A tight correlation between radio and X-ray luminosities of M dwarfs

Güdel, M.; Schmitt, J. H. M. M.; Bookbinder, Jay A.; Fleming, T. A.

doi:10.1086/173158

Cited by 157 publications

(242 citation statements)

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“…From the observations in the ROSAT All-Sky Bright Source Catalogue (Voges et al 1999) and the calibration in Schmitt et al (1995) one obtains an integrated X-ray luminosity of log L X (erg s −1 ) = 29.03 for CU Cnc. Again, this value can be compared with YY Gem's, which was estimated to be log L X (erg s −1 ) = 29.61 (Güdel et al 1993). One must keep in mind that the size of the stars in CU Cnc is significantly smaller than those of YY Gem.…”

Section: Stellar Activitymentioning

confidence: 96%

The 0.4-$M_{\odot}$ eclipsing binary CU Cancri

Ribas¹

2003

A&A

143

193

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Abstract. Photometric observations in the R and I bands of the detached M-type double-lined eclipsing binary CU Cnc have been acquired and analysed. The photometric elements obtained from the analysis of the light curves have been combined with an existing spectroscopic solution to yield high-precision (errors < ∼ 2%) absolute dimensions:0052 R , and R B = 0.3908 ± 0.0094 R . The mean effective temperature of the system has been estimated to be T eff = 3140 ± 150 K by comparing multi-band photometry (optical and infrared) with synthetic colors computed from state-of-the-art model atmospheres. Additionally, we have been able to obtain an estimate for the age (∼320 Myr) and chemical composition ([Fe/H] ≈ 0.0) of the binary system through its membership of the Castor moving group. With all these observational constraints, we have carried out a critical test of recent stellar models for low-mass stars. The comparison reveals that most evolutionary models underestimate the radius of the stars by as much as 10%, thus confirming the trend observed by Torres & Ribas (2002) for YY Gem and V818 Tau. In the mass-absolute magnitude diagram, CU Cnc is observed to be dimmer than other stars of the same mass and this makes the comparison with stellar models not so compelling. After ruling out a number of different scenarios, the apparent faintness of CU Cnc can be explained if its components are some 10% cooler than similar-mass stars or if there is some source of circumstellar dust absorption. The latter could be a tantalizing indirect evidence for a coplanar (Vega-like) dusty disk around this relatively young M-type binary.

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Section: Stellar Activitymentioning

confidence: 96%

The 0.4-$M_{\odot}$ eclipsing binary CU Cancri

Ribas¹

2003

A&A

143

193

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“…From 6 cm and 20 cm VLA observations, O'Dea & McKinnon (1987) could only specify a 3σ upper limit on its radio flux, thus CN Leo is underluminous in this wavelength regime compared to other active M dwarfs. Güdel et al (1993) were able to detect CN Leo in the 3.5 cm and 6 cm bands during a flare in a simultaneous observing campaign with the VLA at radio wavelengths and with the ROSAT PSPC in X-rays. During quiescence, however, again only upper limits were found at radio wavelengths.…”

Section: The Active M Dwarf Cn Leomentioning

confidence: 98%

Multiwavelength observations of a giant flare on CN Leonis

Liefke¹,

Fuhrmeister²,

Schmitt³

2010

A&A

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Context. Stellar flares affect all atmospheric layers from the photosphere over chromosphere and transition region up into the corona. Simultaneous observations in different spectral bands allow to obtain a comprehensive picture of the environmental conditions and the physical processes going on during different phases of the flare. Aims. We investigate the properties of the coronal plasma during a giant flare on the active M dwarf CN Leo observed simultaneously with the UVES spectrograph at the VLT and XMM-Newton. Methods. From the X-ray data, we analyze the temporal evolution of the coronal temperature and emission measure, and investigate variations in electron density and coronal abundances during the flare. Optical Fe xiii line emission traces the cooler quiescent corona.Results. Although of rather short duration (exponential decay time τ LC < 5 min), the X-ray flux at flare peak exceeds the quiescent level by a factor of ≈100. The electron density averaged over the whole flare is greater than 5 × 10 11 cm −3 . The flare plasma shows an enhancement of iron by a factor of ≈2 during the rise and peak phase of the flare. We derive a size of <9000 km for the flaring structure from the evolution of the the emitting plasma during flare rise, peak, and decay. Conclusions. The characteristics of the flare plasma suggest that the flare originates from a compact arcade instead of a single loop. The combined results from X-ray and optical data further confine the plasma properties and the geometry of the flaring structure in different atmospheric layers.

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“…The large discrepancy between the VLA and VLBI flux densities (1.92 and 0.19 mJy, respectively) could be explained by the presence of low-brightness emission from HD 160934, possibly combined with the expected flux variability of the star, which is resolved out by the EVN baselines. Accordingly, some caution has to be exercised when considering the values in Table 2; for example, the fact that the VLA and X-ray luminosities seem to follow the empirical radio/X-ray correlation (Güdel et al 1993) could be regarded, to a certain degree, as a coincidence. The detection of the lower-brightness component in our VLBI map (Fig.…”

Section: Radio Emission Of Hd 160934mentioning

confidence: 99%

Radio detection of the young binary HD 160934

Azulay

Guirado

Marcaide

et al. 2013

A&A

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Context. Precise determination of dynamical masses of pre-main-sequence (PMS) stars is essential to calibrate stellar evolution models that are widely used to derive theoretical masses of young low-mass objects. Binary stars in young, nearby loose associations are particularly good candidates for this calibration since all members share a common age. Interestingly, some of these young binaries present a persistent and compact radio emission, which makes them excellent targets for astrometric VLBI studies. Aims. We aim to monitor the orbital motion of the binary system HD 160934, a member of the AB Doradus moving group. Methods. We observed HD 160934 with the Very Large Array and the European VLBI Network at 8.4 and 5 GHz, respectively. The orbital information derived from these observations was analyzed along with previously reported orbital measurements. Results. We show that the two components of the binary, HD 160934 A and HD 160934 c, display compact radio emission at VLBI scales, providing precise information on the relative orbit. Revised orbital elements were estimated. Conclusions. Future VLBI monitoring of this pair should determine precise model-independent mass estimates for the A and c components, which will serve as calibration tests for PMS evolutionary models.

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A tight correlation between radio and X-ray luminosities of M dwarfs

Cited by 157 publications

References 0 publications

The 0.4-$M_{\odot}$ eclipsing binary CU Cancri

The 0.4-$M_{\odot}$ eclipsing binary CU Cancri

Multiwavelength observations of a giant flare on CN Leonis

Radio detection of the young binary HD 160934

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