KIC10024862 - 600 day Eclipsing Binary or Planet?

This transit occurred in the fourth quarter of the Kepler data release in 2011. Now in Q9, another significant drop has occurred.

Here is the analysis from forum Talk member Kian Jek:

Very nice 17hr drop. Could be a 0.84x RJ planet from the transit profile. However, the Q4 transit appears to have a similar duration, so it's possible that this is a long period, P > 600d, EB and with the secondary eclipse in Q4 and the primary in Q9.

More information here and here.

The Nine PlanetHunters Habitable Zone Candidates

There has been lots of exciting news about alien worlds recently with the announcement of confirmation studies for over 41 Kepler exoplanets across 20 star systems, and in addition the fourth circumbinary system in the form of Kepler-38b. It seems not a day goes by anymore without at least one interesting exoplanet related pre-print hitting ArXiv.org--usually it is several!

The Kepler deluge is perhaps a double edged sword in that the KOI list is ever expanding as the mission proceeds through each Quarter, greatly outpacing the expansion of the confirmed candidate family and surely making it an excruciating process for science teams to decide which targets to allot precious follow-up resources on.

Some of the most lucrative candidates include those where early characterization suggests the exoplanet may reside squarely inside or on the periphery of the Habitable Zone of its host star: these are the potential crown jewel discoveries in an extended Kepler mission and I believe around ~46 such targets are currently listed, with Kepler-22b being the first such confirmed.

A round up of targets from PH not included on the current KOI list which may also possess HZ orbits (based on analysis of their transits c/t predetermined host star parameters) could potentially add a further nine systems. Further spectroscopic investigation is needed to rule out the possibility of blends, but the group seems relatively free of offsets and all possess good looking transits. While none approach the size of a true Earth analog, everything we're learning about the possibilities for exotic life in the Universe still renders them very interesting candidates, especially if considering that many of these bodies may be prone to possession of small to medium size exomoons. No exomoons have been confirmed yet in any system, but currently thirty habitable candidates are predicted on the lists over at the Habitable Exoplanets Catalog!

Additional caveats applicable to the derived impact parameters for the list below: an assumed albedo of 0.3 was used in most cases and the exact planetary mass, eccentricity and atmospheric compositions are not known at this time (the colors and features shown in banner image were chosen rather arbitrarily). Further ambiguity in the accuracy of the KIC parameters for the host star, or dilution from nearby sources, could also dramatically throw off the assumed effective temperatures and radius values.

KIC 4552729

Of the nine targets this is the only one that has received any real follow up so far and was one of two exoplanets discussed in the second PlanetHunters paper by Lintott, et al from February, 2012. The orbital period is 97.46 days and a best fit seems to indicate a planetary radius of 4.65Re, however the presence of an incomplete Transit Timing Variation cycle and some variation in the depths precludes full confirmation at this time, leaving 4552729 in the candidate realm until a background eclipsing binary can be wholly ruled out.

Source

KIC 6878240

Found around a type K dwarf star smaller than the Sun and appears in Q2, Q4 and Q5 with a period of 135.5 days. Object is thought to be around 4.1Re with a possible Teq of 246K.

Source

KIC 7899070

Transits are seen throughout the public data set. Assuming the host star has a radius of .49x Sol, this could be a 3.0Re exoplanet orbiting at the equivalent of .43AU and possessing a Teq of 254K. The long transit duration could be explained by eccentricity or error in the listed KIC value for the host star radius.

Source

KIC 9480535

With several transits visible and a 13.25 hour duration, this could be a 3.5Re exoplanet orbiting the type G host star at a distance of .57AU and a period of 160 days. The assumed Teq is 327K.

Source

KIC 10360722

This is the smallest candidate on the list with a potential radius of 2.7Re, however there is some concern that a background binary could be interfering with the light curve and further follow up is needed. Assumed period is 163 days, at a distance of .43AU and a Teq of 296K; the host star is Type K.

Source

KIC 12735740

Only two transits in the public data thus far, but they look clean and decidedly unlike an EB profile. Also by far the largest candidate on the list with an assumed radius of ~12.0Re (or 1.12Rj). The host star is a 12.6Kmag type G dwarf and the characterization suggest a 282.5 day orbit at .86AU and possible Teq of 292K!

Source

KIC 3326377

This is an interesting potential multi-candidate system that seems to have a possible 'Super-Mercury' exoplanet at a short period of 13 days and then a second candidate much further out at .65AU and a period of 198 days. Uncertainties exist with the host star parameters, but the second candidate could exist in a minimum of the Super-Earth radius domain (2.84Re to 4.4Re) and may lie just outside the HZ possessing a Teq of 225K. *Edit: This co-discovery candidate is also described at the official PlanetHunters blog, found here.

Source

KIC 9958387

The subject of my last blog post and a recent HZ addition to the PlanetHunters list, displaying three very nice transits, with the latter visible in public Quarter 7 data. This candidate has a period of 236.7 days and an assumed radius of 5.1Re with Teq of 325 - 332K.

Source

KIC 2581316

This final entry in the list bears some significant uncertainty and was the subject of another blog post by Tom Jacobs after analysis was renewed on it several weeks ago. It appears to have been associated at one time with the official Kepler False Positive list, although it does not appear there now. The KIC still lists "Unknown" for the host star values of stellar type, temperature and solar radius, however the 217 day period transits are quite good for an 11.7 Kmag target and no significant offsets appear to be involved. If we assume that the host star is a Type G with Teff of ~5200K and solar radius equivalent to or just short of Sol, this could put the candidate inside the habitable zone at .68-.71AU and rough Teq of ~265K. The assumed radius is 10.5Re or .84Rj, making it a large exoplanet in any case and similar in domain to the candidate suspected at KIC 12735740.

Source


Various further reading and links of interest:

The Habitable Exoplanets Catalog @ PHL
Kepler: The Long Road to Other Worlds
How to Find a Habitable Planet -  Kasting
How to Build a Habitable Planet - Broecker & Langmuir
IAU 293: Formation, Detection and Characterization of Extrasolar Habitable Planets (upcoming)
What We're Looking for in the Perfect Exoplanet

Transit plots courtesy of Kian Jek. Comparison banner graphic created using Sphere-Builder app.

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In respectful memory of Neil Armstrong, who inspired us all to explore Strange New Worlds

KIC 2581316 - Unlisted Planet Candidate or Eclipsing Binary?

Planet Hunters forum Talk members flagged this transit for KIC 2581316 around May of 2011. There are now four observed transits through quarter 9 in the released Kepler data set. It appears that this transit was originally flagged as a false positive, but no longer appears on that list. The star has a magnitude of 11.69.

Q9 time plot

Here is Kian Jek's comment:

"From the profile it looks like a classic planetary transit, and may not be an EB after all - rapid drop offs, with a clustering of data points at a U-shaped bottom. Unfortunately we don't know the radius of the star."

Here is Daryll Lacourse's comment on Keppixseries below:

"July released target pixel files for KIC 2581316; the transits/eclipses seem visible and included within the large optimal aperture masks in each case. Contamination does not seem to be involved."

Full view

 Full view

Visit the Planet Hunters forum Talk page for more information on this transit here.

A New Potential Habitable Zone Exo for Kepler

The preliminary characterization of another long period exoplanet within the Habitable Zone of its host star has become possible recently by way of a third transit spotted in public Quarter 7 data, around target KIC 9958387.

This star is listed in the KIC catalog as a main sequence spectral type F just slightly larger than our own Sun, with a temperature of 6159(K) and an apparent visual magnitude of 13.5. The transits for this candidate were noted during manual searches by PH users and display a period of  237 days (with Transits 1 and 2 occurring in Quarter 2 and 4, respectively), if the aforementioned KIC values are accurate then combining them with the observed depth and duration should correspond to a body of roughly 5 times Earth radius and a Teq of 325 to 332K!

Significant pixel offsets that might indicate a contaminating eclipsing binary do not seem readily apparent here and lend some more weight to this initial characterization, although further follow up is of course required.

With a possible radius of ~32 000km, this exoplanet certainly would not resemble Earth despite being at a comfortable distance from the F star; any rocky core is likely well swathed with a thick envelope of gases that could come in a wide range of compositions. But considering the potential HZ orbit, it's interesting to speculate if significant H20, organic molecules and other basics required by the sort of prokaryotes and extremophiles we recognize may be present there--or if there are also any accompanying exomoons!

This is a crude scale approximation to Earth below; the atmospheric colors and distribution are randomly generated.

Graphics courtesy of NEA, Sphere Builder & Kian Jek

Kepler Unlisted Gamma Doradus Star Collection

Planet Hunters forum Talk members have assembled an evolving Kepler "Data Mining" list of unlisted and known Gamma Doradus (GDOR) variable stars like KIC 8364249 above. You can check out the 26 page and counting, collection here.

KIC 9031731 at quarter 9.


This is a pattern recognition list and many of the entries may fail as GDOR stars after further analysis. The list may also provide some exotic stars not currently classified. Consider this thread to be a working list of eligible stars that visually look like GDORs. Members, with the expertise, can later pull interesting stars from the list for further investigation.

From our good friend wikipedia: "Gamma Doradus variables are stars which display variations in luminosity due to non-radial pulsations of their surface. The stars are typically young, early spectral F or A type main sequence stars, and typical brightness fluctuations are 0.1 magnitudes with periods on the order of one day. This is a relatively new class of variable stars, having been first characterized in the second half of the 1990s, and details on the underlying physical cause of the variations remains under investigation. The prototype is Gamma Doradus."

Timing Is Everything

I have a quickly growing appreciation for the importance of TTV (transit timing variations) with respect to the study of extra solar planets and Kepler data in general. TTV studies have been at the forefront of Kepler research for well over a year now, revealing the presence of additional non transiting partners to confirmed exoplanets and offering us powerful new insights into the formation history and dynamical interactions within these star systems. Particularly important benchmark systems can be found detailed in the great seven part series "Transit Timing Observations From Kepler"  (available on ArXiv.org), in the recent submitted paper "Kepler 36: A Pair Of Planets With Neighboring Orbits And Dissimilar Densities", (displayed in header image) and a host of other multi-candidate system studies available in the current literature.

Planetary bodies are not the only objects subject to the tug of a neighbor. We know that the same laws of physics apply everywhere (at least at this point in the history of the Universe!) and we also know that many systems are in fact double star or binary configurations, something that perhaps makes our own home neighborhood a little more noteworthy being it lacks a such a stellar companion. While less common than binaries, triple (trinary) or greater arrangements are very possible and well known in the current literature; as many as 20% of binaries may host a third companion object. Where our viewing angle allows for eclipses, we have means to measure eclipse timing variations in similar manner to TTV's. One well known example in the current Kepler catalog takes the form of KOI-126, an eclipsing pair of M-dwarfs in orbit around an F class star.

Since the Q7-Q9 Kepler data release, additional targets of interest displaying tertiary eclipses and timing variations have been noted by PH users. The first is found at (KIC 5255552): a ~15 K-magnitude target with new anomalous eclipses visible in Quarter 7, suggesting a companion object to a detached binary pair which is itself in a ~34 day period. This companion appears to be known to the Kepler Science team already, although it has yet to be fully modeled and characterized with the available dataset.

O-C diagram for 5255552:

The second case was first noted earlier this year on PH Talk and appears to be a new trinary candidate; it exhibits obvious tertiary eclipses at target KIC 6964043 and preliminary O-C diagrams and plots show some amazing variations that can be measured not on the order of seconds or minutes--but hours!

Jeff L. Coughlin of New Mexico State University stopped by PH Talk and offered his suspicions that this system may best be explained as: "...a G5V star in a 238 day eccentric orbit around a pair of 10.7 day eclipsing M3V+M4V stars, all eclipsing each other."

Some further discussion can be found here.

Plots courtesy of Kian Jek and Jeff Coughlin. 
Banner image credit:  NASA; Frank Melchior, frankacaba.com; Eric Agol

KIC 5871985 Planet Candidate at Planet Hunters

KIC 5871985 is a planet candidate identified by Planet Hunters forum Talk members.

Here is Kian Jek's comment:

"Folded by hand to obtain a 213.25d period. Measured depth of 1939 ppm (0.001939) and duration of 8.65h, compares well with an estimated central transit of 9hr, for a 3.51x RE planet, distance of 0.615 to 0.665AU, a Teq of 198 to 206K, a little on the cold side."

KIC 8912308 Unlisted Heartbeat Binary System at Planet Hunters

The Kepler light curve above for KIC 8912308 has been identified by Planet Hunters forum Talk members as an unlisted Heartbeat binary star. Kian Jek put together a phased curve that is a tell for these type of stars below:

 

Heartbeat stars are "eccentric binary systems undergoing dynamic tidal distortions and tidally induced pulsations in the Kepler data."

Link to the discovery page at Planet Hunters here.

KIC 10074700 Unlisted Eclipsing Binary with One Year Period

KIC 10074700 is an unlisted detached eclipsing binary star system identified by Planet Hunters forum Talk members with a one year period.

Strange Light Curves in Dwarf Novae Clothing

A bit of a follow on to Tom's previous post about Dwarf Novae targets here. The search for faint background Cataclysmic Variables such as DN at the prompting of GO Director Martin Still is a very interesting tangent that has developed at PH since the project's inception. Over 200 such systems similar to the SU UMa target known as NIK 1 (KIC 4378554) could be hiding in the Kepler FOV and thus far this effort has been marked with some early success involving several promising candidates.

Since the recent Q7-Q9 data release, the sharp eyes of several PH users have uncovered a host of light curves that seemed to resemble such Dwarf Nova type variables:

These looked promising at first, but some immediate problems quickly emerged. The events were too intense, possessed no superhumps typically associated with superoutbursts and more importantly they were present only in the Pipeline corrected Kepler data (PDCSAP_FLUX), and not at all in the raw light curves found under SAP_FLUX!

Though no apparent commonality is found across FOV co-ordinates or hardware modules, (and there are several possible explanations common to the pipeline reprocessing that remain to be hashed out), one clue that may offer some explanation can be noted in the August 1st Mission Manager update by Roger Hunter:

"The new data release includes data taken in Quarter 8. This was an operationally challenging quarter, as the spacecraft exhibited a new behavior that resulted in a safe mode event and an extended interruption in data collection at the beginning of the quarter. Mitigation of the new behavior -- excess noise on the perceived sun vector -- resulted in another science loss at the end of the quarter. Quarter 8 represents the winter season for the spacecraft, where it is looking over the sun, with relatively small margins against pointing errors. The mitigations against the excess noise proved to be effective this year, when the Quarter 12 winter season was executed without incident."

In the extreme cases, most of this growing body of 'fake DN's' do appear to be found in the Q8 dataset, which is an interesting coincidence.

When in doubt, always check the SAP_FLUX!

KIC 6292925 Unlisted Heartbeat Binary System at Planet Hunters

The Kepler light curve above for KIC 6292925 has been identified by Planet Hunters forum Talk members as an unlisted Heartbeat binary star. Kian Jek put together a phased curve that is a tell for these type of stars below:

Heartbeat stars are "eccentric binary systems undergoing dynamic tidal distortions and tidally induced pulsations in the Kepler data."

Link to the discovery page at Planet Hunters here.