Exoplanets and Planet Formation meeting

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Exoplanets and Planet Formation meeting

Post by Lazarus on 17th November 2017, 6:03 pm

There's some potentially-interesting stuff in the abstracts booklet for the Exoplanets and Planet Formation meeting, particularly regarding HAT-P-11 and Proxima. Various other interesting subjects, wonder how much will hold up all the way to publication.

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Re: Exoplanets and Planet Formation meeting

Post by Led_Zep on 17th November 2017, 9:57 pm

!!?? Shocked

55
Photometry of Proxima Centauri in Antarctica : A Candidate Transit Event of its Earth-size Planet
Author(s): LIU, Hui-Gen1
Co-author(s): Dr. JIANG, Peng 2
1 SASS, Nanjing University
2 Polar Research Institute of China

Proxima˜Centauri is known as the closest star from the Sun. Recently, radial velocity observations revealed the existence of an Earth–mass planet around it. With an orbital period of 􀀀11 days, the surface of Proxima˜Centauri˜b is temperate and might be habitable. If the planet transits, it would be interesting to probe its radius, internal compositions and atmospheric properties. We took a photometric monitoring campaign of Proxima˜Centauri using the Bright Star Survey Telescope at the Zhongshan Station in Antarctica. A candidate transit event occurring on September 8th, 2016, is identified tentatively. Its transit epoch, TC=2,457,640.19900.0017 HJD, is consistent with the predicted ephemeris based on
RV orbit in a 1  confidence interval. Time-correlated noise is pronounced in the light curve of Proxima ˜Centauri, afflicting detection of transits. We develop a technique, in a Gaussian process framework, to gauge the statistical significance of potential transit detection. The candidate transit event reported in this work, has a confidence level of 2.5 . Kipping et al. (2017) reported two candidate transit events of Proxima˜Centauri˜b, observed by the Microvariability and Oscillation of Stars space Telescope in 2014 and 2015, respectively. However, the midtransit time of our detection is 138 minutes later than that predicted by their transit ephemeris. If all the transit events are real, the misalignment of the epochs plausibly suggests transit timing variations of Proxima˜Centauri˜b induced by an outer planet in this system. We plan to perform follow–up observation of Proxima˜Centauri in next Polar night at Dome A in Antarctica.
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Re: Exoplanets and Planet Formation meeting

Post by Sirius_Alpha on 17th November 2017, 10:22 pm

As interesting as that could be, I am not sure how useful it is. We have evidence from RV that there's a second planet, and we have possible evidence from ALMA that might lend more strength to the idea of a planet exterior to be shaping the orbit of a tentative debris ring. So it's not like a Proxima Centauri c would really be a huge surprise.

Theoretically, one would want to do transmission spectroscopy on the b planet's atmosphere to search for biosignature gases or whatever, but given how hard it is to even establish whether or not the planet transits (thanks to the star being noisy), it's not clear that reliable transmission spectroscopy data for this planet is really within our reach any time soon.

I suspect direct spectroscopy with E-ELT is probably the next avenue forward for studying this particular planet.

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Re: Exoplanets and Planet Formation meeting

Post by Lazarus on 18th November 2017, 10:05 am

Transits would be interesting in light of the (unconfirmed) 45° inclination for the debris disc. But no confirmation yet.

The second planet at HAT-P-11 looks like a configuration similar to hot Jupiter systems, I guess HAT-P-11b is a Hoptune?

Also more details of the circumbinary planet at KIC 10753734. There seem to be a bunch of unpublished Kepler circumbinary planets mentioned at various conferences that haven't been published yet (including some non-transiting ones, plus what happened to Kepler-47d?)
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Re: Exoplanets and Planet Formation meeting

Post by Led_Zep on 18th November 2017, 9:36 pm

"... Kipping et al. (2017) reported two candidate transit events of Proxima˜Centauri˜b, observed by the Microvariability and Oscillation of Stars space Telescope in 2014 and 2015, respectively..."
(chinese abstract)

http://iopscience.iop.org/article/10.3847/1538-3881/153/3/93/meta

No Conclusive Evidence for Transits of Proxima b in MOST Photometry

The analysis of Proxima Centauri's radial velocities recently led Anglada-Escudé et al. to claim the presence of a low-mass planet orbiting the Sun's nearest star once every 11.2 days. Although the a priori probability that Proxima b transits its parent star is just 1.5%, the potential impact of such a discovery would be considerable. Independent of recent radial velocity efforts, we observed Proxima Centauri for 12.5 days in 2014 and 31 days in 2015 with the Microwave and Oscillations of Stars space telescope. We report here that we cannot make a compelling case that Proxima b transits in our precise photometric time series. Imposing an informative prior on the period and phase, we do detect a candidate signal with the expected depth. However, perturbing the phase prior across 100 evenly spaced intervals reveals one strong false positive and one weaker instance. We estimate a false-positive rate of at least a few percent and a much higher false-negative rate of 20%–40%, likely caused by the very high flare rate of Proxima Centauri. Comparing our candidate signal to HATSouth ground-based photometry reveals that the signal is somewhat, but not conclusively, disfavored (1σ–2σ), leading us to argue that the signal is most likely spurious. We expect that infrared photometric follow-up could more conclusively test the existence of this candidate signal, owing to the suppression of flare activity and the impressive infrared brightness of the parent star.
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