The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities

Zhao, Lily; Fischer, Debra A.; Ford, Eric B.; Wise, Alex; Cretignier, M.; Aigrain, S.; Barragán, Oscar; Bedell, Megan; Buchhave, Lars A.; Camacho, J. D.; Cegla, H. M.; Cisewski-Kehe, Jessi; Cameron, A. Collier; Beurs, Zoë L. de; Dodson-Robinson, Sally; Dumusque, X.; Faria, J. P.; Gilbertson, Christian; Haley, Charlotte; Harrell, Justin; Hogg, David W.; Holzer, Parker H.; John, Ancy Anna; Klein, Baptiste; Lafarga, M.; Lienhard, Florian; Rajpaul, Vinesh; Mortier, A.; Nicholson, Belinda; Palumbo, Michael L.; Delgado, Victor Ramirez; Shallue, Christopher J.; Vanderburg, Andrew; Viana, P. T. P.; Zhao, Jun; Zicher, N.; Cabot, Samuel H. C.; Henry, Gregory W.; Roettenbacher, Rachael M.; Brewer, John M.; Llama, Joe; Petersburg, Ryan R.; Szymkowiak, Andrew E.

doi:10.3847/1538-3881/ac5176

Cited by 38 publications

(12 citation statements)

References 127 publications

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“…Efforts to mitigate the impact of stellar RV variations on exoplanet detection have found success by leveraging our understanding (albeit incomplete) of the underlying physical processes to model these signals rather than naïvely treating them as white noise. It has become commonplace, for example, to use Gaussian processes (GPs) to model stellar activity signals and disentangle them from exoplanet-induced Doppler shifts (e.g., Haywood et al 2014;Rajpaul et al 2015;Foreman-Mackey et al 2017;Gilbertson et al 2020;Langellier et al 2021;Zhao et al 2022). But this strategy is only applicable when it is feasible to obtain many observations on the timescale over which the stellar signals remain correlated.…”

Section: Introductionmentioning

confidence: 99%

Detection of p-mode Oscillations in HD 35833 with NEID and TESS

Gupta¹,

Luhn²,

Wright³

et al. 2022

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We report the results of observations of p-mode oscillations in the G0 subgiant star HD 35833 in both radial velocities and photometry with NEID and TESS, respectively. We achieve separate, robust detections of the oscillation signal with both instruments (radial velocity amplitude A RV = 1.11 ± 0.09 m s−1, photometric amplitude A phot = 6.42 ± 0.60 ppm, frequency of maximum power ν max = 595.71 ± 17.28 μHz, and mode spacing Δν = 36.65 ± 0.96 μHz) as well as a nondetection in a TESS sector concurrent with the NEID observations. These data shed light on our ability to mitigate the correlated noise impact of oscillations with radial velocities alone and on the robustness of commonly used asteroseismic scaling relations. The NEID data are used to validate models for the attenuation of oscillation signals for exposure times t < ν max − 1 , and we compare our results to predictions from theoretical scaling relations and find that the observed amplitudes are weaker than expected by >4σ, hinting at gaps in the underlying physical models.

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Section: Introductionmentioning

confidence: 99%

Detection of p-mode Oscillations in HD 35833 with NEID and TESS

Gupta¹,

Luhn²,

Wright³

et al. 2022

Self Cite

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“…The difficulty of measuring stellar radial velocities is dependent on spectral type. For most stars of type F and later, cross-correlation of a star's spectrum with a suitable radial velocity template is a standard technique, utilizing many dozens of spectral features (Tonry & Davis 1979), with precisions now reaching tens of centimeters per second employed to find extra-solar planets (see, e.g., Wright 2018;Zhao et al 2022). Main-sequence stars of earlier types have fewer, and broader, lines, and traditionally lines are measured one by one and the results averaged (see, e.g., Niemela & Gamen 2004;Morrell et al 2014) although sometimes also by cross-correlation techniques (e.g., Gies et al 2008).…”

Section: Methodsmentioning

confidence: 99%

Constraints on the Binarity of the WN3/O3 Class of Wolf–Rayet Stars*

Massey

Neugent

Morrell

2023

ApJ

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The WN3/O3 Wolf–Rayet (WR) stars were discovered as part of our survey for WRs in the Magellanic Clouds. The WN3/O3s show the emission lines of a high-excitation WN star and the absorption lines of a hot O-type star, but our prior work has shown that the absorption spectrum is intrinsic to the WR star. Their place in the evolution of massive stars remains unclear. Here we investigate the possibility that they are the products of binary evolution. Although these are not WN3+O3 V binaries, they could still harbor unseen companions. To address this possibility, we have conducted a multiyear radial velocity study of six of the nine known WN3/O3s. Our study finds no evidence of statistically significant radial velocity variations, and allows us to set stringent upper limits on the mass of any hypothetical companion star: for probable orbital inclinations, any companion with a period less than 100 days must have a mass <2M ⊙. For periods less than 10 days, any companion would have to have a mass <1M ⊙. We argue that scenarios where any such companion is a compact object are unlikely. The absorption lines indicate a normal projected rotational velocity, making it unlikely that these stars evolved with the aid of a companion star that has since merged. The modest rotation also suggests that these stars are not the result of homogenous evolution. Thus it is likely that these stars are a normal but short-lived stage in the evolution of massive stars.

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“…A large number of methods has been compared, to quantify detection performance [44,58] or residuals after correction without injecting planets [59]. In addition, efforts have been devoted to improve the determination of the false alarm level [37,[60][61][62][63].…”

Section: Approachesmentioning

confidence: 99%

Impact of stellar variability on exoplanet detectability and characterisation

Meunier¹

2024

Comptes Rendus. Physique

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Stellar variability has become a major issue to detect low mass planets using the radial velocity technique. I present the approaches followed to characterise the amplitude and the properties of stellar variability in radial velocity. More specifically, the approach consisting in using our knowledge of the Sun to understand better the different processes which are occuring at different scales proved to be very useful. This has been done in different ways, based on observations and models. This is crucial because it is then possible to compare disk-integrated radial velocities with actual structures on the solar surface, such as spots and plages, and with photospheric flows at different spatial scales. Many physical processes indeed affect the radial velocity measurements: they are mostly due to magnetic features (spots and plages), flows (oscillations, granulation, supergranulation, meridional flows), and to the interactions between magnetic fields and flows (inhibition of the convective blueshift in plages). I present in more detail a selection of studies aiming at characterising the impact of stellar variability, in particular the relationship between activity indicators and radial velocities, and then focusing on mass characterisation and detection performance. Finally, I briefly review the impact of stellar variability on photometric transits and astrometry, which are also affected, but to a lesser extent.Résumé. La variabilité stellaire est devenue un problème majeur pour détecter les planètes de faible masse en utilisant la méthode des vitesses radiales. Je présente les approches suivies pour caractériser l'amplitude et les propriétés de la variabilité stellaire en vitesse radiale. Plus précisément, l'approche consistant à utiliser notre connaissance du Soleil pour mieux comprendre les différents processus qui se produisent à différentes échelles s'est avérée très utile. Cela a été fait de différentes manières, sur la base d'observations et de modèles. Ceci est crucial car il est alors possible de comparer les vitesses radiales intégrées au disque avec les structures réelles de la surface solaire, telles que les taches et les plages, et avec les flux photosphériques à différentes échelles spatiales. De nombreux processus physiques affectent en effet les mesures de vitesse radiale : ils sont principalement dus aux caractéristiques magnétiques (taches et plages), aux écoulements (oscillations, granulation, supergranulation, circulation méridienne), et aux interactions entre les champs magnétiques et les écoulements (inhibition du blueshift convectif dans les plages). Je présente plus en détail une sélection d'études visant à caractériser l'impact de la variabilité stellaire, en particulier la relation entre les indicateurs d'activité et les vitesses radiales, puis je me concentre sur la caractérisation des masses et les performances de détection. Enfin, je passe brièvement en revue l'impact de la variabilité stellaire sur les transits photométriques et l'astrométrie, qui sont également affectés, mais dans une...

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The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities

Cited by 38 publications

References 127 publications

Detection of p-mode Oscillations in HD 35833 with NEID and TESS

Detection of p-mode Oscillations in HD 35833 with NEID and TESS

Constraints on the Binarity of the WN3/O3 Class of Wolf–Rayet Stars*

Impact of stellar variability on exoplanet detectability and characterisation

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