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Quasi-periodic pulsations (QPPs) at sub-second periods are frequently detected in the time series of X-rays during stellar flares. However, such rapid pulsations are rarely reported in the hard X-ray (HXR) emission of the small solar flare.…

太阳与恒星天体物理 · 物理学 2025-06-18 Dong Li

Young Stellar Objects (YSOs) and in particular protostars are known to show a variety of high-energy processes. Observations in the X-ray and centimetric radio wavelength ranges are thought to constrain some of these processes, e.g.,…

高能天体物理现象 · 物理学 2015-05-28 Jan Forbrich , Rachel A. Osten , Scott J. Wolk

The far-infrared - radio correlation connects star formation and magnetic fields in galaxies, and has been confirmed over a large range of far-infrared luminosities. Recent investigations indicate that it may even hold in the regime of…

星系天体物理 · 物理学 2016-09-28 Dominik R. G. Schleicher , Rainer Beck

We present the results of a 8.4 GHz Very Large Array radio survey of early-type galaxies extracted from the ACS Virgo Cluster Survey. The aim of this survey is to investigate the origin of radio emission in early-type galaxies and its link…

宇宙学与河外天体物理 · 物理学 2015-05-14 Alessandro Capetti , Preeti Kharb , David J. Axon , David Merritt , Ranieri D. Baldi

We report the results of a multi-wavelength campaign on the blazar Mrk 421 during outburst. We observed four strong flares at X-ray energies that were not seen at other wavelengths (partially because of missing data). From the fastest rise…

We report multi-wavelength observations of four solar flares on 2014 July 07. We firstly select these flares according to the soft X-ray (SXR) and extreme ultraviolet (EUV) emissions recorded by the Extreme Ultraviolet Variability…

太阳与恒星天体物理 · 物理学 2021-05-05 Dong Li , Alexander Warmuth , Lei Lu , Zongjun Ning

We investigate accelerated electron energy spectra for different sources in a large flare using simultaneous observations obtained with two instruments, the Nobeyama Radio Heliograph (NoRH) at 17 and 34 GHz, and the Reuven Ramaty High…

太阳与恒星天体物理 · 物理学 2015-05-13 M. R. Kundu , V. V. Grechnev , S. M. White , E. J. Schmahl , N. S. Meshalkina , L. K. Kashapova

Regular observations by the All Sky Monitor aboard the Rossi X-ray Timing Explorer satellite have yielded well-sampled light-curves with a time baseline of over ten years. We find that up to eight of the sixteen brightest persistent low…

高能天体物理现象 · 物理学 2015-05-14 Martin Durant , Remon Cornelisse , Ron Remillard , Alan Levine

We present a study of the multiwavelength (MW) variability of the blazar AO 0235+164 based on the radio-to-$\gamma$-ray data covering a long time period from 1997 to 2023. The radio data are represented by the 1-22 GHz measurements from the…

We present the first unambiguous case of external variability of a radio gravitational lens, CLASS B1600+434. The VLA 8.5-GHz difference light curve of the lensed images, taking the proper time-delay into account, shows the presence of…

天体物理学 · 物理学 2007-05-23 L. V. E. Koopmans , A. G. de Bruyn

A fraction of very low mass stars and brown dwarfs are known to be radio active, in some cases producing periodic pulses. Extensive studies of two such objects have also revealed optical periodic variability and the nature of this…

Mega-parsec scale radio sources in the form of halos and relics are often detected in dynamically disturbed galaxy clusters. Although they are associated with merger-induced turbulence and shocks, respectively, their formation is not fully…

We have carried out a multifrequency analysis of the radio variability of blazars, exploiting the data obtained during the extensive monitoring programs carried out at the University of Michigan Radio Astronomy Observatory (UMRAO, at 4.8,…

Blazars are known to show periods of quiescence followed by outbursts visible throughout the electromagnetic spectrum. We present a novel maximum likelihood approach to capture this bimodal behavior by examining blazar radio variability in…

高能天体物理现象 · 物理学 2017-03-30 I. Liodakis , V. Pavlidou , T. Hovatta , W. Max-Moerbeck , T. J. Pearson , J. L. Richards , A. C. S. Readhead

The optical-UV and X-ray instruments on-board XMM-Ndewton provide an excellent opportunity to perform simultaneous observations of violently variable objects over a broad wavelength range. The UV and X-ray bright BL Lac object PKS 2155-304…

天体物理学 · 物理学 2008-11-26 Y. H. Zhang , J. M. Bai , S. N. Zhang , A. Treves , L. Maraschi , A. Celotti

Radio halos are megaparsec-scale diffuse, non-thermal radio sources located at the centers of galaxy clusters, tracing relativistic particles and magnetic fields in the intra-cluster medium. Their origin is generally attributed to cluster…

We present multi-frequency radio data for a sample of narrow-line Seyfert 1 galaxies. We first focus on the sub-class of gamma-ray emitting narrow-line Seyfert 1 galaxies, studying the long-term radio variability of five sources and…

星系天体物理 · 物理学 2024-12-10 Xi Shao , Philip G. Edwards , Jamie Stevens , Minfeng Gu , Timothy J. Galvin , Minh T. Huynh

To increase the number of sources with Very Long Baseline Interferometry (VLBI) astrometry available for comparison with the Gaia results, we have observed 31 young stars with recently reported radio emission. These stars are all in the…

太阳与恒星天体物理 · 物理学 2024-06-12 Sergio A. Dzib , Laurent Loinard , Ralf Launhardt , Jazmín Ordóñez-Toro

Based on one-month long MMT time-series observations of the open cluster M37, we monitored light variations of nearly 2500 red dwarfs and successfully identified 420 flare events from 312 cluster M dwarf stars. For each flare light curve,…

太阳与恒星天体物理 · 物理学 2015-10-16 S. -W. Chang , Y. -I. Byun , J. D. Hartman

Several sources of repeating coherent bursts of radio emission with periods of many minutes have now been reported in the literature. These "ultra-long period" (ULP) sources have no clear multi-wavelength counterparts and challenge…