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New spectra of 81 ultracool dwarfs (spectral types M7 and later) are discussed. Spectral classifications of 49 objects are available in the literature, while 32 objects are newly classified. The known spectral types were used to test an…

Solar and Stellar Astrophysics · Physics 2017-01-11 C. Koen , B. Miszalski , P. Väisänen , T. Koen

Over a dozen T dwarfs, brown dwarfs that exhibit methane absorption features at 1.6 and 2.2 $\micron$, have been discovered by the 2MASS survey. We discuss how the search for these objects has been made, point out some of the limitations of…

Astrophysics · Physics 2007-05-23 A. J. Burgasser

We observed with the JVLA at 3.6 and 1.3 cm a sample of 11 proto-brown dwarf candidates in Taurus in a search for thermal radio jets driven by the most embedded brown dwarfs. We detected for the first time four thermal radio jets in…

We report the first direct detection of a strong, 5 kG magnetic field on the surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf exhibiting transient radio and optical emission bursts modulated by fast rotation. We have…

Solar and Stellar Astrophysics · Physics 2017-10-04 S. V. Berdyugina , D. M. Harrington , O. Kuzmychov , J. R. Kuhn , G. Hallinan , A. F. Kowalski , S. L. Hawley

We present results from a search for radio emission in 77 stellar systems hosting 140 exoplanets, predominantly within 17.5 pc using the Very Large Array (VLA) at $4-8$ GHz. This is the largest and most sensitive search to date for radio…

Earth and Planetary Astrophysics · Physics 2024-04-29 Kevin N. Ortiz Ceballos , Yvette Cendes , Edo Berger , Peter K. G. Williams

We report observations of a radio burst that occurred on the flare star AD Leonis over a frequency range of 1120-1620 MHz (lambda ~18-27 cm). These observations, made by the 305m telescope of the Arecibo Observatory, are unique in providing…

Astrophysics · Physics 2009-11-13 R. A. Osten , T. S. Bastian

Using data from the 2MASS All-Sky Point Source Catalogue, we have extended our census of nearby ultracool dwarfs to cover the full celestial sphere above Galactic latitute 15 degrees. Starting with an initial catalogue of 2,139,484 sources,…

Recent discoveries from red optical proper motion and wide-field near-infrared surveys have uncovered a new population of ultracool subdwarfs, metal-poor stars and brown dwarfs extending into the late-type M, L and possibly T spectral…

Astrophysics · Physics 2007-05-23 Adam J. Burgasser

We report the first discovery of a fast radio burst (FRB), FRB 20200125A, by the Green Bank Northern Celestial Cap (GBNCC) Pulsar Survey conducted with the Green Bank Telescope at 350 MHz. FRB 20200125A was detected at a Galactic latitude…

The presence of large-scale magnetic fields and ultra-relativistic electrons in the intra-cluster medium (ICM) is confirmed through the detection of diffuse radio synchrotron sources, so-called radio halos and relics. Due to their…

Ultracool dwarfs (UCDs) are objects with spectral types equal or later than M7. Most of them have been discovered using wide-field imaging surveys. The Virtual Observatory (VO) has proven to be of great utility to efficiently exploit these…

We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and…

Astrophysics of Galaxies · Physics 2016-02-11 D. Hunik , M. Jamrozy

The goal of the present study is to extend our current knowledge of the diffuse radio source (halo and relic) populations to $z$ $>$ 0.3. Here we report GMRT and EVLA radio observations of six galaxy clusters taken from the MAssive Cluster…

Astrophysics of Galaxies · Physics 2016-11-23 Viral Parekh , K. S. Dwarakanath , Ruta Kale , Huib Intema

We report on the discovery of eight repeating fast radio burst (FRB) sources found using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. These sources span a dispersion measure (DM) range of 103.5 to 1281 pc cm$^{-3}$.…

We present new results of a study of the sub-millimetre continuum emission from a sample of 9 radio galaxies and 4 radio-quiet quasars at redshifts $z = 0.75 - 4.26$. The observations were made at 800$\mu m$, using the single-element…

Astrophysics · Physics 2015-06-24 David Hughes , J. S. Dunlop , Steve Rawlings

We have carried out a search for late-type T dwarfs in the UKIDSS Galactic Plane Survey 6th Data Release. The search yielded two persuasive candidates, both of which have been confirmed as T dwarfs. The brightest, UGPS J0521+3640 has been…

The orientation of the jet axis to the line of sight of the observer plays a major role in explaining the phenomena observed from blazars and radio galaxies. In the gamma-ray band, only a handful of radio galaxies have been identified, all…

High Energy Astrophysical Phenomena · Physics 2023-01-04 Vaidehi S. Paliya , D. J. Saikia , C. S. Stalin

[Abridged] We present an 8.5-hour simultaneous radio, X-ray, UV, and optical observation of the L dwarf binary 2MASSW J0746+20. We detect strong radio emission, dominated by short-duration periodic pulses at 4.86 GHz with P=124.32+/-0.11…

As part of our comprehensive, ongoing characterisation of the low-mass end of the main sequence in the Solar neighbourhood, we used the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias to acquire low- and mid-resolution…

This paper continues our study of radio pulsar emission-beam configurations with the primary intent of extending study to the lowest possible frequencies. Here we focus on a group of 133 more recently discovered pulsars, most of which were…

High Energy Astrophysical Phenomena · Physics 2025-07-30 Haley Wahl , Joanna Rankin , Arun Venkataraman , Timothy Olszanski
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