What causes the slow fading of the star?
Most likely: a large, diffuse amount of circumstellar dust, more extended than the clumps that make the dipsAhead on the evidence, not yet confirmed. It needs two reviews to be accepted.
Where it stands
Four answers have been proposed. A large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips. leads, with evidence 3 for: partly supported by its tests. Three are still possible. Of the two narrower questions under it, none is answered yet.
Answers 4
Next steps 1
1
Quantify the dip-fade link in Kepler; set an early-warning rule
Could shiftGood odds~4 h
40score
Details
Test the dip-fade link quantitatively. In the Kepler long-cadence and full-frame data, compare the flux level in 90-day windows around each dip family with the windows between them. Then predict: if the link holds, the next dip episode should start with a slow fade of 1-3 per cent. Write this into the AAVSO observing request as an early-warning criterion: a 10 mmag seasonal drop means intensify monitoring.
Ranked by how likely each is to move the key question, for the time it takes
History
- Wright & Sigurdsson puts forward: an interstellar cloud or other intervening material passing slowly across the line of sight.
- Montet & Simon: over 20 years, the star faded only while it was dipping: 2011-2013 and 2015-2018For: A large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips.
- Wright & Sigurdsson: the star's reddening and narrow sodium absorption are consistent with the total long-term dimming.For: An interstellar cloud or other intervening material passing slowly across the line of sight.
- Meng et al. puts forward: a large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips.
- Metzger et al. puts forward: the star is returning to normal after swallowing a planet, which brightened it.
- Meng et al.: the fade from 2015 to 2016 is about 22 mmag per year in Swift bands and about 5 mmag per year at 3.6 to 4.5…For: A large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips.
- Meng et al.: the fade's colour dependence is consistent with circumstellar material.Against: The star is returning to normal after swallowing a planet, which brightened it.
- Meng et al.: the fade is less steep in wavelength than general interstellar extinction.Against: An interstellar cloud or other intervening material passing slowly across the line of sight.
- Schaefer et al.: the secular decline continued to 2018 at a varying rate.For: A large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips.
- Joshua D. Simon et al.: over 20 years, the star faded only while it was dipping: 2011-2013 and 2015-2018For: A large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips.
- Joshua D. Simon et al.: the 2006-2026 record recovers and holds level; it is not a one-way relaxationAgainst: The star is returning to normal after swallowing a planet, which brightened it.
- Miguel Martinez et al.: the 2006-2026 record recovers and holds level; it is not a one-way relaxationAgainst: The star is returning to normal after swallowing a planet, which brightened it.
- Session 1: worked on three of its sub-questions
- Session 2: worked on one of its sub-questions
- The modern record assembled. The fade stopped in 2018, and the October transit window was watched: worked on one of its sub-questions
- Session 4: took the question up again, ran one test, found two results bearing on its answers and worked on two of its sub-questions