The follow-up European VLBI Network observations of twelve GPS radio sources at 5 GHz

Cui, Lang; Liu, X.; Liu, J.; Song, Haipeng; Ding, Zhaozhao

doi:10.1051/0004-6361/201014075

Cited by 7 publications

(5 citation statements)

References 26 publications

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“…The light curve shows a gentle positive slope of variability (M = 4.3%) with significance ∇S = 6.3 over the entire time-scale of observations (see Figure 5). Cui et al (2010) carried out 5 GHz monitoring over a period of several years and found no significant variability. This object has been monitored for 15 years at 408 MHz (Bondi et al 1996) with a modulation index of 3.2%.…”

Section: Gleam J032320+053413 (Pks B0320+055mentioning

confidence: 99%

The Murchison Widefield Array Transients Survey (MWATS). A search for low frequency variability in a bright Southern hemisphere sample

Bell

Murphy

Hancock

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We report on a search for low-frequency radio variability in 944 bright (> 4 Jy at 154 MHz) unresolved, extragalactic radio sources monitored monthly for several years with the Murchison Widefield Array. In the majority of sources we find very low levels of variability with typical modulation indices < 5%. We detect 15 candidate low frequency variables that show significant long term variability (>2.8 years) with timeaveraged modulation indices M = 3.1 − 7.1%. With 7/15 of these variable sources having peaked spectral energy distributions, and only 5.7% of the overall sample having peaked spectra, we find an increase in the prevalence of variability in this spectral class. We conclude that the variability seen in this survey is most probably a consequence of refractive interstellar scintillation and that these objects must have the majority of their flux density contained within angular diameters less than 50 milliarcsec (which we support with multi-wavelength data). At 154 MHz we demonstrate that interstellar scintillation time-scales become long (∼decades) and have low modulation indices, whilst synchrotron driven variability can only produce dynamic changes on time-scales of hundreds of years, with flux density changes less than one milli-jansky

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Section: Gleam J032320+053413 (Pks B0320+055mentioning

confidence: 99%

The Murchison Widefield Array Transients Survey (MWATS). A search for low frequency variability in a bright Southern hemisphere sample

Bell

Murphy

Hancock

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…In addition, the VLBI flux density at 15 GHz decreases significantly, which again contradicts a classical CSO, whose flux is quite stable on the time scale of years (e.g. Cui et al 2010;An & Baan 2012;Tremblay et al 2016).…”

Section: Discussionmentioning

confidence: 87%

VLBA 24 and 43 GHz observations of massive binary black hole candidate PKS 1155 + 251

Yang

Ling

Yang

et al. 2017

Monthly Notices of the Royal Astronomical Society

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PKS 1155+251 is a radio-loud quasar source at z = 0.203. Observations using very long baseline interferometry (VLBI) at ∼2, 5, 8 and 15 GHz show that the structure of the radio source is quite complicated on parsec scales and that the outer hot spots are apparently undergoing a significant contraction. Because these results cannot be fully explained based on the compact symmetric object (CSO) scenario with a radio core located between the northern and southern complexes, we made observations with the Very Long Baseline Array (VLBA) at 24 and 43 GHz to search for compact substructures and alternative interpretations. The results show that the radio core revealed in the previous VLBI observations remains compact with a flat spectrum in our sub-milli-arcsecond-resolution images; the northern lobe emission becomes faint at 24 GHz and is mostly resolving out at 43 GHz; the southern complex is more bright but has been resolved into the brightest southern-end (S1) and jet or tail alike components westwards. Explaining the southern components aligned westward with a standard CSO scenario alone remains a challenge. As for the flatter spectral index of the southern-end component S1 between 24 and 43 GHz in our observations and the significant 15 GHz VLBA flux variability of S1, an alternative scenario is that the southern complex may be powered by a secondary black hole residing at S1. But more sensitive and high-resolution VLBI monitoring is required to discriminate the CSO and the binary black hole scenarios.

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“…Merloni et al 2003;Liodakis et al 2017). Figure 6 plots the projected linear size of jets versus the BH mass for the six VLBI-detected dwarf AGNs, some young radio sources (O'Dea 1998;Snellen et al 2003;de Vries et al 2009;Kunert-Bajraszewska et al 2010;Cui et al 2010;An & Baan 2012;Orienti & Dallacasa 2012), and Fanaroff-Riley (FR) I and II radio galaxies (Black et al 1992;Nilsson et al 1993;de Koff et al 1996;Martel et al 1999;Harvanek & Stocke 2002;Chandola et al 2013). The additional data for the more massive BHs at 𝑧 < 4 were firstly collected by Liao & Gu (2020).…”

Section: Sourcementioning

confidence: 99%

Intermediate-mass black holes: finding of episodic, large-scale and powerful jet activity in a dwarf galaxy

Yang¹,

Paragi²,

Frey³

et al. 2023

Preprint

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Dwarf galaxies are characterised by a very low luminosity and low mass. Because of significant accretion and ejection activity of massive black holes, some dwarf galaxies also host low-luminosity active galactic nuclei (AGNs). In a few dwarf AGNs, very long baseline interferometry (VLBI) observations have found faint non-thermal radio emission. SDSS J090613.77+561015.2 is a dwarf AGN owning an intermediate-mass black hole (IMBH) with a mass of 𝑀 BH = 3.6 +5.9 −2.3 × 10 5 𝑀 and showing a rarely-seen two-component radio structure in its radio nucleus. To further probe their nature, i.e. the IMBH jet activity, we performed additional deep observations with the European VLBI Network (EVN) at 1.66 GHz and 4.99 GHz. We find the more diffuse emission regions and structure details. These new EVN imaging results allow us to reveal a two-sided jet morphology with a size up to about 150 mas (projected length ∼140 pc) and a radio luminosity of about 3 × 10 38 erg s −1 . The peak feature has an optically thin radio spectrum and thus more likely represents a relatively young ejecta instead of a jet base. The EVN study on SDSS J090613.77+561015.2 demonstrates the existence of episodic, relatively large-scale and powerful IMBH jet activity in dwarf AGNs. Moreover, we collected a small sample of VLBI-detected dwarf AGNs and investigated their connections with normal AGNs. We notice that these radio sources in the dwarf AGNs tend to have steep spectra and small linear sizes, and possibly represent ejecta from scaled-down episodic jet activity.

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The follow-up European VLBI Network observations of twelve GPS radio sources at 5 GHz

Cited by 7 publications

References 26 publications

The Murchison Widefield Array Transients Survey (MWATS). A search for low frequency variability in a bright Southern hemisphere sample

The Murchison Widefield Array Transients Survey (MWATS). A search for low frequency variability in a bright Southern hemisphere sample

VLBA 24 and 43 GHz observations of massive binary black hole candidate PKS 1155 + 251

Intermediate-mass black holes: finding of episodic, large-scale and powerful jet activity in a dwarf galaxy

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