Planet Hunters Talk

Hunting for Exomoons in the Kepler Data and Analysis of KOI-1925/Kepler-409

  • ProtoJeb21 by ProtoJeb21

    Recently I've tried to find evidence of exomoons through Transit Timing/Duration Variations. Feedback/tips would be welcome.

    First target: Kepler-452b (KIC 8311864.01). No TDVs, but it has TTVs of 10, 20 and 30.9 seconds. I felt like that was worth noting, especially since the final TTV is close to that caused by TRAPPIST-1d.

    Posted

  • ajamyajax by ajamyajax

    A daunting task, but perhaps the professionals research would be of assistance:

    "Predictable patterns in planetary transit timing variations and transit duration variations due to exomoons"

    https://arxiv.org/abs/1604.05094

    And that paper was found here:

    https://arxiv.org/find/all/1/all:+AND+kepler+exomoon/0/1/0/all/0/1

    Best of luck! Hard work and determination can achieve many things right? So you could be the first to find an exomoon, as far as know anyway.

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    I'll try my best. It's a challenge understanding the different variables and equations used in the paper. However, I managed to find something else worth noting.

    I tried to find potential TTVs and TDVs for Kepler-90h to re-analyze once I wrap my head around the methods being presented in the research paper. The ones I found were way larger than expected. Just between transits 1 and 2 of 90h was a TTV of 1.5183 minutes and a TDV of 29.42136 minutes. This could signal the presence of an additional, non-transiting planet further out, but with several of 90h's transits absent due to gaps in the data, I can't tell for sure.

    Posted

  • ProtoJeb21 by ProtoJeb21

    Kepler-409b: I've observed multiple significant TTVs and TDVs, some that appear to be in a cycle of sorts. TDVs are usually around 0.3-0.8 seconds, but on a semi-linear pattern, there are larger variations that extend or shorten the duration by 1764-1766 seconds, or about 29.4 minutes. For the first 500-700 days of data, the TDVs were alternating from 29 minutes to less than a second on a consistent basis. However, this pattern was broken by three gaps in the data. TTVs were also significant, with 14 out of the 16 I observed being around 7.8 to 50.4 seconds. One was about 5.11 seconds, while another was 25.54302 minutes.

    I'm not too sure if this could be the signature of an exomoon or an additional exoplanet, but the somewhat periodic nature of some variations makes this quite interesting and probably something for the professionals to investigate.

    Posted

  • ajamyajax by ajamyajax in response to ProtoJeb21's comment.

    Just curious, how does this compare in short cadence vs long cadence?

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    So far I've only check in the long candence set, using all 17 quarters. I'm not too sure how transit size will be affected by viewing it in a smaller piece of the data.

    Posted

  • ajamyajax by ajamyajax in response to ProtoJeb21's comment.

    Well, the transit ingress and egress times might be more precise but the only way to know is to take a look.

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    I've done some initial analysis of a smaller candence (Quarter 2, to be exact) and the transit data appears to be exactly the same as when it is viewed with all 17 quarters. I'll do some more comparisons when I get the time later.

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    Okay, it seems highly likely that using either long or short candences has NO effect on how the data appears. Each data point is still in its exact place, regardless of how many quarters are being analyzed at the same time.

    I'm thinking that the intriguing transit timing/duration variations of Kepler-409b should be reported to someone who specializes in TTV/TDV analysis because of the implications of a second planet, an exomoon, or both. David Kipping and maybe some others working on HEK would definitely be interested in this. What do you think?

    Posted

  • ajamyajax by ajamyajax in response to ProtoJeb21's comment.

    Certainly, message anyone you think might be interested in your findings. I would search the scientific papers and the internet at large for your target first though, just to be sure they haven't already studied it. But who knows, you could be on to something. Good luck!

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    I did find one scientific paper that mentioned 409b. However, it was only about the predicted mass for the planet, which is about 2.69 M_E. It was found in Section 3, which describes the mass-radius relationship for exoplanets below 4 R_E and the predicted masses for some planets in that radius range:
    http://escholarship.org/uc/item/26f2989j#page-6

    Posted

  • ajamyajax by ajamyajax in response to ProtoJeb21's comment.

    Ok good news so far, and these papers might not have any exomoon studies either but here is a full text search of the KIC:

    http://search.arxiv.org:8081/?query=9955598&in=

    Kepler-409, 2MASS J19344300+4651099, KOI-1925, KIC 9955598

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    I've gone through the 27 papers you linked to, and only about 3/4 of them are related to Kepler-409. Of those articles, none talk about exomoons or transit timing/duration variations. Many are about the characterization of Kepler parent stars, and have little to do with the planet itself. They do provide some interesting data of the host star that I would like to read more in-depth about when I get the chance.

    Posted

  • ajamyajax by ajamyajax in response to ProtoJeb21's comment.

    Good news again, and can't beat interesting either. 😃

    Posted

  • ajamyajax by ajamyajax

    This paper might interest. What about asking this scientist about your findings?

    "On the Detection of Extrasolar Moons and Rings"

    https://arxiv.org/pdf/1701.04706.pdf

    And seems like a decent overview of future searches here:

    "Life Outside Our Solar System Might Exist on Exomoons"

    By Elizabeth Howell, Space.com

    http://www.space.com/36251-alien-life-might-exist-on-exomoons.html

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    Those are some interesting articles that seem like will help my searches. Also, I've already E-Mailed David Kipping about the transit variations of Kepler-409b, along with a pdf document listing the TTVs and TDVs found.

    Posted

  • ProtoJeb21 by ProtoJeb21

    @ajamyajax I just discovered something that would make the quest for an exomoon around Kepler-409b even more interesting.

    While going through KOI-1925's data with LcViewer, I realized that the transit of Kepler-409b was WAY too short. For a planet in a 68.9584 day orbit around a 0.92 Msun/0.89 Rsun star, it would have a duration of over 6 hours. This is not what's happening. Instead, Kepler-409b has an average transit duration of 3.6 hours. This means that the host star is much smaller than previously thought. My calculations show that KOI-1925 could be as small as 0.35 solar radii and 0.39 solar masses! That is TINY! This would make Kepler-409b a 0.40 Earth radius planet smack in the middle of the habitable zone. In addition, the strong TTVs and TDVs may hint that this is a BINARY planet.

    Wow. I did not expect such a difference between predicted and actual transit duration. If the star is actually not a red dwarf, then my guess is that Kepler-409b has a very eccentric orbit and only transits around perihelion. This means the planet is going much faster than expected and produces shorter transits. Such an eccentric orbit would lead to dramatic climate swings and an orbit-spin resonance, similar to what Mercury has.

    EDIT: Also, based on the amount of potential extra transit events in the light curve I'm pretty sure there's at least one other planet in the system.

    Posted

  • ajamyajax by ajamyajax in response to ProtoJeb21's comment.

    Re Kepler-409/KOI-1925/9955598: @ProtoJeb21, took a quick look and this target certainly seems to be the K0V to G8V star on record at a bright 9.439 Kepmag too. It just doesn't look like any small red 0.35 M-dwarf I have ever seen from these type of records and a quick look at Aladin Lite. I also saw a "Platinum Standard Star" label on ExoFOP which seem to be for "well-characterized standard stars" according to an internet search. So with this in mind as well it seems unlikely the professional astronomers are as far off as you suggest. So you might want to add some quick looks at Simbad and Aladin Lite to your research and as usual, see what is written in the published papers from astronomers who spend a good deal more time at this than you or I. Best of luck.

    From NEA, K1 Targets within search area:

    KIC RA [decimal degrees] Dec [decimal degrees] Distance [arc sec] Kepler-band [mag]

    9955598 293.6792 46.8528 0.0 9.439 2MASS J19344300+4651099

    9955569 293.6682 46.8437 42.48 14.406 2MASS J19344036+4650372

    9955638 293.695 46.8471 43.74 14.755 2MASS J19344679+4650497

    9955576 293.6707 46.8295 86.27 14.208 2MASS J19344097+4649462

    9955707 293.7216 46.8402 113.86 15.280 2MASS J19345318+4650246

    9955492 293.637 46.8691 119.35 15.051 2MASS J19343288+4652087

    9955702 293.719 46.8256 138.38 13.338 2MASS J19345255+4649322

    9955745 293.7365 46.851 141.31 15.598 2MASS J19345676+4651036

    9955746 293.7367 46.8434 145.54 15.798 2MASS J19345680+4650360

    9955562 293.6663 46.8934 149.73 15.392 2MASS J19343991+4653362

    9955598,2MASS J19344300+4651099,293.679200,46.852760,5460,0.893,0.9180,9.439,(G8V)

    Aliases

    Kepler-409

    KOI-1925

    WISE J193443.00+465109.9

    Listed as BD+46 2726 -- Star on Simbad, Proper motions mas/yr: 6.7 -6.8, Spectral type: K0V, 19 34 43.0038 +46 51 09.945

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    I recently realized that I forgot one major trait of planetary transits: angle. So that means Kepler-409b is a grazing transiting planet.

    facepalm

    I really messed up there. And I want to report something so I don't mess up again. In the light curve of KOI-1925 are two transit-like events at epochs 185.642335 and 440.772429. While these two events are symmetrical and show a clear, strong dip in starlight, I think that they could be caused by rolls and motions of the Kepler spacecraft. I've made this mistake before with KIC 7105665. Are these actual long-period planet transits or nothing more than data glitches.

    Epochs of other interesting events: 548.011582, 549.319365, 609.41499, 616.954896, 816.188834, 1109.502791, 1116.276379, 1191.319124, 1350.429299, 1522.373408, 1530.189302,.

    I also keep finding transit-like events similar to the one at epoch 1555.088042, maybe it's from a new planet?

    Posted

  • ProtoJeb21 by ProtoJeb21

    I averaged out the transits of Kepler-409b and was able to refine its radius. The planet appears to be around 0.9524 (+0.4476/-0.4824) Re, around the same size as Venus.

    Posted

  • ajamyajax by ajamyajax

    We looked into the spacecraft roll issue back in the old PH days and seems like the larger events were Q2, 6, 10, and 14, if that helps:

    http://oldtalk.planethunters.org/objects/APHE3001a95/discussions/DPH101z3nd

    Regarding your pet project, looks like I also speculated on that one for more transits some four years ago.. At a glance anyway my two here look kind of iffy now; hope yours are better and something periodic that folds in LcViewer sure would help your chances! Also any dips at times reoccurring in multiple light curves are most likely glitches right? There are probably lists or posts on oldtalk about all those in K1 too. Good luck.

    http://oldtalk.planethunters.org/science/discussions/DPH101z2pd

    KID 9955598 KOI 1925

    possible second transit that starts at 155.065 BJD with a period of 50.69.

    and a third is possible that starts around 129.50 BJD and has a period of 20.515.

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    I can't find the two transits you mentioned in the Old Talk. Also, it seems like at least one of the two transits I mentioned are caused by spacecraft roll glitches. There are still some more interesting events in need of investigation. However, I'm not going to mark any more candidates until I can use TTVFast and determine if there even are any other planets present. Earlier today I E-Mailed the scientist who submitted the paper on TTVFast, Katherine Deck, for help on installing and operating the program. There were multiple things I didn't understand about it and I didn't want to create any complications by trying to do it on my own. After I'm able to use TTVFast on Kepler-409b, my next target is the system EPIC 220221272, discovered by shutcheon and Vidar87 over on Exoplanet Explorers. I've managed to pin down the radii of the five tightly-packed, likely rocky planets, and I want to try and figure out the masses and compositions of these planets via transit timing variations.

    Posted

  • ProtoJeb21 by ProtoJeb21

    @ajamyajax @zoo3hans

    I think I just found a second planet around Kepler-453AB. It's a Super-Earth of 1.71 Re orbiting every 415.639961 days with a sigma of 11.372. The best transit is at epoch 589.676001. Believe it or not, this is so far my first (and only) good-sigma planet candidate around any Kepler Mission 1 star. Also, there are FAR more likely transit events (excluding secondary eclipses, of course) that do not appear to be from Kepler-453ABb.

    Posted

  • ajamyajax by ajamyajax in response to ProtoJeb21's comment.

    Kepler-453, KIC 9632895, KOI-1451 seems to be a well-studied circumbinary system. But if you were able to get a fold or fit on your candidate it could be interesting these scientists:

    "KIC 9632895 - The 10th Kepler Transiting Circumbinary Planet"

    William F. Welsh, Jerome A. Orosz, Donald R. Short, Nader Haghighipour, Lars A. Buchhave, Laurance R. Doyle, Daniel C. Fabrycky, Tobias Cornelius Hinse, Stephen Kane, Veselin Kostov, Tsevi Mazeh, Sean M. Mills, Tobias W.A. Mueller, Billy Quarles, Samuel N. Quinn, Darin Ragozzine, Avi Shporer, Jason H. Steffen, Lev Tal-Or, Guillermo Torres, Gur Windmiller, William J. Borucki

    (Submitted on 4 Sep 2014)

    https://arxiv.org/abs/1409.1605

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    I decided to use the values and parameters given in the paper to figure out the inner limit of the system and by definition the inner limit of which planets can have stable orbits. 453A is 0.02984 AU from the system's barycenter, while 453B is 0.14366 AU away. Next is the periapsis and apoapsis of the two stars around the barycenter (wait, if around the barycenter, would it be called "peribary" or something like that?). Using the stars' eccentricity of 0.0524, I'm able to find the average separation between the two stars. This ranges between 0.1644086 and 0.1825914 AU. Now, with this information, I can calculate the inner limit for stable planetary orbits. The so-called "Forbidden Zone" of the Kepler-453 system ranges from 0.054803 AU to 0.5477742 AU. This means that any planet candidates with orbital periods between 4.409 and 139.32873 days should not exist and are probably false positives...unless Kepler-453 b just happened to throw a poor planet into that zone within the last 100 million years or so. This also means that any planets inside the orbit of Kepler-453 b must have a close, resonant orbit with the known planet. I believe the only stable resonances for this system would be 5:4, 4:3, 3:2, and 6:5. Because of the low mass of Kepler-453 b, any resonant planets could get much closer without throwing the system into instability. So, in conclusion, the only candidates that are likely to be real must have orbital periods that either fall between 160.335 and 200.419 days, or are greater than 288.6 days (which would be in a 6:5 resonance with Kepler-453 b).

    Regarding my candidate, it has a very stable orbit and is close to a 5:3 resonance with Kepler-453 b. However, it's individual transits do show something odd. While the folded transit looks quite good, only the first two individual transits look great. The final two are...meh. This leaves two possibilities: Either my candidate is a false positive, or it has a precessing orbit like Kepler-453 b. With just four individual transits and a sigma of 11, it's hard to figure out which explanation is the most likely. Right now I'm starting to lean towards the false positive hypothesis.

    Here's the folded transit of my candidate, KOI-1451.02:

    Also, some other transit-like events in need of investigation are at epochs 1341.264546, 248.710199, 455.260976, 449.375902, 209.100287, 219.96066, and 218.366856. I have no idea which ones are noise or not.

    Posted

  • ProtoJeb21 by ProtoJeb21

    Update on my exomoon searching project:
    Since I have not been getting very far with the setup of TTVFast, I have decided to ask David Kipping for help using his method for exomoon detection. This is partially due to his success with the candidate exomoon Kepler-1625b I. So far I have collected TTV and TDV data for Kepler-1630b (KOI-5454.01) to use for my analysis, which as of now shows that something might be affecting the orbit of this planet. While TDVs are marginal and almost definitely caused by image noise, there is a significant TTV of 34.29 seconds between transits 2 and 3. I have inquired David about how to continue.

    Posted

  • ajamyajax by ajamyajax in response to ProtoJeb21's comment.

    If it helps, we made a bit of progress with TTV Fast in the past. I still have my C compiled TTV Fast EXE too, so if you have a Windows PC I could always get that to you to experiment with. The charts are in my custom python code though. And all that you see here as far as I got anyway, before being distracted by new projects (as usual):

    https://talk.planethunters.org/#/boards/BPH0000005/discussions/DPH0000ntu

    https://talk.planethunters.org/#/boards/BPH0000007/discussions/DPH0000nue

    Posted

  • ProtoJeb21 by ProtoJeb21 in response to ajamyajax's comment.

    I'll try them out when I get the chance. It turns out that I really do need TTVFast now, because I noticed something odd about Kepler-1536b. This cold Mini-Neptune has the most promising transit variations I've ever seen. All TTVs are between 29 and 31 seconds, and the four transits alternate in duration from 12.75 to 13.24 hours, then 12.75 to 13.24 again. It's almost like a cycle, which leaves me to believe these are caused by an extra planet or a large exomoon. This odd cyclic variation pattern has not been seen in any other planets I've analyzed. They're not even in the SC SAP data for Kepler-1625b (although it has pretty significant TTVs). If this is caused by a moon, then the satellite is likely in resonance with the orbit of its host.

    Posted

  • ProtoJeb21 by ProtoJeb21

    I just realized how inefficient my method for finding potential moon-hosting planets is. What I do is record the transit depth, transit duration, and mid-point time of all the transits of the planet I'm planning to analyze, then compare these values to those on NASA's Exoplanet Archive. For finding TTVs, I take the planet's orbital period, P, and add it to its first transit mid-point time, M. I will have to multiply P depending on how many transits have gone by since the first. For example, if I want to find the predicted mid-point time of a planet's 5th transit (which is four transits after the first), I would have to use the equation M + (P x 4). TDVs are pretty simple: just calculate how far the transit duration is off from what's given on the Exoplanet Archive.

    Here's the problem with all this:

    I think most of these results, including those of the enigmatic Kepler-1536b, may be caused by differently processed data than what was used to get the parameters on the Exoplanet Archive. To try and find an exomoon transit, which will probably be more effective, I would need to use the same data processing strategy that David Kipping and his team used to find Kepler-1625 b I (which still has yet to be confirmed or disproven). Does anyone know how I would go about processing individual transits where I could easily see a potential exomoon transit?

    Posted