相关论文: Magnitude-range brightness variations of overactiv…
We present high signal-to-noise, moderate spectral resolution (R ~ 2000-2500) near-infrared (0.8-5.0 micron) spectroscopy of the nearby T Tauri star TW Hya. By comparing the spectrum and the equivalent widths of several atomic and molecular…
This paper is the first in a series presenting CCD multicolor photometry for 145 HII regions, selected from 369 candidate regions from Boulesteix et al. (1974), in the nearby spiral galaxy M33. The observations, which covered the whole area…
L and T dwarfs emit most of their radiation in the near infrared and their spectral energy distributions are dominated by strong molecular absorption bands. These highly structured energy distributions lead to JHK magnitudes that are…
We have monitored the photometric variability of nine field L and T brown dwarfs for 10 nights during the course of one month with the Palomar 60 inch Telescope Near-Infrared Camera. Results of statistical analyses indicate that at least…
Over the past few years monitoring programs have shown ultra cool dwarfs (UCDs) to be photometrically variable. Of the 60 sources monitored in the field and some 120 monitored in clusters, about 40% show variability in both cases. For mid…
The gamma-ray binary LS I +61 303 is composed of a Be star and a compact companion orbiting in an eccentric orbit. Variable flux modulated with the orbital period of ~26.5 d has been detected from radio to very high-energy gamma rays. In…
We present a detailed X-ray study of the quiescent and flaring coronae of three active main-sequence K-type stars, V834 Tau, LQ Hya, and BY Dra, using \textit{XMM-Newton} observations. The quiescent coronae are well described by…
We investigate the spot activity of the young chromospherically active main sequence star LQ Hya. Our aims are to identify possible active longitudes, estimate the differential rotation and study long and short term changes in the activity.…
Long-term $JHK$ light curves have recently become available for large numbers of the more luminous stars in the SMC. We have used these $JHK$ light curves, along with OGLE $V$ and $I$ light curves, to examine the variability of a sample of…
We present photometric light curves for a sample of 21 ultra cool M and L dwarfs in the field and in the young open clusters sigma Orionis and the Pleiades. Evidence for variability with RMS amplitudes (in the I band) of 0.01 to 0.055…
We present a study of the variation timescales of the chromospheric activity indicator H$\alpha$ on a sample of 13 fully-convective, active mid-to-late M stars with masses between 0.1--0.3 solar masses. Our goal was to determine the…
We present the combined results of three photometric monitoring campaigns targeting very low mass (VLM) stars and brown dwarfs in the young open cluster IC4665 (age ~40 Myr). In all three runs, we observe ~100 cluster members, allowing us…
We use 1-m class telescopes and the Transiting Exoplanet Survey Satellite (TESS) to explore the photometric variability of all known rapidly rotating ($v\sin{i}\gtrsim30$ km\,s$^{-1}$) ultra-cool ($\geq$M7) dwarfs brighter than…
We propose that the unstable 3.9days photometric periodicity of the hot subdwarf (sdO) KIC10449976 results from a tidally locked planet that is heated to 5000K by the UV radiation from the hot sdO star. Although the bolometric radiation…
Four months of quasi-simultaneous spectroscopic and photometric observations were used to study the variations of the photometric light curve, the evolution of the chromospheric activity from the H$\alpha$ and H$\beta$ lines, and the…
As part of a project to model the integrated spectra and colors of elliptical galaxies through evolutionary synthesis, we have refined our synthetic spectrum calculations of M giants. After critically assessing three effective temperature…
We derive an empirical effective temperature and bolometric luminosity calibration for G and K dwarfs, by applying our own implementation of the InfraRed Flux Method to multi-band photometry. Our study is based on 104 stars for which we…
I present the results of a program to spectrophotometrically monitor the L1.5 dwarf 2MASSW J1145572+231730 to identify the cause of photospheric variability in ultra cool dwarfs. Plausible candidates are magnetically-induced star spots and…
Comprehensive photometric investigation was carried out to the early K-type contact binary - IL Cnc. A few light curves from both ground-based telescopes and the Kepler space telescope were obtained (or downloaded) and then analyzed in…
We report on I band photometric observations of 21 stars with spectral types between M8 and L4 made using the Isaac Newton Telescope. The total amount of time for observations which had a cadence of <2.3 mins was 58.5 hrs, with additional…