Fundamental M-dwarf parameters from high-resolution spectra using PHOENIX ACES models

Passegger, V. M.; Berg, S.; Reiners, A.

doi:10.1051/0004-6361/201322261

Cited by 43 publications

(53 citation statements)

References 44 publications

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“…Assuming that the curves of growth of the lines present in the spectrum do not saturate, we can convert the value of β into an additive number for the metallicity through ∆[Fe/H] = log(β). The metallicity of Proxima is close to solar, as Passegger et al (2016) Koleva & Vazdekis (2012), the metallicity of GJ65 is sub-solar at ([Fe/H] = −0.42 ± 0.10), which is at 2σ from our mean value. But this value is derived from model fitting on a low-resolution combined spectrum of A and B (R = 1000, ∆v ≈ 160 km s − 1), which likely biases [Fe/H] toward lower values for these fastrotating stars.…”

Section: Projected Rotational Velocities Heliocentric Radial Velocitsupporting

confidence: 46%

The red dwarf pair GJ65 AB: inflated, spinning twins of Proxima

Kervella

Mérand

Ledoux

et al. 2016

A&A

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The nearby red dwarf binary GJ65 AB (UV+BL Ceti, M5.5Ve+M6Ve) is a cornerstone system to probe the physics of very low-mass stars. The radii of the two stars are currently known only from indirect photometric estimates, however, and this prevents us from using GJ65 AB as calibrators for the mass-radius (M-R) relation. We present new interferometric measurements of the angular diameters of the two components of GJ65 with the VLTI/PIONIER instrument in the near-infrared H band: θ UD (A) = 0.558 ± 0.008 ± 0.020 mas and θ UD (B) = 0.539 ± 0.009 ± 0.020 mas. They translate into limb-darkened angular diameters of θ LD (A) = 0.573 ± 0.021 mas and θ LD (B) = 0.554 ± 0.022 mas. Based on the known parallax, the linear radii are R(A) = 0.165 ± 0.006 R and R(B) = 0.159 ± 0.006 R (σ(R)/R = 4%). We searched for the signature of flares and faint companions in the interferometric visibilities and closure phases, but we did not identify any significant signal. We also observed GJ65 with the VLT/NACO adaptive optics and refined the orbital parameters and infrared magnitudes of the system. We derived masses for the two components of m(A) = 0.1225 ± 0.0043 M and m(B) = 0.1195 ± 0.0043 M (σ(m)/m = 4%). To derive the radial and rotational velocities of the two stars as well as their relative metallicity with respect to Proxima, we also present new individual UVES high-resolution spectra of the two components. Placing GJ65 A and B in the mass-radius diagram shows that their radii exceed expectations from recent models by 14 ± 4% and 12 ± 4% , respectively. Following previous theories, we propose that this discrepancy is caused by the inhibition of convective energy transport by a strong internal magnetic field generated by dynamo effect in these two fast-rotating stars. A comparison with the almost identical twin Proxima, which is rotating slowly, strengthens this hypothesis because the radius of Proxima does not appear to be inflated compared to models.

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Section: Projected Rotational Velocities Heliocentric Radial Velocitsupporting

confidence: 46%

The red dwarf pair GJ65 AB: inflated, spinning twins of Proxima

Kervella

Mérand

Ledoux

et al. 2016

A&A

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“…Spectra of the PHOENIX-ACE model are computed with the Ames TiO list by Schwenke (1998), whereas BT-Settl model uses TiO line list by Plez (2008). We find that TiO bands matched somewhat better with Plez (2008) as compared to what Passegger et al (2016) have reported. Also, the large differences in T eff could be due to different solar metallicities as mentioned by Passegger et al (2018) and Rajpurohit et al (2014).…”

Section: Analysis and Discussionmentioning

confidence: 52%

Exploring the stellar properties of M dwarfs with high-resolution spectroscopy from the optical to the near-infrared

Rajpurohit

Allard

Rajpurohit

et al. 2018

A&A

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Context. Being the most numerous and oldest stars in the galaxy, M dwarfs are objects of great interest for exoplanet searches. The presence of molecules in their atmosphere complicates our understanding of their atmospheric properties. But great advances have recently been made in the modeling of M dwarfs due to the revision of solar abundances. Aims. We aim to determine stellar parameters of M dwarfs using high resolution spectra (R∼90 000) simultaneously in the visible and the near-infrared. The high resolution spectra and broad wavelength coverage provide an unique opportunity to understand the onset of dust and cloud formation at cool temperatures. Furthermore, this study will help in understanding the physical processes which occur in a cool atmospheres, particularly, the redistribution of energy from the optical to the near-infrared. Methods. The stellar parameters of M dwarfs in our sample have been determined by comparing the high resolution spectra both in the optical and in the near-infrared simultaneously observed by CARMENES with the synthetic spectra obtained from the BT-Settl model atmosphere. The detailed spectral synthesis of these observed spectra both in the optical and in the near-infrared helps to understand the missing continuum opacity. Results. For the first time, we derive fundamental stellar parameters of M dwarfs using the high resolution optical and near-infrared spectra simultaneously. We determine T eff , log g and [M/H] for 292 M dwarfs of spectral type M0 to M9, where the formation of dust and clouds are important. The derived T eff for the sample ranges from 2300 to 4000 K, values of log g ranges from 4.5 ≤ log g ≤ 5.5 and the resulting metallicity ranges from -0.5 ≤ [M/H] ≤ +0.5. We have also explored the possible differences in T eff , log g and [M/H] by comparing them with other studies of the same sample of M dwarfs.

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“…fr/Grids/BT-Settl/CIFIST2011_2015/. Proxima's surface gravity and metallicity are compatible within the error bars with values of log g = 5.0 and [Fe/H] = 0.0 (Passegger et al 2016), which are part of the BT-Settl model grid, and those were adopted in our SED fitting procedure. The free parameters of the fit were the effective temperature and the angular diameter.…”

Section: Rieke Et Al (2004)mentioning

confidence: 68%

The full spectral radiative properties of Proxima Centauri

Ribas

Gregg

Boyajian

et al. 2017

A&A

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Context. The discovery of Proxima b, a terrestrial temperate planet, presents the opportunity of studying a potentially habitable world in optimal conditions. A key aspect to model its habitability is to understand the radiation environment of the planet in the full spectral domain. Aims. We characterize the X-rays to mid-IR radiative properties of Proxima with the goal of providing the top-of-atmosphere fluxes on the planet. We also aim at constraining the fundamental properties of the star, namely its mass, radius, effective temperature and luminosity. Methods. We employ observations from a large number of facilities and make use of different methodologies to piece together the full spectral energy distribution of Proxima. In the high-energy domain, we pay particular attention to the contribution by rotational modulation, activity cycle, and flares so that the data provided are representative of the overall radiation dose received by the atmosphere of the planet. Results. We present the full spectrum of Proxima covering 0.7 to 30000 nm. The integration of the data shows that the top-of-atmosphere average XUV irradiance on Proxima b is 0.293 W m −2 , i.e., nearly 60 times higher than Earth, and that the total irradiance is 877 ± 44 W m −2 , or 64 ± 3% of the solar constant but with a significantly redder spectrum. We also provide laws for the XUV evolution of Proxima corresponding to two scenarios, one with a constant XUV-to-bolometric luminosity value throughout its history and another one in which Proxima left the saturation phase at an age of about 1.6 Gyr and is now in a power-law regime. Regarding the fundamental properties of Proxima, we find M = 0.120 ± 0.003 M , R = 0.146 ± 0.007 R , T eff = 2980 ± 80 K, and L = 0.00151 ± 0.00008 L . In addition, our analysis reveals a ∼20% excess in the 3-30 µm flux of the star that is best interpreted as arising from warm dust in the system. Conclusions. The data provided here should be useful to further investigate the current atmospheric properties of Proxima b as well as its past history, with the overall aim of firmly establishing the habitability of the planet.

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Fundamental M-dwarf parameters from high-resolution spectra using PHOENIX ACES models

Cited by 43 publications

References 44 publications

The red dwarf pair GJ65 AB: inflated, spinning twins of Proxima

The red dwarf pair GJ65 AB: inflated, spinning twins of Proxima

Exploring the stellar properties of M dwarfs with high-resolution spectroscopy from the optical to the near-infrared

The full spectral radiative properties of Proxima Centauri

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