Author Topic: Astronomy Thread  (Read 36978 times)

Offline Star One

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Astronomy Thread
« on: 01/22/2017 07:27 PM »
Seemed a good idea to have a separate thread for miscellaneous exoplanet discoveries.

Is there a circumbinary planet around NSVS 14256825?

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The cyclic behaviour of (O-C) residuals of eclipse timings in the sdB+M eclipsing binary NSVS 14256825 was previously attributed to one or two Jovian-type circumbinary planets. We report 83 new eclipse timings that not only fill in the gaps in those already published but also extend the time span of the (O-C) diagram by three years. Based on the archival and our new data spanning over more than 17 years we re-examined the up to date system (O-C). The data revealed systematic, quasi-sinusoidal variation deviating from an older linear ephemeris by about 100 s. It also exhibits a maximum in the (O-C) near JD 2,456,400 that was previously unknown. We consider two most credible explanations of the (O-C) variability: the light propagation time due to the presence of an invisible companion in a distant circumbinary orbit, and magnetic cycles reshaping one of the binary components, known as the Applegate or Lanza-Rodono effect. We found that the latter mechanism is unlikely due to the insufficient energy budget of the M-dwarf secondary. In the framework of the third-body hypothesis, we obtained meaningful constraints on the Keplerian parameters of a putative companion and its mass. Our best-fitting model indicates that the observed quasi-periodic (O-C) variability can be explained by the presence of a brown dwarf with the minimal mass of 15 Jupiter masses rather than a planet, orbiting the binary in a moderately elliptical orbit (~ 0.175) with the period of ~ 10 years. Our analysis rules out two planets model proposed earlier.

https://arxiv.org/abs/1701.05211
« Last Edit: 11/08/2017 07:50 PM by Star One »

Offline Star One

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Exoplanet Thread
« Reply #1 on: 01/26/2017 06:54 PM »
Wolf 1061 unlikely to host habitable worlds.

http://www.centauri-dreams.org/?p=37016

Here's the pre-print.

Characterization of the Wolf 1061 Planetary System

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A critical component of exoplanetary studies is an exhaustive characterization of the host star, from which the planetary properties are frequently derived. Of particular value are the radius, temperature, and luminosity, which are key stellar parameters for studies of transit and habitability science. Here we present the results of new observations of Wolf~1061, known to host three super-Earths. Our observations from the Center for High Angular Resolution Astronomy (CHARA) interferometric array provide a direct stellar radius measurement of 0.3207±0.0088~R⊙, from which we calculate the effective temperature and luminosity using spectral energy distribution models. We obtained seven years of precise, automated photometry that reveals the correct stellar rotation period of 89.3±1.8~days, finds no evidence of photometric transits, and confirms the radial velocity signals are not due to stellar activity. Finally, our stellar properties are used to calculate the extent of the Habitable Zone for the Wolf~1061 system, for which the optimistic boundaries are 0.09--0.23~AU. Our simulations of the planetary orbital dynamics shows that the eccentricity of the Habitable Zone planet oscillates to values as high as ∼0.15 as it exchanges angular momentum with the other planets in the system.

https://arxiv.org/abs/1612.0934
« Last Edit: 01/26/2017 06:57 PM by Star One »

Offline ikke666

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Re: Exoplanet Thread
« Reply #2 on: 01/27/2017 04:59 PM »
is there a list of stars that have planets on web?  ::) prefably with the kind of planet (gas giant, earth like,...)

Offline testguy

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Re: Exoplanet Thread
« Reply #3 on: 01/27/2017 05:29 PM »
Try this.  Updates daily.

http://exoplanet.eu/catalog/

Offline hop

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Re: Exoplanet Thread
« Reply #4 on: 01/28/2017 06:00 AM »
There's also the NASA Exoplanet archive http://exoplanetarchive.ipac.caltech.edu/

Offline Star One

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Re: Exoplanet Thread
« Reply #5 on: 01/28/2017 12:13 PM »
Took the Keck observatory seven years of observations to produce this.

A Four Planet System in Orbit, Directly Imaged and Remarkable

http://www.manyworlds.space/index.php/2017/01/24/a-four-planet-system-in-orbit-directly-imaged-and-remarkable/

Offline ikke666

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Re: Exoplanet Thread
« Reply #6 on: 01/28/2017 03:55 PM »
thanks for the sites  ;D

Offline Star One

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Re: Exoplanet Thread
« Reply #7 on: 02/02/2017 08:38 PM »

Offline Star One

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Re: Exoplanet Thread
« Reply #8 on: 02/13/2017 07:36 PM »
Quote
Washington, DC— An international team of astronomers released the largest-ever compilation of exoplanet-detecting observations made using a technique called the radial velocity method. They demonstrated how these observations can be used to hunt for planets by detecting more than 100 potential exoplanets, including one orbiting the fourth-closest star to our own Solar System, which is about 8.1 light years away from Earth. The paper is published in The Astronomical Journal.
The radial velocity method is one of the most successful techniques for finding and confirming planets. It takes advantage of the fact that in addition to a planet being influenced by the gravity of the star it orbits, the planet’s gravity also affects the star. Astronomers are able to use sophisticated tools to detect the tiny wobble the planet induces as its gravity tugs on the star.
The virtual mountain of data released to the public in this paper was gathered as part of a two-decade radial velocity planet-hunting program that uses a spectrometer called HIRES, mounted on the 10-meter Keck-I telescope of the W.M. Keck Observatory atop Mauna Kea in Hawaii. The compilation includes almost 61,000 individual measurements made of more than 1,600 stars. By making the data public, the team is offering unprecedented access to one of the best exoplanet searches in the world.
Quote
One of these probable planets is around a star called GJ 411, also known as Lalande 21185. It is the fourth-closest star to our own Sun and is only about 40 percent the mass of the Sun. The planet has a very short orbital period of just under 10 days, so it is no Earth-twin. However, the inferred planet, GJ 411b, continues a trend that has been seen in the overall population of detected exoplanets: the smallest planets are found around the smallest stars.


https://carnegiescience.edu/news/team-makes-planet-hunting-group-effort-finds-more-100-candidates#

Offline Star One

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Exoplanet Thread
« Reply #9 on: 02/15/2017 07:11 PM »
Planet-Induced Stellar Pulsations in HAT-P-2's Eccentric System

J. de Wit, N.K. Lewis, H.A. Knutson, J. Fuller, V. Antoci, B.J. Fulton, G. Laughlin, D. Deming, A. Shporer, K. Batygin, N.B. Cowan, E. Agol, A.S. Burrows, J.J. Fortney, J. Langton, A.P. Showman
(Submitted on 13 Feb 2017)

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Extrasolar planets on eccentric short-period orbits provide a laboratory in which to study radiative and tidal interactions between a planet and its host star under extreme forcing conditions. Studying such systems probes how the planet's atmosphere redistributes the time-varying heat flux from its host and how the host star responds to transient tidal distortion. Here, we report the insights into the planet-star interactions in HAT-P-2's eccentric planetary system gained from the analysis of 350 hr of 4.5 micron observations with the Spitzer Space Telescope. The observations show no sign of orbit-to-orbit variability nor of orbital evolution of the eccentric planetary companion, HAT-P-2 b. The extensive coverage allows us to better differentiate instrumental systematics from the transient heating of HAT-P-2 b's 4.5 micron photosphere and yields the detection of stellar pulsations with an amplitude of approximately 40 ppm. These pulsation modes correspond to exact harmonics of the planet's orbital frequency, indicative of a tidal origin. Transient tidal effects can excite pulsation modes in the envelope of a star, but, to date, such pulsations had only been detected in highly eccentric stellar binaries. Current stellar models are unable to reproduce HAT-P-2's pulsations, suggesting that our understanding of the interactions at play in this system is incomplete.

https://arxiv.org/abs/1702.03797

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« Last Edit: 02/15/2017 08:05 PM by Star One »

Offline Mongo62

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Re: Exoplanet Thread
« Reply #10 on: 02/28/2017 07:23 PM »
Towards Detection of Exoplanetary Rings Via Transit Photometry: Methodology and a Possible Candidate

Abstract: Detection of a planetary ring of exoplanets remains as one of the most attractive but challenging goals in the field. We present a methodology of a systematic search for exoplanetary rings via transit photometry of long-period planets. The methodology relies on a precise integration scheme we develop to compute a transit light curve of a ringed planet. We apply the methodology to 89 long-period planet candidates from the Kepler data so as to estimate, and/or set upper limits on, the parameters of possible rings. While a majority of our samples do not have a sufficiently good signal-to-noise ratio for meaningful constraints on ring parameters, we find that six systems with a higher signal-to-noise ratio are inconsistent with the presence of a ring larger than 1.5 times the planetary radius assuming a grazing orbit and a tilted ring. Furthermore, we identify five preliminary candidate systems whose light curves exhibit ring-like features. After removing four false positives due to the contamination from nearby stars, we identify KIC 10403228 as a reasonable candidate for a ringed planet. A systematic parameter fit of its light curve with a ringed planet model indicates two possible solutions corresponding to a Saturn-like planet with a tilted ring. There also remain other two possible scenarios accounting for the data; a circumstellar disk and a hierarchical triple. Due to large uncertain factors, we cannot choose one specific model among the three.

Offline Star One

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Exoplanet Thread
« Reply #11 on: 03/10/2017 06:51 PM »
Another close by system that may turn out to be suitable for exo-atmosphere observations.

HD 219134: A Nearby System with Multiple Transits

http://www.centauri-dreams.org/?p=37300

Here's the paper.

http://www.nature.com/articles/s41550-017-0056#references
« Last Edit: 03/10/2017 06:51 PM by Star One »

Online jebbo

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Re: Exoplanet Thread
« Reply #12 on: 03/13/2017 05:24 PM »
In news other than Trappist-1, this on Kepler-444 is interesting:

https://arxiv.org/abs/1703.03417

The masses imply a density around that of water, which is quite remarkable as the planets have been at >600K for about 11 billion years ... so keeping hold of volatiles is quite a feat. Oh, it also implies an origin beyond the ice line

--- Tony

Offline Bynaus

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Re: Exoplanet Thread
« Reply #13 on: 03/13/2017 05:36 PM »
Only the nominal densities are close to water, the uncertainties are quite high. Within only one standard deviation (68% confidence interval), the densities are between 0.5 g/cm3 and 3.5 g/cm3 (see Table 2), so a rocky composition can certainly not be excluded at this point. Like you say, it would be very surprising if such low-mass planets would have kept their volatiles at 600 K over the 11 Ga age of the system.

Online jebbo

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Re: Exoplanet Thread
« Reply #14 on: 03/13/2017 05:42 PM »
Absolutely ... and I'm wary of numbers from Bayesian methods (e.g. see Kass & Rafferty, 1995)

Shame the predicted RV is too low, though I wonder if at magnitude 9, we might get transmission spectroscopy


Edit: added figure from arxiv.org paper
--- Tony
« Last Edit: 03/13/2017 05:50 PM by jebbo »

Offline Star One

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Re: Exoplanet Thread
« Reply #15 on: 03/13/2017 08:10 PM »
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The search for extraterrestrial life is increasingly informed by our knowledge of exoplanets. Within three decades, we may know whether extrasolar life is rare.

http://physicstoday.scitation.org/doi/abs/10.1063/PT.3.3494#.WMbXbKSwOf8.twitter

Offline Star One

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Exoplanet Thread
« Reply #16 on: 03/14/2017 11:10 AM »
Mysterious celestial object could be an elusive brown dwarf or a free-floating planet

The object is not part of the AB Doradus moving group, as previous hypothesised.

http://www.ibtimes.co.uk/mysterious-celestial-object-could-be-elusive-brown-dwarf-free-floating-planet-1611441

More details on this topic in this article including the relevant paper.

https://phys.org/news/2017-03-mysterious-isolated-astronomers.html
« Last Edit: 03/14/2017 01:48 PM by Star One »

Offline Star One

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Re: Exoplanet Thread
« Reply #17 on: 03/15/2017 08:11 PM »
Not an exoplanet but an interesting star instead.

Isotope shift and search for metastable superheavy elements in astrophysical

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Spectral lines belonging to the short-lifetime heavy radioactive elements up to Es (Z=99) have been found in the spectra of the Przybylski's star. We suggest that these unstable elements may be decay products of a "magic" metastable nucleus belonging to the the island of stability where the nuclei have a magic number of neutrons N=184. The laboratory-produced nuclei have a significantly smaller number of neutrons. To identify spectra of the N=184 isotopes of these nuclei and their neutron-reach superheavy decay products in astrophysical data we calculate the isotope shift which should be added to the laboratory - measured wavelenghs. The results for the isotopic shifts in the strongest optical electromagnetic transitions in No, Lr, Nh, Fl,and Z=120 elements are presented.

https://arxiv.org/abs/1703.04250

Offline Bynaus

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Re: Exoplanet Thread
« Reply #18 on: 03/17/2017 06:20 AM »
Plenty of Earth-mass worlds around nearby red dwarfs (one of them in the HZ, 3.8 pc away).

https://arxiv.org/abs/1703.05386

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The HARPS search for southern extra-solar planets XLI. A dozen planets around the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628, and GJ 3293

Context. Low mass stars are currently the best targets for searches for rocky planets in the habitable zone of their host star. Over the last 13 years, precise radial velocities measured with the HARPS spectrograph have identified over a dozen super-Earths and Earth-mass planets (msin i<10Mearth ) around M dwarfs, with a well understood selection function. This well defined sample informs on their frequency of occurrence and on the distribution of their orbital parameters, and therefore already constrains our understanding of planetary formation. The subset of these low-mass planets that were found within the habitable zone of their host star also provide prized targets for future atmospheric biomarkers searches. Aims. We are working to extend this planetary sample to lower masses and longer periods through dense and long-term monitoring of the radial velocity of a small M dwarf sample. Methods. We obtained large numbers of HARPS spectra for the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628 and GJ 3293, from which we derived radial velocities (RVs) and spectroscopic activity indicators. We searched them for variabilities, periodicities, Keplerian modulations and correlations, and attribute the radial-velocity variations to combinations of planetary companions and stellar activity. Results. We detect 12 planets, of which 9 are new with masses ranging from 1.17 to 10.5 Mearth . Those planets have relatively short orbital periods (P<40 d), except two of them with periods of 217.6 and 257.8 days. Among these systems, GJ 273 harbor two planets with masses close to the one of the Earth. With a distance of 3.8 parsec only, GJ 273 is the second nearest known planetary system - after Proxima Centauri - with a planet orbiting the circumstellar habitable zone.

I know we already know this from Kepler, but its really astonishing how these red dwarf star systems are all choke full with massive terrestrial-to-neptunian worlds.

GJ 273 - also known as Luyten's Star - is currently located only 1.2 LY away from Procyon. It has a ca. 3 Earth-mass planet which recieves 1.06 times the solar insolation on Earth.

Offline Star One

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Re: Exoplanet Thread
« Reply #19 on: 03/28/2017 08:17 PM »