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تسجيل مستخدم جديدKIC 8462852: Potential repeat of the Kepler day 1540 dip in August 2017
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We report 33 V-band observations by the Hereford Arizona Observatory (HAO) of the enigmatic star KIC 8462852 during the two week period 3-17 August 2017. We find a striking resemblance of these observations to the Kepler day 1540 dip with HAO observations tracking the Kepler light curve (adjusted for egress symmetry). A possible explanation of this potential repeat transit is a brown dwarf and extensive ring system in a 1601-day eccentric orbit. We suggest this object may be detectable through radial velocity observations in October and November 2017, with an amplitude of ~ 1-2 kms-1.
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This paper presents V- and g-band observations of the F2V star KIC 8462852, which exhibited enigmatic fade patterns in Kepler mission data. We introduce a transit simulation model for interpretation of these fades, and use it to interpret an August 2
017 dip as a repeat of the Kepler day 1540 dip (D1540). We suggest the August 2017 and D1540 dips may be caused by a brown dwarf and an associated ring system in a 1601-day elliptical orbit. Transiting icy moons of the proposed brown dwarf, sublimating near periapsis like comets, could provide an explanation for the significant dips observed by Kepler, as well as the recent May to October 2017 dips and the long term variation in flux detected by Simon et al. (2017). Whereas the presence of such a ring structure is attractive for its ability to explain short term fade events, we do not address how such a ring system can be created and maintained. If our speculation is correct, a brightening of about 1-2 percent should occur during October to November 2017. In addition, this scenario predicts that a set of dimming events, similar to those in 2013 (Kepler) and in 2017 (reported here), can be expected to repeat during October 2021 to January 2022 and a repeat of D1540 should occur on 27 December 2021.
We present optical polarimetry in the period May-August 2017 of the enigmatic dipping star KIC 8462852. During that period three ~1% photometric dips were reported by other observers. We measured the average absolute polarization of the source, and f
ind no excess or unusual polarization compared to a nearby comparison star. We place tight upper limits on any change in the degree of polarization of the source between epochs in- and out-of-dip of <0.1% (8500-Ang.) and <0.2% (7050-Ang. and 5300-Ang.). How our limits are interpreted depends on the specific model being considered. If the whole stellar disk were covered by material with an optical depth of ~0.01 then the fractional polarisation introduced by this material must be less than 10-20%. While our non-detection does not constrain the comet scenario, it predicts that even modest amounts of dust that have properties similar to Solar System comets may be detectable. We note that the sensitivity of our method scales with the depth of the dip. Should a future ~20% photometric dip be observed (as was previously detected by Kepler) our method would constrain any induced polarization associated with any occulting material to 0.5-1.0%.
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 October 2015, and a sequence of dipping beg
an 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: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey 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 <<1um, 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.
To explore the hypothesis that KIC 8462852s aperiodic dimming is caused by artificial megastructures in orbit (Wright et al. 2015), rather than a natural cause such as cometary fragments in a highly elliptical orbit (Marengo et al. 2015), we searched
for electromagnetic signals from KIC 8462852 indicative of extraterrestrial intelligence. The primary observations were in the visible optical regime using the Boquete Optical SETI Observatory in Panama. In addition, as a preparatory exercise for the possible future detection of a candidate signal (Heidmann 1991), three of six observing runs simultaneously searched radio frequencies at the Allen Telescope Array in California. No periodic optical signals greater than 67 photons/m2 within a time frame of 25 ns were seen. This limit corresponds to isotropic optical pulses of 8E22 joules. If, however, any inhabitants of KIC 8462852 were targeting our solar system (Shostak & Villard 2004), the required energy would be reduced greatly. The limits on narrowband radio signals were 180 - 300 Jy Hz at 1 and 8 GHz, respectively, corresponding to a transmitter with an effective isotropic radiated power of 4E15 W (and 7E15 W) at the distance of KIC 8462852. While these powers requirements are high, even modest targeting could - just as for optical signals - lower these numbers substantially.
We report on a search for the presence of signals from extraterrestrial intelligence in the direction of the star system KIC 8462852. Observations were made at radio frequencies between 1-10 GHz using the Allen Telescope Array. No narrowband radio si
gnals were found at a level of 180-300 Jy in a 1 Hz channel, or medium band signals above 10 Jy in a 100 kHz channel.
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