Hint of 150 MHz radio emission from the Neptune-mass extrasolar transiting planet HAT-P-11b

Next Big Future ^ | 2/24/2013 | Brian Wang

[Red Badger]

ince the radio-frequency emission from planets is expected to be strongly influenced by their interaction with the magnetic field and corona of the host star, the physics of this process can be effectively constrained by making sensitive measurements of the planetary radio emission.

Up to now, however, numerous searches for radio emission from extrasolar planets at radio wavelengths have only yielded negative results. Here we report deep radio observations of the nearby Neptune-mass extrasolar transiting planet HAT-P-11b at 150 MHz, using the Giant Meterwave Radio Telescope (GMRT).

On July 16, 2009, we detected a 3σ emission whose light curve is consistent with an eclipse when the planet passed behind the star. This emission is at a position 14′′ from the transiting exoplanet’s coordinates; thus, with a synthetized beam of FWHM∼16′′, the position uncertainty of this weak radio signal encompasses the location of HAT-P-11. We estimate a 5% false positive probability that the observed radio light curve mimics the planet’s eclipse light curve. If the faint signature is indeed a radio eclipse event associated with the planet, then its flux would be 3.87 mJy±1.29 mJy at 150 MHz. However, our equally sensitive repeat observations of the system on November 17, 2010 did not detect a significant signal in the radio light curve near the same position. This lack of confirmation leaves us with the possibility of either a variable planetary emission, or a chance occurrence of a false positive.

Although we are not able to draw a definitive conclusion on 150 MHz radio emission from HAT-P-11 b, at the very least the hint of radio detection presented here identifies HAT-P-11 b as a prime candidate for many follow-up observations in the near future. The priority is to try to confirm the present tentative detection, via re-observation with GMRT at 150 MHz and/or new observations with LOFAR in the 30-250 MHz range (providing a 1-100 mJy sensitivity depending on the observation parameters used; van Haarlem et al., submitted, 2013) and UTR-2 in the 10-30 MHz range (providing a sensitivity of ∼100 mJy; Ryabov et al. 2004). The observed spectral range can also be extended toward shorter wavelengths using GMRT, with even higher sensitivities of ∼1 mJy at 240 MHz and ∼50 µJy at 614 MHz (e.g., Lecavelier des Etangs et al. 2009). Observations over a broad range of frequencies will, with any luck, allow confirmation of the existence of the emission and better constraints on the planetary magnetic field strength and determination of the radio spectral index.

The future observations should also be distributed at multiple epochs and at different orbital phases of the planet to characterize the suspected variability of the radio emission in terms of duty cycle, as well as the radio emission as a function of the star-planet angle and the emission directivity (CMI produces narrowly beamed radio emission). In this context, Hess and Zarka (2011) have analyzed all the observables that could be derived from a broadband dynamic spectrum with a sufficient signal-tonoise ratio.

In the long term, it should be possible to investigate if the radio emission from extrasolar planetary systems correlates with the stellar spot activity. In this context, HAT-P-11 represents the target of choice because the Kepler mission has recently demonstrated the possibility of following the spot activity and perhap even of drawing the butterfly diagram of surface spots for this star.

Radio observations of different types of exoplanets are also crucial for comparative exoplanetology. For instance, observations of the other transiting hot-Neptune GJ436 b (Gillon et al. 2007) will allow comparison with a planet similar in mass but orbiting an M-dwarf star which is half the mass and radius of HAT-P-11 and known to have a strong Far-UV and Lyman-αoutput (Ehrenreich et al. 2010). With a 6.55 Earth mass, the nearby exoplanet GJ1214 b should also provide an opportunity to undertake search for radio emission from a water-rich lower mass super-Earth planet (Charbonneau et al. 2009; D´esert et al. 2011). In the near future, more sensitive observations at even lower frequencies will become feasible with the LOFAR observatory, providing a great boost to exoplanetary research.

[FreedomOfExpression]

What I’m going to have to look up is the definition of a radio light curve. The term doesn’t make sense to me.

[nothingnew]

I am from planet HAT-P-11b and you are spreading very false rumors. I take umbrage and will do something about it!

All your rumors are belong to us!

FMCDH(BITS)

[Red Badger]

http://en.wikipedia.org/wiki/Light_curve

[Red Badger]

Perhaps the writer meant to say, “radio/light curve”.........

[Red Badger]

Alien: You wanna piece of me, punk?........

[ModelBreaker]

Nope. The Honeymooners. What happens when we get the Gork IV equivalent of “Pow, to the moon?”

[Red Badger]

Alien: You wanna piece of me, punk?.........

[Red Badger]

Too far away for that. They might have overheard the War of the Worlds broadcast of 1938, though........

[techcor]

Bump to read later.

[Red Badger]

http://en.wikipedia.org/wiki/6-meter_band As transceivers have become more available for the 6-meter band, it has quickly gained popularity. In many countries, including the United States, access is granted to entry-level license holders. Those without access to international HF frequencies often gain their first taste of true long-distance communications on the 6-meter band. Many of these operators develop a real affection for the challenge of the band, and often continue to devote much time to it, even when they gain access to the HF frequencies after upgrading their licenses.

[cuban leaf]

I use subspace to send status reports to the home planet. Different strokes for different folks, I guess.

[spokeshave]

Its just an alien Ham with an off frequency 2m TX....probably asking someone to....

Pack my bags with twelve dozen Phoenician liquor jugs

and some best bent wire.

[FreedomOfExpression]

Thanks!
Still not too clear, though.

[JRandomFreeper]

Yep. I've kept my advanced ticket because they are rare these days, and even with my HF rigs, I still enjoy openings on 6 meters when you can work from Texas to California on a 5W handi-talki.

/johnny

[Red Badger]

Basically, it’s measuring the intensity of the signal, and charting its undulations. If it has a periodic rise and fall, it would indicate that the object is rotating at the rate of the peaks............

[BenLurkin]

Bingo!

[nothingnew]

Alien: You wanna piece of me, punk?.........

No, I want all of you...alien.

FMCDH(BITS)

[SunkenCiv]

Thanks Red Badger!

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