J/A+A/618/A79 FU Orionis small-amplitude light variations (Siwak+, 2018)
Insights into the inner regions of the FU Orionis disc.
Siwak M., Winiarski M., Ogloza W., Drozdz M., Zola S., Moffat A.F.J.,
Stachowski G., Rucinski S.M., Cameron C., Matthews J.M., Weiss W.W.,
Kuschnig R., Rowe J.F., Guenther D.B., Sasselov D.
<Astron. Astrophys. 618, A79 (2018)>
=2018A&A...618A..79S 2018A&A...618A..79S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Stars, variable ; Photometry
Keywords: accretion, accretion discs - star: individual: FU Ori -
stars: pre-main sequence
Abstract:
We investigate small-amplitude light variations in FU Ori occurring in
timescales of days and weeks.
We seek to determine the mechanisms that lead to these light changes.
Methods. The visual light curve of FU Ori gathered by the MOST
satellite continuously for 55 days in the 2013-2014 winter season and
simultaneously obtained ground-based multi-colour data were compared
with the results from a disc and star light synthesis model.
Hotspots on the star are not responsible for the majority of observed
light variations. Instead, we found that the long periodic family of
10.5-11.4d (presumably) quasi-periods showing light variations up to
0.07 mag may arise owing to the rotational revolution of disc
inhomogeneities located between 16-20 solar radii. The same distance
is obtained by assuming that these light variations arise because of a
purely Keplerian revolution of these inhomogeneities for a stellar
mass of 0.7 solar mass. The short-periodic (3-1.38d) small amplitude
(0.01mag) light variations show a clear sign of period shortening,
similar to what was discovered in the first MOST observations of FU
Ori. Our data indicate that these short-periodic oscillations may
arise because of changing visibility of plasma tongues (not included
in our model), revolving in the magnetospheric gap and/or likely
related hotspots as well.
Results obtained for the long-periodic 10-11d family of light
variations appear to be roughly in line with the colour-period
relation, which assumes that longer periods are produced by more
external and cooler parts of the disc. Coordinated observations in a
broad spectral range are still necessary to fully understand the
nature of the short-periodic 1-3d family of light variations and
their period changes.
Description:
We present MOST and ground-based uvyUBVRI(RI)c light curves and colour
indices of FU Ori shown in Figures 1a,b,c,d, Figure 2, and in Figure 5
(second panel). The process of data acquisition and reduction is
described in the paper. The File Summary section shows files ordered
in accord with the Table numbers (A.1-A.21) shown in Sections 2 and 3
of the paper.
Objects:
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RA (2000) DE Designation(s)
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05 45 22.36 +09 04 12.3 FU Ori = V* FU Ori
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 62 4018 Original MOST pipeline result (Fig.1a)
tablea2.dat 56 4018 MOST light curve de-trended (Fig. 1c)
tablea3.dat 56 345 MOST light curve de-trended (orbital averages,
Fig.1d and Fig.2)
tablea4.dat 59 69 *Mount Suhora Johnson B light curve
tablea5.dat 59 66 *Mount Suhora Johnson V light curve
tablea6.dat 60 69 *Mount Suhora Johnson R light curve
tablea7.dat 60 66 *Mount Suhora Johnson I light curve
tablea8.dat 45 17 *Mount Suhora Stromgren u light curve
tablea9.dat 45 22 *Mount Suhora Stromgren v light curve
tablea10.dat 44 21 *Mount Suhora Stromgren y light curve
tablea11.dat 51 24 *SAAO Johnson-Cousins U standardised light curve
tablea12.dat 51 25 *SAAO Johnson-Cousins B standardised light curve
tablea13.dat 51 25 *SAAO Johnson-Cousins V standardised light curve
tablea14.dat 51 25 *SAAO Johnson-Cousins R_c standardised light curve
tablea15.dat 51 25 *SAAO Johnson-Cousins I_c standardised light curve
tablea16.dat 44 24 U-B colour index vs. time (SAAO data, Fig.2)
tablea17.dat 44 24 U-V colour index vs. time (SAAO data, Fig.2)
tablea18.dat 44 25 B-V colour index vs. time (SAAO data, Fig.2)
tablea19.dat 44 25 V-R colour index vs. time (SAAO data, Fig.2)
tablea20.dat 44 25 V-I colour index vs. time (SAAO data, Fig.2)
tablea21.dat 16 13325 *2010-2011 MOST light curve of FU Ori
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Note on tablea4.dat tablea5.dat tablea6.dat tablea7.dat:
(nightly mean averages, Fig.1b), obtained with respect to GSC 00714-00203
and GSC 00715-00188 and aligned to SAAO data.
Note on tablea8.dat:
(nightly mean averages), obtained with respect to GSC 00714-00203 only.
Note on tablea9.dat tablea10.dat:
(nightly mean averages), obtained with respect to GSC 00714-00203 and
GSC 00715-00188.
Note on tablea11.dat:
(nightly mean averages, Fig.1b), obtained with respect to GSC 00714-00203
Note on tablea12.dat, tablea13.dat, tablea14.dat, tablea15.dat:
(nightly mean averages, Fig.1b), obtained with respect to GSC 00714-00203
and GSC 00715-00188.
Note on tablea21.dat: already published by Siwak et al., 2013MNRAS.432..194S 2013MNRAS.432..194S,
but reanalysed in this paper.
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Byte-by-byte Description of file: tablea[14567].dat tablea1[12345].dat
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Bytes Format Units Label Explanations
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1- 13 F13.7 d Date Helocentric Julian Date (HJD-2400000)
15- 22 F8.5 mag mag Magnitude in Band (1)
24- 30 F7.5 mag e_mag rms error on mag
32- 34 A3 --- Band Band for magnitude
36- 65 A30 ---- System Instrument or filter system
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Note (1): tablea4.dat: this MSO B-filter light curve was aligned to standardised
SAAO B-filter light curve with an accuracy of 0.002 mag.
tablea5.dat: this MSO V-filter light curve was aligned to standardised
SAAO V-filter light curve with an accuracy of 0.002 mag
tablea6.dat: this MSO R-filter light curve was aligned to standardised
SAAO Rc-filter light curve with an accuracy of 0.002 mag
tablea6.dat: this MSO I-filter light curve was aligned to standardised
SAAO Ic-filter light curve with an accuracy of 0.002 mag
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Byte-by-byte Description of file: tablea2.dat tablea3.dat
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Bytes Format Units Label Explanations
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1- 13 F13.7 d Date Helocentric Julian Date (HJD-2400000)
16- 22 F7.5 mag mag magnitude in artificial BVRI scale
24- 30 F7.5 mag e_mag rms error on mag
36- 65 A30 --- System System (artificial BVRI scale)
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Byte-by-byte Description of file: tablea[89].dat tablea10.dat
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Bytes Format Units Label Explanations
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1- 13 F13.7 d Date Helocentric Julian Date (HJD-2400000)
15- 22 F8.5 mag mag Differental magnitude in Band (1)
24- 30 F7.5 mag e_mag rms error on mag
32- 34 A3 --- Band Band for magnitude
36- 65 A30 ---- System Instrument or filter system
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Note (1): differential magnitude obtained with respect to GSC 00714-00203
only for u band (tablea8.dat), differential magnitude is obtained with respect
to GSC 00714-00203 and GSC 00715-00188 for v (tablea9.dat) and
y (tablea10.dat) bands.
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Byte-by-byte Description of file: tablea1[6789].dat tablea20.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 F13.7 d Date Helocentric Julian Date (HJD-2400000)
15- 22 F8.5 mag CI Colour index in Band
24- 30 F7.5 mag e_CI rms error on CI
32- 35 A4 --- Band Band for Colour index
37- 51 A15 ---- System Instrument or filter system
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Byte-by-byte Description of file: tablea21.dat
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Bytes Format Units Label Explanations
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1- 9 F9.6 d Date Helocentric Julian Date (HJD-2455500)
11- 16 F6.1 s-1 ct Counts, in ADU/second
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Acknowledgements:
Michal Siwak, siwak(at)oa.uj.edu.pl
(End) M. Siwak [Mount Suhora Obs., Poland], P. Vannier [CDS] 31-Jul-2018