Final Report for SAG 21: The Effect of Stellar Contamination on Space-based Transmission Spectroscopy

Rackham, Benjamin V.; Espinoza, N.; Berdyugina, S. V.; Korhonen, H.; Macdonald, Ryan; Montet, Benjamin T.; Morris, Brett M.; Oshagh, M.; Шапиро, А. И.; Unruh, Y. C.; Quintana, Elisa V.; Zellem, Robert T.; Apai, Dániel; Barclay, Thomas; Barstow, Joanna K.; Bruno, Giovanni; Carone, L.; Casewell, Sarah L.; Cegla, H. M.; Criscuoli, S.; Fournier, Pierre‐Edouard; Giampapa, M. S.; Giles, H.; Iyer, Aishwarya; Kopp, Greg; Костогрыз, Н. М.; Krivova, N. A.; Mallonn, M.; McGruder, Chima; Molaverdikhani, Karan; Newton, Elisabeth R.; Panja, Mayukh; Peacock, Sarah; Reardon, K.; Roettenbacher, Rachael M.; Scandariato, G.; Solanki, S. K.; Stassun, Keivan G.; Steiner, O.; Stevenson, Kevin B.; Tregloan-Reed, J.; Válio, Adriana; Wedemeyer, Sven; Welbanks, Luis; Yu, Jie; Alam, Munazza K.; Davenport, James R. A.; Deming, Drake; Dong, Chuanfei; Ducrot, Elsa; Fisher, Chloe; Gilbert, Emily; Kostov, Veselin B.; López‐Morales, Mercedes; Line, M. R.; Močnik, Teo; Mullally, Fergal; Paudel, Rishi R.; Ribas, I.; Valenti, Jeff A.

doi:10.48550/arxiv.2201.09905

Cited by 11 publications

(15 citation statements)

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“…The retrieved effective temperature however is significantly more overestimated than before with an even larger deviation from interferometry, and this could perhaps be due to a simplified stellar spot parameterization causing degeneracies with other fundamental stellar properties, that don't always prove to be accurate for active M dwarfs (Iyer & Line 2020) (extra figures provided in our zenodo link). It is also well established by now that there is very little knowledge of physically reasonable coverage fractions of stellar photospheric heterogeneities as well as their distribution throughout the photosphere of an M dwarf, posing alongside numerous problems that exist in characterizing the activity environment of such stars (Rackham et al 2022). Spots occur in stars primarily due to pockets of magnetic flux tubules stretching out-…”

Section: Influence Of Photospheric Heterogeneitymentioning

confidence: 99%

The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-Dwarf Properties

Iyer¹,

Line²,

Muirhead³

et al. 2022

Preprint

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About 70-80% of stars in our solar and galactic neighborhood are M dwarfs. They span a range of low masses (0.08 -0.6 solar mass) and low temperatures (between 2500 K -4000 K), facilitating molecule formation throughout their atmospheres. Standard stellar atmosphere models primarily designed for FGK stars have challenges in accurately characterizing broadband molecular features in spectra of cool stars. Here, we introduce SPHINX-a new low-resolution (R∼250) 1-D self-consistent radiativeconvective thermochemical equilibrium chemistry grid of model atmospheres and spectra for characterizing M dwarfs. We incorporate the most up-to-date pre-computed absorption cross-section data with appropriate pressure-broadening treatment for key molecules dominant in late-K, early/main-sequence-M star atmospheres in our grid. We then validate our grid models by acquiring fundamental properties (T ef f , logg, metallicity, radius and C/O ratio) for a sample of 20 stars-10 benchmark M+G binary stars with known host star metallicities and 10 M dwarfs with interferometrically measured angular diameters. Incorporating a Gaussian-process inference tool Starf ish, we also account for correlated and systematic noise sources in our grid-model fitting routine for low-resolution (R∼120) (spectral stitching of SpeX, SN IF S, and HST ST IS) observations and derive robust estimates of fundamental M dwarf atmospheric parameters. We also assess the influence of stellar photospheric heterogeneity on the acquired metallicity for a couple targets and find that could explain some deviations from observations. Moreover, we also probe whether the model-assumed mixing-length parameter for convection influences inferred radii, stellar effective temperature, and [M/H] to explain possible discrepancies compared to interferometry data and again find that this may bridge the gap between observations and model-derived stellar parameter deviations for cooler M dwarfs. Mainly, we show the unique strength in leveraging broadband molecular absorption features occurring in low-resolution M dwarf spectra and demonstrate the ability to improve constraints on fundamental stellar properties of exoplanet hosts and late brown dwarf companions.

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Section: Influence Of Photospheric Heterogeneitymentioning

confidence: 99%

The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-Dwarf Properties

Iyer¹,

Line²,

Muirhead³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Analyses of the spotted areas of stars are also key to studying planet atmospheres using transmission spectroscopy, as stellar activity is a major source of contamination for these observations (Rackham et al 2022). When considering the effect of spots on the surfaces of stars in transmission spectroscopy, the overall fraction of the star that is covered in spots is a key parameter, and Pont et al (2007) showed that for even a total spotted area of 1%, starspots would be the dominant source of uncertainty for a transmission spectrum of an exoplanet.…”

Section: Introductionmentioning

confidence: 99%

“…With some active stars having spotted areas of up to 40% (O' Neal et al 2001), the characterization of the activity on all stars is imperative to correctly understanding the transmission spectra of exoplanets around all stars. At the high levels of spectrophotometric precision that missions like JWST and ARIEL will provide, this is now a critical effect to understand and mitigate (Rackham et al 2022). The Pandora SmallSat mission will also allow for simultaneous visible time-series photometry and near-IR spectroscopy of exoplanet targets to understand and mitigate the effect of stellar activity on exoplanet atmospheres (Quintana et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Modeling Stellar Surface Features on a Subgiant Star with an M-dwarf Companion

Schutte

Hebb

Lowry

et al. 2022

Self Cite

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Understanding magnetic activity on the surface of stars other than the Sun is important for exoplanet analyses to properly characterize an exoplanet’s atmosphere and to further characterize stellar activity on a wide range of stars. Modeling stellar surface features of a variety of spectral types and rotation rates is key to understanding the magnetic activity of these stars. Using data from Kepler, we use the starspot modeling program STarSPot (STSP) to measure the position and size of spots for KOI-340, which is an eclipsing binary consisting of a subgiant star (T eff = 5593 ± 27 K, R ⋆ = 1.98 ± 0.05 R ⊙) with an M-dwarf companion (M ⋆ = 0.214 ± 0.006 M ⊙). STSP uses a novel technique to measure the spot positions and radii by using the transiting secondary to study and model individual active regions on the stellar surface using high-precision photometry. We find that the average size of spot features on KOI-340's primary is ∼10% the radius of the star, i.e., two times larger than the mean size of solar-maximum sunspots. The spots on KOI-340 are present at every longitude and show possible signs of differential rotation. The minimum fractional spotted area of KOI-340's primary is 2 − 2 + 12 % , while the spotted area of the Sun is at most 0.2%. One transit of KOI-340 shows a signal in the transit consistent with a plage; this plage occurs right before a dark spot, indicating that the plage and spot might be colocated on the surface of the star.

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“…Analyses of the spotted areas of stars is also key to studying planet atmospheres using transmission spectroscopy as stellar activity is a major source of contamination for these observations (Rackham et al 2022). When considering the effect of spots on the surfaces of stars in transmission spectroscopy, the overall fraction of the star that is covered in spots is a key parameter, and Pont et al (2007) showed that for even a total spotted area of 1%, starspots would be the dominant source of uncertainty for a transmission spectrum of an exoplanet.…”

Section: Introductionmentioning

confidence: 99%

“…With some active stars having spotted areas of up to 40% (O'Neal et al 2001), the characterization of the activity on all stars is imperative to correctly understanding the transmission spectra of exoplanets around all stars. At the high levels of spectrophotometric precision that missions like JWST and ARIEL will provide, this is now a critical effect to understand and mitigate (Rackham et al 2022). The Pandora SmallSat mission will also allow for simultaneous visible time-series photometry and near-IR spectroscopy of exoplanet targets to understand and mitigate the effect of stellar activity on exoplanet atmospheres (Quintana et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Modeling Stellar Surface Features on Subgiant Star with an M-dwarf Companion

Schutte,

Hebb,

Lowry

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Understanding magnetic activity on the surface of stars other than the Sun is important for exoplanet analyses to properly characterize an exoplanet's atmosphere and to further characterize stellar activity on a wide range of stars. Modeling stellar surface features of a variety of spectral types and rotation rates are key to understanding of the magnetic activity of these stars. Using data from Kepler, we use the starspot modeling program STarSPot (STSP) to measure the position and size of spots for KOI-340 which is an eclipsing binary consisting of a subgiant star (T eff = 5593 ± 27K; R = 1.98 ± 0.05R ) with an M-dwarf companion (M = 0.214 ± 0.006M ). STSP uses a novel technique to measure the spot positions and radii by using the transiting secondary to study and model individual active regions on the stellar surface using high-precision photometry. We find the average size of spot features on KOI-340's primary is ∼10% the radius of the star, i.e. two times larger than the mean size of Solarmaximum sunspots. The spots on KOI-340 are present at every longitude and show possible signs of differential rotation. The minimum fractional spotted area of KOI-340's primary is 2 +12 −2 % while the spotted area of the Sun is at most 0.2%. One transit of KOI-340 shows a signal in the transit consistent with a plage; this plage occurs right before a dark spot indicating the plage and spot might be co-located on the surface of the star.

show abstract

Final Report for SAG 21: The Effect of Stellar Contamination on Space-based Transmission Spectroscopy

Cited by 11 publications

References 0 publications

The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-Dwarf Properties

The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-Dwarf Properties

Modeling Stellar Surface Features on a Subgiant Star with an M-dwarf Companion

Modeling Stellar Surface Features on Subgiant Star with an M-dwarf Companion

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