All observations for 2017.06.18 and later can be found at http://www.brucegary.net/ts/



Kepler Star KIC 8462852 Amateur Photometry Monitoring Project

B. L. Gary, last update: 2017.07.11, 03 UT



"A ... prediction is that future dimming events should occur roughly every 750 days, with one in 2015 April and another in 2017 May." Boyajian et al, 2016 (Section 5.2) link.



Final result for Jun 17 (7.6 hours of data), showing recovery of latest dip.





Normalized flux vs. UT during the Jun 17 observing session, showing a dip recovery in progress.





Links on this Web Page



Basic Info for KIC846



RA/ DE = 20:06:15.5, +44:27:25

All-sky photometry: B = 12.493 ± 0.025, V = 11.912 ± 0.025 (B-V = +0.581 ± 0.035)

APASS Mag's: B = 12.360, V = 11.852 (B-V = +0.51), g' = 12.046, r' = 11.697, i' = 11.554



BV mag's in Boyajian et al (Table 3) and APASS (article is brighter).

There's a 0.23 & 0.21 mag discrepancy between BV mag's in Boyajian et al (Table 3) and my all-sky V-mag (article is brighter).



Speculation About Collisions

Yearly Timescale Fade Observations



My observations began in 2015 October with a month of clear filter observations. On 2016 Sep 25 I resumed observations using a V-filter, and observed for 3 months. A third group of observations began 20 16 May 02, using a V filter . Comparing "clear filter" magnitudes with "V filter" requires an empirical offset adjustment based on near-simultaneous measurements with both filters (obtained during the 2016 May observations) . The results of this adjustment are shown in the next graph. T here's "a hint" of a non-linear fade during the 610-day interval from 2015 October 16 to the present, as first pointed out to me by Fredric Parker (private comm., 2017.06.09). This fade has been modeled using a Gaussian function with a long 1/ e half-width in the date dimension (640 days). The Gaussian is centered on DOY_2016 = 1080, where the depth is 0.030 mag. Th e use of a Gaussian function was guided by the notion that the fade is caused by a dust cloud that is expanding along an orbit (at ~ 1.6 A.U, in the HZ, by the way) in response to a "giant collision" (as described in the Speculation paragraph above , link).





Figure 2.1. Magnitudes on the V - mag scale vs. date (2.3-year interval). C-mag's were adjusted empirically to afford agreement in 2016 May, when both V- and C-filter observations were made. O n ly OOT (out-of-transit) measurements are shown. A "Gaussian Fade Model" has been fitted to the measurements. Fade rate changes throughout this date region, and is currently ~ 1.4 %/year.





Such a dust cloud will eventually disperse and lead to a complete recovery of KIC846 brightness. The early phase of this recovery can be seen in the next figure.







Figure 2.2. Same as above, but showing a 3.8-year interval. The " Gaussian f ade m odel" reaches a maximum fade of 0.030 magnitude at the end of 2018, after which a slow recovery occurs (according to the model). Maximum fade rate, according to this model, occurs in late 2017.



The next graph shows all 2016 V-band measurements, including those identified as occurring during dips.







Figure 2.3. All 2016 V-band measurements to date, including those made during dips, with OOT data fitted by the Gaussian fade model.







Observing Sessions (Most Recent at Top)

we need more data!

Note: On 2016.10.01 the Meade 14"failed to turn on, so I moved the SBIG ST-10XME to my Celestron 11" telescope (also in a dome), and have continued observations with this "back-up" telescope system.



Clear filter observations from 2015 October/November

2015.11.12, B. Gary, C filter LC, V-mag = 11.929, r'-mag = 11.703 ± 0.005

2015.10.24, B. Gary, C filter LC, V-mag = 11.929, r'-mag = 11.689 ± 0.003

2015.10.23, B. Gary, C filter LC, V-mag = 11.932, r'-mag = ??.??? ± ?.??? (dew problem)

2015.10.20, B. Gary, C filter LC, V-mag = 11.933, r'-mag = 11.691

± 0.005

2015.10.16, B. Gary, C filter LC, V-mag = 11.930, r'-mag = 11.697 ± 0.005

2015.10.15, B. Gary, C filter LC, V-mag = ??.???, r'-mag = 11.689

± 0.010 (too short for use)



Observing Project Goals & Plan





This web page records my observations of KIC 8462852 (hereafter KIC846) in an attempt to measure small amplitude variations on timescales of hours, days, weeks and years. In support of both goals 25 nearby stars have been calibrated using all-sky photometry.



My original goal wa s to detect the suggested fade rate of 0.34%/year during the 2016 observing season . The suggested fade rate corresponds to 3.4 mmag/year, or 1.0 mmag every 3.5 mon ths, which is the length of my observing season (due to the summer mon soon ending in mid-September). However, I have determined that systematic errors are present at the level of ~ 3 mmag per observing session , and I do not know what systematic errors may exist during monthly timescales, so it is unreasonable to expect success in measuring a 1.0 mmag fade d uring a 3.5-month in terval. Instead, I will attempt to measure the slow secular fade by comparing results during two observing s easons.



My original secondary goal wa s to search for short timescale variability, and this has become a primary goal for the current observing season. A few observing sessions will be long enough to search for hourly variations, but most observing sessions will be limited to an hour. This should allow for a search of d ay-to-day changes, as well as weekly timescale changes. If none are found then the observations will be viewed as providing an observational upper-limit to such variability.





The observational strategy is to improve the calibration of nearby stars so that each observing session produces a better-calibrated V-mag for that date. The tighter the star color sensitivity scatter plot, which I use for establishing an observing session's calibration, the smaller are the systematic errors for that session's target V-mag. The APASS magnitudes for this star field appear to be flawed, in both average value and internal consistency (star-to-star ratios). I will use all-sky photometry, involving many Landolt stars, to accomplish this calibration.



In order to know how long each weekly observing session will have to be for the average target V-mag to have a stochastic SE smaller than the estimated systematic SE I will conduct a couple long observing sessions (> 6 hrs) and simulate having just limited time chunks of the data, with a sampling chunk lengths. KIC846 is bluer than all but one nearby star to be used for calibration. This means I have to worry about air mass effects that differ between the target (KIC846) and the set of nearby calibrator stars. In order to assess the usability of high air mass data I will determine a best value for my "air mass curvature correction," AMC', and demonstrate the stability of this parameter, and use simulations of long observing sessions to determine how safe it is to use only high air mass observations (made late in the observing season) for monitoring secular fade rate.



I will sue the same hardware configuration for all observations: Made 14" LX200 GPS telescope, in a dome, with a x2 focal reducer (designed for this Meade model, A CFW-10 with an Astrodon V-band filter and an SBIG ST-10XME CCD. All hardware control is performed using MaxIm DL, via 100-foot buried conduit cabling between my residence office and the dome observatory. The unbinned image scale for this system is 0.725 "arc/pixel, and the FOV is 28 x 18 'arc. I will use 2x2 binning for all observations, placing the target at the center of the image, and autoguiding with the 2nd chip of the ST-10XME CCD. This will remove drift of the star field with respect to the pixel field during an observing session, and if I place the target accurately at the same center location for each observing session this should reduce the effects of imperfect flat field calibration.





Finder Image and Calibrated Star B-mag and V-mag Table

Observing Start/Stop Local Times

References

Boyajian et al, 2015, MNRAS, "Planet Hunters X. KIC 8462852 - Where's the flux?"

Landolt, A., 2009, Astron. J., 137, #5

Montet, Benjamin T. and Joshua D. Simon, 2016, "KIC 8462852 Faded Throughout the Kepler Mission," arXiv 1608.01316

Smith et al, 2002, Astron. J., 123, 2121-2144.



Related Links



https://www.youtube.com/watch?v=XI5GDa9r4No Fredric Parker dimming rate analysis (Jun 09)

https://www.youtube.com/watch?v=risNfZxz6DQ Metzger & Stone (Columbia Univ.) YouTube discussion of the state of modeling fluxvariations

Boyajian et al, 2015, MNRAS, "Planet Hunters X. KIC 8462852 - Where's the flux?" link

Ballesteros, F. J., P. Arnalte-Mur, A. Fernandez-Soto and V. J. Martinez, 2017, "KIC8462852: Will the Trojans Return in 2011?", arXiv

Washington Post article, 2015.10.15: link

AAVSO Campaign Notice requesting KIC646 observations

AAVSO LC Generator https://www.aavso.org/data/lcg (enter KIC 8462852)

Web page tutorial: Tips for amateurs observating faint asteroids (useful for any photometry observing)

Book: Exoplanet Observing for Amateurs, Gary (2014): link (useful for any photometry observing)

My web pages master list, resume



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| When Roobs invade and overwhelm a discipline, and present their opinions as having the same legitimacy as an academic's, it's time for the academics to retreat somewhere and abandon public discussion of the subject, leaving it to the Roobs for eventual ruin. This matter was first described by Joe Ortega y Gassett (Revolt of the Masses, 1930), later by Roger Price (The Great Roob Revolution, 1970), and updated in a chapter by Bruce Gary (Genetic Enslavement, 2014). Every academic discipline is subjected to the corrupting influence of the hoi poloi, and during my 78-year lifetime I've seen two of my favorite disciplines (sociobiology and neuropsychology) lose vitality because of the influx of "know-nothing/know-it-all" Roobs. When this web page suddenly went from about one hit per month to a hit every 3 minutes (recently, once per minute), I braced myself for what might happen. For more information about Roobs, go to link.

By the way, the person who cultivates his garden is on a path to liberation from enslavement by "group think."

"Generally speaking, it is quite right if great things – things of much sense for men of rare sense ‑ are expressed but briefly and (hence) darkly, so that barren minds will declare it to be nonsense, rather than translate it into a nonsense that they can comprehend. For mean, vulgar minds have an ugly facility for seeing in the profoundest and most pregnant utterance only their own everyday opinion." Jean Paul, as quoted by Friedrich Nietzsche, Philosophy in the Tragic Age of the Greeks, 1872.

B L G a r y at u m i c h dot e d u

