303.01 — Search for Earth analogues in the habit- able zone around solar type stars: radial velocity or astrometry?
Nadege Meunier1
1 Univ. Grenoble Alpes (Grenoble — cedex, France)
Stellar activity is currently a major limitation to the detection of very low mass planets around solar type stars using radial velocity techniques. Various tech- niques have been implemented to mitigate this prob- lem, without allowing to reach one Mearth planets for stars similar to the Sun yet. It is therefore cru- cial to estimate precisely the effect of activity on ex- oplanet detectability using realistic time series for various types of stars to overcome this problem. I will describe the basic processes at work and how
we extended a realistic solar model to build repre- sentative time series of radial velocity, photometry, astrometry and chromospheric emission variability. We built coherent sets of stellar parameters covering a large range in effective temperature (K4-F6) and av- erage activity levels. Such simulations are extremely useful to better understand the relationship between RV, astrometry and activity indicators and the lim- itations of correction techniques. I will present the impact of activity on the detectability of Earth mass planet in the habitable zones of those stars using ra- dial velocity and high precision astrometry and dis- cuss their respective performance.
303.02 — Stellar activity and wavelength- dependent radial velocity measurements
Maksym Lisogorskyi1; Hugh R.A. Jones1; Fabo Feng2; R. Paul Butler2
1 Centre for Astrophysics Research, University of Hertfordshire (Hatfield, Hertfordshire, United Kingdom)
2 Department of Terrestrial Magnetism, Carnegie Institution of Washington (Washington, Washington, United States)
The Alpha Centauri system is the primary target for planet search as it is the closest star system. Here we look at contaminating signals from telluric lines and activity sensitive lines across the spectrum in HARPS observations of Alpha Centauri B. We compile and quantify the behaviour of 345 spectral lines with a wide range of line shapes and sensitivity to activity and investigate its effect on radial velocity using ob- servations from UVES. Removing parts of the spec- trum that contain activity-sensitive lines removes a radial velocity trend reaching 8 m/s. The differen- tial velocity can be used as an indicator for contam- inating signals and can benefit greatly from careful selection of ”active” and ”inactive” echelle orders.
303.03 — An Expanded Catalog of Long-Period Ex- oplanets, Discovered with HIRES, Lick-Hamilton, and APF
Lee Jesse Rosenthal1; Benjamin J. Fulton2; Lea A.
Hirsch3; Andrew Howard1
1 Astronomy, California Institute of Technology (Pasadena, Califor- nia, United States)
2 NASA Exoplanet Science Institute (Pasadena, California, United States)
3 Kavli Institute for Particle Astrophysics and Cosmology, Stanford University (Stanford, California, United States)
The California Planet Search team has been conduct- ing a radial velocity survey of almost 800 nearby F/G/K stars for the past three decades, using the
HIRES instrument on Keck I, and the Hamilton spec- trograph and Automated Planet Finder at the Lick observatory. We describe a systematic search of this dataset for previously undetected periodic sig- nals and long-term trends, and present a catalog of dozens of newly-detected planet candidates, ranging from warm sub-Neptunes to cold gas giants.
303.04 — The Beginning of the Strategic Large Ex- ploration for Exoplanets Orbiting Nearby Late-M Dwarfs with the InfraRed Doppler (IRD) Spectro- graph on the Subaru Telescope
Masayuki Kuzuhara9,1; Bun’ei Sato2; Motohide
Tamura6,9; Takayuki Kotani9; Nagayoshi Ohashi1,3;
Masashi Omiya9,1; Teruyuki Hirano2; Hiroki
Harakawa3,9; Wako Aoki1,5; Norio Narita9,1; Ya-
sunori Hori9,1; Akitoshi Ueda1,5; Akihiko Fukui4; Hi-
royuki Tako Ishikawa5,1; MASATO ISHIZUKA6;
Takashi Kurokawa9,7; Nobuhiko Kusakabe9,1; Tomoyuki
Kudo3,9; Eiichiro Kokubo1,5; Mihoko Konishi8; Tadashi
Nakajima9,1; Jun Nishikawa1,5; Masahiro Ogihara1; Takuma Serizawa7
1 National Astronomical Observatory of Japan (Mitaka, Japan) 2 Tokyo Institute of Technology (Meguro, Japan)
3 Subaru Telescope (Hilo, Japan) 4 University of Tokyo (Hongo, Japan) 5 SOKENDAI (Mitaka, Japan)
6 Department of Astronomy, University of Tokyo (Taito-ku, Japan) 7 Tokyo University of Agriculture and Technology (Koganei, Japan) 8 Oita University (Oita, Japan)
9 Astrobiology Center, NINS (Mitaka, Japan)
The observations of theKeplerspace telescope sug- gest that small planets are abundant around cool main-sequence stars, among which late-M dwarfs (LMDs) represent the coolest objects. LMDs are the great targets for the exoplanet search with the radial velocity (RV) technique due to their relatively low masses and inner habitable zones. However, LMDs are so faint especially at optical wavelengths that the RV technique for LMDs needs the infrared spectro- graph available on a large-aperture telescope with a stable calibration system of RV measurement. We have developed and operated the InfraRed Doppler (IRD) spectrograph that can be utilized with the adaptive optics of the Subaru Telescope. IRD ob- serves a laser frequency comb simultaneously with an object spectrum, enabling the stable RV calibra- tion comparable to 2 m s−1 at ∼1.0–1.7 μm. Since
February of 2019, we have started a strategic cam- paign to explore planets around LMDs using IRD, which is planned to go on until 2024 with the to- tal allocation of 175 nights. This is the first large- scale survey dedicated to LMDs that is achieved by
the precision RV measurements in the infrared. The IRD survey is expected to discover habitable planets that can be characterized in detail with next gener- ation telescopes. Also, the monitor of LMDs over a few years can reveal the population of rocky to ice-giant planets inside and outside of snow lines. We have listed 150 targets based on the literature and our pre-selection spectroscopic observations to filter out active LMDs unsuitable for precision RV measurements. In addition, the rapid rotators and close-separation multiple stars are removed through the first-year IRD observations, selecting the best 60 LMDs for extensive RV measurement. In parallel with the science observations, we are testing the pre- cision and stability of our RV measurements by ob- serving RV-stable stars and planet-host stars such as GJ 699 and GJ 436. We here present the strategy of the IRD planet survey and its latest progress, as well as the results of the performance verification.
303.05 — The Magellan TESS Survey (MTS): Prob- ing the Formation and Evolution of Small Planets with a Statistically Robust Survey
Xuesong Wang1; Johanna Teske1; Angie Wolfgang2
1 Carnegie Observatories (Pasadena, California, United States) 2 Penn State (State College, Pennsylvania, United States)
We present the design, execution, and latest results of the Magellan TESS Survey (MTS), a systematic radial velocity (RV) follow-up program using the Planet Finder Spectrograph (PFS) on the 6.5m Mag- ellan II telescope in Chile. We will characterize a sta- tistically robust sample of∼30 super-Earths and sub- Neptunes discovered by TESS.
There are several features that make our survey unique: (1) We designed our survey to be most ef- fective in addressing three specific science questions: How do planetary bulk densities depend on stel- lar insolation? How do planetary bulk densities de- pend on host star composition? How do planetary bulk densities depend on system architecture? (2) We have a clearly defined target selection function and observation cadence design formula, enabling more powerful statistical/population studies using our sample. (3) We will publish all RV results regu- larly (∼once per year) and at the end of our study, including non-detections and upper limits. We have already been making our observing schedules public on Exo-FOP.
On behalf of the MTS team, I will present: (1) The design and execution of our program, including a de- scription of our target selection and cadence cover- age schemes, as well as the observation queue man- agement, which is uniquely challenging for first-year
follow-up observations of TESS targets. These would be of general interest to groups that are running or will run similar programs. (2) The latest highlights and lessons learned from the first 10 months of MTS, including our battles with stellar jitter and several uniquely interesting planetary systems (from recent publications and papers in preparation).
303.06 — Radial Velocity Follow-up Program with FIES (Nordic Optical Telescope)
Andreea Gornea1; Lars Buchhave1
1 DTU Space, Technical University of Denmark (Copenhagen, Denmark)
The high resolution Fiber-fed Echelle Spectrograph (FIES) at the Nordic Optical Telescope (NOT) is going under instrumental developments in 2019 to prepare it for a large radial velocity (RV) follow-up program for TESS. The wavelength calibration for FIES will be improved with the installation of a Fabry-Pérot calibration source. The grating of the spectrograph will be enclosed with a pressure chamber which will decrease the variations caused by the atmospheric changes. Increasing the precision and stability of the instrument will make it suitable for the RV follow-up program that will yield mass measurements for the exoplanet candidates that the TESS mission discov- ers. With support from NASA and MIT the program will consists of up-to 200 nights.
303.07 — Results of the SOPHIE search for Nep- tunes and Super-Earths around bright solar-type stars
Nathan Hara1; François Bouchy1; Isabelle Boisse2; Luc
Arnold3; Alexandre Santerne2
1 Université de Genève (Versoix, Switzerland)
2 Laboratoire d’astrophysique de Marseile (Marseille, France) 3 Observatoire de Haute Provence (Saint-Michel l’Observatoire, France)
The SOPHIE spectrograph search for Neptunes and Super-Earths around bright solar-type stars began in 2011. We present the analysis of the 124 systems ob- served, with more than 7000 data points in total. The first part of the presentation will be dedicated to new signal processing techniques, regarding the correc- tion of the drift of the instrument, the selection of de- tection thresholds and the analysis of the time series, in particular the l1-periodogram. In the second part, we will present the ten new planets that have been discovered, most of which are detectable by TESS.
303.08 — Analysis of Exoplanetary Systems as WFIRST Targets
Zhexing Li1; Stephen Kane1; Margaret Turnbull2
1 Earth and Planetary Sciences, University of California, Riverside (Riverside, California, United States)
2 SETI Institute (Mountain View, California, United States) As part of the WFIRST Coronagraph Science Inves- tigation Team (WFIRST-C SIT) to study exoplanets around nearby stars, we aim to characterize nearby exoplanetary systems and provide a list of stars that would be suitable targets for WFIRST to carry out exoplanet direct imaging mission. To achieve that, we will be addressing two primary issues: charac- terization of stellar and orbital properties of nearby exoplanets. Having a better understanding of host star characteristics and the Keplerian orbit properties of the known nearby exoplanets are crucial in deter- mining exoplanet targets for WFIRST direct imaging. These two aspects give us important insights such as the presence of stellar and substellar companion in the system, planet-star separation, reflected light from planets, background star fields etc. We use Ex- oCat as well as other online sources such as Sim- bad, Vizier, and Gaia DR2 to provide the best pos- sible stellar parameters for nearby exoplanet host stars. We provide a strategy to conduct precursor ra- dial velocity observations to refine orbital ephemeris of nearby potential WFIRST exoplanet targets by the use of major telescopes such as the Automated Planet Finder. The combined effort will allow us to progress towards the completion of target selection for WFIRST exoplanet observing program.
303.09 — Exoplanets orbiting giants stars: 10 years observations of theEXPRESSprogram
Matias Jones1
1 European Southern Observatory (Santiago, Chile)
Evolved stars (subgiants and giants) are suited tar- gets for precision radial velocity studies by two main reasons: 1) they are cooler and rotate slower than their former main-sequence progenitor, which allow us to achieve a radial velocity precision at the m/s level for intermediate-mass stars , and 2) we can use them to study the dynamical evolution of planetary orbits due to the interaction with the expanding stel- lar envelope. Since 2009, we have been conducting a radial velocity survey called EXPRESS (EXoPlanets aRoundEvolvedStarS) aimed at studying the pop- ulation of planets orbiting giant stars. We have ob- tained multi-epoch spectroscopic data for a sample of 166 bright giant stars, resulting in thedetection of
∼30 planetary systems(some of these in common with the Pan-Pacific Planet Search), 2 brown dwarf candi- dates in the desert and 24 spectroscopic binaries, two of them with an astrometric orbit resolved using Hip- parcos data. Additionally, we have found that the
planet-metallicity correlation is valid for giant starsand we have also confirmed previous results showing that thegiant planets formation efficiency increases with the stellar mass(up to∼2.0 Msun). In this talk I will
describe our project and present the main results af- ter 10 years of observations. Finally, I will discuss our findings in the context of planetary formation.
303.10 — A New Tool for Simulating Spectra Spec- tra & Validating Machine Learning Models for Ex- oplanet Discovery
Eric B. Ford1,2; Michael Palumbo1; Johannes Löhner-
Böttcher3; Suvrath Mahadevan1; Jason Wright1
1 Astronomy & Astrophysics, Pennsylvania State University (Uni- versity Park, Pennsylvania, United States)
2 Institute for CyberScience, Pennsylvania State University (Uni- versity Park, Pennsylvania, United States)
3 High Altitude Observatory, NCAR (Boulder, Colorado, United States)
Currently, the planet detection sensitivity of state-of- the-art Doppler RV spectrographs is limited by in- trinsic stellar variability for most target stars. Mul- tiple groups are developing improved spectroscopic indicators (e.g., Jones et al. 2017, Zechmesiter et al. 2017, Dumusque 2018, Wise et al. 2018) and pow- erful, but complex statistical models (e.g., Rajpaul et al. 2015; Jones et al. 2017) to mitigate stellar variabil- ity. These methods need to be validated and com- pared, in order to make robust and credible detec- tions of rocky planets in or near the habitable zone of Sun-like stars. Recent results appear promising for mitigating stellar variability originating from active regions rotating across the disk, as long as observ- ing campaigns obtain dense time sampling and high spectral resolution/signal-to-noise. However, it is unclear if these same methods will be effective for stars dominated by granulation, which has a much shorter timescale than rotationally-linked variability. We present a new tool for generating syn- thetic high-resolution stellar spectroscopic time- series. While previous tools (e.g., SOAP, StarSim) have focused on modeling stellar activity, our tool focuses on exploring the effects of convection and granulation on measured radial velocities. Gener- ating synthetic datasets that include these effects is critical for evaluating the performance of strategies for mitigating the stellar variability problem for Sun- like stars. Thus, our tool will play an important role
in validating machine learning algorithms and com- paring the efficacy of various approaches for mit- igating the effects of intrinsic stellar variability on Doppler planet surveys. Additionally the results are likely to have important implications for target selec- tion in upcoming Doppler surveys. We will describe our model and show a movie of the line-profile vari- ations in our simulated data. We will evaluate the apparent radial velocities perturbations predicted by our new model and discuss the implications for up- coming Doppler planet surveys and TESS follow-up campaigns.
303.11 — Distinguishing planets from stellar vari- ability with machine learning
Christian Gilbertson1; Eric B. Ford1; David Jones3;
David Stenning4; Tom Loredo2
1 Astronomy & Astrophysics, Pennsylvania State University (Uni- versity Park, Pennsylvania, United States)
2 Astronomy, Cornell University (Ithaca, New York, United States) 3 Statistics, Texas A&M University (College Station, Texas, United States)
4 Mathematics, imperial College London (London, United Kingdom) The radial velocity method is one of the most suc- cessful techniques for the discovery and characteri- zation of exoplanets. Current RV surveys are sensi- tive to planetary signals of 1 m/s or less, but the vari- ability of stellar spectra (caused by star spots, pul- sations, convective motions, granulation, etc.) can mimic and obscure true planet signals at the same level. A data-driven approach for detecting plane- tary RV signals amidst stellar activity has recently been proposed by Rajpaul et al. (2015) and refined by Jones et al. (2017). This approach uses a physi- cally motivated multivariate Gaussian process (GP) to jointly model the apparent RV and multiple indi- cators of stellar activity, allowing the planetary RV component to be separated from the total RV sig- nal. Our statistical framework combines spectro- scopic and temporal information to reconstruct the apparent RV perturbation and improve sensitivity to low-mass planets. In this work, we build on previ- ous studies by simulating higher-fidelity active solar spectra time series (e.g., distribution of active region sizes, rise and decay timescales, latitudes, and differ- ential rotation) and compare the performance of sev- eral different GP kernel functions. Our early results suggest specific alternative kernel functions that are likely to improve the model and make it more sensi- tive to detecting low-mass planets. We will describe simulated datasets (which may be valuable for re- search groups testing their own approaches to mit- igating stellar variability), demonstrate the features
of our statistical model, and share our most recent results on the impact of the choice covariance ker- nel on sensitivity to low-mass planets and the im- plications for planning RV surveys and follow-up campaigns. The success of current and upcoming planet-hunting instruments hinges on the commu- nity’s ability to overcome the stellar variability chal- lenge. This research represents important steps on the path toward developing, validating and applying powerful machine-learning tools and a robust statis- tical framework for discovering and characterizing low-mass exoplanets in the presence of stellar vari- ability.
303.12 — New Astrophysical Insights into Radial Velocity Jitter
Jacob Luhn1; Fabienne Bastien1; Jason Wright1; Andrew Howard2; Howard Isaacson3
1 Penn State University (State College, Pennsylvania, United States)
2 Caltech (Pasadena, California, United States) 3 UC Berkeley (Berkeley, California, United States)
For nearly 20 years, the California Planet Search (CPS) has simultaneously monitored precise radial velocities and chromospheric activity levels of stars from Keck observatory to search for exoplanets. This sample provides a useful set of stars to better deter- mine the dependence of RV jitter on magnetic ac- tivity and stellar convection. For∼650 stars cover- ing a wide range of stellar parameters (effective tem- perature, surface gravity, and activity, among oth- ers), there are enough RV measurements to distin- guish this astrophysical jitter from accelerations due to orbital companions. To properly isolate RV jitter from these effects, we first remove the RV signal due to these companions. We present some new results from our analysis of the CPS data, highlighting em- pirical evidence of two regimes of RV jitter – activity- dominated and convection-dominated – and the re- sulting “jitter minimum”. A more thorough under- standing of the various sources of RV jitter and the underlying stellar phenomena that drive these in- trinsic RV variations will enable more precise jitter estimates for RV follow-up targets such as those from the K2 or TESS missions.
303.13 — Exoplanet Imitators: A test of stellar ac- tivity behavior in radial velocity signals
Chantanelle Nava1; Mercedes Lopez-Morales1; Raphaëlle
Haywood1; Helen Giles2
1 Astronomy, Center for Astrophysics | Harvard & Smithsonian (Cambridge, Massachusetts, United States)
2 Astronomy, Observatoire de Genève (Geneva, Switzerland) Effects from stellar activity are the largest barrier to detecting radial velocity signals of low-mass exo- planets. Radial velocity (RV) signals due to stellar ac- tivity are primarily caused by stellar magnetic active