KIC 8462852 Observations Options

[HSchirmer]

The escape velocity of a white dwarf is about 6,000 km/s, white dwarfs have a mass of over 100 Jupiters, and collisions are inelastic. That is never going to produce planets.

Agreed. You can't hit a white dwarf and break it up, unless you have a really big hammer.
Consider a white dwarf in a loose binary system where the other star goes supernova.
That shock wave should disrupt the dwarf, possibly leaving planetary mass chunks, or blasting it into smaller chunks.
Since we see planets around pulsars, even after a supernova, the disrupted material should reform planetary mass objects.

I'm not sure what the minimum gravitational force is to keep degenerate matter "packed down", thinking about it, it would seem
that the degenerate matter would "re inflate" violently when a white dwarf is disrupted.

[JRehling]

Consider a white dwarf in a loose binary system where the other star goes supernova.
That shock wave should disrupt the dwarf, possibly leaving planetary mass chunks, or blasting it into smaller chunks.

It's probably not the strongest use of this board to offer qualitative assumptions about never-observed phenomena. The outcomes of huge, cosmic collisions require pretty detailed research to determine, and math-free estimates of how they would proceed doesn't seem likely to be productive. A little math suggests to me that a supernova would not break a white dwarf apart, but that's not really on-topic for this board even if the issue were investigated thoroughly, much less when assumptions are made without math.

[Hungry4info]

Besides, we know of numerous pulsar+WD binaries.

[nprev]

JRehling is correct. Please stay on topic.

[ZLD]

JPL posted a short article yesterday further suggesting the comet swarm hypothesis for the strange occurrence with KIC 8462852. The referenced paper is here for those with access. The reasoning is a continued lack of infrared evidence that would point toward other possibilities, mainly the breakup of a large rocky body.

[Mongo]

Paper is up on ARXIV now:

KIC 8462852 - The Infrared Flux

We analyzed the warm Spitzer/IRAC data of KIC 8462852. We found no evidence of infrared excess at 3.6 micron and a small excess of 0.43 +/- 0.18 mJy at 4.5 micron, below the 3 sigma threshold necessary to claim a detection. The lack of strong infrared excess 2 years after the events responsible for the unusual light curve observed by Kepler, further disfavors the scenarios involving a catastrophic collision in a KIC 8462852 asteroid belt, a giant impact disrupting a planet in the system or a population of a dust-enshrouded planetesimals. The scenario invoking the fragmentation of a family of comets on a highly elliptical orbit is instead consistent with the lack of strong infrared excess found by our analysis.

[Mongo]

KIC 8462852 Faded at an Average Rate of 0.165+-0.013 Magnitudes Per Century From 1890 To 1989

The star KIC 8462852 is a completely-ordinary F3 main sequence star, except that the light curve from the Kepler spacecraft shows episodes of unique and inexplicable day-long dips with up to 20% dimming. Here, I provide a light curve of 1232 Johnson B-band magnitudes from 1890 to 1989 taken from archival photographic plates at Harvard. KIC 8462852 displays a highly significant and highly confident secular dimming at an average rate of 0.165+-0.013 magnitudes per century. From the early 1890s to the late 1980s, KIC 8462852 has faded by 0.193+-0.030 mag. This century-long dimming is completely unprecedented for any F-type main sequence star. So the Harvard light curve provides the first confirmation (past the several dips seen in the Kepler light curve alone) that KIC 8462852 has anything unusual going on. The century-long dimming and the day-long dips are both just extreme ends of a spectrum of timescales for unique dimming events, so by Ockham's Razor, all this is produced by one physical mechanism. This one mechanism does not appear as any isolated catastrophic event in the last century, but rather must be some ongoing process with continuous effects. Within the context of dust-occultation models, the century-long dimming trend requires 10^4 to 10^7 times as much dust as for the one deepest Kepler dip. Within the context of the comet-family idea, the century-long dimming trend requires an estimated 648,000 giant comets (each with 200 km diameter) all orchestrated to pass in front of the star within the last century.

Okay, this is unexpected. Clearly, something very weird is going on around this star.

A decline of 0.193 magnitude over a century equals a drop of 16.3%!

[nprev]

Interesting. First thing this makes me think of is a close hot super-Jupiter that is shedding mass at a rapid rate, though constant over the observation period.

[Mongo]

Interesting. First thing this makes me think of is a close hot super-Jupiter that is shedding mass at a rapid rate, though constant over the observation period.

It appears that no RV variations have been detected, as stated in the discovery paper. In addition, there is no IR flux as would be seen from an evaporating planet. From IRTF/SPEX Observations of the Unusual Kepler LightcurveSystem KIC8462852:

Our observations are consistent with a normal main sequence star without sufficiently large amounts of circumstellar gas or dust, or inflowing or outflowing material, to produce a SpeX detection via the scattering or thermal re-radiation of the star’s insolation. Our observations have eliminated the possibility that there is a sizeable amount of very close-in, very hot (>1000 K) material along our line of sight to the star during the IRTF observations on 31 Oct 2015.

[nprev]

Hmm. Curiouser indeed. Almost seems like it has to be something intrinsic with the star itself, then.

[ZLD]

Clearly just Starkiller Base finishing checkout testing.

Joking aside, maybe this is a heavy element star that is fusing at a more rapid rate than it should be?

Also, what of the possibility of a small wandering black hole? Unfortunately, there doesn't seem to be any xray data of this area that I find. How close would a black hole need to get to start leeching material from the star and how obvious would that be initially in the first 100 years? Seems like it should be immediately when material hits the event horizon, x-rays would begin streaming out but if the intake is low still, would Chandra even be able to detect a faint stream of xrays?

I'm sure this star will turn out to be far more simple than anyone has yet proposed but if nothing else, its been good for getting people to talk about astronomy more.

Edit: Just to update on xray detection, the ROSAT data set has xray coverage of this region and nothing jumps out.

[Gerald]

Black holes (besides hypothesized primordial ones) have a minimum mass a few (1.5 to 3) solar masses, since they form by overcoming the Chandrasekhar mass limit for neutron stars (Tolman–Oppenheimer–Volkoff limit). A Black Hole sufficiently close to a main sequence star to accrete its outer hull would form a fast-rotating binary system with the star, usually causing high radial velocities relative to Earth. This would cause a considerable oscillation of the Doppler shift of the spectrum of the star, and would hence be immediate by spectral observations.

[JRehling]

I wonder if the reality is that the dimming occurred in two sharp declines, with relatively level plateaus before and after each of them. That's how the data points look to me. I have no idea what dynamic, inside or outside a star, might cause that.

[Mongo]

I noticed this statement from the Bradley E. Schaefer paper:

The long-term trend in the DASCH light curve can be described in various ways. One way is simply to note that KIC8462852 faded from B=12.2650.028 in 1892.5 to B=12.4580.012 in 1987.5, for a total fading of 0.1930.030 mag in 95 years. This fade rate is +0.2030.032 magnitudes per century (dashed line in Figure 1). This end-to-end trend line provides an excellent representation of all the Harvard data except for the decade from 1900-1909. The individual plates for this decade show a similar distribution of magnitudes as in adjacent decades, except that there are many more fainter magnitudes (from 12.6-13.0). This might be due to the star suffering many deep dips during the years 1900-1909.

This sounds plausible to me. It would mean that there has been a quite steady decline in brightness over the periods covered by the plates (1890-1953 and 1969-1989) at a rate of about 0.203 magnitude per century. But during the time period 1900-1909, many of the observations showed lower than expected brightnesses, perhaps due to there being a lot more "dips" than in the other years. Many (most?) of the observations in those years were still in line with the 1890-1989 trend, though.

The author also stated that lower than expected brightnesses also occasionally happen at other times, so I assume that the observed rate of "dips" in the Kepler observations (2009-2013) would be consistent with the star's 1890-1900, 1910-1953 and 1969-1989 behavior.

In this podcast Schaefer states that the only other comparable collection of plates to the Harvard Observatory collection that he had used, is the one created by the Sonneberg Observatory in Germany from the 1930s to the 1990s. This could be used to check the results found from the Harvard plate collection.

[Mongo]

Okay, I've decided to download the full archive of Harvard Observatory observations of this object. I went to the DASCH Lightcurve Access page, and entered the object's coordinates: 20 06 15.457 +44 27 24.61 and got a text file that I converted to a spreadsheet file (which I tried to upload to this post, but it was not allowed).

I extracted the magnitude measurements with an RMS equal to or less than 0.2 (1265 data points) and created a chart with a second-order polynomial trend line:



There is a definite decline of about 0.2 magnitude (the trend line appears to underestimate this), but it also appears relatively flat from 1890 to 1953, and when observations resume in the late 1960s, the average brightness appears to be well below the earlier values and steadily declining.