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Exoplanets - worlds of other suns


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#401
Sciencerocks

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A likely planet-induced gap in the disk around T Cha
Nathanial P. Hendler, Paola Pinilla, Ilaria Pascucci, Adriana Pohl, Gijs Mulders, Thomas Henning, Ruobing Dong, Cathie Clarke, James Owen, David Hollenbach
(Submitted on 27 Nov 2017)

   

We present high resolution (0.11"×0.06") 3mm ALMA observations of the highly inclined transition disk around the star T Cha. Our continuum image reveals multiple dust structures: an inner disk, a spatially resolved dust gap, and an outer ring. When fitting sky-brightness models to the real component of the 3mm visibilities, we infer that the inner emission is compact (≤1au in radius), the gap width is between 18-28 au, and the emission from the outer ring peaks at ∼36 au. We compare our ALMA image with previously published 1.6μm VLT/SPHERE imagery. This comparison reveals that the location of the outer ring is wavelength dependent. More specifically, the peak emission of the 3mm ring is at a larger radial distance than that of the 1.6μm ring, suggesting that millimeter-sized grains in the outer disk are located further away from the central star than micron-sized grains. We discuss different scenarios to explain our findings, including dead zones, star-driven photoevaporation, and planet-disk interactions. We find that the most likely origin of the dust gap is from an embedded planet, and estimate --- for a single planet scenario --- that T Cha's gap is carved by a 1.2Mjup planet.

 

https://arxiv.org/abs/1711.09933


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#402
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The Complete transmission spectrum of WASP-39b with a precise water constraint
Hannah R. Wakeford, David K. Sing, Drake Deming, Nikole K. Lewis, Jayesh Goyal, Tom J. Wilson, Joanna Barstow, Tiffany Kataria, Benjamin Drummond, Thomas M. Evans, Aarynn L. Carter, Nikolay Nikolov, Heather A. Knutson, Gilda E. Ballester, Avi M. Mandell
(Submitted on 28 Nov 2017)

    WASP-39b is a hot Saturn-mass exoplanet with a predicted clear atmosphere based on observations in the optical and infrared. Here we complete the transmission spectrum of the atmosphere with observations in the near-infrared (NIR) over three water absorption features with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) G102 (0.8-1.1 microns) and G141 (1.1-1.7 microns) spectroscopic grisms. We measure the predicted high amplitude H2O feature centered at 1.4 microns, and the smaller amplitude features at 0.95 and 1.2 microns, with a maximum water absorption amplitude of 2.4 planetary scale heights. We incorporate these new NIR measurements into previously published observational measurements to complete the transmission spectrum from 0.3-5 microns. From these observed water features, combined with features in the optical and IR, we retrieve a well constrained temperature Teq = 1030(+30,-20) K, and atmospheric metallicity 151 (+48,-46)x solar which is relatively high with respect to the currently established mass-metallicity trends. This new measurement in the Saturn-mass range hints at further diversity in the planet formation process relative to our solar system giants.

 

https://arxiv.org/abs/1711.10529


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#403
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Exoplanet has smothering stratosphere without water
November 30, 2017 by Elizabeth Landau

 

A NASA-led team has found evidence that the oversized exoplanet WASP-18b is wrapped in a smothering stratosphere loaded with carbon monoxide and devoid of water. The findings come from a new analysis of observations made by the Hubble and Spitzer space telescopes.

 

 

Read more at: https://phys.org/new...sphere.html#jCp


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#404
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Possible detection of a bimodal cloud distribution in the atmosphere of HAT-P-32\,A\,b from multi-band photometry
Jeremy Tregloan-Reed, John Southworth, L. Mancini, P. Mollière, S. Ciceri, I. Bruni, D. Ricci, C. Ayala-Loera, T. Henning
(Submitted on 1 Dec 2017)

 

    We present high-precision photometry of eight separate transit events in the HAT-P-32 planetary system. One transit event was observed simultaneously by two telescopes of which one obtained a simultaneous multi-band light curve in three optical bands, giving a total of 11 transit light curves. Due to the filter selection and in conjunction with using the defocussed photometry technique we were able to obtain an extremely high precision, ground-based transit in the \textit{u}-band (350\,nm), with an rms scatter of ≈1\,mmag. All 11 transits were modelled using \textsc{prism} and \textsc{gemc}, and the physical properties of the system calculated. We find the mass and radius of the host star to be $1.182\pm 0.041\Msun$ and $1.225\pm0.015\Rsun$, respectively. For the planet we find a mass of $0.80\pm 0.14\Mjup$, a radius of $1.807\pm0.022\Rjup$ and a density of $0.126\pm0.023\pjup$. These values are consistent with those found in the literature. We also obtain a new orbital ephemeris for the system T0=BJD/TDB2454420.447187(96)+2.15000800(10)×E. We measured the transmission spectrum of HAT-P-32\,A\,b and compared it to theoretical transmission spectra. Our results indicate a bimodal cloud particle distribution consisting of Rayleigh--like haze and grey absorbing cloud particles within the atmosphere of HAT-P-32\,A\,b.

 

https://arxiv.org/abs/1712.00415


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#405
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HD 176986 - Super-Earths around a moderately active K-dwarf
The RoPES project with HARPS and HARPS-N. I. A system of super-Earths orbiting the moderately active K-dwarf HD 176986
https://arxiv.org/abs/1712.01046

 

    We report the discovery of a system of two super-Earths orbiting the moderately active K-dwarf HD 176986. This work is part of the RoPES RV program of G- and K-type stars, which combines radial velocities (RVs) from the HARPS and HARPS-N spectrographs to search for short-period terrestrial planets. HD 176986 b and c are super-Earth planets with masses of 5.74 and 9.18 M⊕, orbital periods of 6.49 and 16.82 days, and distances of 0.063 and 0.119 AU in orbits that are consistent with circular. The host star is a K2.5 dwarf, and despite its modest level of chromospheric activity (log(R'hk) = - 4.90 +- 0.04), it shows a complex activity pattern. Along with the discovery of the planets, we study the magnetic cycle and rotation of the star. HD 176986 proves to be suitable for testing the available RV analysis technique and further our understanding of stellar activity.

 


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#406
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Two super-Earths around star K2-18
December 5, 2017

 

New research using data collected by the European Southern Observatory (ESO) has revealed that a little-known exoplanet called K2-18b could well be a scaled-up version of Earth.

Just as exciting, the same researchers also discovered for the first time that the planet has a neighbor.

"Being able to measure the mass and density of K2-18b was tremendous, but to discover a new exoplanet was lucky and equally exciting," says lead author Ryan Cloutier, a PhD student in U of T Scarborough's Centre for Planet Science, U of T's Department of Astronomy and Astrophysics, and Université de Montréal Institute for research on exoplanets (iREx).

Both planets orbit K2-18, a red-dwarf star located about 111 light years away in the constellation Leo. When the planet K2-18b was first discovered in 2015, it was found to be orbiting within the star's habitable zone, making it an ideal candidate to have liquid surface water, a key element in harbouring conditions for life as we know it.

The data set used by the researchers came from the High Accuracy Radial Velocity Planet Searcher (HARPS) using the ESO's 3.6m telescope at La Silla Observatory, in Chile. HARPS allows for measurements of radial velocities of stars, which are affected by the presence of planets, to be taken with the highest accuracy currently available. Hence, this instrument allows for the detection of very small planets around them.

In order to figure out whether K2-18b was a scaled-up version of Earth (mostly rock), or a scaled-down version of Neptune (mostly gas), researchers had to first figure out the planet's mass, using radial velocity measurements taken with HARPS.

"If you can get the mass and radius, you can measure the bulk density of the planet and that can tell you what the bulk of the planet is made of," says Cloutier.

After using a machine-learning approach to figure out the mass measurement, Cloutier and his team were able to determine the planet is either a mostly rocky planet with a small gaseous atmosphere – like Earth, but bigger – or a mostly water planet with a thick layer of ice on top of it.

"With the current data, we can't distinguish between those two possibilities," he says. "But with the James Webb Space Telescope (JWST) we can probe the atmosphere and see whether it has an extensive atmosphere or it's a planet covered in water."

 

Read more at: https://phys.org/new...ar-k2-.html#jCp


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#407
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HD 147379 b - temperate super-Neptune around an M0 dwarf

Reiners et al. (2017) "The CARMENES search for exoplanets around M dwarfs: HD 147379 b: A nearby Neptune in the temperate zone of an early-M dwarf"
https://www.aanda.or.../aa32165-17.pdf

The star is part of a common proper motion binary, the secondary is EW Draconis. The planet HD 147379 b has minimum mass of about 25 Earth masses.


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#408
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HD 147379 b - temperate super-Neptune around an M0 dwarf

Reiners et al. (2017) "The CARMENES search for exoplanets around M dwarfs: HD 147379 b: A nearby Neptune in the temperate zone of an early-M dwarf"
https://www.aanda.or.../aa32165-17.pdf

The star is part of a common proper motion binary, the secondary is EW Draconis. The planet HD 147379 b has minimum mass of about 25 Earth masses.

An investigation shows that this planet is just 30-ish light years away. I will make a post on it in my story thread sometime.


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#409
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Qatar Exoplanet Survey: Qatar-6b -- a grazing transiting hot Jupiter
https://arxiv.org/abs/1712.03216

 

    We report the discovery of Qatar-6b, a new transiting planet identified by the Qatar Exoplanet Survey (QES). The planet orbits a relatively bright (V=11.44), early-K main-sequence star at an orbital period of P~3.506 days. An SED fit to available multi-band photometry, ranging from the near-UV to the mid-IR, yields a distance of d = 101 +/- 6 pc to the system. From a global fit to follow-up photometric and spectroscopic observations, we calculate the mass and radius of the planet to be Mp = 0.67 +/- 0.07 Mjup and Rp = 1.06 +/- 0.07 Rjup, respectively. We use multi-color photometric light curves to show that the transit is grazing, making Qatar-6b one of the few exoplanets known in a grazing transit configuration. It adds to the short list of targets that offer the best opportunity to look for additional bodies in the host planetary system through variations in the transit impact factor and duration.

 


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#410
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KELT-21b: A Hot Jupiter Transiting the Rapidly-Rotating Metal-Poor Late-A Primary of a Likely Hierarchical Triple System
https://arxiv.org/abs/1712.03241

    We present the discovery of KELT-21b, a hot Jupiter transiting the V=10.5 A8V star HD 332124. The planet has an orbital period of P=3.6127647±0.0000033 days and a radius of 1.586+0.039−0.040 RJ. We set an upper limit on the planetary mass of MP<3.91 MJ at 3σ confidence. We confirmed the planetary nature of the transiting companion using this mass limit and Doppler tomographic observations to verify that the companion transits HD 332124. These data also demonstrate that the planetary orbit is well-aligned with the stellar spin, with a sky-projected spin-orbit misalignment of λ=−5.6+1.7∘−1.9. The star has Teff=7598+81−84 K, M∗=1.458+0.029−0.028 M⊙, R∗=1.638±0.034 R⊙, and vsinI∗=146 km s−1, the highest projected rotation velocity of any star known to host a transiting hot Jupiter. The star also appears to be somewhat metal-poor and α-enhanced, with [Fe/H]=−0.405+0.032−0.033 and [α/Fe]=0.145±0.053; these abundances are unusual, but not extraordinary, for a young star with thin-disk kinematics like KELT-21. High-resolution imaging observations revealed the presence of a pair of stellar companions to KELT-21, located at a separation of 1.2" and with a combined contrast of ΔKS=6.39±0.06 with respect to the primary. Although these companions are most likely physically associated with KELT-21, we cannot confirm this with our current data. If associated, the candidate companions KELT-21 B and C would each have masses of ∼0.12 M⊙, a projected mutual separation of ∼20 AU, and a projected separation of ∼500 AU from KELT-21. KELT-21b may be one of only a handful of known transiting planets in hierarchical triple stellar systems.

 


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#411
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HATS-50b through HATS-53b: four transiting hot Jupiters orbiting G-type stars discovered by the HATSouth survey
https://arxiv.org/abs/1712.04324

 

    We report the discovery of four close-in transiting exoplanets, HATS-50 through HATS-53, discovered using the HATSouth three-continent network of homogeneous and automated telescopes. These new exoplanets belong to the class of hot Jupiters and orbit G-type dwarf stars, with brightness in the range V=12.5-14.0 mag. While HATS-53 has many physical characteristics similar to the Sun, the other three stars appear to be metal rich, larger and more massive. Three of the new exoplanets, namely HATS-50, HATS-51 and HATS-53, have low density and similar orbital period. Instead, HATS-52 is more dense and has a shorter orbital period. It also receives an intensive radiation from its parent star and, consequently, presents a high equilibrium temperature. HATS-50 shows a marginal additional transit feature consistent with an ultra-short period hot super Neptune, which will be able to be confirmed with TESS photometry.

 


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#412
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It's funny how we've gotten to the point where the discovery of a bunch of new planets is dull.


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#413
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It's funny how we've gotten to the point where the discovery of a bunch of new planets is dull.

 

Yes, not wonder anymore, just the matter of statistics. The new wonder will be the discovery of earth-like world with biomarkers. This, too, should happen in not so distant future. And then there will be a long (few centuries) pause before the next important step.


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--- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

 

"And the Russian land, let God keep it! Under heavens, there is no other land like this. And although Russian nobles are not righteous neither kind, let God arrange the Russian land and give us enough justice" - Afanasy Nikitin, medieval traveler of XV century.


#414
BasilBerylium

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Yes, not wonder anymore, just the matter of statistics. The new wonder will be the discovery of earth-like world with biomarkers. This, too, should happen in not so distant future. And then there will be a long (few centuries) pause before the next important step.

"Meh, let me know when they find something more interesting than a ugly beast on a planet that I can not visit in my lifetime."


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#415
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^ I guess my English will be better by then.


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#416
PhoenixRu

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Yes, not wonder anymore, just the matter of statistics. The new wonder will be the discovery of earth-like world with biomarkers. This, too, should happen in not so distant future. And then there will be a long (few centuries) pause before the next important step.

"Meh, let me know when they find something more interesting than a ugly beast on a planet that I can not visit in my lifetime."

 

Actually, ugly beast would be very interesting but i meant the indirect signs: oxygen, water, complex organics. That's all we can see from Earth(s orbit). And this will be almost the discovery of alien life. The time of ugly beasts will come centuries later.

 

The second option: discovery of alien civilization. Unpredictable thing: may happen today or not happen at all.


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--- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

 

"And the Russian land, let God keep it! Under heavens, there is no other land like this. And although Russian nobles are not righteous neither kind, let God arrange the Russian land and give us enough justice" - Afanasy Nikitin, medieval traveler of XV century.


#417
Jakob

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It's funny how we've gotten to the point where the discovery of a bunch of new planets is dull.

 

Yes, not wonder anymore, just the matter of statistics. The new wonder will be the discovery of earth-like world with biomarkers. This, too, should happen in not so distant future. And then there will be a long (few centuries) pause before the next important step.

 

I still get excited about Earthlike worlds--and even habitable zone gas planets that might have nice moons, see above--(especially ones <100 light years away), just not any old hot Jupiter.


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#418
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https://arxiv.org/abs/1712.04483

A Candidate Transit Event around Proxima Centauri

We present a single candidate transit event around Proxima Centauri, found during a blind transit search using a robotic 30\,cm telescope at Las Campanas Observatory. The event lasted 1 hour, with an estimated depth of 5\,mmag, and is inconsistent with the transit window predicted for the recently discovered planet b. We modeled the lightcurve under the assumption that the event was caused by a transiting exoplanet, and our model predicts the planet has a radius R∼1R earth . We encourage continued monitoring of Proxima to elucidate the origin of this event

 


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#419
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https://arxiv.org/abs/1712.04483

A Candidate Transit Event around Proxima Centauri

We present a single candidate transit event around Proxima Centauri, found during a blind transit search using a robotic 30\,cm telescope at Las Campanas Observatory. The event lasted 1 hour, with an estimated depth of 5\,mmag, and is inconsistent with the transit window predicted for the recently discovered planet b. We modeled the lightcurve under the assumption that the event was caused by a transiting exoplanet, and our model predicts the planet has a radius R∼1R earth . We encourage continued monitoring of Proxima to elucidate the origin of this event

 

 

OMG just when I said this thread was getting dull.

 

EDIT: eh, probably not in the HZ.


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