J/ApJ/853/77 KIC 8462852 ASAS V-band long-term variability (Simon+, 2018)
Where is the flux going? The long-term photometric variability of Boyajian's
Star.
Simon J.D., Shappee B.J., Pojmanski G., Montet B.T., Kochanek C.S.,
van Saders J., Holoien T.W.-S., Henden A.A.
<Astrophys. J., 853, 77 (2018)>
=2018ApJ...853...77S 2018ApJ...853...77S
ADC_Keywords: Stars, F-type; Photometry; Optical; Stars, variable
Keywords: stars: activity ; stars: individual (Boyajian's Star) ;
stars: peculiar (except chemically peculiar) ;
stars: variables: general
Abstract:
We present ∼800 days of photometric monitoring of Boyajian's Star
(KIC8462852) from the All-Sky Automated Survey for Supernovae
(ASAS-SN) and ∼4000d 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±1.4mmag/yr,
such that the star is now 1.5% fainter than it was in 2015 February.
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.
Description:
ASAS-SN is an all-sky survey that monitors the entire sky for
transients every ∼2 days down to a V-band magnitude of ∼17. The survey
currently consists of two fully robotic units, one on Haleakala,
Hawaii and one on Cerro Tololo, Chile, each with four 14cm telescopes.
The field containing Boyajian's Star was observed a total of 377 times
from 2015 February 24 (UT) to 2017 May 15 by the northern ASAS-SN
unit, "Brutus." This ASAS-SN field is labeled F2006+46_0982, which is
centered on RAJ2000=20:06:46.5, DEJ2000=+45:59:27.8.
ASAS is a long-term variability survey that scans a large fraction of
the sky from two locations, Las Campanas, Chile (since 1997) and
Haleakala, Hawaii (since 2006). From Hawaii, ASAS simultaneously
monitors the sky in two filters (V and I) with two 10cm telescopes.
ASAS has obtained a total of 564 V-band images of Boyajian's Star
spanning from 2006 May 31 to the beginning of the 2017 May dipping
activity. A large majority of these images (517) are in ASAS field
616, centered at RAJ2000=20:15:00, DEJ2000=+48:00:00.
Objects:
-----------------------------------------------------------
RA (ICRS) DE Designation(s)
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20 06 15.45 +44 27 24.8 Boyajian's Star = KIC 8462852
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 37 111 ASAS-SN photometry of Boyajian's Star
table3.dat 26 496 ASAS photometry of Boyajian's Star
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See also:
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
II/264 : ASAS Variable Stars in Southern hemisphere (Pojmanski+, 2002-2005)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
J/AJ/135/850 : Properties of eclipsing binaries found in TrES (Devor+, 2008)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/AcA/59/33 : ASAS. Variable stars catalog in Kepler field. (Pigulski+, 2009)
J/ApJ/733/50 : MIR photometric monitoring of the ONC (Morales-Calderon+, 2011)
J/AJ/144/24 : The Kepler-INT survey (Greiss+, 2012)
J/ApJ/776/67 : Rotational tracks (van Saders+, 2013)
J/AJ/147/82 : Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/MNRAS/463/4210 : All-sky catalog of solar-type dwarfs (Nascimbeni+, 2016)
J/ApJS/224/19 : The KepVIM catalog (Makarov+, 2016)
J/ApJ/847/131 : KIC 8462852 one-yr obs. from UV to MIR (Meng+, 2017)
J/A+A/610/L12 : KIC 8462852 GTC spectra (Deeg+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD Heliocentric Julian Date
15- 20 F6.3 mag Vmag [11.8/12] Apparent V band magnitude
22- 26 F5.3 mag e_Vmag [0.008/0.02] Uncertainty in Vmag
28- 31 F4.2 pix FWHM [1.4/2.3] Full-Width at Half-Maximum of stellar PSF
33- 37 F5.2 mag ZP [-3/-2.1] Zero point (1)
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Note (1): The ASAS-SN zero point (ZP) of each image is defined such that a
source with a flux of one count has a magnitude of 25+ZP.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD Heliocentric Julian Date
15- 20 F6.3 mag Vmag [11.8/12.1] Apparent V band magnitude
22- 26 F5.3 mag e_Vmag [0.01/0.06] Uncertainty in Vmag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Oct-2018