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The signal induced by a temperate, terrestrial planet orbiting a Sun-like star is an order of magnitude smaller than the host stars' intrinsic variability. Understanding stellar activity is, therefore, a fundamental obstacle in confirming the smallest exoplanets. We present the Lowell Observatory Solar Telescope (LOST), a solar feed for the EXtreme PREcision Spectrometer (EXPRES) at the 4.3-m Lowell Discovery Telescope (LDT). EXPRES is one of the newest high-resolution spectrographs that accurately measure extreme radial velocity. With LOST/EXPRES, we observe disk-integrated sunlight autonomously throughout the day. In clear conditions, we achieve a ~137,500 optical spectrum of the Sun with a signal-to-noise of 500 in ~150s. Data is reduced using the standard EXPRES pipeline with minimal modification to ensure the data are comparable to the observations of other stars with the LDT. During the first three years of operation, we find a daily RMS of 71 cm/s. Additionally, having two EPRV spectrometers located in Arizona gives us an unprecedented opportunity to benchmark the performance of these planet-finders. We find a RMS of just 55 cm/s when comparing data taken simultaneously with EXPRES and NEID., Comment: SPIE Astronomical Telescopes & Instrumentation proceedings paper

We present an analysis of Sun-as-a-star observations from four different high-resolution, stabilized spectrographs -- HARPS, HARPS-N, EXPRES, and NEID. With simultaneous observations of the Sun from four different instruments, we are able to gain insight into the radial velocity precision and accuracy delivered by each of these instruments and isolate instrumental systematics that differ from true astrophysical signals. With solar observations, we can completely characterize the expected Doppler shift contributed by orbiting Solar System bodies and remove them. This results in a data set with measured velocity variations that purely trace flows on the solar surface. Direct comparisons of the radial velocities measured by each instrument show remarkable agreement with residual intra-day scatter of only 15-30 cm/s. This shows that current ultra-stabilized instruments have broken through to a new level of measurement precision that reveals stellar variability with high fidelity and detail. We end by discussing how radial velocities from different instruments can be combined to provide powerful leverage for testing techniques to mitigate stellar signals., Comment: 17 pages, 9 figures, accepted for publication

To accurately characterize the planets a star may be hosting, stellar parameters must first be well-determined. $\tau$ Ceti is a nearby solar analog and often a target for exoplanet searches. Uncertainties in the observed rotational velocities have made constraining $\tau$ Ceti's inclination difficult. For planet candidates from radial velocity (RV) observations, this leads to substantial uncertainties in the planetary masses, as only the minimum mass ($m \sin i$) can be constrained with RV. In this paper, we used new long-baseline optical interferometric data from the CHARA Array with the MIRC-X beam combiner and extreme precision spectroscopic data from the Lowell Discovery Telescope with EXPRES to improve constraints on the stellar parameters of $\tau$ Ceti. Additional archival data were obtained from a Tennessee State University Automatic Photometric Telescope and the Mount Wilson Observatory HK project. These new and archival data sets led to improved stellar parameter determinations, including a limb-darkened angular diameter of $2.019 \pm 0.012$ mas and rotation period of $46 \pm 4$ days. By combining parameters from our data sets, we obtained an estimate for the stellar inclination of $7\pm7^\circ$. This nearly-pole-on orientation has implications for the previously-reported exoplanets. An analysis of the system dynamics suggests that the planetary architecture described by Feng et al. (2017) may not retain long-term stability for low orbital inclinations. Additionally, the inclination of $\tau$ Ceti reveals a misalignment between the inclinations of the stellar rotation axis and the previously-measured debris disk rotation axis ($i_\mathrm{disk} = 35 \pm 10^\circ$)., Comment: 14 pages, 3 figures, 4 tables, 1 appendix, accepted for publication to AJ

Thousands of exoplanet detections have been made over the last twenty-five years using Doppler observations, transit photometry, direct imaging, and astrometry. Each of these methods is sensitive to different ranges of orbital separations and planetary radii (or masses). This makes it difficult to fully characterize exoplanet architectures and to place our solar system in context with the wealth of discoveries that have been made. Here, we use the EXtreme PREcision Spectrograph (EXPRES) to reveal planets in previously undetectable regions of the mass-period parameter space for the star $\rho$ Coronae Borealis. We add two new planets to the previously known system with one hot Jupiter in a 39-day orbit and a warm super-Neptune in a 102-day orbit. The new detections include a temperate Neptune planet ($M{\sin{i}} \sim 20$ M$_\oplus$) in a 281.4-day orbit and a hot super-Earth ($M{\sin{i}} = 3.7$ M$_\oplus$) in a 12.95-day orbit. This result shows that details of planetary system architectures have been hiding just below our previous detection limits; this signals an exciting era for the next generation of extreme precision spectrographs., Comment: Accepted to AJ; 20 pages, 13 figures, 5 Tables

A planet's orbital alignment places important constraints on how a planet formed and consequently evolved. The dominant formation pathway of ultra-short period planets ($P<1$ day) is particularly mysterious as such planets most likely formed further out, and it is not well understood what drove their migration inwards to their current positions. Measuring the orbital alignment is difficult for smaller super-Earth/sub-Neptune planets, which give rise to smaller amplitude signals. Here we present radial velocities across two transits of 55 Cancri e, an ultra-short period Super-Earth, observed with the Extreme Precision Spectrograph (EXPRES). Using the classical Rossiter-McLaughlin (RM) method, we measure 55 Cnc e's sky-projected stellar spin-orbit alignment (i.e., the projected angle between the planet's orbital axis and its host star's spin axis) to be $\lambda=10\substack{+17\\ -20}^{\circ}$ with an unprojected angle of $\psi=23\substack{+14\\ -12}^{\circ}$. The best-fit RM model to the EXPRES data has a radial velocity semi-amplitude of just $0.41\substack{+0.09\\ -0.10} m s^{-1}$. The spin-orbit alignment of 55 Cnc e favors dynamically gentle migration theories for ultra-short period planets, namely tidal dissipation through low-eccentricity planet-planet interactions and/or planetary obliquity tides., Comment: 12 pages, 4 figures, published in Nature Astronomy

The arrival of the Keck Planet Finder (KPF) in 2022 represents a major advance in the precision radial velocity (PRV) capabilities of the W. M. Keck Observatory. In preparation for KPF science, our committee of PRV experts and WMKO staff studied the current implementation of cadence observing at Keck and other PRV facilities. We find that many of KPF's major science cases are not feasible through Keck's standard allocations of full or half nights to individual PIs. Pooling time among several PIs as is currently done by the California Planet Search (CPS) collaboration with HIRES results in lower quality science results than is possible when KPF is available at higher observational cadence. This strategy also creates barriers to entry, particularly for researchers wishing to lead small proposals. This report makes recommendations for optimizing PRV cadence at Keck subject to the following constraints: preservation of clear boundaries between cadence observations and classically scheduled time; and ensuring fairness and scientific independence of different Keck TACs and different KPF PIs. We recommend establishing a new category of Keck time allocation, "KPF Community Cadence" (KPF-CC). In many ways, KPF-CC will formalize observing strategies provided by CPS, but with higher observational cadence appropriate for KPF science and with universal access to the program for all Keck users. We recommend that KPF-CC time be scheduled classically into blocks as small as a quarter night subject to considerations of bright/dark time, variations in proposal pressure with the seasons, and the needs of non-KPF observing programs. Within KPF-CC time, the Keck Observing Assistants would execute observations generated by a dynamic scheduler. We recommend that Keck staff and a board of PRV experts design and maintain the scheduling software., Comment: 31 pages, 10 figures, prepared for the Keck Science Steering Committee, report delivered on Nov 7, 2021

Measured spectral shifts due to intrinsic stellar variability (e.g., pulsations, granulation) and activity (e.g., spots, plages) are the largest source of error for extreme precision radial velocity (EPRV) exoplanet detection. Several methods are designed to disentangle stellar signals from true center-of-mass shifts due to planets. The EXPRES Stellar Signals Project (ESSP) presents a self-consistent comparison of 22 different methods tested on the same extreme-precision spectroscopic data from EXPRES. Methods derived new activity indicators, constructed models for mapping an indicator to the needed RV correction, or separated out shape- and shift-driven RV components. Since no ground truth is known when using real data, relative method performance is assessed using the total and nightly scatter of returned RVs and agreement between the results of different methods. Nearly all submitted methods return a lower RV RMS than classic linear decorrelation, but no method is yet consistently reducing the RV RMS to sub-meter-per-second levels. There is a concerning lack of agreement between the RVs returned by different methods. These results suggest that continued progress in this field necessitates increased interpretability of methods, high-cadence data to capture stellar signals at all timescales, and continued tests like the ESSP using consistent data sets with more advanced metrics for method performance. Future comparisons should make use of various well-characterized data sets -- such as solar data or data with known injected planetary and/or stellar signals -- to better understand method performance and whether planetary signals are preserved., Comment: 33 pages (+12 pages of Appendix), 10 figures, 8 tables, accepted for publication in AJ

The distortions of absorption line profiles caused by photospheric brightness variations on the surfaces of cool, main-sequence stars can mimic or overwhelm radial velocity (RV) shifts due to the presence of exoplanets. The latest generation of precision RV spectrographs aims to detect velocity amplitudes $\lesssim 10$ cm s$^{-1}$, but requires mitigation of stellar signals. Statistical techniques are being developed to differentiate between Keplerian and activity-related velocity perturbations. Two important challenges, however, are the interpretability of the stellar activity component as RV models become more sophisticated, and ensuring the lowest-amplitude Keplerian signatures are not inadvertently accounted for in flexible models of stellar activity. For the K2V exoplanet host $\epsilon$ Eridani, we separately use ground-based photometry to constrain Gaussian processes for modeling RVs and TESS photometry with a light-curve inversion algorithm to reconstruct the stellar surface. From the reconstructions of TESS photometry, we produce an activity model, which reduces the rms scatter in RVs obtained with EXPRES from 4.72 m s$^{-1}$ to 1.98 m s$^{-1}$. We present a pilot study using the CHARA Array and MIRC-X beam combiner to directly image the starspots seen in the TESS photometry. With the limited phase coverage, our spot detections are marginal with current data but a future dedicated observing campaign should allow for imaging, as well as the stellar inclination and orientation with respect to its debris disk to be definitely determined. This work shows that stellar surface maps obtained with high cadence, time-series photometric and interferometric data can provide the constraints needed to accurately reduce RV scatter., Comment: 24 pages, 12 figures, 5 tables, accepted for publication in AJ

We present the discovery of TOI-1518b -- an ultra-hot Jupiter orbiting a bright star $V = 8.95$. The transiting planet is confirmed using high-resolution optical transmission spectra from EXPRES. It is inflated, with $R_p = 1.875\pm0.053\,R_{\rm J}$, and exhibits several interesting properties, including a misaligned orbit (${240.34^{+0.93}_{-0.98}}$ degrees) and nearly grazing transit ($b =0.9036^{+0.0061}_{-0.0053}$). The planet orbits a fast-rotating F0 host star ($T_{\mathrm{eff}} \simeq 7300$ K) in 1.9 days and experiences intense irradiation. Notably, the TESS data show a clear secondary eclipse with a depth of $364\pm28$ ppm and a significant phase curve signal, from which we obtain a relative day-night planetary flux difference of roughly 320 ppm and a 5.2$\sigma$ detection of ellipsoidal distortion on the host star. Prompted by recent detections of atomic and ionized species in ultra-hot Jupiter atmospheres, we conduct an atmospheric cross-correlation analysis. We detect neutral iron (${5.2\sigma}$), at $K_p = 157^{+68}_{-44}$ km s$^{-1}$ and $V_{\rm sys} = -16^{+2}_{-4}$ km s$^{-1}$, adding another object to the small sample of highly irradiated gas-giant planets with Fe detections in transmission. Detections so far favor particularly inflated gas giants with radii $\gtrsim 1.78\,R_{\rm J}$; although this may be due to observational bias. With an equilibrium temperature of $T_{\rm eq}=2492\pm38$ K and a measured dayside brightness temperature of $3237\pm59$ K (assuming zero geometric albedo), TOI-1518b is a promising candidate for future emission spectroscopy to probe for a thermal inversion., Comment: 25 pages, 11 figures, accepted to AJ

We present a high-precision radial velocity (RV) survey of 719 FGKM stars, which host 164 known exoplanets and 14 newly discovered or revised exoplanets and substellar companions. This catalog updated the orbital parameters of known exoplanets and long-period candidates, some of which have decades-longer observational baselines than they did upon initial detection. The newly discovered exoplanets range from warm sub-Neptunes and super-Earths to cold gas giants. We present the catalog sample selection criteria, as well as over 100,000 radial velocity measurements, which come from the Keck-HIRES, APF-Levy, and Lick-Hamilton spectrographs. We introduce the new RV search pipeline RVSearch that we used to generate our planet catalog, and we make it available to the public as an open-source Python package. This paper is the first study in a planned series that will measure exoplanet occurrence rates and compare exoplanet populations, including studies of giant planet occurrence beyond the water ice line, and eccentricity distributions to explore giant planet formation pathways. We have made public all radial velocities and associated data that we use in this catalog., Comment: Accepted to ApJS

We used high-precision radial velocity measurements of FGKM stars to determine the occurrence of giant planets as a function of orbital separation spanning 0.03-30 au. Giant planets are more prevalent at orbital distances of 1-10 au compared to orbits interior or exterior of this range. The increase in planet occurrence at $\sim$1 au by a factor of $\sim$4 is highly statistically significant. A fall-off in giant planet occurrence at larger orbital distances is favored over models with flat or increasing occurrence. We measure $14.1^{+2.0}_{-1.8}$ giant planets per 100 stars with semi-major axes of 2-8 au and $8.9^{+3.0}_{-2.4}$ giant planets per 100 stars in the range 8-32 au, a decrease in giant planet occurrence with increasing orbital separation that is significant at the $\sim$2$\sigma$ level. We find that the occurrence rate of sub-Jovian planets (0.1-1 Jupiter masses) is also enhanced for 1-10 au orbits. This suggests that lower mass planets may share the formation or migration mechanisms that drive the increased prevalence near the water-ice line for their Jovian counterparts. Our measurements of cold gas giant occurrence are consistent with the latest results from direct imaging surveys and gravitational lensing surveys despite different stellar samples. We corroborate previous findings that giant planet occurrence increases with stellar mass and metallicity., Comment: accepted to ApJS

We present the discovery of a highly irradiated and moderately inflated ultra-hot Jupiter, TOI-1431b/MASCARA-5b (HD 201033b), first detected by NASA's Transiting Exoplanet Survey Satellite mission (TESS) and the Multi-site All-Sky CAmeRA (MASCARA). The signal was established to be of planetary origin through radial velocity measurements obtained using SONG, SOPHIE, FIES, NRES, and EXPRES, which show a reflex motion of $K=294.1\pm1.1$ m s$^{-1}$. A joint analysis of the TESS and ground-based photometry and radial velocity measurements reveals that TOI-1431b has a mass of $M_{p}=3.12\pm0.18$ $\rm{M_J}$ ($990\pm60$ M$_{\oplus}$), an inflated radius of $R_{p}=1.49\pm0.05$ $\rm{R_J}$ ($16.7\pm0.6$ R$_{\oplus}$), and an orbital period of $P=2.650237\pm0.000003$ d. Analysis of the spectral energy distribution of the host star reveals that the planet orbits a bright ($\mathrm{V}=8.049$ mag) and young ($0.29^{+0.32}_{-0.19}$ Gyr) Am type star with $T_{\rm eff}=7690^{+400}_{-250}$ $\rm{K}$, resulting in a highly irradiated planet with an incident flux of $\langle F \rangle=7.24^{+0.68}_{-0.64}\times$10$^9$ erg s$^{-1}$ cm$^{-2}$ ($5300^{+500}_{-470}\mathrm{S_{\oplus}}$) and an equilibrium temperature of $T_{eq}=2370\pm70$ K. TESS photometry also reveals a secondary eclipse with a depth of $127^{+4}_{-5}$ppm as well as the full phase curve of the planet's thermal emission in the red-optical. This has allowed us to measure the dayside and nightside temperature of its atmosphere as $T_\mathrm{day}=3004\pm64$ K and $T_\mathrm{night}=2583\pm63$ K, the second hottest measured nightside temperature. The planet's low day/night temperature contrast ($\sim$420 K) suggests very efficient heat transport between the dayside and nightside hemispheres., Comment: Accepted for publication in the Astronomical Journal. 39 pages, 18 figures, and 4 tables

In the search for planets orbiting distant stars the presence of stellar activity in the atmospheres of observed stars can obscure the radial velocity signal used to detect such planets. Furthermore, this stellar activity contamination is set by the star itself and cannot simply be avoided with better instrumentation. Various stellar activity indicators have been developed that may correlate with this contamination. We introduce a new stellar activity indicator called the Stellar Activity F-statistic for Exoplanet surveys (SAFE) that has higher statistical power (i.e., probability of detecting a true stellar activity signal) than many traditional stellar activity indicators in a simulation study of an active region on a Sun-like star with moderate to high signal-to-noise. Also through simulation, the SAFE is demonstrated to be associated with the projected area on the visible side of the star covered by active regions. We also demonstrate that the SAFE detects statistically significant stellar activity in most of the spectra for HD 22049, a star known to have high stellar variability. Additionally, the SAFE is calculated for recent observations of the three low-variability stars HD 34411, HD 10700, and HD 3651, the latter of which is known to have a planetary companion. As expected, the SAFE for these three only occasionally detects activity. Furthermore, initial exploration appears to indicate that the SAFE may be useful for disentangling stellar activity signals from planet-induced Doppler shifts., Comment: 20 pages, 12 figures, accepted for publication in The Astronomical Journal

By controlling instrumental errors to below 10 cm/s, the EXtreme PREcision Spectrograph (EXPRES) allows for a more insightful study of photospheric velocities that can mask weak Keplerian signals. Gaussian Processes (GP) have become a standard tool for modeling correlated noise in radial velocity datasets. While GPs are constrained and motivated by physical properties of the star, in some cases they are still flexible enough to absorb unresolved Keplerian signals. We apply GP regression to EXPRES radial velocity measurements of the 3.5 Gyr old chromospherically active Sun-like star, HD 101501. We obtain tight constraints on the stellar rotation period and the evolution of spot distributions using 28 seasons of ground-based photometry, as well as recent $TESS$ data. Light curve inversion was carried out on both photometry datasets to reveal the spot distribution and spot evolution timescales on the star. We find that the $> 5$ m/s rms radial velocity variations in HD 101501 are well-modeled with a GP stellar activity model without planets, yielding a residual rms scatter of 45 cm/s. We carry out simulations, injecting and recovering signals with the GP framework, to demonstrate that high-cadence observations are required to use GPs most efficiently to detect low-mass planets around active stars like HD 101501. Sparse sampling prevents GPs from learning the correlated noise structure and can allow it to absorb prospective Keplerian signals. We quantify the moderate to high-cadence monitoring that provides the necessary information to disentangle photospheric features using GPs and to detect planets around active stars., Comment: 25 pages, 16 figures, accepted to AJ

EarthFinder is a NASA Astrophysics Probe mission concept selected for study as input to the 2020 Astrophysics National Academies Decadal Survey. The EarthFinder concept is based on a dramatic shift in our understanding of how PRV measurements should be made. We propose a new paradigm which brings the high precision, high cadence domain of transit photometry as demonstrated by Kepler and TESS to the challenges of PRV measurements at the cm/s level. This new paradigm takes advantage of: 1) broad wavelength coverage from the UV to NIR which is only possible from space to minimize the effects of stellar activity; 2) extremely compact, highly stable, highly efficient spectrometers (R>150,000) which require the diffraction-limited imaging possible only from space over a broad wavelength range; 3) the revolution in laser-based wavelength standards to ensure cm/s precision over many years; 4) a high cadence observing program which minimizes sampling-induced period aliases; 5) exploiting the absolute flux stability from space for continuum normalization for unprecedented line-by-line analysis not possible from the ground; and 6) focusing on the bright stars which will be the targets of future imaging missions so that EarthFinder can use a ~1.5 m telescope., Comment: NASA Probe Mission concept white paper for 2020 Astrophysics National Academies Decadal Survey

The next generation of exoplanet-hunting spectrographs should deliver up to an order of magnitude improvement in radial velocity precision over the standard 1 m/s state of the art. This advance is critical for enabling the detection of Earth-mass planets around Sun-like stars. New calibration techniques such as laser frequency combs and stabilized etalons ensure that the instrumental stability is well characterized. However, additional sources of error include stellar noise, undetected short-period planets, and telluric contamination. To understand and ultimately mitigate error sources, the contributing terms in the error budget must be isolated to the greatest extent possible. Here, we introduce a new high cadence radial velocity program, the EXPRES 100 Earths program, which aims to identify rocky planets around bright, nearby G and K dwarfs. We also present a benchmark case: the 62-d orbit of a Saturn-mass planet orbiting the chromospherically quiet star, HD 3651. The combination of high eccentricity (0.6) and a moderately long orbital period, ensures significant dynamical clearing of any inner planets. Our Keplerian model for this planetary orbit has a residual RMS of 58 cm/s over a $\sim 6$ month time baseline. By eliminating significant contributors to the radial velocity error budget, HD 3651 serves as a standard for evaluating the long term precision of extreme precision radial velocity (EPRV) programs., Comment: 11 pages, 6 figures, accepted for publication in Astronomical Journal

As the first successful technique used to detect exoplanets orbiting distant stars, the Radial Velocity Method aims to detect a periodic Doppler shift in a star's spectrum. We introduce a new, mathematically rigorous, approach to detect such a signal that accounts for functional relationships of neighboring wavelengths, minimizes the role of wavelength interpolation, accounts for heteroskedastic noise, and easily allows for statistical inference. Using Hermite-Gaussian functions, we show that the problem of detecting a Doppler shift in the spectrum can be reduced to linear regression in many settings. A simulation study demonstrates that the proposed method is able to accurately estimate an individual spectrum's radial velocity with precision below 0.3 m/s. Furthermore, the new method outperforms the traditional Cross-Correlation Function approach by reducing the root mean squared error up to 15 cm/s. The proposed method is also demonstrated on a new set of observations from the EXtreme PREcision Spectrometer (EXPRES) for the star 51 Pegasi, and successfully recovers estimates that agree well with previous studies of this planetary system. Data and Python3 code associated with this work can be found at https://github.com/parkerholzer/hgrv_method. The method is also implemented in the open source R package rvmethod., Comment: 48 pages, 19 figures

We report detections of atomic species in the atmosphere of MASCARA-2 b, using the first transit observations obtained with the newly commissioned EXPRES spectrograph. EXPRES is a highly stabilised optical echelle spectrograph, designed to detect stellar reflex motions with amplitudes down to 30 cm/s, and was recently deployed at the Lowell Discovery Telescope. By analysing the transmission spectrum of the ultra-hot Jupiter MASCARA-2 b using the cross-correlation method, we confirm previous detections of Fe I, Fe II and Na I, which likely originate in the upper regions of the inflated atmosphere. In addition, we report significant detections of Mg I and Cr II. The absorption strengths change slightly with time, possibly indicating different temperatures and chemistry in the day-side and night-side terminators. Using the effective stellar line-shape variation induced by the transiting planet, we constrain the projected spin-orbit misalignment of the system to $1.6\pm3.1$ degrees, consistent with an aligned orbit. We demonstrate that EXPRES joins a suite of instruments capable of phase-resolved spectroscopy of exoplanet atmospheres., Comment: Accepted for publication in A&A, 20 pages, 22 figures

The EXtreme PREcision Spectrograph (EXPRES) is a new Doppler spectrograph designed to reach a radial velocity measurement precision sufficient to detect Earth-like exoplanets orbiting nearby, bright stars. We report on extensive laboratory testing and on-sky observations to quantitatively assess the instrumental radial velocity measurement precision of EXPRES, with a focused discussion of individual terms in the instrument error budget. We find that EXPRES can reach a single-measurement instrument calibration precision better than 10 cm/s, not including photon noise from stellar observations. We also report on the performance of the various environmental, mechanical, and optical subsystems of EXPRES, assessing any contributions to radial velocity error. For atmospheric and telescope related effects, this includes the fast tip-tilt guiding system, atmospheric dispersion compensation, and the chromatic exposure meter. For instrument calibration, this includes the laser frequency comb (LFC), flat-field light source, CCD detector, and effects in the optical fibers. Modal noise is mitigated to a negligible level via a chaotic fiber agitator, which is especially important for wavelength calibration with the LFC. Regarding detector effects, we empirically assess the impact on radial velocity precision due to pixel-position non-uniformities (PPNU) and charge transfer inefficiency (CTI). EXPRES has begun its science survey to discover exoplanets orbiting G-dwarf and K-dwarf stars, in addition to transit spectroscopy and measurements of the Rossiter-McLaughlin effect., Comment: 39 pages, 30 figures, accepted to AJ

The EXtreme PREcision Spectrograph (EXPRES) is an environmentally stabilized, fiber-fed, $R=137,500$, optical spectrograph. It was recently commissioned at the 4.3-m Lowell Discovery Telescope (LDT) near Flagstaff, Arizona. The spectrograph was designed with a target radial-velocity (RV) precision of 30$\mathrm{~cm~s^{-1}}$. In addition to instrumental innovations, the EXPRES pipeline, presented here, is the first for an on-sky, optical, fiber-fed spectrograph to employ many novel techniques---including an "extended flat" fiber used for wavelength-dependent quantum efficiency characterization of the CCD, a flat-relative optimal extraction algorithm, chromatic barycentric corrections, chromatic calibration offsets, and an ultra-precise laser frequency comb for wavelength calibration. We describe the reduction, calibration, and radial-velocity analysis pipeline used for EXPRES and present an example of our current sub-meter-per-second RV measurement precision, which reaches a formal, single-measurement error of 0.3$\mathrm{~m~s^{-1}}$ for an observation with a per-pixel signal-to-noise ratio of 250. These velocities yield an orbital solution on the known exoplanet host 51 Peg that matches literature values with a residual RMS of 0.895$\mathrm{~m~s^{-1}}$.

The Transit Ephemeris Refinement and Monitoring Survey (TERMS) is a project which aims to detect transits of intermediate-long period planets by refining orbital parameters of the known radial velocity planets using additional data from ground based telescopes, calculating a revised transit ephemeris for the planet, then monitoring the planet host star during the predicted transit window. Here we present the results from three systems that had high probabilities of transiting planets: HD 9446 b & c, HD 43691 b, & HD 179079 b. We provide new radial velocity (RV) measurements that are then used to improve the orbital solution for the known planets. We search the RV data for indications of additional planets in orbit and find that HD 9446 shows a strong linear trend of 4.8$\sigma$. Using the newly refined planet orbital solutions, which include a new best-fit solution for the orbital period of HD 9446 c, and an improved transit ephemerides, we found no evidence of transiting planets in the photometry for each system. Transits of HD 9446 b can be ruled out completely and transits HD 9446 c & HD 43691 b can be ruled out for impact parameters up to b = 0.5778 and b = 0.898 respectively due to gaps in the photometry. A transit of HD 179079 b cannot be ruled out however due to the relatively small size of this planet compared to the large star and thus low signal to noise. We determine properties of the three host stars through spectroscopic analysis and find through photometric analysis that HD 9446 exhibits periodic variability., Comment: Accepted for publication in The Astronomical Journal. 23 pages, 21 figures

We report the discovery and confirmation of two new hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS): TOI 564 b and TOI 905 b. The transits of these two planets were initially observed by TESS with orbital periods of 1.651 d and 3.739 d, respectively. We conducted follow-up observations of each system from the ground, including photometry in multiple filters, speckle interferometry, and radial velocity measurements. For TOI 564 b, our global fitting revealed a classical hot Jupiter with a mass of $1.463^{+0.10}_{-0.096}\ M_J$ and a radius of $1.02^{+0.71}_{-0.29}\ R_J$. TOI 905 b is a classical hot Jupiter as well, with a mass of $0.667^{+0.042}_{-0.041}\ M_J$ and radius of $1.171^{+0.053}_{-0.051}\ R_J$. Both planets orbit Sun-like, moderately bright, mid-G dwarf stars with V ~ 11. While TOI 905 b fully transits its star, we found that TOI 564 b has a very high transit impact parameter of $0.994^{+0.083}_{-0.049}$, making it one of only ~20 known systems to exhibit a grazing transit and one of the brightest host stars among them. TOI 564 b is therefore one of the most attractive systems to search for additional non-transiting, smaller planets by exploiting the sensitivity of grazing transits to small changes in inclination and transit duration over the time scale of several years., Comment: 21 pages and 10 figures. Submitted to AJ

The Hubble Space Telescope (HST) has been the most impactful science-driven mission ever flown by NASA. However, when HST reaches the end of its life, there will be a void due to the loss of some of the science capabilities afforded by HST to astronomers world-wide. The previous 2010 Decadal Survey (DS) noted this void, arguing for the need for a successor to HST with UV capabilities in three separate places in the main report (pp. 190, 203, and 220). The large strategic missions that will follow HST, namely JWST and WFIRST, will continue to spark the interest of the public in space-based astronomy. In order to ensure continued US preeminence in the arena of large space-based astrophysics missions, and a seamless transition after WFIRST, a future flagship mission must be waiting in the wings. Anticipating this need, NASA initiated four large strategic mission concept studies (HabEx, LUVOIR, Lynx, and Origins), which have mature designs, including detailed technology assessments and development plans. Two of these concepts, HabEx and LUVOIR, are responsive to the recommendations of the previous DS regarding a UV-capable mission. Both are more powerful successors to HST, with UV-to-optical capabilities that range from significant enhancements to orders-of-magnitude improvement. At the same time, technological and scientific advances over the past decade only now make it feasible to marry such a mission with one that can search for life outside the solar system. Acknowledging that the constraints that the Astro2020 DS must consider may be difficult to anticipate, the HabEx and LUVOIR studies present eleven different variants, each of which enable groundbreaking science, including the direct imaging and characterization of exoplanets. The HabEx and LUVOIR mission studies offer a full suite of options to the Astro2020 DS, with corresponding flexibility in budgeting and phasing., Comment: 11 pages, 9 figures, Astro2020 APC White Paper. Corrected with the proper attribution of Figure 3 to Todd Tripp

One source of error in high-precision radial velocity measurements of exoplanet host stars is chromatic change in Earth's atmospheric transmission during observations. Mitigation of this error requires that the photon-weighted barycentric correction be applied as a function of wavelength across the stellar spectrum. We have designed a system for chromatic photon-weighted barycentric corrections with the EXtreme PREcision Spectrograph (EXPRES) and present results from the first year of operations, based on radial velocity measurements of more than $10^3$ high-resolution stellar spectra. For observation times longer than 250 seconds, we find that if the chromatic component of the barycentric corrections is ignored, a range of radial velocity errors up to 1 m s$^{-1}$ can be incurred with cross-correlation, depending on the nightly atmospheric conditions. For this distribution of errors, the standard deviation is 8.4 cm s$^{-1}$ for G-type stars, 8.5 cm s$^{-1}$ for K-type stars, and 2.1 cm s$^{-1}$ for M-type stars. This error is reduced to well-below the instrumental and photon-noise limited floor by frequent flux sampling of the observed star with a low-resolution exposure meter spectrograph., Comment: 11 pages, 7 figures, accepted to AJ

Continuum normalization of echelle spectra is an important data analysis step that is difficult to automate. Polynomial fitting requires a reasonably high order model to follow the steep slope of the blaze function. However, in the presence of deep spectral lines, a high order polynomial fit can result in ripples in the normalized continuum that increase errors in spectral analysis. Here, we present two algorithms for flattening the spectrum continuum. The Alpha-shape Fitting to Spectrum algorithm (AFS) is completely data-driven, using an alpha shape to obtain an initial estimate of the blaze function. The Alpha-shape and Lab Source Fitting to Spectrum algorithm (ALSFS) incorporates a continuum constraint from a lab source reference spectrum for the blaze function estimation. These algorithms are tested on a simulated spectrum, where we demonstrate improved normalization compared to polynomial regression for continuum fitting. We show an additional application, using the algorithms for mitigation of spatially correlated quantum efficiency variations and fringing in the CCD detector of the EXtreme PREcision Spectrometer (EXPRES).

To discover Earth analogs around other stars, next generation spectrographs must measure radial velocity (RV) with 10 cm/s precision. To achieve 10cm/s precision, however, the effects of telluric contamination must be accounted for. The standard approaches to telluric removal are: (a) observing a standard star and (b) using a radiative transfer code. Observing standard stars, however, takes valuable observing time away from science targets. Radiative transfer codes, meanwhile, rely on imprecise line data in the HITRAN database (typical line position uncertainties range from a few to several hundred m/s) and require difficult-to-obtain measurements of water vapor column density for best performance. To address these issues, we present SELENITE: a SELf-calibrating, Empricial, Light-Weight liNear regressIon TElluric model for high-resolution spectra. The model exploits two simple observations: (a) water tellurics grow proportionally to precipitable water vapor and therefore proportionally to each other and (b) non-water tellurics grow proportionally to airmass. Water tellurics can be identified by looking for pixels whose growth correlates with a known calibration water telluric and modelled by regression against it, and likewise non-water tellurics with airmass. The model doesn't require line data, water vapor measurements and additional observations (beyond one-time calibration observations), achieves fits with a reduced chi squared of 1.17 on B stars and 2.95 on K dwarfs, and leaves residuals of 1% (B stars) and 1.1% (K dwarfs) of continuum. Fitting takes seconds on laptop PCs: SELENITE is light-weight enough to guide observing runs.

In systems with detected planets, hot-Jupiters and compact systems of multiple planets are nearly mutually exclusive. We compare the relative occurrence of these two architectures as a fraction of detected planetary systems to determine the role that metallicity plays in planet formation. We show that compact multi-planet systems occur more frequently around stars of increasingly lower metallicities using spectroscopically derived abundances for more than 700 planet hosts. At higher metallicities, compact multi-planet systems comprise a nearly constant fraction of the planet hosts despite the steep rise in the fraction of hosts containing hot and cool-Jupiters. Since metal poor stars have been underrepresented in planet searches, this implies that the occurrence rate of compact multis is higher than previously reported. Due to observational limits, radial velocity planet searches have focused mainly on high-metallicity stars where they have a higher chance of finding giant planets. New extreme-precision radial velocity instruments coming online that can detect these compact multi-planet systems can target lower metallicity stars to find them., Comment: 5 pages, 2 figures, accepted to ApJ Letters

We report the first confirmation of a hot Jupiter discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HD 202772A b. The transit signal was detected in the data from TESS Sector 1, and was confirmed to be of planetary origin through radial-velocity measurements. HD 202772A b is orbiting a mildly evolved star with a period of 3.3 days. With an apparent magnitude of V = 8.3, the star is among the brightest known to host a hot Jupiter. Based on the 27days of TESS photometry, and radial velocity data from the CHIRON and HARPS spectrographs, the planet has a mass of 1.008+/-0.074 M_J and radius of 1.562+/-0.053 R_J , making it an inflated gas giant. HD 202772A b is a rare example of a transiting hot Jupiter around a quickly evolving star. It is also one of the most strongly irradiated hot Jupiters currently known., Comment: Submitted to AAS Journal

The N2K planet search program was designed to exploit the planet-metallicity correlation by searching for gas giant planets orbiting metal-rich stars. Here, we present the radial velocity measurements for 378 N2K target stars that were observed with the HIRES spectrograph at Keck Observatory between 2004 and 2017. With this data set, we announce the discovery of six new gas giant exoplanets: a double-planet system orbiting HD 148164 ($M \sin i$ of 1.23 and 5.16 M$_{\rm JUP}$) and single planet detections around HD 55696 ($M \sin i$ = 3.87 M$_{\rm JUP}$), HD 98736 ($M \sin i$ = 2.33 M$_{\rm JUP}$), HD 203473 ($M \sin i$ = 7.8 M$_{\rm JUP}$), and HD 211810 ($M \sin i$ = 0.67 M$_{\rm JUP}$). These gas giant companions have orbital semi-major axes between 1.0 and 6.2 AU and eccentricities ranging from 0.13 to 0.71. We also report evidence for three gravitationally bound companions with $M \sin i$ between 20 to 30 M$_{\rm JUP}$, placing them in the mass range of brown dwarfs, around HD 148284, HD 214823, and HD 217850, and four low mass stellar companions orbiting HD 3404, HD 24505, HD 98630, and HD 103459. In addition, we present updated orbital parameters for 42 previously announced planets. We also report a nondetection of the putative companion HD 73256 b. Finally, we highlight the most promising candidates for direct imaging and astrometric detection, and find that many hot Jupiters from our sample could be detectable by state-of-the-art telescopes such as Gaia., Comment: Accepted by the Astronomical Journal. 75 pages, 49 figures

The star 55 Cancri was one of the first known exoplanet hosts and each of the planets in this system is remarkable. Planets b and c are in a near 1:3 resonance. Planet d has a 14.5 year orbit, and is one of the longest known orbital periods for a gas giant planet. Planet e has a mass of 8 M? and transits this bright star, providing a unique case for modeling of the interior structure and atmospheric composition of an exoplanet. Planet f resides in the habitable zone of the star. If the planets are approximately co-planar, then by virtue of having one transiting planet, this is a system where the Doppler technique has essentially measured the true mass of the planets, rather than just Msin i. The unfolding history of planet discovery for this system provides a good example of the challenges and importance of understanding the star to understand the planets., Comment: 13 pages

Accurate stellar parameters and precise elemental abundances are vital pieces to correctly characterize discovered planetary systems, better understand planet formation, and trace galactic chemical evolution. We have performed a uniform spectroscopic analysis for 1127 stars, yielding accurate gravity, temperature, and projected rotational velocity in addition to precise abundances for 15 elements (C, N, O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, and Y). Most of the stars in this sample are Kepler Objects of Interest, observed by the California-Kepler Survey (CKS) and include 1,003 stars hosting 1,562 confirmed planets. This catalog extends the uniform analysis of our previous catalog, bringing the total of homogeneously analyzed stars to almost 2,700 F, G, and K dwarfs. To ensure consistency between the catalogs, we performed an analysis of our ability to recover parameters as a function of S/N ratio and present individual uncertainties as well as functions to calculate uncertainties for parameters derived from lower S/N ratio spectra. With the updated parameters, we used isochrone fitting to derived new radii, masses and ages for the stars. Finally, we look at the Mg/Si ratios of super-Earth and sub-Neptune hosts to test whether differences in initial composition might lead to differences in planet radius. We find no differences in the Mg/Si distribution as a function of planet radius., Comment: 19 pages, 12 figures, 6 tables, accepted to ApJ Supplement. Full data tables available in machine readable format in source file

Project Blue is designed to deliver a small coronagraphic space telescope mission to low-Earth orbit capable of detecting an Earth-like planet in the habitable zones of the Sun-like stars Alpha Centauri A and B within the next 4 years within a Mission of Opportunity budget envelope. The concept heavily leverages emerging commercial capabilities -- including the telescope optics, spacecraft bus and launch vehicle -- and emphasizes a public-private partnership approach., Comment: 5 pages; White paper submitted to the Exoplanet Science Strategy study of the National Academies of Sciences, Engineering and Medicine

EarthFinder is a Probe Mission concept selected for study by NASA for input to the 2020 astronomy decadal survey. This study is currently active and a final white paper report is due to NASA at the end of calendar 2018. We are tasked with evaluating the scientific rationale for obtaining precise radial velocity (PRV) measurements in space, which is a two-part inquiry: What can be gained from going to space? What can't be done form the ground? These two questions flow down to these specific tasks for our study - Identify the velocity limit, if any, introduced from micro- and macro-telluric absorption in the Earth's atmosphere; Evaluate the unique advantages that a space-based platform provides to emable the identification and mitigation of stellar acitivity for multi-planet signal recovery., Comment: Submitted to the National Academies Committee on Exoplanet Science Strategy

Because of the recent technological advances, the key technologies needed for precision space optical astrometry are now in hand. The Microarcsecond Astrometry Probe (MAP) mission concept is designed to find 1 Earth mass planets at 1AU orbit (scaled to solar luminosity) around the nearest ~90 FGK stars. The MAP payload includes i) a single three-mirror anastigmatic telescope with a 1-m primary mirror and metrology subsystems, and ii) a camera. The camera focal plane consists of 42 detectors, providing a Nyquist sampled FOV of 0.4-deg. Its metrology subsystems ensure that MAP can achieve the 0.8 uas astrometric precision in 1 hr, which is required to detect Earth-like exoplanets in our stellar neighborhood. MAP mission could provide ~10 specific targets for a much larger coronagraphic mission that would measure its spectra. We argue for the development of the space astrometric missions capable of finding Earth-2.0. Given the current technology readiness such missions relying on precision astrometry could be flown in the next decade, perhaps in collaboration with other national space agencies., Comment: A White Paper to the National Academy of Sciences Committee on an Exoplanet Science Strategy Call for Papers. 6 pages, 2 figures, 1 table

Optical fiber modal noise is a limiting factor for high precision spectroscopy signal-to-noise in the near-infrared and visible. Unabated, especially when using highly coherent light sources for wavelength calibration, modal noise can induce radial velocity (RV) errors that hinder the discovery of low-mass (and potentially Earth-like) planets. Previous research in this field has found sufficient modal noise mitigation through the use of an integrating sphere, but this requires extremely bright light sources, a luxury not necessarily afforded by the next generation of high-resolution optical spectrographs. Otherwise, mechanical agitation, which "mixes" the fiber's modal patterns and allows the noise to be averaged over minutes-long exposures, provides some noise reduction but the exact mechanism behind improvement in signal-to-noise and RV drift has not been fully explored or optimized by the community. Therefore, we have filled out the parameter space of modal noise agitation techniques in order to better understand agitation's contribution to mitigating modal noise and to discover a better method for agitating fibers. We find that modal noise is best suppressed by the quasi-chaotic motion of two high-amplitude agitators oscillating with varying phase for fibers with large core diameters and low azimuthal symmetry. This work has subsequently influenced the design of a fiber agitator, to be installed with the EXtreme PREcision Spectrograph, that we estimate will reduce modal-noise-induced RV error to less than 3.2 cm/s., Comment: Accepted by The Astrophysical Journal

We present spectroscopic measurements of the Rossiter-McLaughlin effect for the planet b of Kepler-9 multi-transiting planet system. The resulting sky-projected spin-orbit angle is $\lambda=-13^{\circ} \pm 16^{\circ}$, which favors an aligned system and strongly disfavors highly misaligned, polar, and retrograde orbits. Including Kepler-9, there are now a total of 4 Rossiter-McLaughlin effect measurements for multiplanet systems, all of which are consistent with spin-orbit alignment., Comment: Accepted for publication in the Astronomical Journal

We use more than a decade of radial velocity measurements for $\alpha$ Cen A, B, and Proxima Centauri from HARPS, CHIRON, and UVES to identify the $M \sin i$ and orbital periods of planets that could have been detected if they existed. At each point in a mass-period grid, we sample a simulated, Keplerian signal with the precision and cadence of existing data and assess the probability that the signal could have been produced by noise alone. Existing data places detection thresholds in the classically defined habitable zones at about $M \sin i$ of 53 M$_{\oplus}$ for $\alpha$ Cen A, 8.4 M$_{\oplus}$ for $\alpha$ Cen B, and 0.47 M$_{\oplus}$ for Proxima Centauri. Additionally, we examine the impact of systematic errors, or "red noise" in the data. A comparison of white- and red-noise simulations highlights quasi-periodic variability in the radial velocities that may be caused by systematic errors, photospheric velocity signals, or planetary signals. For example, the red-noise simulations show a peak above white-noise simulations at the period of Proxima Centauri b. We also carry out a spectroscopic analysis of the chemical composition of the $\alpha$ Centauri stars. The stars have super-solar metallicity with ratios of C/O and Mg/Si that are similar to the Sun, suggesting that any small planets in the $\alpha$ Cen system may be compositionally similar to our terrestrial planets. Although the small projected separation of $\alpha$ Cen A and B currently hampers extreme-precision radial velocity measurements, the angular separation is now increasing. By 2019, $\alpha$ Cen A and B will be ideal targets for renewed Doppler planet surveys., Comment: 16 pages, 7 figures, data provided in appendix. Accepted for publication in ApJ

Photospheric velocities and stellar activity features such as spots and faculae produce measurable radial velocity signals that currently obscure the detection of sub-meter-per-second planetary signals. However, photospheric velocities are imprinted differently in a high-resolution spectrum than Keplerian Doppler shifts. Photospheric activity produces subtle differences in the shapes of absorption lines due to differences in how temperature or pressure affects the atomic transitions. In contrast, Keplerian Doppler shifts affect every spectral line in the same way. With high enough S/N and high enough resolution, statistical techniques can exploit differences in spectra to disentangle the photospheric velocities and detect lower-amplitude exoplanet signals. We use simulated disk-integrated time-series spectra and principal component analysis (PCA) to show that photospheric signals introduce spectral line variability that is distinct from Doppler shifts. We quantify the impact of instrumental resolution and S/N for this work., Comment: 12 pages, 7 figures, accepted to ApJ

The vast majority of the 4700 confirmed planets and planet candidates discovered by the Kepler mission were first found by the Kepler pipeline. In the pipeline, after a transit signal is found, all data points associated with those transits are removed, creating a "Swiss cheese"-like light curve full of holes, which is then used for subsequent transit searches. These holes could render an additional planet undetectable (or "lost"). We examine a sample of 114 stars with $3+$ confirmed planets to evaluate the effect of this "Swiss cheesing". A simulation determines that the probability that a transiting planet is lost due to the transit masking is low, but non-negligible, reaching a plateau at $\sim3.3\%$ lost in the period range of $P=400-500$ days. We then model all planet transits and subtract out the transit signals for each star, restoring the in-transit data points, and use the Kepler pipeline to search the transit-subtracted (i.e., transit-cleaned) light curves. However, the pipeline did not discover any credible new transit signals. This demonstrates the validity and robustness of the Kepler pipeline's choice to use transit masking over transit subtraction. However, a follow-up visual search through all the transit-subtracted data, which allows for easier visual identification of new transits, revealed the existence of a new, Neptune-sized exoplanet (Kepler-150 f) and a potential single transit of a likely false positive (Kepler-208). Kepler-150 f ($P=637.2$ days, $R_{\rm{P}}=3.64^{+0.52}_{-0.39}$ R$_{\oplus}$) is confirmed with $>99.998\%$ confidence using a combination of the planet multiplicity argument, a false positive probability analysis, and a transit duration analysis., Comment: 11 pages, 5 figures, 2 tables. Accepted into AJ

Atmospheric effects on stellar radial velocity measurements for exoplanet discovery and characterization have not yet been fully investigated for extreme precision levels. We carry out calculations to determine the wavelength dependence of barycentric corrections across optical wavelengths, due to the ubiquitous variations in air mass during observations. We demonstrate that radial velocity errors of at least several cm/s can be incurred if the wavelength dependence is not included in the photon-weighted barycentric corrections. A minimum of four wavelength channels across optical spectra (380-680 nm) are required to account for this effect at the 10 cm/s level, with polynomial fits of the barycentric corrections applied to cover all wavelengths. Additional channels may be required in poor observing conditions or to avoid strong telluric absorption features. Furthermore, consistent flux sampling on the order of seconds throughout the observation is necessary to ensure that accurate photon weights are obtained. Finally, we describe how a multiple-channel exposure meter will be implemented in the EXtreme PREcision Spectrograph (EXPRES)., Comment: 7 pages, 5 figures, accepted for publication in ApJ

The elemental compositions of planet hosting stars serve as proxies for the primordial compositions of the protoplanetary disks within which the planets form. The temperature profile of the disk governs the condensation fronts of various compounds, and although these chemically distinct regions migrate and mix during the disk lifetime, they can still leave an imprint on the compositions of the forming planets. Observable atmospheric compositions of hot Jupiters when compared against their host stars could potentially constrain their formation and migration processes. We compared the measured planetary and stellar abundances of carbon and oxygen for ten systems with hot Jupiters. If the planets formed by core accretion with significant planetesimal accretion and migrated through the disk, the hot Jupiter atmospheres should be substantially super-stellar in O/H and sub-stellar in C/O. On the contrary, however, we find that currently reported abundances of hot Jupiters have generally super-stellar C/O ratios, though present uncertainties on the reported O/H and C/O ratios are too large to reach a firm conclusion. In one case however, HD 209458b, the elevated C/O and depleted O/H of the planet compared to the host star is significant enough to suggest an origin far beyond the ice line, with predominantly gas accretion, and subsequent disk-free migration. Improved measurements from the James Webb Space Telescope will enable more precise measurements for more hot Jupiters and we predict, based on the current marginal trend, that a sizable fraction of hot Jupiters will show enrichment of C/O and lower O/H than their hosts, similar to HD 209458b., Comment: 8 pages, 4 figures, Accepted to AJ (December 13, 2016) Updated to correct math error (0.5x vs. 2x) in calculation of (O/H)_planet from (H2O/H2)

We target the thermal emission spectrum of the non-transiting gas giant HD 88133 b with high-resolution near-infrared spectroscopy, by treating the planet and its host star as a spectroscopic binary. For sufficiently deep summed flux observations of the star and planet across multiple epochs, it is possible to resolve the signal of the hot gas giant's atmosphere compared to the brighter stellar spectrum, at a level consistent with the aggregate shot noise of the full data set. To do this, we first perform a principal component analysis to remove the contribution of the Earth's atmosphere to the observed spectra. Then, we use a cross-correlation analysis to tease out the spectra of the host star and HD 88133 b to determine its orbit and identify key sources of atmospheric opacity. In total, six epochs of Keck NIRSPEC L band observations and three epochs of Keck NIRSPEC K band observations of the HD 88133 system were obtained. Based on an analysis of the maximum likelihood curves calculated from the multi-epoch cross correlation of the full data set with two atmospheric models, we report the direct detection of the emission spectrum of the non-transiting exoplanet HD 88133 b and measure a radial projection of the Keplerian orbital velocity of 40 $\pm$ 15 km/s, a true mass of 1.02$^{+0.61}_{-0.28}M_J$, a nearly face-on orbital inclination of 15${^{+6}_{-5}}^{\circ}$, and an atmosphere opacity structure at high dispersion dominated by water vapor. This, combined with eleven years of radial velocity measurements of the system, provides the most up-to-date ephemeris for HD 88133., Comment: 9 pages, 6 figures; accepted for publication in ApJ

The carbon to oxygen ratio in a protoplanetary disk can have a dramatic influence on the compositions of any terrestrial planets formed. In regions of high C/O, planets form primarily from carbonates and in regions of low C/O, the ratio of magnesium to silicon determines the types of silicates which dominate the compositions. We present C/O and Mg/Si ratios for 849 F, G, and K dwarfs in the solar neighborhood. We find that the frequency of carbon-rich dwarfs in the solar neighborhood is < 0.13% and that 156 known planet hosts in the sample follow a similar distribution as all of the stars as a whole. The cosmic distribution of Mg/Si for these same stars is broader than the C/O distribution and peaks near 1.0 with $\sim 60$% of systems having $1 \leq$ Mg/Si $< 2$, leading to rocky planet compositions similar to the Earth. This leaves 40% of systems that can have planets that are silicate rich and may have very different compositions than our own., Comment: 9 pages, 5 figures, 1 ancillary data table. Accepted for publication to ApJ

Context: For over 12 yr, we have carried out a precise radial velocity survey of a sample of 373 G and K giant stars using the Hamilton \'Echelle Spectrograph at Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims: We aim at detecting and characterizing substellar+stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods: We obtained high precision radial velocity (RV) measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. In order to discriminate between RV variations due to non-radial pulsation or stellar spots we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to further characterize the system, we obtain high-resolution images with LMIRCam at the Large Binocular Telescope. Results: We report the likely discovery of a giant planet with a mass of $m_{p}~\sin i=6.92_{-0.24}^{+0.18}~M_{Jup}$ orbiting at $a_{p}=1.0860_{-0.0007}^{+0.0006}$ au from the giant star HD 59686 A. Besides the planetary signal, we discover an eccentric ($e_{B}=0.729_{-0.003}^{+0.004}$) binary companion with a mass of $m_{B}~\sin i=0.5296_{-0.0008}^{+0.0011}~M_{Sun}$ orbiting at a semi-major axis of just $a_{B}=13.56_{-0.14}^{+0.18}$ au. Conclusions: The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second generation planets or dynamical interactions in an early phase of the system's lifetime should be seriously considered in order to better understand the origin of this enigmatic planet., Comment: 14 pages, 11 figures, 2 tables. Accepted for publication in A&A. Updated version to match the published paper

We present simultaneous ground-based radial velocity (RV) measurements and space-based photometric measurements of the young and active K dwarf Epsilon Eridani. These measurements provide a data set for exploring methods of identifying and ultimately distinguishing stellar photospheric velocities from Keplerian motion. We compare three methods we have used in exploring this data set: Dalmatian, an MCMC spot modeling code that fits photometric and RV measurements simultaneously; the FF$'$ method, which uses photometric measurements to predict the stellar activity signal in simultaneous RV measurements; and H$\alpha$ analysis. We show that our H$\alpha$ measurements are strongly correlated with photometry from the Microvariability and Oscillations of STars (MOST) instrument, which led to a promising new method based solely on the spectroscopic observations. This new method, which we refer to as the HH$'$ method, uses H$\alpha$ measurements as input into the FF$'$ model. While the Dalmatian spot modeling analysis and the FF$'$ method with MOST space-based photometry are currently more robust, the HH$'$ method only makes use of one of the thousands of stellar lines in the visible spectrum. By leveraging additional spectral activity indicators, we believe the HH$'$ method may prove quite useful in disentangling stellar signals.

We present a catalog of uniformly determined stellar properties and abundances for 1626 F, G, and K stars using an automated spectral synthesis modeling procedure. All stars were observed using the HIRES spectrograph at Keck Observatory. Our procedure used a single line list to fit model spectra to observations of all stars to determine effective temperature, surface gravity, metallicity, projected rotational velocity, and the abundances of 15 elements (C, N, O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, & Y). Sixty percent of the sample had Hipparcos parallaxes and V-band photometry which we combined with the spectroscopic results to obtain mass, radius, and luminosity. Additionally, we used the luminosity, effective temperature, metallicity and alpha-element enhancement to interpolate in the Yonsei-Yale isochrones to derive mass, radius, gravity, and age ranges for those stars. Finally, we determined new relations between effective temperature and macroturbulence for dwarfs and subgiants. Our analysis achieved precisions of 25 K in Teff , 0.01 dex in [M/H], 0.028 dex for log g and 0.5 km/s in v sin ibased on multiple observations of the same stars. The abundance results were similarly precise, between 0.01 and - 0.04 dex, though trends with respect to Teff remained for which we derived empirical corrections. The trends, though small, were much larger than our uncertainties and are shared with published abundances. We show that changing our model atmosphere grid accounts for most of the trend in [M/H] between 5000 K and 5500 K indicating a possible problem with the atmosphere models or opacities., Comment: 41 pages, 23 figures, 11 tables, accepted for publication in ApJS

We present high-resolution observations of a sample of 75 K2 targets from Campaigns 1-3 using speckle interferometry on the Southern Astrophysical Research (SOAR) telescope and adaptive optics (AO) imaging at the Keck II telescope. The median SOAR $I$-band and Keck $K_s$-band detection limits at 1" were $\Delta m_{I}=4.4$~mag and $\Delta m_{K_s}=6.1$~mag, respectively. This sample includes 37 stars likely to host planets, 32 targets likely to be eclipsing binaries (EBs), and 6 other targets previously labeled as likely planetary false positives. We find nine likely physically bound companion stars within 3" of three candidate transiting exoplanet host stars and six likely EBs. Six of the nine detected companions are new discoveries; one of the six, EPIC 206061524, is associated with a planet candidate. Among the EB candidates, companions were only found near the shortest period ones ($P<3$ days), which is in line with previous results showing high multiplicity near short-period binary stars. This high-resolution data, including both the detected companions and the limits on potential unseen companions, will be useful in future planet vetting and stellar multiplicity rate studies for planets and binaries., Comment: Accepted in AJ

A historical problem for indirect exoplanet detection has been contending with the intrinsic variability of the host star. If the variability is periodic, it can easily mimic various exoplanet signatures, such as radial velocity variations that originate with the stellar surface rather than the presence of a planet. Here we present an update for the HD~99492 planetary system, using new radial velocity and photometric measurements from the Transit Ephemeris Refinement and Monitoring Survey (TERMS). Our extended time series and subsequent analyses of the Ca II H\&K emission lines show that the host star has an activity cycle of $\sim$13 years. The activity cycle correlates with the purported orbital period of the outer planet, the signature of which is thus likely due to the host star activity. We further include a revised Keplerian orbital solution for the remaining planet, along with a new transit ephemeris. Our transit-search observations were inconclusive., Comment: 6 pages, 3 figures, 2 tables, accepted for publication in ApJ Letters