Detection of an energetic flare from the M5V secondary star in the Polar MQ Dra

Abstract MQ Dra is a strongly magnetic Cataclysmic Variable whose white dwarf accretes material from its secondary star through a stellar wind at a low rate. TESS observations were made of MQ Dra in four sectors in Cycle 2 and show a short duration, high energy flare (∼1035 erg) which has a profile characteristic of a flare from the M5V secondary star. This is one of the few occasions where an energetic flare has been seen from a Polar. We find no evidence that the flare caused a change in the light curve following the event and consider whether a coronal mass ejection was associated with the flare. We compare the frequency of energetic flares from the secondary star in MQ Dra with M dwarf stars and discuss the overall flare rate of stars with rotation periods shorter than 0.2 d and how such fast rotators can generate magnetic fields with low differential rotation rates.

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The CARMENES search for exoplanets around M dwarfs

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833440 ◽

2018 ◽

Vol 619 ◽

pp. A32 ◽

Cited By ~ 10

Author(s):

D. Baroch ◽

J. C. Morales ◽

I. Ribas ◽

L. Tal-Or ◽

M. Zechmeister ◽

...

Keyword(s):

Binary Systems ◽

Spectroscopic Binaries ◽

M Dwarfs ◽

Dwarf Stars ◽

Double Line ◽

Orbital Parameters ◽

Rotation Periods ◽

Spectroscopic Binary ◽

M Dwarf Stars ◽

M Dwarf

Context. The CARMENES spectrograph is surveying ∼300 M dwarf stars in search for exoplanets. Among the target stars, spectroscopic binary systems have been discovered, which can be used to measure fundamental properties of stars. Aims. Using spectroscopic observations, we determine the orbital and physical properties of nine new double-line spectroscopic binary systems by analysing their radial velocity curves. Methods. We use two-dimensional cross-correlation techniques to derive the radial velocities of the targets, which are then employed to determine the orbital properties. Photometric data from the literature are also analysed to search for possible eclipses and to measure stellar variability, which can yield rotation periods. Results. Out of the 342 stars selected for the CARMENES survey, 9 have been found to be double-line spectroscopic binaries, with periods ranging from 1.13 to ∼8000 days and orbits with eccentricities up to 0.54. We provide empirical orbital properties and minimum masses for the sample of spectroscopic binaries. Absolute masses are also estimated from mass-luminosity calibrations, ranging between ∼0.1 and ∼0.6 M⊙. Conclusions. These new binary systems increase the number of double-line M dwarf binary systems with known orbital parameters by 15%, and they have lower mass ratios on average.

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Chromospheres of M Dwarf Stars with Incipient Hα Emission

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000023158 ◽

1989 ◽

Vol 8 (2) ◽

pp. 132-136

Author(s):

R. D. Robinson ◽

L. E. Cram

Keyword(s):

Emission Lines ◽

Energy Fluxes ◽

Dwarf Stars ◽

Rotation Rates ◽

Chromospheric Emission ◽

Hα Emission ◽

M Dwarf Stars ◽

M Dwarf

AbstractWe present observations of Hα and CaII resonance lines in 4 stars having Hα features which place them intermediately between the non-(e) and (e) classifications of dK/dM stars. There is considerable variety in the shape of the Hα line, presumably due in part to differences in rotation rates. As expected, the energy fluxes in the CaII emission lines lie between those typical of non-(e) and (e) stars. There is some evidence (especially from the binary Gl 876A) that the energy fluxes in the CaII and Hα emission lines do not vary from star to star according to a simple proportionality. An intriguing result is the apparent detection of spatially displaced chromospheric emission in Gl 907.1 and Gl 890.

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The CARMENES search for exoplanets around M dwarfs

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038279 ◽

2020 ◽

Vol 640 ◽

pp. A52

Author(s):

B. Fuhrmeister ◽

S. Czesla ◽

L. Hildebrandt ◽

E. Nagel ◽

J. H. M. M. Schmitt ◽

...

Keyword(s):

Near Infrared ◽

Extreme Ultraviolet ◽

High Energy ◽

M Dwarfs ◽

Dwarf Stars ◽

Transmission Spectroscopy ◽

Solar Type ◽

Energy Irradiation ◽

Planetary Transmission ◽

M Dwarf Stars

The He I infrared (IR) triplet at 10 830 Å is known as an activity indicator in solar-type stars and has become a primary diagnostic in exoplanetary transmission spectroscopy. He I IR lines are a tracer of the stellar extreme-ultraviolet irradiation from the transition region and corona. We study the variability of the He I triplet lines in a spectral time series of 319 M dwarf stars that was obtained with the CARMENES high-resolution optical and near-infrared spectrograph at Calar Alto. We detect He I IR line variability in 18% of our sample stars, all of which show Hα in emission. Therefore, we find detectable He I variability in 78% of the sub-sample of stars with Hα emission. Detectable variability is strongly concentrated in the latest spectral sub-types, where the He I lines during quiescence are typically weak. The fraction of stars with detectable He I variation remains lower than 10% for stars earlier than M3.0 V, while it exceeds 30% for the later spectral sub-types. Flares are accompanied by particularly pronounced line variations, including strongly broadened lines with red and blue asymmetries. However, we also find evidence for enhanced He I absorption, which is potentially associated with increased high-energy irradiation levels at flare onset. Generally, He I and Hα line variations tend to be correlated, with Hα being the most sensitive indicator in terms of pseudo-equivalent width variation. This makes the He I triplet a favourable target for planetary transmission spectroscopy.

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An Astrobiological Experiment to Explore the Habitability of Tidally Locked M-Dwarf Planets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313012817 ◽

2012 ◽

Vol 8 (S293) ◽

pp. 192-196

Author(s):

Daniel Angerhausen ◽

Haley Sapers ◽

Eugenio Simoncini ◽

Stefanie Lutz ◽

Marcelo da Rosa Alexandre ◽

...

Keyword(s):

Academic Research ◽

Environmental Parameters ◽

Climate Simulation ◽

Habitable Zone ◽

Dwarf Stars ◽

Dwarf Planets ◽

Late Type Star ◽

M Dwarf Stars ◽

M Dwarf ◽

Simulation Chamber

AbstractWe present a summary of a three-year academic research proposal drafted during the Sao Paulo Advanced School of Astrobiology (SPASA) to prepare for upcoming observations of tidally locked planets orbiting M-dwarf stars. The primary experimental goal of the suggested research is to expose extremophiles from analogue environments to a modified space simulation chamber reproducing the environmental parameters of a tidally locked planet in the habitable zone of a late-type star. Here we focus on a description of the astronomical analysis used to define the parameters for this climate simulation.

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Coronal Structure in M Dwarf Stars

Magnetodynamic Phenomena in the Solar Atmosphere ◽

10.1007/978-94-009-0315-9_16 ◽

1996 ◽

pp. 81-82

Author(s):

M. S. Giampapa ◽

R. Rosner ◽

V. Kashyap ◽

T. A. Fleming ◽

J. H. M. M. Schmitt ◽

...

Keyword(s):

Coronal Structure ◽

Dwarf Stars ◽

M Dwarf Stars ◽

M Dwarf

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The habitability of stagnant-lid Earths around dwarf stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834658 ◽

2019 ◽

Vol 625 ◽

pp. A12 ◽

Cited By ~ 8

Author(s):

Mareike Godolt ◽

Nicola Tosi ◽

Barbara Stracke ◽

John Lee Grenfell ◽

Thomas Ruedas ◽

...

Keyword(s):

Water Loss ◽

Main Sequence ◽

Extrasolar Planets ◽

Water Reservoir ◽

Habitable Zone ◽

High Luminosity ◽

Dwarf Stars ◽

Surface Conditions ◽

M Dwarf Stars ◽

M Dwarf

Context. The habitability of a planet depends on various factors, such as the delivery of water during its formation, the co-evolution of the interior and the atmosphere, and the stellar irradiation which changes in time. Aims. Since an unknown number of rocky extrasolar planets may operate in a one-plate convective regime, i.e. without plate tectonics, our aim is to understand the conditions under which planets in such a stagnant-lid regime may support habitable surface conditions. Understanding the interaction of the planetary interior and outgassing of volatiles in combination with the evolution of the host star is crucial to determining the potential habitability. M-dwarf stars in particular possess a high-luminosity pre-main sequence phase that endangers the habitability of planets around them via water loss. We therefore explore the potential of secondary outgassing from the planetary interior to rebuild a water reservoir allowing for habitability at a later stage. Methods. We compute the boundaries of the habitable zone around M-, K-, G-, and F-dwarf stars using a 1D cloud-free radiative-convective climate model accounting for the outgassing history of CO2 and H2O from an interior evolution and outgassing model for different interior compositions and stellar luminosity evolutions. Results. The outer edge of the habitable zone strongly depends on the amount of CO2 outgassed from the interior, while the inner edge is mainly determined via the stellar irradiation, as soon as a sufficiently large water reservoir has been outgassed. A build-up of a secondary surface and atmospheric water reservoir for planets around M-dwarf stars is possible even after severe water loss during the high-luminosity pre-main sequence phase as long as some water has been retained within the mantle. For small mantle water reservoirs, between 62 and 125 ppm, a time delay in outgassing from the interior permits such a secondary water reservoir build-up especially for early and mid-M dwarfs because their pre-main sequence lifetimes are shorter than the outgassing timescale. Conclusions. We show that Earth-like stagnant-lid planets allow for habitable surface conditions within a continuous habitable zone that is dependent on interior composition. Secondary outgassing from the interior may allow for habitability of planets around M-dwarf stars after severe water loss during the high-luminosity pre-main sequence phase by rebuilding a surface water reservoir.

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