Related papers: Steady and Transient Radio Emission from Ultracool…
A growing population of long-period radio transients has been discovered and their physical origin is still up to debate. Recently, a new such source named ILT J1101 + 5521 was discovered, which is in a white dwarf (WD) -- red dwarf (RD)…
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…
Serendipitously, we have rediscovered radio emission from the binary system Ross 867 (M4.5V) and Ross 868 (M3.5V) while inspecting archival Giant Metrewave Radio Telescope (GMRT) observations. The binary system consists of two M-dwarf stars…
In order to understand the possible mechanisms of recurrent jet activity in radio galaxies and quasars, which are still unclear, we have identified such sources with a large range of linear sizes (220 $-$ 917 kpc), and hence time scales of…
Photometric variability attributed to cloud phenomena is common in L/T transition brown dwarfs. Recent studies show that such variability may also trace aurorae, suggesting that localized magnetic heating may contribute to observed brown…
We report on the results of an I-band photometric variability survey of eighteen L dwarfs. We find that seven exhibit statistically significant variations above the 95.4% confidence level with root-mean-square scatter (including photometric…
We present multi-telescope, ground-based, multiwavelength optical and near-infrared photometry of the variable L3.5 ultra-cool dwarf 2MASSW J0036159+182110. We present 22 nights of photometry of 2MASSW J0036159+182110, including 7 nights of…
In the framework of the cosmological model LambdaCDM the features of properties of giant radio sources with steep low-frequency spectra of linear (S) and break (C+) types are examined. Our estimates of characteristic age of galaxies and…
Long-period radio transients (LPTs) are a recently identified phenomenon that challenge our current understanding of compact objects and coherent radio emission mechanisms. These objects emit radio pulses similar to those of pulsars, but at…
Recently, studies of brown dwarfs have demonstrated that they possess strong magnetic fields and have the potential to produce radio and optical auroral emissions powered by magnetospheric currents. This emission provides the only window on…
We present the discovery of the first T dwarf + white dwarf binary system LSPM 1459+0857AB, confirmed through common proper motion and spectroscopy. The white dwarf is a high proper motion object from the LSPM catalogue that we confirm…
We present new results from the Parallaxes of Southern Extremely Cool dwarfs program to measure parallaxes, proper motions and multi-epoch photometry of L and early T dwarfs. The observations were made on 108 nights over the course of 8…
Pulsars are typically characterized by their stable, highly magnetized, and fast-rotating nature, which underpins their persistent radio emissions. However, the discovery of prolonged radio-quiet ("off") states in intermittent pulsars, such…
We present HST/WFPC2 observations of a sample of 134 ultra-cool objects (spectral types later than M7) coming from the DENIS, 2MASS and SDSS surveys, with distances estimated to range from 7 pc to 105 pc. Fifteen new ultra-cool binary…
The electron-cyclotron maser instability (ECMI) is responsible for generation of the planetary auroral radio emissions. Most likely, the same mechanism produces radio bursts from ultracool dwarfs. We investigate amplification of plasma…
The population of radio-loud stars has to date been studied primarily through either targeted observations of a small number of highly active stars or widefield, single-epoch surveys that cannot easily distinguish stellar emission from…
We use ~12,000 spectra of ~3,500 magnetically active M0-M9 dwarfs from the Sloan Digital Sky Survey taken at 10-15 minute intervals, together with ~300 spectra of ~60 M0-M8 stars obtained hourly with the Hydra multi-object spectrometer, to…
J191213.72-441045.1 is a binary system composed of a white dwarf and an M-dwarf in a 4.03-hour orbit. It shows emission in radio, optical, and X-ray, all modulated at the white dwarf spin period of 5.3 min, as well as various orbital…
Blazars present highly variable $\gamma$-ray emission. This variability, which can range from a few minutes to several years, is also observed at other wavelengths across the entire electromagnetic spectrum. We make use of the first 12…
A growing number of white dwarfs (WDs) exhibit one or more signs of remnant planetary systems, including transits, infrared excesses, and atmospheric metal pollution. WD 1054-226 stands out for its unique, highly structured, and persistent…