The GALEX View of “Boyajian’s Star” (KIC 8462852)

Davenport, James R. A.; Covey, Kevin R.; Clarke, Riley; Laycock, Zachery; Fleming, Scott W.; Boyajian, Tabetha S.; Montet, Benjamin T.; Shiao, Bernie; Million, Chase; Wilson, D. J.; Olmedo, Manuel; Mamajek, Eric E.; Olmedo, D.; Chávez, M.; Bertone, E.

doi:10.3847/1538-4357/aaa413

Cited by 29 publications

(9 citation statements)

References 27 publications

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“…In this case, we have no measure of the chromaticity of the secular evolution. (But Davenport et al 2018 andMeng et al 2018 already show that the secular evolution has a chromaticity comparable to our findings.) We are not able to say whether the general decline from 1890-1990 is just the ingress of a very-long dip, nor whether the 120-180 day duration minima in our light curve are just the fast component of the secular decline.…”

Section: Kic 8462852 Light Curvessupporting

confidence: 74%

“…The near-ultraviolet (centered at 2317Å) 1 Claims by Hippke et al (2016) are refuted as being due to multiple technical errors, see for example https://www.centauridreams.org/?p=35666. flux faded by 3.5±1.0% from 2011 to 2012 as seen with the GALEX satellite (Davenport et al 2018). With 835 Maria Mitchell plates, the light curve from 1922 to 1991 shows an average fading of 0.12±0.02 mag per century, confirming the measured decline from the Harvard plates (Castelaz & Barker 2018).…”

supporting

confidence: 66%

“…Our measured ratios are within reasonable agreement, to within the error bars for both R=3.1 and R=5, although the agreement is better for R=3.1. This can be compared to independent estimates of R 5 from Meng et al (2018), R ∼ 5 based on B/i = 1.94 ± 0.06 from Boyajian et al (2018), and R = 5.0 ± 0.9 from Davenport et al (2018).…”

Section: Discussionmentioning

confidence: 99%

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The KIC 8462852 light curve from 2015.75 to 2018.18 shows a variable secular decline

Schaefer

Bentley

Boyajian

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The star KIC 8462852 (Boyajian's Star) displays both fast dips of up to 20% on time scales of days, plus long-term secular fading by up to 19% on time scales from a year to a century. We report on CCD photometry of KIC 8462852 from 2015.75 to 2018.18, with 19,176 images making for 1,866 nightly magnitudes in BVRI. Our light curves show a continuing secular decline (by 0.023±0.003 mags in the B-band) with three superposed dips with duration 120-180 days. This demonstrates that there is a continuum of dip durations from a day to a century, so that the secular fading is seen to be by the same physical mechanism as the short-duration Kepler dips. The BVRI light curves all have the same shape, with the slopes and amplitudes for VRI being systematically smaller than in the B-band by factors of 0.77±0.05, 0.50±0.05, and 0.31±0.05. We rule out any hypothesis involving occultation of the primary star by any star, planet, solid body, or optically thick cloud. But these ratios are the same as that expected for ordinary extinction by dust clouds. This chromatic extinction implies dust particle sizes going down to ∼0.1 micron, suggesting that this dust will be rapidly blown away by stellar radiation pressure, so the dust clouds must have formed within months. The modern infrared observations were taken at a time when there was at least 12.4%±1.3% dust coverage (as part of the secular dimming), and this is consistent with dimming originating in circumstellar dust.

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Section: Kic 8462852 Light Curvessupporting

confidence: 74%

supporting

confidence: 66%

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The KIC 8462852 light curve from 2015.75 to 2018.18 shows a variable secular decline

Schaefer

Bentley

Boyajian

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Despite the large range in R V , it is interesting that our favoured value is biased towards steeper extinctions, similar to that which is associated with material in the interstellar medium. Perhaps crucially, the studies of Meng et al (2017) and Davenport et al (2018) relied on measurements taken hundreds of days apart, while this study, as in Schaefer et al (2018), has used data with a time resolution of tens of days or finer. Meng et al (2017) suffer from ∼ 100-day gaps in their Swift, Spitzer and BVR observations.…”

Section: Comparison With Measurements Of Extinction Associated With Tmentioning

confidence: 99%

Non-gray, Month-long Brightening of KIC 8462852 in the Immediate Aftermath of a Deep Dip

Hitchcock¹,

Fossey²,

Savini³

2019

PASP

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We present an analysis of the results of long-term multi-band photometric monitoring of the enigmatic star, KIC 8462852. Observations in the B, g , V , r and I C passbands have been acquired at University College London Observatory (UCLO) between May 2017 and September 2018. We interrogate the wavelength dependence of the ∼month-long dimming and brightening exhibited by the target star over an 85-day interval, immediately following a days-long ∼ 5 per cent drop in brightness on Julian Date (JD) 2458203. Between JD 2458215-300 we measure brightness variations which correspond to relative extinctions of A B /A V = 1.39±0.27, A g /A V = 1.16±0.11, A r /A V = 0.80±0.25 and A Ic /A V = 0.49 ± 0.19, from which we infer an Angstrom absorption coefficient of 1.33 ± 0.43 (R V 3.2 +2.6 −1.0 ). As with the days-long 'dips', the wavelength dependence of the longer-term brightness variations must also be associated with extinction arising from a dust distribution containing a substantial fraction of sub-micron-sized grains. This implies some common mechanism is responsible for the star's variability over both these short and longer timescales.

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“…This tool, however, has only been used to examine single objects (e.g. Davenport et al 2018) or specific stellar populations in varying sample sizes (e.g. Boudreaux et al 2017;Tucker et al 2018) and on time scales of 15 -30 sec.…”

Section: Introductionmentioning

confidence: 99%

Searching for Short-timescale Variability in the Ultraviolet with the GALEX gPhoton Archive. I. Artifacts and Spurious Periodicities

Vega

Bianchi

2018

ApJS

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In order to develop and test a methodology to search for UV variability over the entire GALEX database down to the shortest time scales, we analyzed time-domain photometry of ∼ 5000 light curves of ∼ 300 bright (m FUV , m NUV ≤ 14) and blue (m FUV − m NUV < 0) GALEX sources. Using the gPhoton database tool, we discovered and characterized instrumentally-induced variabilities in time-resolved GALEX photometry, which may severely impact automated searches for short-period variations. The most notable artifact is a quasi-sinusoidal variation mimicking light curves typical of pulsators, seen occasionally in either one or both detectors, with amplitudes of up to 0.3 mag and periods corresponding to the periodicity of the spiral dithering pattern used during the observation (P∼120 sec). Therefore, the artifact may arise from small-scale response variations. Other artifacts include visit-long "sagging" or "hump" in flux, occurring when the dithering pattern is not a spiral, or a one-time change in flux level during the exposure. These instrumentally-caused variations were not reported before, and are not due to known (and flagged) artifacts such as hot spots, which can be easily eliminated. To characterize the frequency and causality of such artifacts, we apply Fourier transform analysis to both light curves and dithering patterns, and examine whether artificial brightness variations correlate with visit or instrumental parameters. Artifacts do not correlate with source position on the detector. We suggest methods to identify artifact variations and to correct them when possible.

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The GALEX View of “Boyajian’s Star” (KIC 8462852)

Cited by 29 publications

References 27 publications

The KIC 8462852 light curve from 2015.75 to 2018.18 shows a variable secular decline

The KIC 8462852 light curve from 2015.75 to 2018.18 shows a variable secular decline

Non-gray, Month-long Brightening of KIC 8462852 in the Immediate Aftermath of a Deep Dip

Searching for Short-timescale Variability in the Ultraviolet with the GALEX gPhoton Archive. I. Artifacts and Spurious Periodicities

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