Observation of a possible superflare on Proxima Centauri

Kielkopf, John F.; Hart, Rhodes; Carter, Brad; Marsden, S. C.

doi:10.1093/mnrasl/slz054

Cited by 7 publications

(6 citation statements)

References 34 publications

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“…The maximum of the flare occurs at a similar time for all spectral lines, though we are aware that the real peak of the flare is unresolved in time. Kielkopf et al (2019) report a stellar flare in the M dwarf Proxima Centauri with similar duration as the one detected here. As can be seen in their Fig.…”

Section: The Response Of the Stellar Atmosphere To A Flaring Eventsupporting

confidence: 81%

Evidence of a flare ignited above a low-latitude spotted active region in the ultrafast rotator HK Aqr

González

Ramos

González-Fernández

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We study the magnetic activity in the ultra fast rotator dMe HK Aqr using tomography techniques with high resolution spectroscopy. We aim to characterise how this magnetic activity appears in a regime of very fast rotation without external forces, given that HK Aqr is, very likely, a single star. We find dark spots located at low latitudes. We also detect prominences below the co-rotation radius and at low latitudes, coinciding with the spot latitudes. This apparent low-latitude activity contrasts with what is typically observed in fast rotators, which tend to form large polar spots. Moreover, we detect a stellar flare which produces an enhancement of the continuum and additional emission in the core of most photospheric and chromospheric lines. We find evidence that the flare is ignited above an active region, as seen in solar flares. This means that, with high probability, the flare is initiated by magnetic reconnection in complex active regions. We also present evidence of bulk red-shifted velocities of about 15 km s−1 during the rise of the flare, and velocities of 5-10 km s−1 during the decay phase. An estimation of the heating during the flare results in about 200 kK close to the peak and in 100 kK at the end of the observations.

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Section: The Response Of the Stellar Atmosphere To A Flaring Eventsupporting

confidence: 81%

Evidence of a flare ignited above a low-latitude spotted active region in the ultrafast rotator HK Aqr

González

Ramos

González-Fernández

et al. 2022

Monthly Notices of the Royal Astronomical Society

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“…Another interesting example is Proxima Centauri. Kielkopf et al (2019) observed a superflare on this star in which the energy of the flare was 100 times the star's luminosity, and such large flares may endanger life on a planet in the habitable zone.…”

Section: Introductionmentioning

confidence: 97%

High-resolution spectroscopy of flares and CMEs on AD Leonis

Muheki

Guenther

Mutabazi

et al. 2020

A&A

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Context. Flares and coronal mass ejections (CMEs) are important for the evolution of the atmospheres of planets and their potential habitability, particularly for planets orbiting M stars at a distance <0.4 AU. Detections of CMEs on these stars have been sparse, and previous studies have therefore modelled their occurrence frequency by scaling up solar relations. However, because the topology and strength of the magnetic fields on M stars is different from that of the Sun, it is not obvious that this approach works well. Aims. We used a large number of high-resolution spectra to study flares, CMEs, and their dynamics of the active M dwarf star AD Leo. The results can then be used as reference for other M dwarfs. Methods. We obtained more than 2000 high-resolution spectra (R ~ 35 000) of the highly active M dwarf AD Leo, which is viewed nearly pole on. Using these data, we studied the behaviour of the spectral lines Hα, Hβ, and He I 5876 in detail and investigated asymmetric features that might be Doppler signatures of CMEs. Results. We detected numerous flares. The largest flare emitted 8.32 × 1031 erg in Hβ and 2.12 × 1032 erg in Hα. Although the spectral lines in this and other events showed a significant blue asymmetry, the velocities associated with it are far below the escape velocity. Conclusions. Although AD Leo shows a high level of flare activity, the number of CMEs is relatively low. It is thus not appropriate to use the same flare-to-CME relation for M dwarfs as for the Sun.

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“…This is especially true for exoplanets orbiting M dwarfs, which are much more active than Sun-like stars. Without a magnetic field to shield against magnetic phenomena such as flares and Coronal Mass Ejections (CMEs), planets around such stars may undergo mass loss and atmospheric erosion on relatively short timescales (see, e.g., Kielkopf et al 2019). The initial mass may also determine whether planets will have moons, a factor which has been hypothesized to play a role in the habitability of a planet, as it does for the Earth.…”

Section: Discussionmentioning

confidence: 99%

Analytic Estimates of the Achievable Precision on the Physical Properties of Transiting Planets Using Purely Empirical Measurements

Martínez

Stevens

Gaudi

et al. 2021

ApJ

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We present analytic estimates of the fractional uncertainties on the mass, radius, surface gravity, and density of a transiting planet, using only empirical or semi-empirical measurements. We first express these parameters in terms of transit photometry and radial velocity (RV) observables, as well as the stellar radius R ⋆, if required. In agreement with previous results, we find that, assuming a circular orbit, the surface gravity of the planet (g p ) depends only on empirical transit and RV parameters, namely the planet period P, the transit depth δ, the RV semi-amplitude K ⋆, the transit duration T, and the ingress/egress duration τ. However, the planet mass and density depend on all these quantities, plus R ⋆. Thus, an inference about the planet mass, radius, and density must rely upon an external constraint such as the stellar radius. For bright stars, stellar radii can now be measured nearly empirically by using measurements of the stellar bolometric flux, the effective temperature, and the distance to the star via its parallax, with the extinction A V being the only free parameter. For any given system, there is a hierarchy of achievable precisions on the planetary parameters, such that the planetary surface gravity is more accurately measured than the density, which in turn is more accurately measured than the mass. We find that surface gravity provides a strong constraint on the core mass fraction of terrestrial planets. This is useful, given that the surface gravity may be one of the best measured properties of a terrestrial planet.

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Observation of a possible superflare on Proxima Centauri

Cited by 7 publications

References 34 publications

Evidence of a flare ignited above a low-latitude spotted active region in the ultrafast rotator HK Aqr

Evidence of a flare ignited above a low-latitude spotted active region in the ultrafast rotator HK Aqr

High-resolution spectroscopy of flares and CMEs on AD Leonis

Analytic Estimates of the Achievable Precision on the Physical Properties of Transiting Planets Using Purely Empirical Measurements

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