J/A+A/644/A135 V646 Pup TESS and ground photometry and spectrum (Siwak+, 2020)
Disc light variability in the FUor star V646 Puppis as seen by TESS and
from the ground.
Siwak M., Ogloza W., Krzesinski J.
<Astron. Astrophys. 644, A135 (2020)>
=2020A&A...644A.135S 2020A&A...644A.135S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, UBVRI ; Photometry, SDSS ;
Spectra, optical
Keywords: accretion, accretion disks - stars: formation -
stars: pre-main sequence - star: individual: V646 Puppis -
protoplanetary discs
Abstract:
We investigate small-scale light variations in V646 Pup occurring in
the timescales of days, weeks and years.
To check if this variability is similar to that observed in FU Ori.
We observed V646 Pup on six occasions at the SAAO and CTIO during
2013-2018 in Johnson and Sloan filters, typically with 1 d cadence
maintained for 2-4 weeks. We also utilise the public-domain 1512 day
long ASAS-SN light curve and TESS photometry obtained in 2019 during
24.1 days with 30 min cadence. New SAAO low-resolution spectra help to
update major disc parameters, while the archival high-resolution Keck
spectra are used to search for temporal changes in the disc rotational
profiles.
The ground-based observations confirm the constantly decreasing
brightness of V646 Pup at the rate of 0.018mag per year. Precise
i-band sensitive TESS data show that the little 0.005-0.01mag light
variations imposed on this general trend do consist of a few
independent wave trains of apparently time-coherent nature. Assuming
that this is typical situation, from analysis of colour-magnitude
diagrams obtained on earlier epochs we preliminarily inferred that the
bulk of observed light changes could be owing to rotation of disc
photosphere inhomogeneities, arising between 10-12 solar radii from
the star. It is not excluded that these inhomogeneities could also
manifest themselves in rotational profiles of the disc, as obtained
from the high-resolution spectra. Assuming Keplerian rotation of these
inhomogeneities, we preliminarily determine the stellar mass at
0.7-0.9 solar masses.
At least during certain weeks V646 Pup shows time-coherent light
variability pattern(s) that could be explained by rotation of an
inhomogeneous disc photosphere. These preliminary results are similar
to those better established for FU Ori, what suggests a common driving
mechanism(s).
Description:
We present SAAO and CTIO ground-based BVRI(RI)c (Johnson and
Johnson-Cousins) and gri (Sloan) light curves of V646 Pup shown in
Figure 1 and in Figure 2 in this paper. The process of data
acquisition and reduction is described in the paper. SAAO spectrum
used in Fig. 8, but left in the original form.
Objects:
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RA (2000) DE Designation(s)
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07 50 35.59 -33 06 23.9 V646 Pup = V* V646 Pup
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 33 63 SAAO Johnson-Cousins VRcIc standardised light
curves (nightly averages, Fig.1a)
tablea2.dat 32 13 CTIO Sloan-i differential magnitudes
(nightly averages, Fig.1b)
tablea3.dat 32 28 CTIO Sloan-gi differential magnitudes
(nightly averages, Fig.1c)
tablea4.dat 32 54 SAAO Johnson BVI standardised light curves
(nightly averages, Fig.1d)
tablea5.dat 32 39 SAAO Sloan-gri differential magnitudes
(nightly averages, Fig.1e)
tablea6.dat 32 33 SAAO Sloan-gri differential magnitudes
(nightly averages, Fig.1f)
tablea7.dat 26 1053 Reprocessed TESS data (Fig.2c)
spectrum.dat 29 2029 Spectrum obtained in Mar 12, 2017, calibrated to
absolute flux [cgs] units by means of LTT 3864
spectrophotometric standard
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Byte-by-byte Description of file: tablea1.dat tablea4.dat
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Bytes Format Units Label Explanations
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1- 15 F15.7 d Date Helocentric Julian Date
17- 23 F7.4 mag mag Standard magnitude
25- 30 F6.4 mag e_mag rms error of std. magnitude
32- 33 A2 --- Filter [VRcIc BVI] Filter name (1)
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Note (1): B and I standard magnitudes are uncertain for tablea4.dat.
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Byte-by-byte Description of file: tablea[2356].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 F15.7 d Date Helocentric Julian Date
17- 23 F7.4 mag dmag Differential magnitude
25- 30 F6.4 mag e_dmag rms error of differential magnitude
32 A1 --- Filter [gri] Filter name
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Byte-by-byte Description of file: tablea7.dat
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Bytes Format Units Label Explanations
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1- 16 F16.8 d Date Barrycentric TESS Julian Date
18- 26 F9.7 --- Flux Flux normalised to unity at mean brightness
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Byte-by-byte Description of file: spectrum.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda Wavelength in Angstroms
9- 29 F21.19 10mW/m2/nm Flux Flux calibrated to cgs units (erg/cm2/s/Å)
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Acknowledgements:
Michal Siwak, siwak(at)oa.uj.edu.pl
(End) Michal Siwak [Konkoly Obs., Hungary], Patricia Vannier [CDS] 05-Oct-2020