Montag, 17. Oktober 2016

Meditation over the WTF Star Dips, Part II

KIC 8462852 and the really deep dips

This is the second part of my meditation over the strange dips in the light curve of Tabby's Star. You find the first part here: "Some aspects of KIC 8462852".

Dip 9 

The following dip 9 is not very spectacular, the signal is near the noise limit. 
Fig 1: Dip 9 at d848
Be aware, that most of the signal in this plot is due to the rotation of the star, period 0.88 days, and the fluctuation of the brightness is, as far as we understand other stars, a result of sun spots.

Beside this very natural signal change we see a dip, that starts at day 846 goes down to a minimum near day 848 and then the brightness recovers again. The exact shape is not known, due to the noise and influence of the sun spots. The shape in depth and time is not unlike a small planet, similar a transit of the earth in front of our sun. 

Dip 10 and 11

The dip numbers, to be exact the time frame, are automatically generated by the computer. The size of any signals in this period is not useful for any further discussion. May be we find a periodicity then it could be a hint for any object like a planet.

Dip 12

In the case of dip 12a we have no information for the dimming part, due to some measurement errors. 
The recovery of this relative small dip, 0,11% depth, shows a unusual behavior for a planet transit. But it has a very similar shape as dip 8, going back to normal brightness with some type of exponential looking shape.
Fig 2: Dip 12a at d1126
The strange thing with this dip is, why do we see the measurement error at the beginning and then an exponential recovery? We can only understand the quality of the shape, if we understand exactly the reason, why we see a measurement error. If anyone reads this blog with more background on the detector system of Kepler and this glitch, he is welcomed to give me a hint.

The case of dip 12b looks again structured.

Fig 3: Dip 12b at d1143
The dip 12b has a deepth of 0,12% and has a ramp before a very steep dip follows. this is a little bit similar to dip 1, although there is much more signal available. Then follows a floor as already seen in dip 2, and then a similar ramp to recover from the dip. A planet with a accreditation disc might show a similar shape, the problem is the timing. The central dip lasts more than two days, this is hardly possible for a planet orbiting a large star.
Fig 4: Dip 12b with manually interpretation of the shape
Short, within the ramp of dip 12b follows dip 12c, a small dip with a typical shape of a planet transit,
Fig 5: Dip 12c at d1151 lasts about one day
The duration of one day is about 2 times shorter as the central part of dip 12b.

Dip 13

 Dip 13 may be a member of another class of dips, looking very symmetrical. But it could also be interpreted as a case of 3 to 4 consecutive dips, which are by chance similar in size.
Fig 6: Dip 13 at d1205 a very symmetric shape
We could compare this dip with dip 4a, also a set of dips, that starts with a small dip, then a center dip and then another small dip. There has been some discussion about timing and depth within this dip.
Depending on the baseline, there could be a rational 1:2 between the minor dips and the major dip in the center.

Fig 7: Dip at d1205 with a projection of the mirror of the image.
I will look in the interesting symmetric shape of the dip. Therefore I include the mirror image into figure 7. We could see at least four elements, A, B, C, D, ups and downs in the flux, which apperare with perfect timing relative to the central symmetric line. It is hard to believe, that this happens by chance. Some physical reason could be a ring system around a planet. But the shape of the central dip does not support this idea. Very strange is, that dip 16d at day 1536 has a similar shape, but a different size, I will discuss this later.

A Planet?

If we look into some details of the complex dip structure, it should be mentioned, that at d1208,2 a small rectangular dip shows up, similar do other dips like 12c at d1143. A time difference or 137 days.  Adding this, the next expected dip should be at d1417 and the at d1554. At d1417, Kepler has no signal due to technical problems, but at 1554 there seems to be the same dip (depth delta 21 [e-/sec]), may be the same object! There is also a small dip at 1007, nothing at 869, no data at 732, and 321, but a small signal at 185. Planet hunters should look into the details.

Period 14 and 15

Due the time interval from day 1274 till day 1471 no very significant event appears. It should be mentioned, that at d1433 a drop in the flux with the typical duration, often seen before, of 8 days but with a small amplitude 38 (s-/sec) is visible.
Fig 8: Dip at d1433, amplitude in the range of typical fluctuations due to sunspots(?).

Period 16 and 17

Period 16 and 17 contain the most dramatic fluctuations ever seen in a star of this type. The flux is up to 22% dimmed. Very hard to understand by well known astronomic events. The shapes seem to be part of one larger, symmetric event, as pointed by Gary D. Sacco in the reddit thread "95 Day Abnormal Equilibrium of Periodicity and Flux Variation" [1]
Fig 9: a 95 day period with more or less symetric deep dips, source gdsacco [1]
As Gary D. Sacco points out, the distance between the different dips seem to be arranged near a central dip at day 1539. The shape of dip d1539 (depth 670 [e-/sec]) is visual similar to dip 13 at d1205 (deepth 111 [e-/sec]), although 6,03 times deeper.  

The symmetry is by far not perfect and the optical center of the dips is not the center of symmetry. Very strange is the aspect, that the sequence before the first and second large dips are a little bit similar on the time axis. If we look into the structure of d1519 in fig 10, we see a complex structure.

Fig 10: The left large dip at day 1519 seems to be a double dip 
To get the details, I added some lines see fig 11. 
Fig 11: The elements of dip group around d1519.
After two small dips A,B, the flux recovers and starts to drop strong along a line C. Another object D comes into the scene and accelerates the drop. The flux recovers a little before dip E and F come in. For some reasons, after dip F recovers, a linear flux reduction, given by line G appears this might be part of another element that is wider than the object that resulted in E and F. Object H might produce the next dip and another, different thing, shown by line I leads to the final recovered intensity.

Together at least nine different elements of whatever nature result in the strange flux signature.

Now look into the second big dip:
Fig 11: The right dip at day 1568 has a single full dip.
I also try to introduce some helpful lines shown in fig 12:
Fig 12: The elements of the dip group around d1568.
It starts with a slight decay of the flux during period A, and a first dip B five days before the full dip F shows up. But before that after s light lower plateau, again a slight decay C and then the first large dip D, and similar to d1590 dip C, and then a stronger dip E, similar to D in d1590. After a slight recovery the main dip F appears. During return to normal, a small dip G appears, might be in some way similar to dip H in d1590.

The choreography is similar, the values are not similar and they are not simple mirror signals around the symmetric center. This makes the understanding of the reason of the signal much more difficult. For example a disk like Saturns rings could not explain the flux.

It should also be mentioned, that the choreography is by the structure similar to dip 7 d694, although this dip is are much smaller in depth.

Conclusions so far

  • The different dips seem not to be from the same family of natural events, of whatever type they are. 
  • Interestingly, most of the dips have an internal structure. Only very weak dips don't show a visible structure, but this is a effect of noise, we are not able to see them.
  • Most events have a similar choreographic structure, they start with small events and the biggest dip is at the end of the event, a little like in a firework (:-).
  • There are at least two events d1205 and d1540 (and d359 a little) that show an astonishing symmetric structure, that is hard to be explained by accident, like comets coming with the right timing. Although there might exist natural explanations like ring systems around a planet, which could lead to such a flux variation.
  • The strangest of all dips is d792, it seems not to be the product of a multi event. My best guess is, that something pointing away from the star, like a column of smoke, is the cause. This is implied by the tangent function and the exponential function, that fits very well (see first part). If the "smoke" is a little bend to one side, even the asymmetric structure can be plausible explained. 
  • The reason of the smoke column could be a internal event of the star, similar to a solar flare, but millions of miles high and cooling down. The artificial star lifting should be included into the discussion.
  • All events seem to happen within a time frame of less than 10 days and last at least five days. This tight time frame is another strange independent element of the KIC 8462852 story.

back to part one of the meditation over WTF Star dips

Next part is the dip of day 792 a sign of star lifting, the post contains some mathematical analysis.


[1] Gary D. Sacco,

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