A search for radio emission from exoplanets around evolved
stars

O’Gorman, Eamon; Coughlan, Colm P.; Vlemmings, Wouter; Sirothia, S. K.; Ray, T. P.; Olofsson, H.

doi:10.1051/0004-6361/201731965

Cited by 27 publications

(20 citation statements)

References 68 publications

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“…Stronger magnetic Figure 5. The rms flux densities for some of the previous attempts at detecting radio emission from exoplanets as a function of the frequency of observations (Lazio et al 2004;Lynch et al 2018;Bastian et al 2000;Lazio & Farrell 2007;George & Stevens 2007;Hallinan et al 2013;O'Gorman et al 2018;Lecavelier des Etangs et al 2013;Lecavelier Des Etangs et al 2011;Lazio et al 2010;Smith et al 2009;Stroe et al 2012) along with the rms sensitivity we reached in this work (black solid line) for the 150MHz and 400 MHz uGMRT observations. Also shown is the detection of radio emission from the system GJ 1151 by Vedantham et al (2020).…”

Section: Incorrect Maximum Cyclotron Frequency Estimatesmentioning

confidence: 85%

“…The low-frequency radio emission from the solar system planets is highly variable over time. For example, Jupiter's decameter emission varies on timescales of several minutes and can produce emissions that are ten times higher than the median level (Zucker et al 2004;O'Gorman et al 2018). The radio emission from exoplanets could also be episodic.…”

Section: Variable/episodic Emissionmentioning

confidence: 99%

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In search of radio emission from exoplanets: GMRT observations of the binary system HD 41004

Narang

Manoj

Chandra

et al. 2020

Monthly Notices of the Royal Astronomical Society

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This paper reports Giant Metrewave Radio Telescope (GMRT) observations of the binary system HD 41004 that are among the deepest images ever obtained at 150 MHz and 400 MHz in the search for radio emission from exoplanets. The HD 41004 binary system consists of a K1 V primary star and an M2 V secondary; both stars are host to a massive planet or brown dwarf. Analogous to planets in our solar system that emit at radio wavelengths due to their strong magnetic fields, one or both of the planet or brown dwarf in the HD 41004 binary system are also thought to be sources of radio emission. Various models predict HD 41004Bb to have one of the largest expected flux densities at 150 MHz. The observations at 150 MHz cover almost the entire orbital period of HD 41004Bb, and about $20\%$ of the orbit is covered at 400 MHz. We do not detect radio emission, setting 3σ limits of 1.8 mJy at 150 MHz and 0.12 mJy at 400 MHz. We also discuss some of the possible reasons why no radio emission was detected from the HD 41004 binary system.

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Section: Incorrect Maximum Cyclotron Frequency Estimatesmentioning

confidence: 85%

Section: Variable/episodic Emissionmentioning

confidence: 99%

In search of radio emission from exoplanets: GMRT observations of the binary system HD 41004

Narang

Manoj

Chandra

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…If detectable, this would serve as a new direct detection method for exoplanets, show that exoplanets are magnetised, and also act as a method to probe the stellar wind of the host star. So far, there has yet to be a conclusive detection of exoplanetary radio emission, despite numerous efforts (Smith et al 2009;Lazio et al 2010;Lecavelier des Etangs et al 2013;Sirothia et al 2014;O'Gorman et al 2018).…”

Section: Introductionmentioning

confidence: 99%

MOVES – II. Tuning in to the radio environment of HD189733b

Kavanagh

Vidotto

Fionnagáin

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present stellar wind modelling of the hot Jupiter host HD189733, and predict radio emission from the stellar wind and the planet, the latter arising from the interaction of the stellar wind with the planetary magnetosphere. Our stellar wind models incorporate surface stellar magnetic field maps at the epochs as boundary conditions. We find that the mass-loss rate, angular momentumloss rate, and open magnetic flux of HD189733 vary by 9%, 40%, and 19% over these three epochs. Solving the equations of radiative transfer, we find that from 10 MHz-100 GHz the stellar wind emits fluxes in the range of 10 −3 -5 µJy, and becomes optically thin above 10 GHz. Our planetary radio emission model uses the radiometric Bode's law, and neglects the presence of a planetary atmosphere. For assumed planetary magnetic fields of 1-10 G, we estimate that the planet emits at frequencies of 2-25 MHz, with peak flux densities of ∼ 10 2 mJy. We find that the planet orbits through regions of the stellar wind that are optically thick to the emitted frequency from the planet. As a result, unattenuated planetary radio emission can only propagate out of the system and reach the observer for 67% of the orbit for a 10 G planetary field, corresponding to when the planet is approaching and leaving primary transit. We also find that the plasma frequency of the stellar wind is too high to allow propagation of the planetary radio emission below 21 MHz. This means a planetary field of at least 8 G is required to produce detectable radio emission.

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“…However, radio signatures of cyclotron emission from close-in exoplanets had not yet been detected due to instrumental sensitivity limitations at the ∼ 100 MHz frequency range (Bastian et al 2000), though subtle hints of such emission had been claimed (e.g. O'Gorman et al (2018)), and was postulated that the beaming of the emission could explain the non-detections ). Since only a small fraction of the exoplanets orbits is sampled 6 8 10 12 Table 1: Detectability of non-thermal emission from exoplanet bow shock at a distance of 150 pc.…”

Section: Discussionmentioning

confidence: 99%

Nonthermal Emission from the Interaction of Magnetized Exoplanets with the Wind of Their Host Star

Wang

Loeb

2019

ApJL

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We study the non-thermal emission from the interaction between magnetized Jupiter-like exoplanets and the wind from their host star. The supersonic motion of planets through the wind forms a bow shock that accelerates electrons which produces non-thermal radiation across a broad wavelength range. We discuss three wind mass loss rates:Ṁ w ∼ 10 −14 , 10 −9 , 10 −6 M ⊙ yr −1 corresponding to solar-type, T Tauri and massive O/B type stars, respectively. We find that the expected radio synchrotron emission from a Jupiter-like planet is detectable by the Jansky Very Large Array and the Square Kilometer Array at ∼ 1 − 10 GHz out to a distance ∼ 100 pc, whereas the infrared emission is detectable by the James Webb Space Telescope out to a similar distance. Inverse Compton scattering of the stellar radiation results in X-ray emission detectable by Chandra X-ray Observatory out to ∼ 150 pc. Finally, we apply our model to the upper limit constraints on V380 Tau, the first star-hot Jupiter system observed in radio wavelength. Our bow shock model provides constraints on the magnetic field, the interplanetary medium and the non-thermal emission efficiency in V380 Tau.

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A search for radio emission from exoplanets around evolved stars

Cited by 27 publications

References 68 publications

In search of radio emission from exoplanets: GMRT observations of the binary system HD 41004

In search of radio emission from exoplanets: GMRT observations of the binary system HD 41004

MOVES – II. Tuning in to the radio environment of HD189733b

Nonthermal Emission from the Interaction of Magnetized Exoplanets with the Wind of Their Host Star

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