A Statistical Analysis of the Accuracy of the Digitized Magnitudes of Photometric Plates on the Timescale of Decades With an Application to the Century-Long Light Curve of Kic 8462852

Hippke, Michael; Angerhausen, Daniel; Lund, Michael B.; Pepper, Joshua; Stassun, Keivan G.

doi:10.3847/0004-637x/825/1/73

Cited by 46 publications

(23 citation statements)

References 31 publications

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“…This tendency refutes the apparent brightening of AR Sco in DASCH. It is worth noting that there has been a recent disagreement between Schaefer (2016) and Hippke et al (2016) over whether the Damons North Blue series exhibits a flux discontinuity relative to the rest of the DASCH light curve. 5 We take no position on their debate.…”

Section: The Apparent Long-term Brightening Is An Instrumental Effectmentioning

confidence: 99%

Analysis of a Century’s Worth of AR Scorpii Photometry from DASCH and ASAS-SN

Peterson

Garnavich

2019

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AR Scorpii (AR Sco) is a binary-star system containing the only known white dwarf pulsar. Previously reported photometric datasets only provide coverage back to 2005, but we extend the observational baseline for AR Sco back to the beginning of the twentieth century by analyzing observations from the Digital Access to a Sky Century at Harvard project (DASCH). We find that the orbital waveform of AR Sco remained constant across that baseline with no significant deviations from its average brightness. This result strongly suggests that the absence of accretion in modern observations is a long-term feature of AR Sco. Additionally, the DASCH light curve provides an opportunity to test an earlier prediction that an obliquity of the white dwarf would result in a precessional period observable in long-term studies of the orbital light curve. The DASCH observations do not indicate the presence of such a period, and we show that previous, inconclusive tests of this hypothesis were insensitive to the existence of a precessional period. Furthermore, the long DASCH baseline enables us to constrain the rate of change of the orbital frequency toν 3.8 × 10 −20 Hz/s, constraining the efficacy of magnetic braking as a mechanism of angular-momentum loss in this system. Finally, we discuss how the combination of the orbital waveform's stability, high amplitude, and short period should make it possible to identify additional white-dwarf pulsars in all-sky survey data.

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Section: The Apparent Long-term Brightening Is An Instrumental Effectmentioning

confidence: 99%

Analysis of a Century’s Worth of AR Scorpii Photometry from DASCH and ASAS-SN

Peterson

Garnavich

2019

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“…Evidence was found that the light from the star has been dimming over century timescales, with a 16% decrease in brightness from 1890 to 1980 (Schaefer 2016), the so-called secular dimming. This secular dimming remains controversial, since analysis of the same archival data found no evidence for the dimming (Hippke et al 2016), and a different set of archival data also found no evidence for secular dimming (Hippke et al 2017). Nevertheless, reanalysis of the Kepler data, which had been baselined to remove any long-term trends in the original analysis, showed evidence for a long-term dimming trend of ∼ 3% over a 4 year timescale (Montet & Simon 2016).…”

Section: Introductionmentioning

confidence: 97%

Modelling the KIC8462852 light curves: compatibility of the dips and secular dimming with an exocomet interpretation

Wyatt

Lieshout

Kennedy

et al. 2017

Monthly Notices of the Royal Astronomical Society

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This paper shows how the dips and secular dimming in the KIC8462852 light curve can originate in circumstellar material distributed around a single elliptical orbit (e.g., exocomets). The expected thermal emission and wavelength dependent dimming is derived for different orbital parameters and geometries, including dust that is optically thick to stellar radiation, and for a size distribution of dust with realistic optical properties. We first consider dust distributed evenly around the orbit, then show how to derive its uneven distribution from the optical light curve and to predict light curves at different wavelengths. The fractional luminosity of an even distribution is approximately the level of dimming times stellar radius divided by distance from the star at transit. Non-detection of dust thermal emission for KIC8462852 thus provides a lower limit on the transit distance to complement the 0.6 au upper limit imposed by 0.4 day dips. Unless the dust distribution is optically thick, the putative 16% centurylong secular dimming must have disappeared before the WISE 12 µm measurement in 2010, and subsequent 4.5 µm observations require transits at > 0.05 au. However, self-absorption of thermal emission removes these constraints for opaque dust distributions. The passage of dust clumps through pericentre is predicted to cause infrared brightening lasting 10s of days and dimming during transit, such that total flux received decreases at wavelengths < 5 µm, but increases to potentially detectable levels at longer wavelengths. We suggest that lower dimming levels than seen for KIC8462852 are more common in the Galactic population and may be detected in future transit surveys.

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“…KIC 8462852 is an F3V star located at about 454±35 pc away from us (Hippke et al 2016). The Kepler Spacecraft photometric data revealed an enigmatic lightcurve for this star, with erratic, up to ∼20% deep, stellar flux dimmings (Boyajian et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Detection of a repeated transit signature in the light curve of the enigma star KIC 8462852: A possible 928-day period

Kiefer

Étangs

Vidal‐Madjar

et al. 2017

A&A

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As revealed by its peculiar Kepler light curve, the enigmatic star KIC 8462852 undergoes short and deep flux dimmings at a priori unrelated epochs. It presents nonetheless all other characteristics of a quiet 1 Gyr old F3V star. These dimmings resemble the absorption features expected for the transit of dust cometary tails. The exocomet scenario is therefore most commonly advocated. We reanalyzed the Kepler data and extracted a new high-quality light curve to allow for the search of shallow signature of single or a few exocomets. We discovered that among the 22 flux dimming events that we identified, two events present a striking similarity. These events occurred 928.25 days apart, lasted for 4.4 days with a drop of the star brightness by 1000 ppm. We show that the light curve of these events is well explained by the occultation of the star by a giant ring system, or the transit of a string of half a dozen of exocomets with a typical dust production rate of 10 5 -10 6 kg/s. Assuming that these two similar events are related to the transit of the same object, we derive a period of 928.25 days. The following transit was expected in March 2017 but bad weather prohibited us to detect it from ground-based spectroscopy. We predict that the next event will occur from the 3 rd to the 8 th of October 2019.

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A Statistical Analysis of the Accuracy of the Digitized Magnitudes of Photometric Plates on the Timescale of Decades With an Application to the Century-Long Light Curve of Kic 8462852

Cited by 46 publications

References 31 publications

Analysis of a Century’s Worth of AR Scorpii Photometry from DASCH and ASAS-SN

Analysis of a Century’s Worth of AR Scorpii Photometry from DASCH and ASAS-SN

Modelling the KIC8462852 light curves: compatibility of the dips and secular dimming with an exocomet interpretation

Detection of a repeated transit signature in the light curve of the enigma star KIC 8462852: A possible 928-day period

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