Giant Coronal Loops Dominate the Quiescent X-Ray Emission in Rapidly Rotating M Stars

Cohen, Ofer; Yadav, Rakesh K.; Garraffo, Cecilia; Saar, S. H.; Wolk, S. J.; Kashyap, Vinay; Drake, J. J.; Pillitteri, I.

doi:10.3847/1538-4357/834/1/14

Cited by 14 publications

(15 citation statements)

References 43 publications

(51 reference statements)

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“…Likewise, stellar wind simulations have shown that stronger large-scale fields lead to higher mass loss rates (c.f., Garraffo et al 2015b, Pognan et al 2018, and more dense coronae (c.f. Cohen et al 2014Cohen et al , 2017. It is expected then that escaping CMEs under those conditions would sweep up more mass than in a weaker large-scale field case.…”

Section: Cme Massesmentioning

confidence: 98%

Suppression of Coronal Mass Ejections in Active Stars by an Overlying Large-scale Magnetic Field: A Numerical Study

Alvarado‐Gómez

Drake

Cohen

et al. 2018

ApJ

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144

119

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We present results from a set of numerical simulations aimed at exploring the mechanism of coronal mass ejection (CME) suppression in active stars by an overlying large-scale magnetic field. We use a state-of-the-art 3D magnetohydrodynamic (MHD) code which considers a self-consistent coupling between an Alfvén wave-driven stellar wind solution, and a first-principles CME model based on the eruption of a flux-rope anchored to a mixed polarity region. By replicating the driving conditions used in simulations of strong solar CMEs, we show that a large-scale dipolar magnetic field of 75 G is able to fully confine eruptions within the stellar corona. Our simulations also consider CMEs exceeding the magnetic energy used in solar studies, which are able to escape the large-scale magnetic field confinement. The analysis includes a qualitative and quantitative description of the simulated CMEs and their dynamics, which reveals a drastic reduction of the radial speed caused by the overlying magnetic field. With the aid of recent observational studies, we place our numerical results in the context of solar and stellar flaring events. In this way, we find that this particular large-scale magnetic field configuration establishes a suppression threshold around ∼ 3 × 10 32 erg in the CME kinetic energy. Extending the solar flare-CME relations to other stars, such CME kinetic energies could be typically achieved during erupting flaring events with total energies larger than 6 × 10 32 erg (GOES class ∼X70).

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Section: Cme Massesmentioning

confidence: 98%

Suppression of Coronal Mass Ejections in Active Stars by an Overlying Large-scale Magnetic Field: A Numerical Study

Alvarado‐Gómez

Drake

Cohen

et al. 2018

ApJ

Self Cite

144

119

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“…- Cohen et al (2017) perform magnetohydrodynamic calculations for a rapidly rotating, fully convective M star. Their simulations use a rotating spherical shell as a surrogate for a convection zone, generating both complex small-scale and dipole large-scale magnetic fields, combined with the Alfvén wave turbulence to mimic coronal heating.…”

Section: Applicability Of the Solar Single Loop Modelmentioning

confidence: 99%

“…PMS stars on the Hayashi track are fully convective and, even when slowed by star-disk coupling, rapidly rotating. It is widely believed that such stars generate magnetic fields through distributed turbulent α 2 -type magnetic dynamos rather than tachoclinal αΩ-type dynamos (Durney et al 1993;Yadav et al 2015;Cohen et al 2017;Warnecke & Käpylä 2020). Some calculations suggest that surface magnetic fields may be concentrated in high-latitude areas, but Zeeman effect observations of individual PMS stars indicate that complex multi-polar surface magnetic field configurations are typical (Gregory et al 2010).…”

Section: Applicability Of the Solar Single Loop Modelmentioning

confidence: 99%

X-ray Super-Flares From Pre-Main Sequence Stars: Flare Modeling

Getman,

Feigelson,

Garmire

2021

Preprint

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Getman et al. (2021) reports the discovery, energetics, frequencies, and effects on environs of > 1000 X-ray super-flares with X-ray energies E X ∼ 10 34 − 10 38 erg from pre-main sequence (PMS) stars identified in the Chandra MYStIX and SFiNCs surveys. Here we perform detailed plasma evolution modeling of 55 bright MYStIX/SFiNCs super-flares from these events. This is the largest sample of highly energetic flares analyzed in a uniform fashion. They are compared with published X-ray super-flares from young stars in the Orion Nebula Cluster, older active stars, and the Sun. Several results emerge. First, the properties of PMS super-flares are independent of the presence or absence of protoplanetary disks, supporting the solar-type model of PMS flaring magnetic loops with both footpoints anchored in the stellar surface. Second, most PMS super-flares resemble solar long-duration events associated with coronal mass ejections. Slow rise PMS super-flares are an interesting exception. Third, strong correlations of super-flare peak emission measure and plasma temperature with the stellar mass are similar to established correlations for the PMS X-ray emission likely composed of numerous smaller flares. Fourth, a new correlation of loop geometry is linked to stellar mass; more massive stars have thicker flaring loops. Finally, the slope of a long-standing relationship between the X-ray luminosity and magnetic flux of various solar-stellar magnetic elements appears steeper in PMS super-flares than for solar events.

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“…This dynamo model not only has been tailored to match the mass, radius, and rotation period of Proxima Centauri (hereafter, Prox Cen), but also yields a long-term cyclic magnetic field evolution that roughly captures the observed time-scale of the activity cycle in this star (P cyc ∼ 7 years, see Suárez Mascareño et al 2016, Wargelin et al 2017. Cohen et al (2017) followed a similar approach to study the coronal structure of rapidly-rotating M-dwarf stars.…”

Section: Stellar Magnetic Fieldmentioning

confidence: 99%

Coronal Response to Magnetically Suppressed CME Events in M-dwarf Stars

Alvarado‐Gómez

Drake

Moschou

et al. 2019

ApJL

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We report the results of the first state-of-the-art numerical simulations of Coronal Mass Ejections (CMEs) taking place in realistic magnetic field configurations of moderately active M-dwarf stars. Our analysis indicates that a clear, novel, and observable, coronal response is generated due to the collapse of the eruption and its eventual release into the stellar wind. Escaping CME events, weakly suppressed by the large-scale field, induce a flare-like signature in the emission from coronal material at different temperatures due to compression and associated heating. Such flare-like profiles display a distinctive temporal evolution in their Doppler shift signal (from red to blue), as the eruption first collapses towards the star and then perturbs the ambient magnetized plasma on its way outwards. For stellar fields providing partial confinement, CME fragmentation takes place, leading to rise and fall flow patterns which resemble the solar coronal rain cycle. In strongly suppressed events, the response is better described as a gradual brightening, in which the failed CME is deposited in the form of a coronal rain cloud leading to a much slower rise in the ambient high-energy flux by relatively small factors (∼ 2 − 3). In all the considered cases (escaping/confined) a fractional decrease in the emission from mid-range coronal temperature plasma occurs, similar to the coronal dimming events observed on the Sun. Detection of the observational signatures of these CME-induced features requires a sensitive next generation X-ray space telescope.

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Giant Coronal Loops Dominate the Quiescent X-Ray Emission in Rapidly Rotating M Stars

Cited by 14 publications

References 43 publications

Suppression of Coronal Mass Ejections in Active Stars by an Overlying Large-scale Magnetic Field: A Numerical Study

Suppression of Coronal Mass Ejections in Active Stars by an Overlying Large-scale Magnetic Field: A Numerical Study

X-ray Super-Flares From Pre-Main Sequence Stars: Flare Modeling

Coronal Response to Magnetically Suppressed CME Events in M-dwarf Stars

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