Avalanche Statistics Identify Intrinsic Stellar Processes near Criticality in KIC 8462852

Sheikh, M. A.; Weaver, Richard L.; Dahmen, Karin A.

doi:10.1103/physrevlett.117.261101

Cited by 34 publications

(33 citation statements)

References 38 publications

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“…Published ideas to account for the unusual changes in the brightness of Boyajian's Star generally suffer from one of two flaws: they are either statistically unlikely (e.g., Metzger et al 2017) or they explain only one aspect of the observed flux variations (e.g., Bodman & Quillen 2016;Makarov & Goldin 2016;Sheikh et al 2016;Neslušan & Budaj 2017;Ballesteros et al 2017;Katz 2017). The hypotheses that can potentially account for both the brief dips and the long-term variability include the consumption of a planet (Metzger et al 2017), an internal obstruction of heat flux in the star (Foukal 2017), or an intervening disk-bearing object (Wright & Sigurðsson 2016).…”

Section: Discussionmentioning

confidence: 99%

Where Is the Flux Going? The Long-term Photometric Variability of Boyajian’s Star

Simon

Shappee

Pojmański

et al. 2018

ApJ

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We present ∼ 800 days of photometric monitoring of Boyajian's Star (KIC 8462852) from the AllSky Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian's Star has steadily decreased at a rate of 6.3 ± 1.4 mmag yr −1 , such that the star is now 1.5% fainter than it was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian's Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in the same ASAS-SN field and demonstrate that the recent fading is significant at 99.4% confidence. The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models for the star's behavior proposed to date.

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Section: Discussionmentioning

confidence: 99%

Where Is the Flux Going? The Long-term Photometric Variability of Boyajian’s Star

Simon

Shappee

Pojmański

et al. 2018

ApJ

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“…Extinction by clumpy material in the outer Solar System has also been suggested (Katz 2017). In addition, instabilities in the star itself have been proposed (Sheikh et al 2016;Foukal 2017).…”

Section: Introductionmentioning

confidence: 99%

Extinction and the Dimming of KIC 8462852

Meng

Rieke

Dubois³

et al. 2017

ApJ

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To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star over a wide wavelength range from the UV to the mid-infrared from October 2015 through December 2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period reported is 22.1 ± 9.7 milli-mag yr −1 in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2 mmag yr −1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at 3 σ by three different observatories operating from the UV to the IR. The presence of long-term secular dimming means that previous SED models of the star based on photometric measurements taken years apart may not be accurate. We find that stellar models with T ef f = 7000 -7100 K and A V ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of the fading favors a relatively neutral color (i.e., R V 5, but not flat across all the bands) compared with the extinction law for the general ISM (R V = 3.1), suggesting that the dimming arises from circumstellar material.

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“…These included broad categories of solutions such as those invoking occulting material in the solar system, material in the interstellar medium (ISM) or orbiting an intervening compact object, circumstellar material, and variations intrinsic to the star. Specific models for the brightness variations have been explored by Katz (2017), who modeled a circumstellar ring; Makarov & Goldin (2016), who suggested interstellar "comets"; giant circumstellar exocomets, suggested by Boyajian et al (2016) and modeled by Bodman & Quillen (2016); Neslušan & Budaj (2017), who modeled dust clouds associated with a smaller number of more massive bodies; Ballesteros et al (2018), who suggested a ringed planet and associated Trojan asteroid swarms; Sheikh et al (2016), who find the statistics of the dips to be consistent with intrinsic processes; Metzger et al (2017), who model the consumption of a secondary body; and Foukal (2017a), who invoke intrinsic variations perhaps related to magnetocovection.…”

Section: Introductionmentioning

confidence: 99%

The First Post-Kepler Brightness Dips of KIC 8462852

Boyajian

Alonso

Ammerman

et al. 2018

ApJL

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We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in 2015 October, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1%-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor," which persist on timescales from several days to weeks. Our main results so far are as follows: (i) there are no apparent changes of the stellar spectrum or polarization during the dips and (ii) the multiband photometry of the dips shows differential reddening favoring non-gray extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale =1 μm, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process.

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Avalanche Statistics Identify Intrinsic Stellar Processes near Criticality in KIC 8462852

Cited by 34 publications

References 38 publications

Where Is the Flux Going? The Long-term Photometric Variability of Boyajian’s Star

Where Is the Flux Going? The Long-term Photometric Variability of Boyajian’s Star

Extinction and the Dimming of KIC 8462852

The First Post-Kepler Brightness Dips of KIC 8462852

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