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KIC 8462852 dimming events
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Author | Message |
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Jon Golding Send message Joined: 20 Apr 00 Posts: 105 Credit: 841,861 RAC: 0 |
Seems like there was a recent dimming of KIC 8462852 (Tabby's star), as monitored by the American Association of Variable Star Observers. https://www.aavso.org/lcg Is this star planned to be included in the Breakthrough targeted search when Parkes telescope data becomes available? |
Michael Watson Send message Joined: 7 Feb 08 Posts: 1383 Credit: 2,098,506 RAC: 5 |
Thanks for that news, Jon! It appears that the visual magnitude dipped from a typical 11.85 value to around 12.05. My math quite rusty, but I believe that makes a dimming of about 9 percent. That's far too much to be caused by an eclipsing planet. This dip apparently occurred briefly on May 4th. Unclear if it lasted long enough to allow detailed inspection, such as high resolution spectroscopy. In any case, if these observations stand up to scrutiny, we have evidence that the short term dimming incidents on Tabby's Star continue to occur. |
Jon Golding Send message Joined: 20 Apr 00 Posts: 105 Credit: 841,861 RAC: 0 |
Seems that the series of observations showing a possible transit were all recorded by the same observer, so the results could be explained by a technical problem or local atmospheric effect that day. Going back to the original paper on KIC 8462852, some of those dimming events happened in clusters, so there may be more along anytime soon now. Hopefully someone can get a spectrum of the star during a dimming event and that might yield some clues as to what (or who!) is doing this. |
Michael Watson Send message Joined: 7 Feb 08 Posts: 1383 Credit: 2,098,506 RAC: 5 |
As I understand it, AAVSO observers are trained to estimate magnitudes by comparing the target star to nearby stars of known brightness. This would tend to reveal atmospheric and technical effects on stars' magnitudes. Naturally, multi-observer data are preferable. I'm told that a reduction in magnitude of ~11.85 to ~12.05 means a reduction of brightness of something over 30 percent, not 9 percent, as I estimated. So much for my early morning math skills! |
Jon Golding Send message Joined: 20 Apr 00 Posts: 105 Credit: 841,861 RAC: 0 |
Wow! That's a huge reduction in brightness. Even bigger than the largest 20% dip reported (https://arxiv.org/abs/1509.03622) |
Jon Golding Send message Joined: 20 Apr 00 Posts: 105 Credit: 841,861 RAC: 0 |
Here's the plot showing the dip in brightness in the context of the (usually) steady brightness of around 11.8 - 11.9 mag. I've taken the raw data from https://www.aavso.org/apps/webobs/results/?star=KIC+8462852&page=21 and made a plot of the dimming event. The entire dimming event lasts around 2 hr and is made up of a series of rapid dips in brightness. This would appear to fit with a cluster of objects rapidly moving across the face of the star (comets?) |
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