GJ 357 b

Modirrousta-Galian, Darius; Stelzer, B.; Magaudda, E.; Maldonado, J.; Güdel, M.; Sanz-Forcada, J.; Edwards, Billy; Micela, G.

doi:10.1051/0004-6361/202038280

Cited by 8 publications

(5 citation statements)

References 86 publications

(105 reference statements)

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“…However, what makes GJ 357 b unique is that it orbits a very low active M-type star (Modirrousta-Galian et al 2020b). In spite of the abnormally low XUV levels, a careful backwards evaporation reconstruction model shows that up to ∼ 38 M ⊕ of hydrogen could have been lost (Modirrousta-Galian et al 2020b). Although GJ 357 b was probably born with a hydrogen envelope significantly smaller than this (perhaps M atm 0.02 M ⊕ Ikoma & Hori (2012); Chachan & Stevenson (2018)), this calculation shows that even stars with very low activity levels could completely strip off the primordial atmosphere of a planet.…”

Section: The Physical Implications Of Our Resultsmentioning

confidence: 99%

ARES V: No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b

Mugnai,

Modirrousta-Galian,

Edwards

et al. 2021

Preprint

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We present a study on the spatially scanned spectroscopic observations of the transit of GJ 1132 b, a warm (∼500 K) Super-Earth (1.13 R ⊕ ) that was obtained with the G141 grism (1.125 -1.650 µm) of the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope. We used the publicly available Iraclis pipeline to extract the planetary transmission spectra from the five visits and produce a precise transmission spectrum. We analysed the spectrum using the TauREx3 atmospheric retrieval code with which we show that the measurements do not contain molecular signatures in the investigated wavelength range and are best-fit with a flat-line model. Our results suggest that the planet does not have a clear primordial, hydrogen-dominated atmosphere. Instead, GJ 1132 b could have a cloudy hydrogen-dominated envelope, a very enriched secondary atmosphere, be airless, or have a tenuous atmosphere that has not been detected. Due to the narrow wavelength coverage of WFC3, these scenarios cannot be distinguished yet but the James Webb Space Telescope may be capable of detecting atmospheric features, although several observations may be required to provide useful constraints.

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Section: The Physical Implications Of Our Resultsmentioning

confidence: 99%

ARES V: No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b

Mugnai,

Modirrousta-Galian,

Edwards

et al. 2021

Preprint

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“…≤ 5 because of the poor statistics of their spectra. For comparison we show also the results from for a sample of GKM stars collected by these authors from the literature, and the recent XMM-Newton measurement for the planet host star GJ 357 from Modirrousta-Galian et al (2020). This latter one is a representative of the faintest and coolest M dwarf coronae studied so far.…”

Section: The Coronal Temperature -Luminosity Relationmentioning

confidence: 94%

First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS

Magaudda,

B.,

Raetz

et al. 2021

Preprint

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We present the first results with the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission (SRG), and we combine the new X-ray data with observations with the Transiting Exoplanet Survey Satellite (TESS). We use the superblink proper motion catalog of nearby M dwarfs as input sample to search for eROSITA and TESS data. We have extracted Gaia DR2 data for the full M dwarf catalog that comprises ∼ 9000 stars, and we calculated the stellar parameters from empirical relations with optical/IR colors. Then we cross-matched this catalog with the eROSITA Final Equatorial Depth Survey (eFEDS) and the first eROSITA all-sky survey (eRASS1). After a meticulous source identification in which we associate the closest Gaia source to the eROSITA X-ray detections, our sample of M dwarfs is defined by 704 stars with SpT = K5..M7 (690 from eRASS1 and 14 from eFEDS). While for eRASS1 we used the data from the source catalog provided by the eROSITA_DE consortium, for the much smaller eFEDS sample we performed the data extraction and we analyzed the X-ray spectra and light curves. This unprecedented data base for X-ray emitting M dwarfs allowed us to put a quantitative constraint on the mass dependence of the X-ray luminosity, and to determine the change in the activity level with respect to pre-main-sequence stars. TESS observations are available for 501 of 704 X-ray detected M dwarfs, and applying standard period search methods we could determine the rotation period for 180 X-ray detected M dwarfs, about one forth of the X-ray sample. With the joint eROSITA and TESS sample, and combining it with our compilation of historical X-ray and rotation data for M dwarfs, we examine the mass dependence of the 'saturated' regime of the rotation-activity relation. A first comparison of eROSITA hardness ratios and spectra shows that 65 % of the X-ray detected M dwarfs have coronal temperatures of ∼ 0.5 keV. We performed a statistical investigation of the long-term X-ray variability of M dwarfs comparing the eROSITA measurements to those obtained ∼ 30 years earlier during the ROSAT all-sky survey (RASS). Evidence for X-ray flares are found in various parts of our analysis: directly from an inspection of the eFEDS light curves, in the relation between RASS and eRASS1 X-ray luminosities, and in a subset of stars that displays X-ray emission hotter than the bulk of the sample according to the hardness ratios. Finally, we point out the need to obtain X-ray spectroscopy for more M dwarfs to study the coronal temperature-luminosity relation that is not well constrained by our eFEDS results.

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“…L 678-39 L 678-39 (GJ 357, TOI-562) is a M2.5 dwarf with a DR3 distance of 9 pc and a subsolar to solar metallicity of [Fe/ H] = − 0.12 ± 0.16 (Schweitzer et al 2019). A long stellar rotation period, low ¢ R log HK value of −5.37, and low X-ray flux place the star in a regime of old age and low activity (Luque et al 2019;Modirrousta-Galian et al 2020). The L 678-39 system contains three confirmed exoplanets consisting of one Earth-sized planet and two super-Earth planets (Luque et al 2019).…”

Section: A8 Wasp-43mentioning

confidence: 99%

The MUSCLES Extension for Atmospheric Transmission Spectroscopy: UV and X-Ray Host-star Observations for JWST ERS & GTO Targets

Behr

France

Brown

et al. 2023

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X-ray through infrared spectral energy distributions (SEDs) are essential for understanding a star’s effect on exoplanet atmospheric composition and evolution. We present a catalog of panchromatic SEDs, hosted on the Barbara A. Mikulski Archive for Space Telescopes, for 11 exoplanet-hosting stars that have guaranteed JWST observation time as part of the ERS or GTO programs but have no previous UV characterization. The stars in this survey range from spectral type F4-M6 (0.14–1.57 M ☉), rotation periods of 4–132 days, and ages of approximately 0.5–11.4 Gyr. The SEDs are composite spectra using data from the Chandra X-ray Observatory and XMM-Newton, the Hubble Space Telescope, BT-Settl stellar atmosphere models, and scaled spectra of proxy stars of similar spectral type and activity. From our observations, we have measured a set of UV and X-ray fluxes as indicators of stellar activity level. We compare the chromospheric and coronal activity indicators of our exoplanet-hosting stars to the broader population of field stars and find that a majority of our targets have activity levels lower than the average population of cool stars in the solar neighborhood. This suggests that using SEDs of stars selected from exoplanet surveys to compute generic exoplanet atmosphere models may underestimate the typical host star’s UV flux by an order of magnitude or more, and consequently, that the observed population of exoplanetary atmospheres receive lower high-energy flux levels than the typical planet in the solar neighborhood.

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GJ 357 b

Cited by 8 publications

References 86 publications

ARES V: No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b

ARES V: No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b

First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS

The MUSCLES Extension for Atmospheric Transmission Spectroscopy: UV and X-Ray Host-star Observations for JWST ERS & GTO Targets

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