read More

Doppler observations from Keck Observatory have revealed a triple planet system orbiting the nearby mid-type K dwarf, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with \msini\ = 11.6 \mearth (0. Read More

Feedbacks that can destabilize the climates of synchronously-rotating rocky planets may arise on planets with strong day-night surface temperature contrasts. Earth-like habitable-zone (HZ) planets maintain stable surface liquid water over geological time. This requires equilibrium between the temperature-dependent rate of greenhouse-gas consumption by weathering,and greenhouse-gas resupply by other processes. Read More

We demonstrate ground-based submillimagnitude (<10^-3) photometry of widely separated bright stars using snapshot CCD imaging. We routinely achieved this photometric precision by (1) choosing nearby comparison stars of a similar magnitude and spectral type, (2) defocusing the telescope to allow high signal (>10^7 electrons) to be acquired in a single integration, (3) pointing the telescope so that all stellar images fall on the same detector pixels, and (4) using a region of the CCD detector that is free of nonlinear or aberrant pixels. We describe semiautomated observations with the Supernova Integrated Field Spectrograph (SNIFS) on the University of Hawaii 2. Read More

We constrain the densities of Earth- to Neptune-size planets around very cool (Te =3660-4660K) Kepler stars by comparing 1202 Keck/HIRES radial velocity measurements of 150 nearby stars to a model based on Kepler candidate planet radii and a power-law mass-radius relation. Our analysis is based on the presumption that the planet populations around the two sets of stars are the same. The model can reproduce the observed distribution of radial velocity variation over a range of parameter values, but, for the expected level of Doppler systematic error, the highest Kolmogorov-Smirnov probabilities occur for a power-law index alpha ~ 4, indicating that rocky-metal planets dominate the planet population in this size range. Read More

We present an all-sky catalog of M dwarf stars with apparent infrared magnitude J<10. The 8,889 stars are selected from the ongoing SUPERBLINK survey of stars with proper motion >40 mas/yr, supplemented on the bright end with the TYCHO-2 catalog. Completeness tests which account for kinematic (proper motion) bias suggest that our catalog represents ~75% of the estimated ~11,900 M dwarfs with J<10 expected to populate the entire sky. Read More

Recently discovered exoplanets on close-in orbits should have surface temperatures of 100's to 1000's of K. They are likely tidally locked and synchronously rotating around their parent stars and, if an atmosphere is absent, have surface temperature contrasts of many 100's to 1000's K between permanent day and night sides. We investigated the effect of elevated surface temperature and strong surface temperature contrasts for Earth-mass planets on the (i) pattern of mantle convection, (ii) tectonic regime, and (iii) rate and distribution of partial melting, using numerical simulations of mantle convection with a composite viscous/pseudo-plastic rheology. Read More

It is believed that Al-26, a short-lived (t1/2 = 0.73 Ma) and now extinct radionuclide, was uniformly distributed in the nascent Solar System with the initial Al-26/Al-27 ratio of ~5.2\times10-5, suggesting its external stellar origin. Read More

We show that collision-induced absorption allows molecular hydrogen to act as an incondensible greenhouse gas, and that bars or tens of bars of primordial H2-He mixtures can maintain surface temperatures above the freezing point of water well beyond the "classical" habitable zone defined for CO2 greenhouse atmospheres. Using a 1-D radiative-convective model we find that 40 bars of pure H2 on a 3 Earth-mass planet can maintain a surface temperature of 280K out to 1.5AU from an early-type M dwarf star and 10 AU from a G-type star. Read More

Affiliations: 1Dept. of Terrestrial Magnetism, Carnegie Institution of Washington, 2Dept. of Geology and Geophysics, University of Hawaii

We model the heating of a primordial planetesimal by decay of the short-lived radionuclides Al-26 and Fe-60 to determine (i) the timescale on which melting will occur; (ii) the minimum size of a body that will produce silicate melt and differentiate; (iii) the migration rate of molten material within the interior; and (iv) the thermal consequences of the transport of Al-26 in partial melt. Our models incorporate results from previous studies of planetary differentiation and are constrained by petrologic (i.e. Read More

We present 230 realizations of a numerical model of planet formation in systems without gas giants. These represent a scenario in which protoplanets grow in a region of a circumstellar disk where water ice condenses (the "ice line''), but fail to accrete massive gas envelopes before the gaseous disk is dispersed. Each simulation consists of a small number of gravitationally interacting oligarchs and a much larger number of small bodies that represent the natal disk of planetesimals. Read More

To ascertain whether magnetic dynamos operate in rocky exoplanets more massive or hotter than the Earth, we developed a parametric model of a differentiated rocky planet and its thermal evolution. Our model reproduces the established properties of Earth's interior and magnetic field at the present time. When applied to Venus, assuming that planet lacks plate tectonics and has a dehydrated mantle with an elevated viscosity, the model shows that the dynamo shuts down or never operated. Read More

Doppler observations from Keck Observatory reveal the presence of a planet with Msini of 2.1 Mjup orbiting the M3V star HIP79431. This is the sixth giant planet to be detected in Doppler surveys of M dwarfs and it is one of the most massive planets discovered around an M dwarf star. Read More

The 18O/17O ratio of the Solar System is 5.2 while that of the interstellar medium (ISM) and young stellar objects is ~4. This difference cannot be explained by pollution of the Sun's natal molecular cloud by 18O-rich supernova ejecta because (1) the necessary B-star progenitors live longer than the duration of star formation in molecular clouds; (2) the delivery of ejecta gas is too inefficient and the amount of dust in supernova ejecta is too small compared to the required pollution (2% of total mass or ~20% of oxygen); and (3) the predicted amounts of concomitant short-lived radionuclides (SLRs) conflicts with the abundances of 26Al and 41Ca in the early Solar System. Read More

In agreement with previous work, we show that the presence of the short-lived radionuclide Al-26 in the early Solar System was unlikely (<2% a priori probability) to be the result of direct introduction of supernova ejecta into the gaseous disk during the Class II stage of protosolar evolution. We also show that any Bondi-Hoyle accretion of contaminated residual gas from the natal star cluster made a negligible contribution to the primordial Al-26 inventory of the Solar System. These results are consistent with the absence of the oxygen isotopic signature expected with any late introduction of supernova ejecta into the protoplanetary disk. Read More

Affiliations: 1Institute for Astronomy, Univ. of Hawaii, 2Dept. of Geology and Geophysics, Univ. of Hawaii, 3Penn State Erie, The Behrend College
Category: Astrophysics

We investigate the influence of lunar-like satellites on the infrared orbital light curves of Earth-analog extra-solar planets. Such light curves will be obtained by NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin missions as a consequence of repeat observations to confirm the companion status of a putative planet. We use an energy balance model to calculate disk-averaged infrared (bolometric) fluxes from planet-satellite systems over a full orbital period (one year). Read More

We provide estimates of volcanism versus time for planets with Earth-like composition and masses from 0.25 to 25 times Earth, as a step toward predicting atmospheric mass on extrasolar rocky planets. Volcanism requires melting of the silicate mantle. Read More