On the uncertain nature of the core of α Cen A

Bazot, M.; Christensen‐Dalsgaard, J.; Gizon, Laurent; Benomar, O.

doi:10.1093/mnras/stw921

Cited by 50 publications

(70 citation statements)

References 65 publications

(60 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We employed the recent models of Baraffe et al (2015) that are well suited for very low mass stars and include the most up-to-date physical ingredients. We linearly interpolated the evolutionary tracks from the models corresponding to 0.110 and 0.130 M to find a good match of the model predictions with our determined values for L bol and T eff at the estimated age of the star of 4.8 Gyr (Bazot et al 2016). A stellar mass of 0.120 M yields the best simultaneous agreement of all parameters within the corresponding uncertainties, resulting in values of L bol = 0.00150 L and T eff = 2980 K. A formal uncertainty of 0.003 M can be estimated from the errors associated to L bol and T eff .…”

Section: Bolometric Fluxmentioning

confidence: 96%

The full spectral radiative properties of Proxima Centauri

Ribas

Gregg

Boyajian

et al. 2017

A&A

View full text Add to dashboard Cite

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.

show abstract

Section: Bolometric Fluxmentioning

confidence: 96%

The full spectral radiative properties of Proxima Centauri

Ribas

Gregg

Boyajian

et al. 2017

A&A

View full text Add to dashboard Cite

show abstract

“…The third star Proxima is a cool red dwarf (M5.5V), that is closer to Earth by approximately 7800 au, at d = 1.3008 ± 0.0006 pc (Benedict et al 1999). Owing to their similarity to the Sun, α Cen A and B are benchmarks for both stellar physics (Bazot et al 2016) and extrasolar planet research (Demory et al 2015). In August 2016, Anglada-Escudé et al (2016) announced the discovery of a terrestrial-mass planet orbiting Proxima in its habitable zone (Proxima b).…”

Section: Introductionmentioning

confidence: 99%

Proxima’s orbit around α Centauri

Kervella

Thévenin

Lovis

2017

A&A

119

View full text Add to dashboard Cite

Proxima and α Centauri AB have almost identical distances and proper motions with respect to the Sun. Although the probability of such similar parameters is, in principle, very low, the question as to whether they actually form a single gravitationally bound triple system has been open since the discovery of Proxima one century ago. Owing to HARPS high-precision absolute radial velocity measurements and the recent revision of the parameters of the α Cen pair, we show that Proxima and α Cen are gravitationally bound with a high degree of confidence. The orbital period of Proxima is ≈550 000 yr. With an eccentricity of 0.50

show abstract

“…α Cen A and B are dwarf stars of spectral types G2V (A, HD 128620) and K1V (B, HD 128621). Their proximity and similarity to the Sun in terms of mass and spectral type make α Cen extremely attractive from the standpoint of stellar physics (Bazot et al 2016;Pourbaix & Boffin 2016;Brito & Lopes 2016;Salaris & Cassisi 2015;Ayres 2015;Liseau et al 2015;Blanco-Cuaresma et al 2014) and extrasolar planet research (Quarles & Lissauer 2016;Rajpaul et al 2016;Demory et al 2015;Worth & Sigurdsson 2016;AndradeInes & Michtchenko 2014;Kaltenegger & Haghighipour 2013; The interferometric data are available in OIFITS format via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128. 5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/ Dumusque et al (2012)).…”

Section: Introductionmentioning

confidence: 99%

The radii and limb darkenings of α Centauri A and B

Kervella

Bigot

Gallenne

et al. 2017

A&A

View full text Add to dashboard Cite

The photospheric radius is one of the fundamental parameters governing the radiative equilibrium of a star. We report new observations of the nearest solar-type stars α Centauri A (G2V) and B (K1V) with the VLTI/PIONIER optical interferometer. The combination of four configurations of the VLTI enable us to measure simultaneously the limb darkened angular diameter θ LD and the limb darkening parameters of the two solar-type stars in the near-infrared H band (λ = 1.65 µm). We obtain photospheric angular diameters of θ LD (A) = 8.502 ± 0.038 mas (0.43%) and θ LD (B) = 5.999 ± 0.025 mas (0.42%), through the adjustment of a power law limb darkening model. We find H band power law exponents of α(A) = 0.1404 ± 0.0050 (3.6%) and α(B) = 0.1545 ± 0.0044 (2.8%), which closely bracket the observed solar value (α = 0.15027). Combined with the parallax π = 747.17 ± 0.61 mas previously determined, we derive linear radii of R A = 1.2234 ± 0.0053 R (0.43%) and R B = 0.8632 ± 0.0037 R (0.43%). The power law exponents that we derive for the two stars indicate a significantly weaker limb darkening than predicted by both 1D and 3D stellar atmosphere models. As this discrepancy is also observed on near-infrared limb darkening profile of the Sun, an improvement of the calibration of stellar atmosphere models is clearly needed. The reported PIONIER visibility measurements of α Cen A and B provide a robust basis to validate the future evolutions of these models.

show abstract

On the uncertain nature of the core of α Cen A

Cited by 50 publications

References 65 publications

The full spectral radiative properties of Proxima Centauri

The full spectral radiative properties of Proxima Centauri

Proxima’s orbit around α Centauri

The radii and limb darkenings of α Centauri A and B

Contact Info

Product

Resources

About