The ASKAP Variables and Slow Transients (VAST) Pilot Survey

Abstract The Variables and Slow Transients Survey (VAST) on the Australian Square Kilometre Array Pathfinder (ASKAP) is designed to detect highly variable and transient radio sources on timescales from 5 s to $\sim\!5$ yr. In this paper, we present the survey description, observation strategy and initial results from the VAST Phase I Pilot Survey. This pilot survey consists of $\sim\!162$ h of observations conducted at a central frequency of 888 MHz between 2019 August and 2020 August, with a typical rms sensitivity of $0.24\ \mathrm{mJy\ beam}^{-1}$ and angular resolution of $12-20$ arcseconds. There are 113 fields, each of which was observed for 12 min integration time, with between 5 and 13 repeats, with cadences between 1 day and 8 months. The total area of the pilot survey footprint is 5 131 square degrees, covering six distinct regions of the sky. An initial search of two of these regions, totalling 1 646 square degrees, revealed 28 highly variable and/or transient sources. Seven of these are known pulsars, including the millisecond pulsar J2039–5617. Another seven are stars, four of which have no previously reported radio detection (SCR J0533–4257, LEHPM 2-783, UCAC3 89–412162 and 2MASS J22414436–6119311). Of the remaining 14 sources, two are active galactic nuclei, six are associated with galaxies and the other six have no multi-wavelength counterparts and are yet to be identified.

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Understanding galaxy mergers and AGN feedback with UVIT

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003300 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 345-347

Author(s):

Khatun Rubinur ◽

Mousumi Das ◽

Preeti Kharb ◽

P. T. Rahne

Keyword(s):

Star Formation ◽

Pilot Study ◽

Active Galactic Nuclei ◽

Negative Feedback ◽

Galactic Nuclei ◽

Galaxy Mergers ◽

Imaging Telescope ◽

Multi Wavelength ◽

Initial Results

AbstractSimulations expect an enhanced star-formation and active galactic nuclei (AGN) activity during galaxy mergers, which can lead to formation of binary/dual AGN. AGN feedback can enhance or suppress star-formation. We have carried out a pilot study of a sample of ˜10 dual nuclei galaxies with AstroSat’s Ultraviolet Imaging Telescope (UVIT). Here, we present the initial results for two sample galaxies (Mrk 739, ESO 509) and deep multi-wavelength data of another galaxy (Mrk 212). UVIT observations have revealed signatures of positive AGN feedback in Mrk 739 and Mrk 212, and negative feedback in ESO 509. Deeper UVIT observations have recently been approved; these will provide better constraints on star-formation as well as AGN feedback in these systems.

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Peering into the heart of darkness: Radio VLBI survey of the NEP deep field

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003385 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 366-366

Author(s):

Joseph Gelfand

Keyword(s):

Active Galactic Nuclei ◽

Angular Resolution ◽

Galactic Nuclei ◽

Powerful Radio ◽

Host Galaxies ◽

Radio Jets ◽

Heart Of Darkness ◽

Multi Wavelength ◽

Initial Results ◽

Size Scales

AbstractActive Galactic Nuclei (AGN), accreting supermassive black holes at the centers of galaxies, are believed to produce powerful outflows – often observed as radio jets – which significantly influence the evolution of the surrounding galaxy and inter-galactic medium. However, how these jets – which are produced in the central parsecs of the AGN – impact gas on scales thousands to millions times larger is poorly understood. Doing so requires measuring the properties on all the relevant size scales. In this talk I will present initial results from the deepest-ever radio VLBI survey of an extragalactic field, whose milli-arcsecond angular resolution allows us to probe the central parsecs around these AGN. By comparing the radio properties of the detected radio jets with the multi-wavelength properties of their host galaxies, we are better to understand what galaxies generate powerful radio jets, and how do these outflows affect their host galaxies.

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Polarimetric Properties of Blazars Caught by the WEBT

Galaxies ◽

10.3390/galaxies9020042 ◽

2021 ◽

Vol 9 (2) ◽

pp. 42

Author(s):

Claudia M. Raiteri ◽

Massimo Villata

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Plasma Jets ◽

Line Of Sight ◽

Optical Behaviour ◽

Relativistic Jets ◽

Comprehensive Picture ◽

Multi Wavelength ◽

Extreme Variability ◽

Continuous Range

Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called “blazars”. The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the γ-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies.

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Proper motion in lensed radio jets at redshift 3: A possible dual super-massive black hole system in the early Universe

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935427 ◽

2019 ◽

Vol 630 ◽

pp. A108 ◽

Cited By ~ 4

Author(s):

C. Spingola ◽

J. P. McKean ◽

D. Massari ◽

L. V. E. Koopmans

Keyword(s):

Active Galactic Nuclei ◽

Early Universe ◽

Gravitational Lensing ◽

Proper Motion ◽

Galactic Nuclei ◽

Massive Black Hole ◽

Radio Jets ◽

Long Baseline ◽

Multi Wavelength ◽

Low Probability

In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6 mas in the lensed images by comparing two Very Long Baseline Interferometric (VLBI) radio observations at 1.7 GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of μas. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-components separated by ∼175 pc, with proper motion of the order of tens μas yr−1 for the two components at highest magnification (μ ∼ 350) and of the order of a few mas yr−1 for the two components at lower magnification (μ ∼ 2). We propose single active galactic nuclei (AGN) and dual AGN scenarios to explain the source plane. Although, the latter interpretation is supported by the archival multi-wavelength properties of the object. In this case, MG B2016+112 would represent the highest redshift dual radio-loud AGN system discovered thus far, and would support the merger interpretation for such systems. Also, given the low probability (∼10−5) of detecting a dual AGN system that is also gravitationally lensed, if confirmed, this would suggest that such dual AGN systems must be more abundant in the early Universe than currently thought.

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Monitoring the Extragalactic High Energy Sky

Galaxies ◽

10.3390/galaxies7010009 ◽

2019 ◽

Vol 7 (1) ◽

pp. 9 ◽

Cited By ~ 2

Author(s):

Jean-Philippe Lenain

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

High Energy ◽

Line Of Sight ◽

Data Sets ◽

High Energies ◽

Multi Wavelength ◽

Rich Data ◽

Very High

Blazars are jetted active galactic nuclei with a jet pointing close to the line of sight, hence enhancing their intrinsic luminosity and variability. Monitoring these sources is essential in order to catch them flaring and promptly organize follow-up multi-wavelength observations, which are key to providing rich data sets used to derive e.g., the emission mechanisms at work, and the size and location of the flaring zone. In this context, the Fermi-LAT has proven to be an invaluable instrument, whose data are used to trigger many follow-up observations at high and very high energies. A few examples are illustrated here, as well as a description of different data products and pipelines, with a focus given on FLaapLUC, a tool in use within the H.E.S.S. collaboration.

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6.8. A multi wavelength study of the circumnuclear region of NGC 1365

Symposium - International Astronomical Union ◽

10.1017/s0074180900084916 ◽

1998 ◽

Vol 184 ◽

pp. 277-278

Author(s):

H. Kristen ◽

Aa. Sandqvist ◽

P.O. Lindblad

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Radio Continuum ◽

Nuclear Region ◽

High Excitation ◽

Multi Wavelength ◽

Optical Wavelengths ◽

Barred Spiral Galaxy ◽

Seyfert Nucleus ◽

Ngc 1365

The nuclear region of the supergiant barred spiral galaxy NGC 1365 contains bright “hot spots”, as seen at optical wavelengths, as well as a number of non-thermal radio continuum sources, some of which remain unresolved at 0.25” × 0.10” resolution (Sandqvist et al. 1995, A&A 295, 585).The distribution of [OIII] λ5007 emission from the nuclear region supports the scenario of an [OIII] cone emanating from the Seyfert nucleus. The velocity field of the high excitation gas in the cone has been modeled by Hjelm & Lindblad (1996, A&A 305, 727) in terms of an accelerated bipolar conical outflow. Such conical or biconical high-excitation emission-line structures extending from the position of the nucleus are found in several active galactic nuclei.

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A Multi-Wavelength Study of X-ray Selected AGN

Symposium - International Astronomical Union ◽

10.1017/s0074180900140823 ◽

1989 ◽

Vol 134 ◽

pp. 199-200

Author(s):

R. J. V. Brissenden ◽

I. R. Tuohy ◽

G. V. Bicknell ◽

R. A. Remillard ◽

D. A. Schwartz

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

High Energy ◽

Astronomy Observatory ◽

X Ray ◽

Preliminary Results ◽

Multi Wavelength ◽

Uv Excess ◽

Modulation Collimator

A sample of Active Galactic Nuclei (AGN) have been discovered during a program to identify the optical counterparts of X-ray sources detected by the Modulation Collimator experiment of the High Energy Astronomy Observatory-1 (HEAO-1). UV-excess techniques were used to identify the X-ray sources (Remillard et al. 1986) and the details of the identifications are given elsewhere (Remillard et al. 1988, Brissenden et al. 1988). We report here the preliminary results of a multi-wavelength study of these new AGN.

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The Extremes of AGN Variability

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317001648 ◽

2016 ◽

Vol 12 (S324) ◽

pp. 168-171 ◽

Cited By ~ 3

Author(s):

S. Komossa ◽

D. Grupe ◽

N. Schartel ◽

L. Gallo ◽

J. L. Gomez ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

X Ray ◽

Accretion Flow ◽

Multi Wavelength ◽

Long Term Monitoring ◽

Term Monitoring ◽

Spectral States ◽

Ongoing Monitoring

AbstractWe present results from our ongoing monitoring programs aimed at identifying and understanding Active Galactic Nuclei (AGN) in extreme flux and spectral states. Observations of AGN in extreme states can reveal the nature of the inner accretion flow, the physics of matter under strong gravity, and they provide insight on the properties of ionized absorbers and outflows launched near supermassive black holes (SMBHs). We present new results from our long-term monitoring of IC 3599, WPVS007, and Mrk 335, multi-wavelength follow-ups of the newly identified changing-look AGN HE 1136–2304, and UV–X-ray follow-ups of the binary SMBH candidate OJ 287 after its 2015 optical maximum, now in a new optical-X-ray–high-state.

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Multi-wavelength observations of the narrow-line Seyfert 1 galaxy RX J2314.9+2243

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315007486 ◽

2014 ◽

Vol 10 (S312) ◽

pp. 61-62

Author(s):

S. Komossa ◽

I. Myserlis ◽

L. Fuhrmann ◽

D. Xu ◽

D. Grupe ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Extreme Case ◽

Narrow Line ◽

Relativistic Jets ◽

Uv Spectrum ◽

New Radio ◽

Multi Wavelength ◽

Low Mass ◽

Black Hole Masses

AbstractNarrow-line Seyfert 1 (NLS1) galaxies are a sub-class of active galactic nuclei (AGN) with relatively low-mass black holes, accreting near the Eddington rate. A small fraction of them is radio-loud and harbors relativistic jets. As a class, these provide us with new insights into the cause(s) of radio-loudness, the blazar phenomenon at low black hole masses, and the operation of radio-mode feedback. The NLS1 galaxy RXJ2314.9+2243 is remarkable for its multi-wavelength properties. We present new radio observations taken at Effelsberg, and a summary of the recent results from our multi-wavelength study. RXJ2314.9+2243 is radio-loud, luminous in the infrared, has a flat X-ray spectrum and peculiar UV spectrum, and hosts an exceptionally broad and blueshifted [OIII]λ5007 emission line, indicating the presence of a strong outflow. RXJ2314.9+2243 likely represents an extreme case of AGN induced feedback in the local universe.

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