Related papers: H\alpha\ Emission Variability in Active M Dwarfs
We present the first detection of photometric variability of a spectroscopically-confirmed Y dwarf. The Infrared Array Camera on board the Spitzer Space Telescope was used to obtain times series photometry at 3.6 and 4.5 microns over a…
A great deal of our understanding of star formation in the local universe has been built upon an extensive foundation of H-alpha observational studies. However, recent work in the ultraviolet (UV) with GALEX has shown that star formation…
*Abbreviated abstract* Context: Brown dwarfs in the spectral range L9-T3.5, within the so called L/T transition, have been shown to be variable at higher amplitudes and with greater frequency than other field dwarfs. [...] Now, more…
The M dwarf Gliese 581 is believed to host four planets, including one (GJ 581d) near the habitable zone that could possibly support liquid water on its surface if it is a rocky planet. The detection of another habitable-zone planet--GJ…
In this work we investigate the effect of the H$\alpha$ bandpass width in the correlation between the CaII H&K and H$\alpha$ indices with the aim of improving the H$\alpha$ index to better identify and model the signals coming from activity…
The HI Ly$\alpha$ (1215.67 $\unicode{xC5}$) emission line dominates the far-UV spectra of M dwarf stars, but strong absorption from neutral hydrogen in the interstellar medium makes observing Ly$\alpha$ challenging even for the closest…
In an effort to locate the sites of emission at different frequencies and physical processes causing variability in blazar jets, we have obtained high time-resolution observations of BL Lacertae over a wide wavelength range: with the…
Theoretical models and observations suggest that the abundances of molecular ions in protoplanetary disks should be highly sensitive to the variable ionization conditions set by the young central star. We present a search for temporal flux…
The light curves of solar-type stars present both periodic fluctuation and flare spikes. The gradual periodic fluctuation is interpreted as the rotational modulation of magnetic features on the stellar surface and is used to deduce magnetic…
We present multi-epoch radio and optical observations of the M7 dwarf 2MASS J13142039+1320011. We detect a ~1 mJy source at 1.43, 4.86, 8.46 and 22.5 GHz, making it the most luminous radio emission over the widest frequency range detected…
We present the optical photometric variability of 32 planet-hosting M dwarfs within 25 parsecs over timescales of months to decades. The primary goal of this project, ATLAS -- A Trail to Life Around Stars, is to follow the trail to life by…
Chromospheric wave activity around flares and filaments has been a research focus for years, and could provide indirect measurements of local conditions that are not otherwise accessible. One interesting observed phenomenon is oscillations…
With the improvements in radio interferometry sensitivity, the quest for coherent radio emission from exoplanets and ultra-cool dwarfs, which is indicative of their magnetic fields, has gained significant momentum in recent years. We…
Using the Hopkins Ultraviolet Telescope (HUT), we have obtained 850-1850 angstrom spectra of the magnetic cataclysmic variable star AM Her in the high state. These observations provide high time resolution spectra of AM Her in the FUV and…
We make use of the largest and most homogeneous sample of white dwarf/M dwarf (WD/dM) binaries from the Sloan Digital Sky Survey (SDSS DR7) to investigate relations between magnetic activity, rotation, magnetic braking and age in M stars.…
Stellar activity and rotation frustrate the detection of exoplanets through the radial velocity technique. This effect is particularly of concern for M dwarfs, which can remain magnetically active for billions of years. We compile rotation…
We are obtaining spectra, spectral types and basic physical parameters for the nearly 3600 dwarf and giant stars earlier than M0 in the Hipparcos catalog within 40pc of the Sun. Here we report on results for 1676 stars in the southern…
The ultraviolet (UV) emission from the most numerous stars in the universe, M dwarfs, impacts the formation, chemistry, atmospheric stability, and surface habitability of their planets. We have analyzed the spectral evolution of UV emission…
[Abridged] We present maps of CO 2-1 emission covering the entire star-forming disks of 16 nearby dwarf galaxies observed by the IRAM HERACLES survey. The data have 13 arcsec angular resolution, ~250 pc at our average distance of 4 Mpc, and…
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…