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Artikel ; Online: A long-period radio transient active for three decades.

Hurley-Walker, N / Rea, N / McSweeney, S J / Meyers, B W / Lenc, E / Heywood, I / Hyman, S D / Men, Y P / Clarke, T E / Coti Zelati, F / Price, D C / Horváth, C / Galvin, T J / Anderson, G E / Bahramian, A / Barr, E D / Bhat, N D R / Caleb, M / Dall'Ora, M /

de Martino, D / Giacintucci, S / Morgan, J S / Rajwade, K M / Stappers, B / Williams, A

Nature

2023 Band 619, Heft 7970, Seite(n) 487–490

Abstract: Several long-period radio transients have recently been discovered, with strongly polarized coherent radio pulses appearing on timescales between tens to thousands of ... ...

Abstract	Several long-period radio transients have recently been discovered, with strongly polarized coherent radio pulses appearing on timescales between tens to thousands of seconds
Sprache	Englisch
Erscheinungsdatum	2023-07-19
Erscheinungsland	England
Dokumenttyp	Journal Article
ZDB-ID	120714-3
ISSN	1476-4687 ; 0028-0836
ISSN (online)	1476-4687
ISSN	0028-0836
DOI	10.1038/s41586-023-06202-5
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: Super-Eddington mechanical power of an accreting black hole in M83.

Soria, R / Long, K S / Blair, W P / Godfrey, L / Kuntz, K D / Lenc, E / Stockdale, C / Winkler, P F

Science (New York, N.Y.)

2014 Band 343, Heft 6177, Seite(n) 1330–1333

Abstract: Mass accretion onto black holes releases energy in the form of radiation and outflows. Although the radiative flux cannot substantially exceed the Eddington limit, at which the outgoing radiation pressure impedes the inflow of matter, it remains unclear ... ...

Abstract	Mass accretion onto black holes releases energy in the form of radiation and outflows. Although the radiative flux cannot substantially exceed the Eddington limit, at which the outgoing radiation pressure impedes the inflow of matter, it remains unclear whether the kinetic energy flux is bounded by this same limit. Here, we present the detection of a radio-optical structure, powered by outflows from a non-nuclear black hole. Its accretion disk properties indicate that this black hole is less than 100 solar masses. The optical-infrared line emission implies an average kinetic power of 3 × 10(40) erg second(-1), higher than the Eddington luminosity of the black hole. These results demonstrate kinetic power exceeding the Eddington limit over a sustained period, which implies greater ability to influence the evolution of the black hole's environment.
Sprache	Englisch
Erscheinungsdatum	2014-03-21
Erscheinungsland	United States
Dokumenttyp	Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	128410-1
ISSN	1095-9203 ; 0036-8075
ISSN (online)	1095-9203
ISSN	0036-8075
DOI	10.1126/science.1248759
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: A mildly relativistic wide-angle outflow in the neutron-star merger event GW170817.

Mooley, K P / Nakar, E / Hotokezaka, K / Hallinan, G / Corsi, A / Frail, D A / Horesh, A / Murphy, T / Lenc, E / Kaplan, D L / De, K / Dobie, D / Chandra, P / Deller, A / Gottlieb, O / Kasliwal, M M / Kulkarni, S R / Myers, S T / Nissanke, S /

Piran, T / Lynch, C / Bhalerao, V / Bourke, S / Bannister, K W / Singer, L P

Nature

2018 Band 554, Heft 7691, Seite(n) 207–210

Abstract: GW170817 was the first gravitational-wave detection of a binary neutron-star merger. It was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of 40 megaparsecs. It has been proposed that the ... ...

Abstract	GW170817 was the first gravitational-wave detection of a binary neutron-star merger. It was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of 40 megaparsecs. It has been proposed that the observed γ-ray, X-ray and radio emission is due to an ultra-relativistic jet being launched during the merger (and successfully breaking out of the surrounding material), directed away from our line of sight (off-axis). The presence of such a jet is predicted from models that posit neutron-star mergers as the drivers of short hard-γ-ray bursts. Here we report that the radio light curve of GW170817 has no direct signature of the afterglow of an off-axis jet. Although we cannot completely rule out the existence of a jet directed away from the line of sight, the observed γ-ray emission could not have originated from such a jet. Instead, the radio data require the existence of a mildly relativistic wide-angle outflow moving towards us. This outflow could be the high-velocity tail of the neutron-rich material that was ejected dynamically during the merger, or a cocoon of material that breaks out when a jet launched during the merger transfers its energy to the dynamical ejecta. Because the cocoon model explains the radio light curve of GW170817, as well as the γ-ray and X-ray emission (and possibly also the ultraviolet and optical emission), it is the model that is most consistent with the observational data. Cocoons may be a ubiquitous phenomenon produced in neutron-star mergers, giving rise to a hitherto unidentified population of radio, ultraviolet, X-ray and γ-ray transients in the local Universe.
Sprache	Englisch
Erscheinungsdatum	2018--08
Erscheinungsland	England
Dokumenttyp	Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	120714-3
ISSN	1476-4687 ; 0028-0836
ISSN (online)	1476-4687
ISSN	0028-0836
DOI	10.1038/nature25452
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: A radio counterpart to a neutron star merger.

Hallinan, G / Corsi, A / Mooley, K P / Hotokezaka, K / Nakar, E / Kasliwal, M M / Kaplan, D L / Frail, D A / Myers, S T / Murphy, T / De, K / Dobie, D / Allison, J R / Bannister, K W / Bhalerao, V / Chandra, P / Clarke, T E / Giacintucci, S / Ho, A Y Q /

Horesh, A / Kassim, N E / Kulkarni, S R / Lenc, E / Lockman, F J / Lynch, C / Nichols, D / Nissanke, S / Palliyaguru, N / Peters, W M / Piran, T / Rana, J / Sadler, E M / Singer, L P

Science (New York, N.Y.)

2017

Abstract: Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 ... ...

Abstract	Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultra-relativistic jet viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will distinguish between these models and very long baseline interferometry will have the capability to directly measure the angular velocity and geometry of the debris.
Sprache	Englisch
Erscheinungsdatum	2017-10-16
Erscheinungsland	United States
Dokumenttyp	Journal Article
ZDB-ID	128410-1
ISSN	1095-9203 ; 0036-8075
ISSN (online)	1095-9203
ISSN	0036-8075
DOI	10.1126/science.aap9855
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Artikel ; Online: Radio detections during two state transitions of the intermediate-mass black hole HLX-1.

Webb, Natalie / Cseh, David / Lenc, Emil / Godet, Olivier / Barret, Didier / Corbel, Stephane / Farrell, Sean / Fender, Robert / Gehrels, Neil / Heywood, Ian

Science (New York, N.Y.)

2012 Band 337, Heft 6094, Seite(n) 554–556

Abstract: Relativistic jets are streams of plasma moving at appreciable fractions of the speed of light. They have been observed from stellar-mass black holes (~3 to 20 solar masses, M(⊙)) as well as supermassive black holes (~10(6) to 10(9) M(⊙)) found in the ... ...

Abstract	Relativistic jets are streams of plasma moving at appreciable fractions of the speed of light. They have been observed from stellar-mass black holes (~3 to 20 solar masses, M(⊙)) as well as supermassive black holes (~10(6) to 10(9) M(⊙)) found in the centers of most galaxies. Jets should also be produced by intermediate-mass black holes (~10(2) to 10(5) M(⊙)), although evidence for this third class of black hole has, until recently, been weak. We report the detection of transient radio emission at the location of the intermediate-mass black hole candidate ESO 243-49 HLX-1, which is consistent with a discrete jet ejection event. These observations also allow us to refine the mass estimate of the black hole to be between ~9 × 10(3) M(⊙) and ~9 × 10(4) M(⊙).
Sprache	Englisch
Erscheinungsdatum	2012-08-03
Erscheinungsland	United States
Dokumenttyp	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	128410-1
ISSN	1095-9203 ; 0036-8075
ISSN (online)	1095-9203
ISSN	0036-8075
DOI	10.1126/science.1222779
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Buch ; Online: Ionospheric Modelling using GPS to Calibrate the MWA. II

Regional ionospheric modelling using GPS and GLONASS to estimate ionospheric gradients

2016

Abstract: We estimate spatial gradients in the ionosphere using the Global Positioning System (GPS) and GLONASS (Russian global navigation system) observations, utilising data from multiple GPS stations in the vicinity of Murchison Radio-astronomy Observatory (MRO) ...

Abstract	We estimate spatial gradients in the ionosphere using the Global Positioning System (GPS) and GLONASS (Russian global navigation system) observations, utilising data from multiple GPS stations in the vicinity of Murchison Radio-astronomy Observatory (MRO). In previous work the ionosphere was characterised using a single-station to model the ionosphere as a single layer of fixed height and this was compared with ionospheric data derived from radio astronomy observations obtained from the Murchison Widefield Array (MWA). Having made improvements to our data quality (via cycle slip detection and repair) and incorporating data from the GLONASS system, we now present a multi-station approach. These two developments significantly improve our modelling of the ionosphere. We also explore the effects of a variable-height model. We conclude that modelling the small-scale features in the ionosphere that have been observed with the MWA will require a much denser network of Global Navigation Satellite System (GNSS) stations than is currently available at the MRO. Comment: 15 pages, 12 Figures, paper accepted for publication in Publications of the Astronomical Society of Australia (PASA)
Schlagwörter	Astrophysics - Instrumentation and Methods for Astrophysics
Thema/Rubrik (Code)	551
Erscheinungsdatum	2016-05-08
Erscheinungsland	us
Dokumenttyp	Buch ; Online
Datenquelle	BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

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Artikel ; Online: A single fast radio burst localized to a massive galaxy at cosmological distance.

Bannister, K W / Deller, A T / Phillips, C / Macquart, J-P / Prochaska, J X / Tejos, N / Ryder, S D / Sadler, E M / Shannon, R M / Simha, S / Day, C K / McQuinn, M / North-Hickey, F O / Bhandari, S / Arcus, W R / Bennert, V N / Burchett, J / Bouwhuis, M / Dodson, R /

Ekers, R D / Farah, W / Flynn, C / James, C W / Kerr, M / Lenc, E / Mahony, E K / O'Meara, J / Osłowski, S / Qiu, H / Treu, T / U, V / Bateman, T J / Bock, D C-J / Bolton, R J / Brown, A / Bunton, J D / Chippendale, A P / Cooray, F R / Cornwell, T / Gupta, N / Hayman, D B / Kesteven, M / Koribalski, B S / MacLeod, A / McClure-Griffiths, N M / Neuhold, S / Norris, R P / Pilawa, M A / Qiao, R-Y / Reynolds, J / Roxby, D N / Shimwell, T W / Voronkov, M A / Wilson, C D

Science (New York, N.Y.)

2019 Band 365, Heft 6453, Seite(n) 565–570

Abstract: Fast radio bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Nonrepeating FRB observations have had insufficient positional accuracy to localize them to an individual host ... ...

Abstract	Fast radio bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Nonrepeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single-pulse FRB 180924 to a position 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from those of the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.
Sprache	Englisch
Erscheinungsdatum	2019-06-27
Erscheinungsland	United States
Dokumenttyp	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	128410-1
ISSN	1095-9203 ; 0036-8075
ISSN (online)	1095-9203
ISSN	0036-8075
DOI	10.1126/science.aaw5903
Datenquelle	MEDical Literature Analysis and Retrieval System OnLINE

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Buch ; Online: Ionospheric modelling using GPS to calibrate the MWA. 1

Arora, B. S. / Morgan, J. / Ord, S. M. / Tingay, S. J. / Hurley-Walker, N. / Bell, M. / Bernardi, G. / Bhat, R. / Briggs, F. / Callingham, J. R. / Deshpande, A. A. / Dwarakanath, K. S. / Ewall-Wice, A. / Feng, L. / For, B. -Q. / Hancock, P. / Hazelton, B. J. / Hindson, L. / Jacobs, D. /

Johnston-Hollitt, M. / Kapińska, A. D. / Kudryavtseva, N. / Lenc, E. / McKinley, B. / Mitchell, D. / Oberoi, D. / Offringa, A. R. / Pindor, B. / Procopio, P. / Riding, J. / Staveley-Smith, L. / Wayth, R. B. / Wu, C. / Zheng, Q. / Bowman, J. D. / Cappallo, R. J. / Corey, B. E. / Emrich, D. / Goeke, R. / Greenhill, L. J. / Kaplan, D. L. / Kasper, J. C. / Kratzenberg, E. / Lonsdale, C. J. / Lynch, M. J. / McWhirter, S. R. / Morales, M. F. / Morgan, E. / Prabu, T. / Rogers, A. E. E. / Roshi, A. / Shankar, N. Udaya / Srivani, K. S. / Subrahmanyan, R. / Waterson, M. / Webster, R. L. / Whitney, A. R. / Williams, A. / Williams, C. L.

Comparison of first order ionospheric effects between GPS models and MWA observations

2015

Abstract: We compare first order (refractive) ionospheric effects seen by the Murchison Widefield Array (MWA) with the ionosphere as inferred from Global Positioning System (GPS) data. The first order ionosphere manifests itself as a bulk position shift of the ... ...

Abstract	We compare first order (refractive) ionospheric effects seen by the Murchison Widefield Array (MWA) with the ionosphere as inferred from Global Positioning System (GPS) data. The first order ionosphere manifests itself as a bulk position shift of the observed sources across an MWA field of view. These effects can be computed from global ionosphere maps provided by GPS analysis centres, namely the Center for Orbit Determination in Europe (CODE), using data from globally distributed GPS receivers. However, for the more accurate local ionosphere estimates required for precision radio astronomy applications, data from local GPS networks needs to be incorporated into ionospheric modelling. For GPS observations, the ionospheric parameters are biased by GPS receiver instrument delays, among other effects, also known as receiver Differential Code Biases (DCBs). The receiver DCBs need to be estimated for any non-CODE GPS station used for ionosphere modelling, a requirement for establishing dense GPS networks in arbitrary locations in the vicinity of the MWA. In this work, single GPS station-based ionospheric modelling is performed at a time resolution of 10 minutes. Also the receiver DCBs are estimated for selected Geoscience Australia (GA) GPS receivers, located at Murchison Radio Observatory (MRO1), Yarragadee (YAR3), Mount Magnet (MTMA) and Wiluna (WILU). The ionospheric gradients estimated from GPS are compared with the ionospheric gradients inferred from radio source position shifts observed with the MWA. The ionospheric gradients at all the GPS stations show a correlation with the gradients observed with the MWA. The ionosphere estimates obtained using GPS measurements show promise in terms of providing calibration information for the MWA. Comment: 24 pages
Schlagwörter	Astrophysics - Instrumentation and Methods for Astrophysics
Thema/Rubrik (Code)	551
Erscheinungsdatum	2015-07-05
Erscheinungsland	us
Dokumenttyp	Buch ; Online
Datenquelle	BASE - Bielefeld Academic Search Engine (Lebenswissenschaftliche Auswahl)

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