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We have performed monitoring observations of the 3-mm flux density toward the Galactic Center compact radio source Sgr A* with the Australia Telescope Compact Array since 2005 October. Careful calibrations of both elevation-dependent and…

Astrophysics of Galaxies · Physics 2009-07-22 Juan Li , Zhi-Qiang Shen , Atsushi Miyazaki , Lei Huang , R. J. Sault , Makoto Miyoshi , Masato Tsuboi , Takahiro Tsutsumi

Two dozens of radio loud active galactic nuclei (AGNs) have been observed with Urumqi 25 m radio telescope in order to search for intra-day variability (IDV). The target sources are blazars (namely flat spectrum radio quasars and BL Lac…

High Energy Astrophysical Phenomena · Physics 2021-08-23 Xiang Liu , Xin Wang , Ning Chang , Jun Liu , Lang Cui , Xiaofeng Yang , Thomas P. Krichbaum

Fast radio bursts (FRBs) are extragalactic astrophysical transients whose brightness requires emitters that are highly energetic, yet compact enough to produce the short, millisecond-duration bursts. FRBs have thus far been detected between…

We have observed S4 0954+658 in the BVRI bands in 2001, and in the BI bands in 2002. The observations resulted in almost evenly sampled light curves, 3-8 hours long, with an average sampling interval of ~5-15 min. Because of the dense…

Astrophysics · Physics 2009-11-10 I. E. Papadakis , V. Samaritakis , P. Boumis , J. Papamastorakis

We present a broadband polarization analysis of 36 discrete polarized radio sources over a very broad, densely-sampled frequency band. Our sample was selected on the basis of polarization behaviour apparent in narrowband archival data at…

High Energy Astrophysical Phenomena · Physics 2016-07-06 C. S. Anderson , B. M. Gaensler , I. J. Feain

We present results from four years of twice-weekly 15 GHz radio monitoring of about 1500 blazars with the Owens Valley Radio Observatory 40 m telescope. Using the intrinsic modulation index to measure variability amplitude, we find that,…

High Energy Astrophysical Phenomena · Physics 2014-01-16 Joseph L. Richards , Talvikki Hovatta , Walter Max-Moerbeck , Vasiliki Pavlidou , Timothy J. Pearson , Anthony C. S. Readhead

In this paper we examine to what extent the radio continuum can be used as an extinction free probe of star formation in dwarf galaxies. To that aim we observe $40$ nearby dwarf galaxies with the Very Large Array at 6 cm ($4$-$8$ GHz) in…

A number of brown dwarfs are now known to be variable with observed amplitudes as large as 10-30% at some wavelengths. While spatial inhomogeneities in cloud coverage and thickness are likely responsible for much of the observed…

Solar and Stellar Astrophysics · Physics 2014-04-24 Tyler D. Robinson , Mark S. Marley

We present multi-frequency simultaneous VLBI radio observations of the flat spectrum radio quasar 1633+382 (4C~38.41) as part of the interferometric monitoring of gamma-ray bright active galactic nuclei (iMOGABA) program combined with…

GLEAM-X J1627-52 was discovered as a periodic (~18 min) radio signal over a duration of three months in 2018. It is an enigmatic example of a growing population of 'long-period radio transients' consistent with Galactic origins. Their…

Solar and Stellar Astrophysics · Physics 2025-02-21 J. D. Lyman , V. S. Dhillon , S. Kamann , A. A. Chrimes , A. J. Levan , I. Pelisoli , D. T. H. Steeghs , K. Wiersema

We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R~20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC…

Solar and Stellar Astrophysics · Physics 2015-08-06 L. Prato , G. N. Mace , E. L. Rice , I. S. McLean , J. D. Kirkpatrick , A. J. Burgasser , S. S. Kim

Coherent low-frequency ($\lesssim 200$ MHz) radio emission from stars encodes the conditions of the outer corona, mass-ejection events, and space weather. Previous low-frequency searches for radio emitting stellar systems have lacked the…

Starting from December 2004, a program for the monitoring of intraday variable sources at a frequency of 5 GHz was performed at the Urumqi Observatory. The analysis of the variability characteristics of the flat-spectrum radio source AO…

Solar and Stellar Astrophysics · Physics 2015-05-27 N. Marchili , T. P. Krichbaum , X. Liu , H. -G. Song , J. M. Anderson , A. Witzel , J. A. Zensus

We present sensitive 3.0 cm JVLA radio continuum observations of six regions of low-mass star formation that include twelve young brown dwarfs and four young brown dwarf candidates. We detect a total of 49 compact radio sources in the…

Solar and Stellar Astrophysics · Physics 2017-04-19 L. F. Rodriguez , L. Zapata , A. Palau

We present multi-epoch simultaneous radio, optical, H{\alpha}, UV, and X-ray observations of the active, young, low-mass binary NLTT 33370 AB (blended spectral type M7e). This system is remarkable for its extreme levels of magnetic…

Solar and Stellar Astrophysics · Physics 2015-06-22 P. K. G. Williams , E. Berger , J. Irwin , Z. K. Berta-Thompson , D. Charbonneau

We present the detection of the binary system 2MASS J02132062+3648506 AB using the Karl G. Jansky Very Large Array (VLA) archive data observed at 4-8 GHz. The system is a triple consisting of a tight binary ($\sim0.2"$) of two M dwarfs of…

The spectra of repeating fast radio bursts (FRBs) are complex and time-variable, sometimes peaking within the observing band and showing a fractional emission bandwidth of about 10-30%. These spectral features may provide insight into the…

A huge multiwavelength campaign targeting the blazar AO 0235+164 was organized by the Whole Earth Blazar Telescope (WEBT) in 2003-2005 to study the variability properties of the source. Monitoring observations were carried out at cm and mm…

Astrophysics · Physics 2009-11-11 C. M. Raiteri , M. Villata , M. Kadler , M. A. Ibrahimov , O. M. Kurtanidze , V. M. Larionov

Using three epochs of VLA observations of the Galactic Plane in the first quadrant taken ~15 years apart, we have conducted a search for a population of variable Galactic radio emitters in the flux density range 1-100 mJy at 6 cm. We find…

Astrophysics of Galaxies · Physics 2015-05-18 Robert H. Becker , David J. Helfand , Richard L. White , Deanne D. Proctor