Investigation of late-type stars in the FBS survey. I. M stars

AbstractWe present the results of two three-year surveys of young and nearby stars to search for wide orbit giant planets. On the one hand, we focus on early-type and massive, namely β Pictoris analogs. On the other hand, we observe late type and very low mass stars, i.e., M dwarfs. We report individual detections of new planetary mass objects. According to our deep detection performances, we derive the observed frequency of giant planets between these two classes of parent stars. We find frequency between 6 to 12% but we are not able to assess a/no correlation with the host-mass.

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Quiescent and flaring lyman-α radiation of host stars and effects on exoplanets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316002258 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 391-396

Author(s):

Jeffrey L. Linsky ◽

Kevin France ◽

Yamila Miguel ◽

Lisa Kaltenegger

Keyword(s):

Emission Lines ◽

Late Type ◽

Chemical Abundances ◽

Interstellar Absorption ◽

Ultraviolet Spectra ◽

M Stars ◽

Host Stars ◽

Stars Flare ◽

Photochemical Models

AbstractLyman-α radiation dominates the ultraviolet spectra of G, K, and M stars and is a major photodissociation source for H2O, CO2, and CH4 in the upper atmospheres of exoplanets. We obtain intrinsic Lyman-α line fluxes for late-type stars by correcting for interstellar absorption or by scaling from other spectroscopic observables. When stars flare, all emission lines brighten by large factors as shown by HST spectra. We describe photochemical models of the atmosphere of the mini-Neptune GJ 436b (Miguel et al. 2015) that show the effects of flaring Lyman-α fluxes on atmospheric chemical abundances.

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Radio Emission from Flares in Single Late-type Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100034485 ◽

1995 ◽

Vol 151 ◽

pp. 22-31

Author(s):

Arnold O. Benz

Keyword(s):

Radio Emission ◽

High Energy ◽

Primary Energy ◽

Relativistic Electrons ◽

Late Type ◽

Loss Cone ◽

Magnetically Trapped ◽

Stellar Flares ◽

Gyrosynchrotron Emission ◽

M Stars

AbstractRadio observations provide the most direct information on non-thermal electrons in stellar flares and in the coronae of late-type stars. Radio emissions of single main-sequence F, G, and of many K stars have recently been discovered, in addition to the well-known dwarf M stars. Their long-duration radio flares with low circular polarization, slow variations and broad bandwidth can be attributed to gyrosynchrotron emission of mildly relativistic electrons. The same holds for the low-level (‘quiescent’) radio emission. On the other hand, highly polarized radio flares of M stars have been interpreted by coherent emissions from loss-cone instabilities of magnetically trapped electrons. These conjectures are consistent with recent VLBI observations. The identification of the radio emission process allows to estimate the high-energy component of the flare and compare it to the total flare energy. The weakly polarized radio emission may serve as a proxy for hard X-ray signatures of relativistic electrons. The fraction of primary energy released into energetic electrons then appears to be large and similar to solar flares.

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Extensions of the Wilson-Bappu Effect Among Very Luminous Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900145267 ◽

1978 ◽

Vol 80 ◽

pp. 59-62

Author(s):

Robert E. Stencel

Keyword(s):

Emission Lines ◽

Full Width ◽

Half Maximum ◽

Late Type ◽

New Class ◽

Line Core ◽

M Stars ◽

Type Giant

Twenty years ago, Wilson and Bappu (1957) published their observational correlation of MVand the logarithm of the full width at half maximum of the CaII K-line central emission for G, K and M stars. The technique was stated to have ± 0m.5 accuracy, while a tabulation of MV(K) by Wilson (1976) suggests the error may only be ± 0m.3. This accuracy makes the approach valuable for late-type supergiants since other methods suffer from comparable errors. However, for F through M supergiants (Ia, 0), circumstellar absorption obscures the chromospheric K-line core emission and excludes such objects from the Wilson-Bappu correlation. I report here on a new class of emission lines in late-type giant and supergiant spectra that exhibit MVcorrelated widths, yet are detectable among the brightest stars.

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Late-Type Giants in the Bulge, at High Galactic Latitudes and in the Plane

Symposium - International Astronomical Union ◽

10.1017/s0074180900230003 ◽

1996 ◽

Vol 169 ◽

pp. 411-417

Author(s):

Patricia Whitelock

Keyword(s):

Near Infrared ◽

Large Range ◽

Scale Height ◽

Late Type ◽

The South ◽

Strong Function ◽

Period Distribution ◽

M Stars ◽

K 12 ◽

Galactic Distribution

Mira and non-Mira M stars are easily distinguished by means of their near-infrared colours. The Miras show a large range of mass-loss rates, and the actual rates are a strong function of the K-[12] colour. The kinematics and scale heights of these Miras are a function of their pulsation periods. The period distribution of Miras in the South Galactic Cap is similar to that of Miras in the Bulge. Non-Mira M stars in the South Galactic Cap have similar colours to their counterparts in the Bulge but differ from bright M-giants in the solar neighbourhood. The galactic distribution and scale height of the M giants is a function of colour and it is suggested that differences in composition influence the colours.

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Temporal Behaviour of Sources in the ROSAT Extreme-Ultraviolet All-Sky Survey

International Astronomical Union Colloquium ◽

10.1017/s0252921100035697 ◽

1996 ◽

Vol 152 ◽

pp. 15-19

Author(s):

Paul McGale ◽

J.P. Pye ◽

C.R. Barber ◽

C.G. Page

Keyword(s):

Extreme Ultraviolet ◽

Cataclysmic Variables ◽

Eclipsing Binaries ◽

High Mass ◽

Late Type ◽

Temporal Behaviour ◽

Source Type ◽

Luminosity Functions ◽

Sky Survey ◽

M Stars

From a total catalogue of 479 2RE sources, 31 have been found to be variable. All the variable sources are optically identified, with a breakdown by source type as follows: cataclysmic variables 9, late-type (F-M) stars 18, the high-mass X-ray binary Her X-1, the eclipsing binaries Algol and V471 Tau, and the active galaxy Mkn 478. The most highly variable objects in the EUV band are cataclysmic variables. The survey was sensitive to timescales from ~ 1.5 h to ~ 5 d, and observed variability ranges from flare-like events lasting < 1.5 h to irregular and periodic flux changes over ~ 0.5–2 d. With the exception of the cataclysmic variables, and possibly a few late-type dK-dMe stars with large flares, the observed variability levels should not substantially affect EUV luminosity functions

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Chromospheric activities of late-type stars based on Guoshoujing Telescope

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313007199 ◽

2013 ◽

Vol 9 (S298) ◽

pp. 454-454

Author(s):

L. Y. Zhang ◽

G. Y. Zhang ◽

J. R. Shi ◽

A. L. Luo ◽

J. K. Zhao ◽

...

Keyword(s):

Late Type ◽

Stellar Spectrum ◽

Active Stars ◽

M Stars

AbstractWe present chromospheric activities of late-type stars based on stellar spectrum survey of LAMOST (also called GuoShouJing telescope) in 2010-2013. Using the equivalent widths of the Hα line (larger than 1 Å), we have found 6391 active stars from 99741 M stars.

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Chromospheric activity of late-type stars based on Guoshoujing Telescope

Proceedings of the International Astronomical Union ◽

10.1017/s174392131300255x ◽

2012 ◽

Vol 8 (S294) ◽

pp. 209-210 ◽

Cited By ~ 2

Author(s):

Liyun Zhang ◽

Jianrong Shi ◽

Jingkun Zhao ◽

Ali Luo ◽

Guoyin Zhang ◽

...

Keyword(s):

Late Type ◽

Stellar Spectrum ◽

Pilot Survey ◽

Preliminary Results ◽

Chromospheric Activity ◽

M Stars

AbstractWe introduced our preliminary results of chromospheric activity of late-type stars based on the stellar spectrum of the pilot survey of the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST, also called Guo Shou Jing telescope). We have found 1151 active M stars from 17471 M samples using the chromospheric active indicator of the Hα line.

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Magnetic Fields and Stellar Evolution

Symposium - International Astronomical Union ◽

10.1017/s0074180900074003 ◽

1981 ◽

Vol 93 ◽

pp. 257-272 ◽

Cited By ~ 1

Author(s):

L. Mestel

Keyword(s):

Magnetic Fields ◽

Large Scale ◽

Main Sequence ◽

Late Type ◽

Main Sequence Stars ◽

Stellar Objects ◽

Cool Stars ◽

Solar Type ◽

Early Type Stars ◽

M Stars

Magnetic fields are now observed or inferred in a wide variety of stellar objects. The class of early-type stars with strong large-scale fields extends from types B to F, with effective fields from 300 gauss up to several x 104 gauss (Borra and Landstreet 1980). Fields between 4 × 106 and 108 gauss have been inferred in a small percentage of white dwarfs, and of over 1012 gauss in neutron stars. Some Cepheids show measurable fields. Evidence has built up of solar-type activity in late-type stars. The pioneering work by Wilson (1978) on Ca activity has shown convincingly the occurrence of periodicity reminiscent of the solar cycle in a number of G, K and M stars. Ca II emission appears to be a good predictor of simultaneous X-ray emission from hot coronae around cool stars (Vaiana 1979, Mewe and Zwaan 1980). Fields of some 2 × 103 gauss have been reported in two late-type main sequence stars (Robinson, Worden and Harvey 1980).

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Radio Evidence for Nonthermal Particle Acceleration on Stars of Late Spectral Type

International Astronomical Union Colloquium ◽

10.1017/s0252921100078064 ◽

1994 ◽

Vol 142 ◽

pp. 753-764

Author(s):

Kenneth R. Lang

Keyword(s):

Particle Acceleration ◽

Radio Emission ◽

Binary Stars ◽

Main Sequence ◽

Late Type ◽

T Tauri ◽

Rs Cvn Stars ◽

Vlbi Data ◽

Flare Stars ◽

M Stars

AbstractRadio evidence for nonthermal particle acceleration on stars of late spectral type (G, K, and M) is reviewed, including the pre-main-sequence T Tauri stars, the dwarf M flare stars, and the RS CVn binary stars. Both the long-lasting radio emission and the transient radio flares can be attributed to nonthermal electrons accelerated in magnetically confined coronae, radiating by either incoherent gyrosynchrotron radiation or by coherent processes. Related observations of the Sun provide the framework for interpreting the radio emission of late-type stars. We review recent VLBI observations of single and binary stars, observations of rapid acceleration and dynamic spectra of dwarf M flare stars, and models for long-lasting radio emission from dwarf M flare stars and RS CVn stars. The VLBI data provide evidence for nonthermal particle acceleration in large-scale magneto-spheres several times larger than the stellar radius for T Tauri and RS CVn stars. In contrast, rapid radio flares on dwarf M stars require sources much smaller than the visible star in size, and this is consistent with the VLBI data.Dynamic spectra suggest particle acceleration by relativistic electron beams on dwarf M stars. The long-lived radio radiation of dwarf M stars and RS CVn stars requires more-or-less continuous particle acceleration over periods of hours, perhaps by persistent low-amplitude flaring.Subject headings: acceleration of particles — binaries: close — radio continuum: stars — stars: flare — stars: late-type — stars: pre-main-sequence

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