Most Observations of Our Nearest Neighbor: Flares on Proxima Centauri

Davenport, James R. A.; Kipping, David; Sasselov, Dimitar; Matthews, J. M.; Cameron, Chris

doi:10.3847/2041-8205/829/2/l31

Cited by 119 publications

(122 citation statements)

References 55 publications

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“…Davenport et al (2016) observe Proxima to exhibit small flares 63 times per day, with larger flares occurring many times per year. Proxima's frequent flaring presents a challenge for the detection-or confident non-detection-of a transit for Proxima b.…”

Section: Notes On Proxima's Activitymentioning

confidence: 87%

Proxima Centauri as a Benchmark for Stellar Activity Indicators in the Near-Infrared

Robertson

Bender

Mahadevan

et al. 2016

ApJ

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A new generation of dedicated Doppler spectrographs will attempt to detect low-mass exoplanets around mid-late M stars at near infrared (NIR) wavelengths, where those stars are brightest and have the most Doppler information content. A central requirement for the success of these instruments is to properly measure the component of radial velocity (RV) variability contributed by stellar magnetic activity and to account for it in exoplanet models of RV data. The wavelength coverage for many of these new instruments will not include the Ca II H&K or Hα lines, the most frequently used absorption-line tracers of magnetic activity. Thus, it is necessary to define and characterize NIR activity indicators for mid-late M stars in order to provide simultaneous activity metrics for NIR RV data. We have used the high-cadence UVES observations of the M5.5 dwarf Proxima Centauri from Fuhrmeister et al. (2011) to compare the activity sensitivity of 8 NIR atomic lines to that of Hα. We find that equivalent width-type measurements of the NIR K I doublet and the Ca II NIR triplet are excellent proxies for the canonical optical tracers. The Ca II triplet will be acquired by most of the new and upcoming NIR Doppler spectrographs, offering a common, reliable indicator of activity.

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Section: Notes On Proxima's Activitymentioning

confidence: 87%

Proxima Centauri as a Benchmark for Stellar Activity Indicators in the Near-Infrared

Robertson

Bender

Mahadevan

et al. 2016

ApJ

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“…This provides a viable explanation for the 3-6% difference in the results of the comparisons between different measurements. The analysis of Davenport et al (2016) using MOS T satellite observations covering roughly 430 to 760 nm and taken over a time period of nearly 38 days reveal frequent white-light flares. There are 5-8 measurable flares per day with a typical duration of ∼1 hour.…”

Section: Final Spectrummentioning

confidence: 99%

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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“…The rotation period of Proxima is nevertheless uncertain. The rotation period is of interest for various studies, including flare cycles (Davenport et al 2016) and for the correct identification of radial velocity signals from orbiting planets (Anglada-Escudé et al 2016) and subsequent work (Ribas et al 2016). Previous studies have reported periods ranging from 31.5 ± 1.5 days (Guinan & Morgan 1996), through 41.3 days (Benedict et al 1993) to between 82 and 84 days (Benedict et al 1992(Benedict et al , 1998.…”

Section: Introductionmentioning

confidence: 99%

Calculations of periodicity from Hαprofiles of Proxima Centauri

Collins

Jones

Barnes

2017

A&A

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We investigate retrieval of the stellar rotation signal for Proxima Centauri. We make use of high-resolution spectra taken with UVES and HARPS of Proxima Centauri over a 13-yr period as well as photometric observations of Proxima Centauri from ASAS and HST. We measure the Hα equivalent width and Hα index, skewness and kurtosis and introduce a method that investigates the symmetry of the line, the peak ratio, which appears to return better results than the other measurements. Our investigations return a most significant period of 82.6 ± 0.1 days, confirming earlier photometric results and ruling out a more recent result of 116.6 days which we conclude to be an alias induced by the specific HARPS observation times. We conclude that whilst spectroscopic Hα measurements can be used for period recovery, in the case of Proxima Centauri the available photometric measurements are more reliable. We make 2D models of Proxima Centauri to generate simulated Hα, finding that reasonable distributions of plage and chromospheric features are able to reproduce the equivalent width variations in observed data and recover the rotation period, including after the addition of simulated noise and flares. However the 2D models used fail to generate the observed variety of line shapes measured by the peak ratio. We conclude that only 3D models which incorporate vertical motions in the chromosphere can achieve this.

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Most Observations of Our Nearest Neighbor: Flares on Proxima Centauri

Cited by 119 publications

References 55 publications

Proxima Centauri as a Benchmark for Stellar Activity Indicators in the Near-Infrared

Proxima Centauri as a Benchmark for Stellar Activity Indicators in the Near-Infrared

The full spectral radiative properties of Proxima Centauri

Calculations of periodicity from Hαprofiles of Proxima Centauri

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