Related papers: EXTraS discovery of an X-ray superflare from an L …
The X-ray emission from flares on cool (i.e. spectral-type F-M) stars is indicative of very energetic, transient phenomena, associated with energy release via magnetic reconnection. We present a uniform, large-scale survey of X-ray flare…
We report and characterize a white-light superflare on a previously undiscovered M dwarf detected by the ASAS-SN survey. Employing various color-magnitude and color-spectral type relationships, we estimate several stellar parameters,…
(abridged) In the hunt for rare time-domain events, confusing exotic extragalactic phenomena with more common Galactic foreground events is an important consideration. We show how observations from multiple wavebands, in this case optical…
We have obtained an XMM-Newton observation and a broad-band spectrum from the ultraviolet to the near infrared with X-Shooter for one of the nearest M9 dwarfs, DENIS-P J1048-3956 (4pc). We integrate these data by a compilation of activity…
The nearby (d=5.0 pc) brown dwarf LP944-20 was observed with the XMM-Newton satellite on 07 January 2001. The target was detected with the Optical Monitor (V=16.736$\pm$0.081), but it was not detected during the $\approx 48$ ks observation…
We present {\it Spitzer}/IRAC observations of the L5 dwarf, 2MASSI J1315309-264951 (2M1315). This ultracool dwarf is known to display strong emission in the H$\alpha$ line. The SED for this object does not show any IR excess, that would…
The M-dwarf AD Leonis has been observed with the Reflection Grating Spectrometers and the European Photon Imaging Camera aboard XMM-Newton and also with the Low Energy Transmission Grating Spectrometer aboard the Chandra X-ray Observatory.…
X-ray emission provides the most direct diagnostics of the energy-release process in solar flares. Occasionally, a superhot X-ray source is found to be above hot flare loops of ~10 MK temperature. While the origin of the superhot plasma is…
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…
We present the results of a 4.75 GHz survey of 33 brown dwarfs and one young exoplanetary system for flaring radio emission, conducted with the 305-m Arecibo radio telescope. The goal of this program was to detect and characterize the…
We report new nearby L and late-M dwarfs (d_phot <= 30 pc) discovered in our search for nearby ultracool dwarfs (I-J >= 3.0, later than M8.0) at low Galactic latitude (|b| < 15 degr) over 4,800 square degrees in the DENIS database. We used…
We have detected a bright X-ray flare from the nearby brown dwarf LP 944-20 with the Chandra/ACIS-S. This is an old (500 Myr), rapidly rotating, lithium-bearing M9 object, with a bolometric luminosity of 6e29 ergs cm-2 s-1. It was only…
Energetic flares are observed in the Galactic supermassive black hole Sagittarius A* from radio to X-ray wavelengths. On a few occasions, simultaneous flares have been detected in IR and X-ray observations, but clear counterparts at longer…
We present the results of an observational campaign which obtained high time cadence, high precision, simultaneous optical and IR photometric observations of three M dwarf flare stars for 47 hours. The campaign was designed to characterize…
We present the serendipitous discovery of an L subdwarf, 2MASS J06164006-6407194, in a search of the Two Micron All Sky Survey for T dwarfs. Its spectrum exhibits features indicative of both a cool and metal poor atmosphere including a…
We report the discovery of a peculiar L dwarf from the UKIDSS LAS, ULAS J222711-004547. The very red infrared photometry (MKO J-K = 2.79$\pm$0.06, WISE W1-W2 = 0.65$\pm$0.05) of ULAS J222711-004547 makes it one of the reddest brown dwarfs…
A search of the Two Micron All Sky Survey and Sloan Digital Sky Survey reveals 36 previously unknown high proper motion objects with J<17. Their red-optical colors indicate that 27 are M dwarfs, 8 are early-type L dwarfs, and 1 is a…
We observed strong superflares (defined as flares with energy in excess of 10^33 erg) on three late-M dwarfs: 2MASS J08315742+2042213 (hereafter 2M0831+2042; M7 V), 2MASS J08371832+2050349 (hereafter 2M0837+2050; M8 V) and 2MASS…
We study the spectral and temporal behavior of X-ray flares from the active M-dwarf EV Lac in 200 ks of exposure with the Chandra/HETGS. We derive flare parameters by fitting an empirical function which characterizes the amplitude, shape,…
This Letter is to investigate the physics of a newly discovered phenomenon -- contracting flare loops in the early phase of solar flares. In classical flare models, which were constructed based on the phenomenon of expansion of flare loops,…