<i>Radio Astrophysics: Nonthermal Processes in Galactic and Extragalactic Sources</i>

Pacholczyk, A. G.; Roberts, Jane

doi:10.1063/1.3022939

Cited by 515 publications

(714 citation statements)

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“…This is the same model used to fit the radio emission from the relativistic TDE Sw J1644+57 (Zauderer et al 2011(Zauderer et al , 2013Berger et al 2012), as well as from core-collapse SNe and GRBs. We follow the procedures of Barniol Duran et al (2013) by assuming the outflow energy is minimized when the electron and magnetic field energy densities are in equipartition (Pacholczyk 1970;Scott & Readhead 1977;Chevalier 1998). Given the shape of the observed SEDs, we associate the peak frequency ν p with the synchrotron self-absorption frequency ν a and assume that the frequency corresponding to γ m is ; ) optically thin power laws indicates that p≈3 (Granot & Sari 2002).…”

Section: Synchrotron Emission Modelmentioning

confidence: 99%

DISCOVERY OF AN OUTFLOW FROM RADIO OBSERVATIONS OF THE TIDAL DISRUPTION EVENT ASASSN-14li

Alexander

Berger

Guillochon

et al. 2016

ApJL

229

290

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We report the discovery of transient radio emission from the nearby optically discovered tidal disruption event (TDE) ASASSN-14li (distance of 90 Mpc), making it the first typical TDE detected in the radio, and unambiguously pointing to the formation of a non-relativistic outflow with a kinetic energy of ≈(4-10)×10 47 erg, a velocity of ≈12,000-36,000 km s −1 , and a mass of ≈3×10 −5 -7 × 10 −4 M e . We show that the outflow was ejected on 2014 August 11-25, in agreement with an independent estimate of the timing of super-Eddington accretion based on the optical, ultraviolet, and X-ray observations, and that the ejected mass corresponds to about 1%-10% of the mass accreted in the super-Eddington phase. The temporal evolution of the radio emission also uncovers the circumnuclear density profile, R R 2.5 ( ) r µ -on a scale of about 0.01 pc, a scale that cannot be probed via direct measurements even in the nearest supermassive black holes. Our discovery of radio emission from the nearest well-studied TDE to date, with a radio luminosity lower than all previous limits, indicates that nonrelativistic outflows are ubiquitous in TDEs, and that future, more sensitive, radio surveys will uncover similar events.

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Section: Synchrotron Emission Modelmentioning

confidence: 99%

DISCOVERY OF AN OUTFLOW FROM RADIO OBSERVATIONS OF THE TIDAL DISRUPTION EVENT ASASSN-14li

Alexander

Berger

Guillochon

et al. 2016

ApJL

229

290

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“…The value of K is unknown and is expected to lie between 1 and 2000. A value of 100 is considered appropriate for electrons produced following collisions in a circumstellar medium (Pacholczyk 1970) but Miley (1980 adopted a value of K = 1 for minimum energy conditions. In this case, if we consider K = 100, the magnetic field values are higher by ∼ 30%.…”

Section: Magnetic Field Estimates In the Radio Condensationsmentioning

confidence: 99%

Detection of non-thermal emission from the massive protostellar jet HH80-81 at low radio frequencies using GMRT

Vig

Veena

Mandal

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Low radio frequencies are favourable for the identification of emission from non-thermal processes such as synchrotron emission. The massive protostellar jet associated with IRAS 18162-2048 (also known as the HH80-81 system) has been imaged at low radio frequencies: 325, 610 and 1300 MHz, using the Giant Metrewave Radio Telescope, India. This is the first instance of detection of non-thermal emission from a massive protostellar jet at such low radio frequencies. The central region displays an elongated structure characteristic of the jet. In addition, the associated Herbig-Haro objects such as HH80, HH81, HH80N, and other condensations along the inner regions of the jet exhibit negative spectral indices. The spectral indices of most condensations are ∼ −0.7, higher than the value of −0.3 determined earlier using high frequency measurements. The magnetic field values derived using radio flux densities in the present work, under the assumption of equipartition near minimum energy condition, lie in the range 116 − 180 µG. We probe into the hard X-ray nature of a source that has been attributed to HH80, in an attempt to reconcile the non-thermal characteristics of radio and X-ray measurements. The flux densities of condensations at 610 MHz, measured nearly 11 yrs apart, display variability that could be ascribed to the cooling of condensations, and emphasize the importance of coeval or nearly-coeval measurements for estimation of spectral indices.

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“…A.9 and Eq. A.8 we can estimate the so called equipartition magnetic field H eq (Pacholczyk, 1970) as follows:…”

Section: Discussionmentioning

confidence: 99%

“…The magnetic field was estimated according to the equipartition condition (Pacholczyk, 1970). I obtained the equipartition magnetic field, H eq according to Eq.5.3 and Eq.5.4 as follows:…”

Section: Physical Parameters Chapter 5 Discussionmentioning

confidence: 99%

Multifrequency VLBA observations of two compact symmetric objects

2016

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We present the results of multifrequency VLBA observations of J1944+5448 and J0111+3906. These sources are compact symmetric objects, completely embedded in the narrow line region of the host galaxy. Multi-epoch observations allowed us to derive the hot-spot separation speed that was used to estimate the kinematic age of both sources. Their asymmetric shape is likely due to an inhomogeneous ambient medium with which these sources interact. Finally we present the results on the spectral analysis of J0111+3906 whose spectrum is ﬁtted with either a synchrotron self-absorption mechanism or a free free absorption model

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Radio Astrophysics: Nonthermal Processes in Galactic and Extragalactic Sources

Cited by 515 publications

References 0 publications

DISCOVERY OF AN OUTFLOW FROM RADIO OBSERVATIONS OF THE TIDAL DISRUPTION EVENT ASASSN-14li

DISCOVERY OF AN OUTFLOW FROM RADIO OBSERVATIONS OF THE TIDAL DISRUPTION EVENT ASASSN-14li

Detection of non-thermal emission from the massive protostellar jet HH80-81 at low radio frequencies using GMRT

Multifrequency VLBA observations of two compact symmetric objects

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