J/AJ/134/1877 Spectropolarimetry of R CrB in 1998-2003 (Kawabata+, 2007)
Spectropolarimetry of R Coronae Borealis in 1998-2003: discovery of transient
polarization at maximum brightness.
Kawabata K.S., Ikeda Y., Akitaya H., Isogai M., Matsuda K., Matsumura M.,
Nagae O., Seki M.
<Astron. J., 134, 1877-1889 (2007)>
=2007AJ....134.1877K 2007AJ....134.1877K
ADC_Keywords: Stars, variable ; Polarization
Keywords: circumstellar matter - dust, extinction -
stars: individual (R Coronae Borealis) - stars: mass loss -
techniques: polarimetric
Abstract:
We present an extended optical spectropolarimetry of R CrB from 1998
January to 2003 September. The polarization was almost constant in the
phase of maximum brightness, being consistent with past observations.
We detected, however, temporary changes of the polarization (∼0.5%) in
2001 March and August, which were the first detections of large
polarization variability in R CrB near maximum brightness. The
amplitude and the position angle of the "transient polarization" were
almost constant with wavelength in both events. There was a difference
of about 20° in the position angle between the two events. Each
event could be explained by light scattering due to a short-lived dust
puff occasionally ejected off the line of sight.
Description:
The data were obtained with the low-resolution spectropolarimeter HBS
(an acronym for "Henkou-Bunkou-Sokkou-Ki," which means
spectropolarimeter in Japanese) from 1998 January 28 to 2003 September
29 at the Dodaira Observatory and the Okayama Astrophysical
Observatory of the National Astronomical Observatory of Japan (NAOJ).
Objects:
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RA (2000) DE Designation(s)
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15 48 34.4 +28 09 24 R CrB = HD 141527
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 97 84 Polarimetry of R CrB
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See also:
J/A+A/353/287 : The R CrB stars (Asplund+, 2000)
J/A+A/394/617 : UBVJHKLM photometry of R Corona Borealis (Yudin+, 2002)
J/A+A/412/405 : Polarimetry of evolved stars. III. (Yudin+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "YYYY/MM/DD" ObsDate Date of the observation
12- 21 F10.2 d JD Julian date
23- 27 F5.2 mag DVmag Change from normal V magnitude of 6.11mag (1)
29- 31 A3 --- Tel Telescope code (2)
33- 34 A2 --- Ap Aperture description code (3)
36 A1 --- CCD CCD, as T=TI CCD, or S = SITe CCD
38- 42 I5 s Exptime Exposure time
44- 45 I2 0.1nm EW ? Equivalent width of C2 (5165Å) (5)
47- 50 F4.2 % Pobs Observed polarization in the V band (6)
52- 55 F4.2 % e_Pobs Uncertainty in Pobs
57- 61 F5.1 deg PAobs Observed polarization angle in the V band (6)
63- 65 F3.1 deg e_PAobs Uncertainty in PAobs
67- 70 F4.2 % Pvar Variable component polarization in the V band
72- 75 F4.2 % e_Pvar Uncertainty in Pvar
77- 81 F5.1 deg PAvar Variable component polarization angle in
the V band
83- 87 F5.1 deg e_PAvar Uncertainty in PAvar
89- 91 I3 10-5 Fpol Polarized flux fraction (7)
93- 97 F5.1 10-5 e_Fpol Uncertainty in Fpol
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Note (1): Visual magnitude averaged for all data within ±2.5-days
in VSNET database.
Note (2): Telescope code as follows:
D36 = 0.91m at Dodaira
O36 = 0.91m at Okayama
O74 = 1.88m at Okayama
Note (3): Aperture description code:
D1 = 1.4mm diameter circle
D2 = 0.2mmx1.4mm rectangle
Note (5): Measured between 4970Å and 5200Å for D2 observations.
Note (6): Observed polarization is considered as a vectorial summation of a
constant component and a variable component (see text).
Note (7): Polarized flux pvar*10-0.4DVmagF*
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 08-Jan-2010