相关论文: Chromospheric Variability in SDSS M Dwarfs. II. Sh…
We detect radio emission in an additional two epochs of the ultracool dwarf binary LP 349- 25, finding that the observed emission is broadband and steady on timescales between 10s and 10.7 hours, as well as on timescales of 0.6 and 1.6…
We present simultaneous photometric and spectroscopic observations of seven young and highly variable M dwarfs in star forming regions in Orion, conducted in 4 observing nights with FORS2 at ESO/VLT. All seven targets show significant…
We present a spectroscopic catalog of 70,841 visually inspected M dwarfs from the seventh data release (DR7) of the Sloan Digital Sky Survey (SDSS). For each spectrum, we provide measurements of the spectral type, a number of molecular…
Chromospheric swirls are considered to play a significant role in the dynamics and heating of the upper solar atmosphere. It is important to automatically detect and track them in chromospheric observations and determine their properties.…
In this paper we present results of a short-term optical monitoring of 13 blazars. The objects were monitored mostly in the R-band for a total of ~ 160 hours between 2006 and 2011. We study the nature of the short-term variations and show…
We investigate the `intrinsic' H$\alpha$ EW distributions of $z \sim 0.4 - 2.2$ narrowband-selected H$\alpha$ samples from HiZELS and DAWN using a forward modeling approach. We find an EW - stellar mass anti-correlation with steepening…
The re-emergence of the 0.99 $\mu$m FeH feature in brown dwarfs of early- to mid-T spectral type has been suggested as evidence for cloud disruption where flux from deep, hot regions below the Fe cloud deck can emerge. The same mechanism…
We conducted a volume-limited survey at 4.9 GHz of 32 nearby ultracool dwarfs with spectral types covering the range M7 -- T8. A statistical analysis was performed on the combined data from the present survey and previous radio observations…
We present a method which uses colour-colour cuts on SDSS photometry to select white dwarfs with hydrogen rich (DA) atmospheres without the recourse to spectroscopy. This method results in a sample of DA white dwarfs that is 95% complete at…
We increase the spectroscopic completeness of the 100 pc white dwarf sample in the SDSS footprint with 840 additional spectra. Our spectroscopy is 86% complete for white dwarfs hotter than $T_{\rm eff}= 5000$ K, where H$\alpha$ remains…
We study the relationship between the mid-infrared and sub-mm variability of deeply embedded protostars using the multi-epoch data from the Wide Infrared Survey Explorer ($WISE$/NEOWISE) and the ongoing James Clerk Maxwell Telescope (JCMT)…
Brown dwarfs of a variety of spectral types have been observed to be photometrically variable. Previous studies have focused on objects at the L/T transition, where the iron and silicate clouds in L dwarfs break up or dissipate. However,…
We present a sample of 17 newly discovered ultracool dwarf candidates later than ~M8, drawn from 231.90 arcmin2 of {\it Hubble Space Telescope} Wide Field Camera 3 infrared imaging. By comparing the observed number counts for…
Variability is a characteristic feature of young stellar objects (YSOs) and could contribute to the large scatter observed in HR diagrams for star forming regions. For typical YSOs, however, the long-term effects of variability are poorly…
We present a study of high-cadence, high-precision, optical light curves from the TESS satellite of 67 blazars in the southern sky. We provide descriptive flux statistics, power spectral density model parameters, and characteristic…
The space density of late M dwarfs, subtypes M7-M9.5, is not well determined. We applied the photo-type method to $iz$ photometry from the Sloan Digital Sky Survey and $YJHK$ photometry from the UKIRT Infrared Deep Sky Survey, over an…
The chromospheric emission estimated in the core of different lines, such as Ca II H & K, Na D1 and D2, and Halpha, is not always correlated between lines, as the Ca II H & K and Halpha emission time series are anti-correlated for a few…
Observations of molecular hydrogen (H$_2$) fluorescence are a potentially useful tool for measuring the H$_2$ abundance in exoplanet atmospheres. This emission was previously observed in M$\;$dwarfs with planetary systems. However, low…
Based on the near infrared spectra (R~20000) of M dwarfs, oxygen abundances are determined from the ro-vibrational lines of H2O. Although H2O lines in M dwarfs are badly blended each other and the continuum levels are depressed appreciably…
(abridged) Using a complete sample of ~300 star-forming galaxies within 11 Mpc, we evaluate the consistency between star formation rates (SFRs) inferred from the far ultraviolet (FUV) non-ionizing continuum and H-alpha nebular emission,…