J/A+A/558/A82 V4332 Sgr optical spectropolarimetry (Kaminski+, 2013)
Optical spectropolarimetry of V4332 Sagittarii.
Kaminski T., Tylenda R.
<Astron. Astrophys. 558, A82 (2013)>
=2013A&A...558A..82K 2013A&A...558A..82K
ADC_Keywords: Stars, emission ; Stars, peculiar; Polarization ; Spectroscopy
Keywords: line: formation - polarization - stars: individual: V4332 Sagittarii -
stars: late-type - circumstellar matter
Abstract:
The eruption of V4332 Sgr was observed in 1994 and was classified as
belonging to red transients of the V838 Mon type. Optical spectroscopy
obtained a few years after the eruption showed a faint M-type stellar
spectrum underlying numerous molecular and atomic emission features.
We suggested that the central object in V4332 Sgr is now hidden in a
dusty disc and that the photospheric spectrum of this object observed
in the optical results from scattering of the radiation of the central
star on dust grains in the circumstellar matter. The optical continuum
of the object, as resulting from scattering on dust grains, is
expected to be polarized. The emission features on the contrary - as
observed directly from circumstellar regions, are expected to be
unpolarized. We present and analyse spectropolarimetric observations
of V4332 Sgr in the optical region. The continuum is linearly
polarized with a typical degree of 16.6%. A clear depolarization is
observed in the spectral regions where emission features contribute
significantly to the observed flux. The only prominent exception is
the CaI emission line at 6573Å, which is polarized in 21%. The
results of our spectropolarimetric observations are in accord with the
proposed geometry of the system and the advocated nature of the
observed optical spectrum of V4332 Sgr - the continuum is not seen
directly but due to scattering on dust within the disk and polar
outflow, while most of the gas emission comes from the polar outflow
excited by the radiation field of the central source. Additionally,
the observed polarization patterns suggest a stratification of the
outflow.
Description:
The results of the linear spectropolarimetry of V4332 Sgr are
presented. The spectra were obtained in 2011 May 18 with FORS2 at VLT
and cover the spectral range between 5800 and 7300Å. We present a
pipleine-processed data of the degree and the angle of linear
polarization after box-car smoothing, and the total-power spectrum in
the original resolution of R∼2100.
Objects:
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RA (2000) DE Designation(s)
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18 50 36.70 -21 23 28.9 V4332 Sgr = V* V4332 Sgr
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
pa_sm13.dat 28 1981 Linear polarization angle
pl_sm13.dat 28 1981 Linear polarization degree
totpower.dat 27 1969 Total-power spectrum
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See also:
J/AZh/84/147 : Light curves of V838 Mon and V4332 Sgr (Goranskii+, 2007)
Byte-by-byte Description of file: pa_sm13.dat
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Bytes Format Units Label Explanations
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1- 16 F16.11 0.1nm lambda [5799/7305] Wavelength λ (Å)
19- 28 F10.6 deg PA [0/180] Angle of linear polarization
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Byte-by-byte Description of file: pl_sm13.dat
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Bytes Format Units Label Explanations
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1- 16 F16.11 0.1nm lambda [5799/7305] Wavelength λ (Å)
18- 28 F11.9 --- PL Degree of linear polarization (fraction)
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Byte-by-byte Description of file: totpower.dat
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Bytes Format Units Label Explanations
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1- 16 F16.11 0.1nm lambda [5799/7305] Wavelength λ (Å)
18- 27 F10.7 ct I Total power spectrum (arbitrary units)
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Acknowledgements:
Tomasz Kaminski, tomkam (at)ncac.torun.pl
(End) T. Kaminski [MPIfR Germany/NCAC Poland], P. Vannier [CDS] 22-Aug-2013