Impact of Correlated Noise on the Mass Precision of Earth-analog Planets in Radial Velocity Surveys
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Jacob K. Luhn↗
Engineering topics
Peter Plavchan
Publications and source records attributed to Peter Plavchan.
The Variable Detection of Atmospheric Escape around the Young, Hot Neptune AU Mic b
Photoevaporation is a potential explanation for several features within exoplanet demographics. Atmospheric escape observed in young Neptune-sized exoplanets can provide insight into and characterize which mechanisms drive this evolution and at what times they dominate. AU Mic b is one such exoplanet, slightly larger than Neptune (4.19 R ⊕ ). It closely orbits a 23 Myr pre-main-sequence M dwarf with an orbital period of 8.46 days. We obtained two visits of AU Mic b at Lyα with Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph. One flare within the first HST visit is characterized and removed from our search for a planetary transit. We present a nondetection in our first visit, followed by the detection of escaping neutral hydrogen ahead of the planet in our second visit. The outflow absorbed ∼30% of the star’s Lyα blue wing 2.5 hr before the planet’s white-light transit. We estimate that the highest-velocity escaping material has a column density of 10 13.96 cm −2 and is moving 61.26 km s −1 away from the host star. AU Mic b’s large high-energy irradiation could photoionize its escaping neutral hydrogen in 44 minutes, rendering it temporarily unobservable. Our time-variable Lyα transit ahead of AU Mic b could also be explained by an intermediate stellar wind strength from AU Mic that shapes the escaping material into a leading tail. Future Lyα observations of this system will confirm and characterize the unique variable nature of its Lyα transit, which, combined with modeling, will tune the importance of stellar wind and photoionization.
Exoplanets↗
AU Microscopii in the Far-UV Observations in Quiescence, During Flares, and Implications for AU Mic b and c
High-energy X-ray and ultraviolet(UV)radiation from young stars impacts planetary atmospheric chemistry and mass loss. The active∼22 Myr M dwarf AU Mic hosts two exoplanets orbiting interior to its debris disk. Therefore, this system provides a unique opportunity to quantify the effects of stellar X-ray and UV irradiation on planetary atmospheres as a function of both age and orbital separation. In this paper, we present over 5 hr of far-UV (FUV)observations of AU Mic taken with the Cosmic Origins Spectrograph (COS; 1070-1360Å) on the Hubble Space Telescope (HST). We provide an itemization of 120 emission features in the HST/COS FUV spectrum and quantify the flux contributions from formation temperatures ranging from 104 to 107K. We detect 13 flares in the FUV white-light curve with energies ranging from 1029 to 1031erg s. The majority of the energy in each of these flares is released from the transition region between the chromosphere and the corona. There is a 100×increase influx at continuum wavelengths λ<1100 Å in each flare, which may be caused by thermal Bremsstrahlung emission. We calculate that the baseline atmospheric mass-loss rate for AU Mic b is∼108 g s−1, although this rate can be as high as∼1014 g s−1during flares with Lflare 10-33 erg s−1. Finally, we model the transmission spectra for AU Mic b and c with a new panchromatic spectrum of AU Mic and motivate future JWST observations of these planets.
Adina D Feinstein↗
ORCAS - Keck Instrument Development - ORKID
A new breed of space-ground hybrid observatory, the Orbiting Configurable Artificial Star (ORCAS) mission is working with the W. M. Keck Observatory (WMKO) to demonstrate the viability of diffraction-limited visible imaging from large ground telescopes. To support that, we have built and delivered ORKID (The ORCAS Keck Instrument Demonstrator) as an early visible-wavelength performance demonstration with the Keck II Adaptive Optics (AO) system. By enabling AO and flux calibration observations, the low-cost ORCAS/ORKID mission will deliver highly detailed images to support many scientific advances. A community driven observation plan will provide Great Observatory quality capabilities open to all US observers. These observations will result in unique science for the mission, while also complementing and extending space-borne science.
Eliad Peretz↗
Faster Exo-Earth Yield for HabEx and LUVOIR via Extreme Precision Radial Velocity Prior Knowledge
The HabEx and LUVOIR mission concepts reported science yields for mission scenarios in which the instruments must search for potentially habitable planets, determine their orbits, and, if worthwhile, invest the integration time for a spectral characterization. We evaluate the impact of prior knowledge of planet existence and orbital parameters on yield for four mission concept architectures: HabEx 4m telescope with hybrid starshade and coronagraph, HabEx4m telescope with starshade only, HabEx 4m telescope with coronagraph only, and LUVOIR B8m telescope with coronagraph only. We use perfect prior knowledge to establish an upperbound on yield and use partial prior knowledge from a potential future extreme precision radial velocity (EPRV) instrument with3cm∕ssensitivity. We detail a modeling framework that per-forms dynamically responsive observation scheduling with realistic mission constraints. We evaluate exo-Earth yields against three metrics of spectral characterization for the four mission architectures and three levels of prior knowledge (none, partial, and perfect). The EPRV pro-vided prior knowledge increases yields by∼30%and accelerates by a factor of 3 to 6 the time to achieve half of the yield of the mission. Prior knowledge makes all the mission architectures more nimble and powerful, and most especially starshade-based architectures. With prior knowledge, a small telescope with a starshade can achieve comparable yield to a larger telescope with a coronagraph.
Rhonda Morgan↗
TESS Delivers Five New Hot Giant Planets Orbiting Bright Stars from the Full-frame Images
We present the discovery and characterization of five hot and warm Jupiters—TOI-628 b(TIC 281408474; HD288842), TOI-640 b(TIC 147977348), TOI-1333 b (TIC 395171208, BD+47 3521A), TOI-1478 b (TIC409794137), and TOI-1601 b (TIC 139375960)—based on data from NASA’s Transiting Exoplanet Survey Satellite(TESS). The five planets were identified from the full-frame images and were confirmed through a series of photometric and spectroscopic follow-up observations by the TESS Follow-up Observing Program Working Group. The planets are all Jovian size (RP=1.01–1.77RJ) and have masses that range from 0.85 to 6.33MJ. The host stars of these systems have F and G spectral types (5595Teff 6460 K)and are all relatively bright (9.5 1.7RJ, possibly a result of its host star’s evolution) and resides on an orbit with a period longer than 5 days. TOI-628 b is the most massive, hot Jupiter discovered to date by TESS with a measured mass of-+6.310.300.28MJ and a statistically significant, nonzero orbital eccentricity of e=-+0.0740.0220.021. This planet would not have had enough time to circularize through tidal forces from our analysis, suggesting that it might be remnant eccentricity from its migration. The longest-period planet in this sample, TOI-1478 b (P=10.18 days), is a warm Jupiter in a circular orbit around a near-solar analog. NASA’s TESS mission is continuing to increase the sample of well-characterized hot and warm Jupiters, complementing its primary mission goals.
Exoplanet astronomy↗
HD 183579b: a warm sub-Neptune transiting a solar twin detected by TESS
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Tianjun Gan↗
TOI-257b (HD 19916b): a warm sub-saturn orbiting an evolved F-type star
We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA’s Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of M(P) = 0.138 ± 0.023 M(J) (43.9 ± 7.3 Mꚛ), a radius of R(P) = 0.639 ± 0.013 R(J) (7.16 ± 0.15 Rꚛ), bulk density of 0.65 (+0.12,−0.11) (cgs), and period 18.38818 (+0.00085,−0.00084) days. TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M⁎ = 1.390 ± 0.046 M(sun), R⁎ = 1.888 ± 0.033 R(sun), T(eff) = 6075 ± 90 K, and 𝜈sin 𝑖 = 11.3 ± 0.5 km/s. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems.
asteroseismology↗
TOI-257b (HD 19916b): a warm sub-saturn orbiting an evolved F-type star
We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA’s Transiting Exoplanet Survey Satellite ( TESS ). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of M P = 0.138 ± 0.023 M J (43.9 ± 7.3 M ⊕ ), a radius of R P = 0.639 ± 0.013 R J (7.16 ± 0.15 R ⊕ ), bulk density of 0.65+0.12 −0.11 (cgs), and period 18.38818+0.00085 −0.00084 days. TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M ∗ = 1.390 ± 0.046 M sun , R ∗ = 1.888 ± 0.033 R sun , T eff = 6075 ± 90 K, and vsin i = 11.3 ± 0.5 km s −1 . Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems.
Brett C. Addison↗
An Unusual Transmission Spectrum for the Sub-Saturn KELT-11b Suggestive of a Subsolar Water Abundance
We present an optical-to-infrared transmission spectrum of the inflated sub-Saturn KELT-11b measured with the Transiting Exoplanet Survey Satellite (TESS), the Hubble Space Telescope (HST) Wide Field Camera 3 G141 spectroscopic grism, and the Spitzer Space Telescope (Spitzer) at 3.6 μm, in addition to a Spitzer 4.5 μm secondary eclipse. The precise HST transmission spectrum notably reveals a low-amplitude water feature with an unusual shape. Based on free-retrieval analyses with varying molecular abundances, we find strong evidence for water absorption. Depending on model assumptions, we also find tentative evidence for other absorbers (HCN, TiO, and AlO). The retrieved water abundance is generally ≲ 0.1× solar (0.001–0.7× solar over a range of model assumptions), several orders of magnitude lower than expected from planet formation models based on the solar system metallicity trend. We also consider chemical-equilibrium and self-consistent 1D radiative-convective equilibrium model fits and find that they, too, prefer low metallicities ([M/H] ≲ −2, consistent with the free-retrieval results). However, all of the retrievals should be interpreted with some caution because they either require additional absorbers that are far out of chemical equilibrium to explain the shape of the spectrum or are simply poor fits to the data. Finally, we find that the Spitzer secondary eclipse is indicative of full heat redistribution from KELT-11b's dayside to nightside, assuming a clear dayside. These potentially unusual results for KELT-11b's composition are suggestive of new challenges on the horizon for atmosphere and formation models in the face of increasingly precise measurements of exoplanet spectra.
Knicole D. Colón↗
TOI-481 b and TOI-892 b: Two Long-period Hot Jupiters from the Transiting Exoplanet Survey Satellite
We present the discovery of two new 10 day period giant planets from the Transiting Exoplanet Survey Satellite mission, whose masses were precisely determined using a wide diversity of ground-based facilities. TOI-481 b and TOI-892 b have similar radii (0.99 ± 0.01 R(J) and 1.07 ± 0.02 R(J), respectively), and orbital periods (10.3311 days and 10.6266 days, respectively), but significantly different masses (1.53 ± 0.03 M(J) versus 0.95 ± 0.07 M(J), respectively). Both planets orbit metal-rich stars ([Fe/HG] = +0.26 ± 0.05 dex and [Fe/H] = +0.24 ± 0.05 for TOI-481 and TOI-892, respectively) but at different evolutionary stages. TOI-481 is a M(*) = 1.14 ± 0.02 Mꙩ, R(*) = 1.66 ± 0.02 Rꙩ G-type star (T(eff) = 5735 ± 72 K), that with an age of 6.7 Gyr, is in the turn-off point of the main sequence. TOI-892 on the other hand, is a F-type dwarf star (T(eff) = 6261 ± 80 K), which has a mass of M(*) = 1.28 ± 0.03 Mꙩ and a radius of R(*) = 1.39 ± 0.02 Rꙩ. TOI-481 b and TOI-892 b join the scarcely populated region of transiting gas giants with orbital periods longer than 10 days, which is important to constrain theories of the formation and structure of hot Jupiters.
Rafael Brahm↗
KELT-25 b and KELT-26 b: A Hot Jupiter and a Substellar Companion Transiting Young A Stars Observed by TESS
We present the discoveries of KELT-25 b (TIC 65412605, TOI-626.01) and KELT-26 b (TIC 160708862, TOI-1337.01), two transiting companions orbiting relatively bright, early A stars. The transit signals were initially detected by the KELT survey and subsequently confirmed by Transiting Exoplanet Survey Satellite (TESS) photometry. KELT-25 b is on a 4.40 day orbit around the V=9.66 star CD-24 5016(=-+T8280eff180440K,Må=-+2.180.110.12Me), while KELT-26 b is on a 3.34 day orbit around the V=9.95 star HD 134004 (Teff=-+8640240500K,Må=-+1.930.160.14Me), which is likely an Am star. We have confirmed the substellar nature of both companions through detailed characterization of each system using ground-based and TESS photometry, radial velocity measurements, Doppler tomography, and high-resolution imaging. For KELT-25, we determine a companion radius of RP=-+1.640.0430.039RJ and a 3σupper limit on the companion’s mass of64MJ. For KELT-26 b, we infer a planetary mass and radius of MP=-+1.410.510.43MJ and RP=-+1.940.0580.060RJ. From Doppler tomographic observations, we find KELT-26 b to reside in a highly misaligned orbit. This conclusion is weakly corroborated by a subtle asymmetry in the transit light curve from the TESS data. KELT-25 b appears to be in a well-aligned, prograde orbit, and the system is likely a member of the cluster Theia 449.
Exoplanet astronomy↗
The First Habitable-zone Earth-sized Planet from TESS. I. Validation of the TOI-700 System
We present the discovery and validation of a three-planet system orbiting the nearby (31.1 pc) M2 dwarf star TOI-700 (TIC 150428135). TOI-700 lies in the TESS continuous viewing zone in the Southern Ecliptic Hemisphere; observations spanning 11 sectors reveal three planets with radii ranging from 1 R⊕ to 2.6 R⊕ and orbital periods ranging from 9.98 to 37.43 days. Ground-based follow-up combined with diagnostic vetting and validation tests enables us to rule out common astrophysical false-positive scenarios and validate the system of planets. The outermost planet, TOI-700 d, has a radius of 1.19 ± 0.11 R⊕ and resides within a conservative estimate of the host star's habitable zone, where it receives a flux from its star that is approximately 86% of Earth's insolation. In contrast to some other low-mass stars that host Earth-sized planets in their habitable zones, TOI-700 exhibits low levels of stellar activity, presenting a valuable opportunity to study potentially rocky planets over a wide range of conditions affecting atmospheric escape. While atmospheric characterization of TOI-700 d with the James Webb Space Telescope (JWST) will be challenging, the larger sub-Neptune, TOI-700 c (R = 2.63 R⊕), will be an excellent target for JWST and future space-based observatories. TESS is scheduled to once again observe the Southern Hemisphere, and it will monitor TOI-700 for an additional 11 sectors in its extended mission. These observations should allow further constraints on the known planet parameters and searches for additional planets and transit timing variations in the system.
Emily A. Gilbert↗
Toward Complete Characterization: Prospects for Directly Imaging Transiting Exoplanets
High-contrast direct imaging of exoplanets can provide many important observables, including measurements of the orbit, spectra that probe the lower layers of the atmosphere, and phase variations of the planet, but cannot directly measure planet radius or mass. Our future understanding of directly imaged exoplanets will therefore rely on extrapolated models of planetary atmospheres and bulk composition, which need robust calibration. We estimate the population of extrasolar planets that could serve as calibrators for these models. Critically, this population of "standard planets" must be accessible to both direct imaging and the transit method, allowing for radius measurement. We show that the search volume of a direct imaging mission eventually overcomes the transit probability falloff with semimajor axis, so that as long as cold planets are not exceedingly rare, the population of transiting planets and directly imageable planets overlaps. Using current extrapolations of Kepler occurrence rates, we estimate that ~8 standard planets could be characterized shortward of 800 nm with an ambitious future direct imaging mission like LUVOIR-A and several dozen could be detected at the V band. We show the design space that would expand the sample size and discuss the extent to which ground- and space-based surveys could detect this small but crucial population of planets.
Christopher C. Stark↗
TOI-677b: A Warm Jupiter (P=11.2 days) on an Eccentric Orbit Transiting a Late F-type Star
We report the discovery of TOI-677b,first identified as a candidate in light curves obtained within Sectors 9 and 10 of the Transiting Exoplanet Survey Satellite(TESS)mission and confirmed with radial velocities. TOI-677b has a mass of M(p) = 1.236(+0.069,- 0.067) M(J), a radius of R(P)=1.170 ± 0.03 R(J), and orbits its bright host star (V = 9.8 mag) with an orbital period of 11.23660 ± 0.00011 d, on an eccentric orbit with e = 0.435 ± 0.024. The host star has a mass of M(*) = 1.181 ± 0.058 M(ʘ), a radius of R(*)= 1.28(+0.03,-0.03) R(ʘ), an age of 2.92 (+0.80,-0.73) Gyr and solar metallicity, properties consistent with a main-sequence late-F star with T(eff)=6295 ± 77K. We find evidence in the radial velocity measurements of a secondary long-term signal, which could be due to an outer companion. The TOI-677 b system is a well-suited target for Rossiter–Mclaughlin observations that can constrain migration mechanisms of close-in giant planets.
Andrés Jordán↗
QUASAR - QUAsi-Stationary Absolute Radiance Mission
This paper describes the scientific and developmental aspects behind the QUAsi-Stationary Absolute Radiance (QUASAR) mission study. The scientific motivation on which the mission is built is established, including the absolute flux calibration of standard and exoplanet host stars, supernova cosmology, and interferometry. Furthermore, we present a science traceability matrix that determines the requirements for the mission through the scientific objectives. Additionally, we provide the mission configuration. This includes the spacecraft structure, its payload, and the component architecture. Finally, we describe how components within the payload provide efficiency and redundancy within the mission.
Eliad Peretz↗
Optical Design of Multi-field Integral Field Unit Spectrograph for the ORCAS Keck Instrument Development II (ORKID II) Instrument
We have designed an Integral Field Unit Spectrometer for the ORCAS Keck Instrument Development II (ORKID II) Instrument. Building on the success of the ORKID instrument (which achieved 15.1 masec FWHM visible spectrum imaging), ORKID II will add Integral Field Spectroscopy to analyze Active Galactic Nuclei (AGN), Supernovae redshift and brightness, and other science observations. Several design options have been explored based on image slicers manufactured by the Canon Corporation’s machining process. Field layouts can include up to three disparate spatial sampling, with a lower limit of 6.7 masec. Spectral resolutions are considered from R 100 to R 10,000. The modular design of the concept allows for configuring the instrument for various observing campaigns.
Instrumentation and Photography↗
Optical Design of Multi-field Integral Field Unit Spectrograph for the ORCAS Keck Instrument Development II (ORKID II) Instrument
We have designed an Integral Field Unit for the ORCAS Keck Instrument Development II (ORKID II) Instrument. Building on the success of the ORKID camera which achieved 15.2 masec PSF FWHM visible light imaging, ORKID II will add Integral Field Spectroscopy to analyze Active Galactic Nuclei (AGN), supernovae redshift and brightness, and other observations. Several design options have been explored based on image slicers manufactured by the Canon Corporation’s machining process. Field layouts can include up to three disparate spatial sampling, with a lower limit of 6.7 masec. Spectral resolutions are considered from R 100 to R 10,000.
Space Instrumentation↗