X-ray emission from the M9 dwarf 1RXS J115928.5-524717

Robrade, J.; Schmitt, J. H. M. M.

doi:10.1051/0004-6361/200811224

Cited by 15 publications

(14 citation statements)

References 21 publications

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“…Despite their fully convective interior structure, the X-ray activity of very low mass M dwarfs shows similar trends to more massive stars, for example an ultra-cool M9 star has been detected in X-rays at a quasi-quiescent level (Robrade & Schmitt 2009). Although F, G and K-type stars display higher X-ray luminosity than M dwarfs, only the "tip of the iceberg" of the stellar coronal population has been sampled here.…”

Section: Normal Starsmentioning

confidence: 87%

The X-ray source content of the XMM-Newton Galactic plane survey

Motch

Warwick

Cropper

et al. 2010

A&A

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We report the results of an optical campaign carried out by the XMM-Newton Survey Science Centre with the specific goal of identifying the brightest X-ray sources in the XMM-Newton Galactic plane survey. In addition to photometric and spectroscopic observations obtained at the ESO-VLT and ESO-3.6 m, we used cross-correlations with the 2XMMi, USNO-B1.0, 2MASS, and GLIMPSE catalogues to advance the identification process. Active coronae account for 16 of the 30 positively or tentatively identified X-ray sources and exhibit the softest X-ray spectra. Many of the identified hard X-ray sources are associated with massive stars, possible members of binary systems and emitting at intermediate X-ray luminosities of 10 32−34 erg s −1 . Among these are (i) a very absorbed, likely hyper-luminous star with X-ray/optical spectra and luminosities comparable to those of η Carina; (ii) a new X-rayselected WN8 Wolf-Rayet star in which most of the X-ray emission probably arises from wind collision in a binary; (iii) a new Be/X-ray star belonging to the growing class of γ-Cas analogues; and (iv) a possible supergiant X-ray binary of the kind discovered recently by INTEGRAL. One of the sources, XGPS-25, has a counterpart of moderate optical luminosity that exhibits HeII λ4686 and Bowen CIII-NIII emission lines, suggesting that this may be a quiescent or X-ray shielded low mass X-ray binary, although its X-ray properties might also be consistent with a rare kind of cataclysmic variable (CV). We also report the discovery of three new CVs, one of which is a likely magnetic system displaying strong X-ray variability. The soft (0.4-2.0 keV) band log N(>S )−log S curve is completely dominated by active stars in the flux range of 1 × 10 −13 to 1 × 10 −14 erg cm −2 s −1 . Several active coronae are also detected above 2 keV suggesting that the population of RS CVn binaries contributes significantly to the hard X-ray source population. In total, we are able to identify a large fraction of the hard (2-10 keV) X-ray sources in the flux range of 1 × 10 −12 to 1 × 10 −13 erg cm −2 s −1 with Galactic objects at a rate consistent with what is expected for the Galactic contribution alone.

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Section: Normal Starsmentioning

confidence: 87%

The X-ray source content of the XMM-Newton Galactic plane survey

Motch

Warwick

Cropper

et al. 2010

A&A

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“…With its X-ray luminosity and activity level SCR 1845 is intermediate to LHS 2065 and 1RXS J115928.5-524717, two M 9 dwarfs that are the latest X-ray detected dwarf stars (Robrade & Schmitt 2008, 2009. Given the age estimate of a few Gyr for SCR 1845, high activity levels appear as long-lasting phenomena for very low mass stars.…”

Section: Spectral Modelingmentioning

confidence: 97%

Quiescent and flaring X-ray emission from the nearby M/T dwarf binary SCR 1845-6357

Robrade¹,

Poppenhaeger²,

Schmitt³

2010

A&A

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Aims. X-ray emission is an important diagnostics to study magnetic activity in very low mass stars that are presumably fully convective and have an effectively neutral photosphere. Methods. We investigate an XMM-Newton observation of SCR 1845-6357, a nearby, ultracool M 8.5 / T 5.5 dwarf binary. The binary is unresolved in the XMM detectors, but the X-ray emission is very likely from the M 8.5 dwarf. We compare its flaring emission to those of similar very low mass stars and additionally present an XMM observation of the M 8 dwarf VB 10. Results. We detect quasi-quiescent X-ray emission from SCR 1845-6357 at soft X-ray energies in the 0.2-2.0 keV band, as well as a strong flare with a count rate increase of a factor of 30 and a duration of only 10 min. The quasi-quiescent X-ray luminosity of log L X = 26.2 erg/s and the corresponding activity level of log L X /L bol = −3.8 point to a fairly active star. Coronal temperatures of up to 5 MK and frequent minor variability support this picture. During the flare, which is accompanied by a significant brightening in the near-UV, plasma temperatures of 25-30 MK are observed and an X-ray luminosity of L X = 8 × 10 27 erg/s is reached. Conclusions. The source SCR 1845-6357 is a nearby, very low mass star that emits X-rays at detectable levels in quasi-quiescence, implying the existence of a corona. The high activity level, coronal temperatures and the observed large flare point to a rather active star, despite its estimated age of a few Gyr.

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“…Blake et al (2010) collected five NIR radial velocity measurements spanning 360 days that do not show the signature of a companion. DE1159−52 was reported to be an X-ray source and both flares (Hambaryan et al 2004) and quasi-quiescent emission (Robrade & Schmitt 2009) have been observed. It is the brightest target in our sample and the only one that is closer than 10 pc.…”

Section: Notes On Individual Objectsmentioning

confidence: 99%

Astrometric planet search around southern ultracool dwarfs

Lazorenko

Ségransan

Martín

et al. 2014

A&A

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Context. Extrasolar-planet searches that target very low-mass stars and brown dwarfs are hampered by intrinsic or instrumental limitations. Time series of astrometric measurements with precisions better than one milli-arcsecond can yield new evidence on the planet occurrence around these objects. Aims. We present first results of an astrometric search for planets around 20 nearby dwarf stars with spectral types M8-L2. Methods. Over a time-span of two years, we obtained I-band images of the target fields with the FORS2 camera at the Very Large Telescope. Using background stars as references, we monitored the targets' astrometric trajectories, which allowed us to measure parallax and proper motions, set limits on the presence of planets, and to discover the orbital motions of two binary systems. Results. We determined trigonometric parallaxes with an average accuracy of 0.09 mas ( 0.2%), which resulted in a reference sample for the study of ultracool dwarfs at the M/L transition, whose members are located at distances of 9.5-40 pc. This sample contains two newly discovered tight binaries (DE0630−18 and DE0823−49) and one previously known wide binary (DE1520−44). Only one target shows I-band variability >5 mmag rms. We derived planet exclusion limits that set an upper limit of 9% on the occurrence of giant planets with masses 5 M J in intermediate-separation (0.01-0.8 AU) orbits around M8-L2 dwarfs. Conclusions. We demonstrate that astrometric observations with an accuracy of 120 µas over two years are feasible from the ground and can be used for a planet-search survey. The detection of two tight very low-mass binaries shows that our search strategy is efficient and may lead to the detection of planetary-mass companions through follow-up observations.

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X-ray emission from the M9 dwarf 1RXS J115928.5-524717

Cited by 15 publications

References 21 publications

The X-ray source content of the XMM-Newton Galactic plane survey

The X-ray source content of the XMM-Newton Galactic plane survey

Quiescent and flaring X-ray emission from the nearby M/T dwarf binary SCR 1845-6357

Astrometric planet search around southern ultracool dwarfs

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