J/ApJ/750/59 BVR polarimetric observations of β Lyr (Lomax+, 2012)
Geometrical constraints on the hot spot in β Lyrae.
Lomax J.R., Hoffman J.L., Elias Ii N.M., Bastien F.A., Holenstein B.D.
<Astrophys. J., 750, 59 (2012)>
=2012ApJ...750...59L 2012ApJ...750...59L
ADC_Keywords: Polarization ; Binaries, eclipsing
Keywords: accretion, accretion disks - binaries: eclipsing -
stars: individual: (beta Lyr) - techniques: polarimetric
Abstract:
We present results from six years of recalibrated and new
spectropolarimetric data taken with the University of Wisconsin's
Half-Wave Spectropolarimeter and six years of new data taken with the
photoelastic modulating polarimeter at the Flower and Cook Observatory
of beta Lyrae. Combining these data with polarimetric data from the
literature allows us to characterize the intrinsic BVRI polarized
light curves. A repeatable discrepancy of 0.245 days (approximately
6hr) between the secondary minima in the total light curve and the
polarization curve in the V band, with similar behavior in the other
bands, may represent the first direct evidence for an accretion hot
spot on the disk edge.
Description:
The first observations data set consists of 69 optical
spectropolarimetric observations of β Lyr taken over six years.
14 HPOL (the University of Wisconsin's Half-Wave Spectropolarimeter)
observations were obtained between 1992 September and 1994 November,
with a wavelength range of 3200-7600Å while 55 observations were
taken between 1995 March and 1998 September with a wavelength range,
3200-10500Å and increased resolution (7.5Å below 6000Å), at
the 0.9m telescope at Pine Bluff Observatory (PBO).
Our second data set is made up of 19 B-band, 88 V-band, and 17 R-band
observations obtained at FCO (the Flower and Cook Observatory) between
1987 and 1992 with the photoelastic modulating polarimeter instrument.
And a third data set is the three years of archived broadband optical
polarimetric data from AH taken with the 24 inch rotatable telescope
at the Yerkes Observatory.
Objects:
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RA (2000) DE Designation(s)
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18 50 04.80 +33 21 45.6 beta Lyrae = * bet Lyr
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 59 124 Flower and Cook Observatory (FCO) polarimetry
table4.dat 85 272 University of Wisconsin HPOL polarimetry
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See also:
J/A+A/463/233 : UBV and radial velocity light curves of beta Lyr (Ak+, 2007)
J/A+A/368/912 : Polarization & rotational velocities of Be stars (Yudin, 2001)
J/A+A/312/879 : Beta Lyr radial velocities and UBV data (Harmanec+, 1996)
J/AJ/110/1350 : Beta Lyrae light curve changes (Van Hamme+ 1995)
J/A+AS/101/551 : Optical polarization of 1000 stars (Leroy 1993)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [FCO] Observatory/Instrument code
5 A1 --- Filt [BVR] Filter used in the observation
7- 11 F5.3 --- Phase Phase of observation (G1)
13- 20 F8.2 d HJD Heliocentric Julian Date (HJD-2400000)
22- 26 F5.3 % Q [0.1/0.9] Polarization percentage in Q
28- 33 F6.3 % U [-0.8/-0.1] Polarization percentage in U
35- 40 F6.3 % ISP-Q [-0.09/0.7] Interstellar polarization
subtracted Q value (1)
42- 47 F6.3 % ISP-U [-0.5/0.2] Interstellar polarization
subtracted U value (1)
49- 53 F5.3 % e_Q [0.004/0.1] Internal error in Q
55- 59 F5.3 % e_U [0.004/0.1] Internal error in U
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Note (1): We have no observations of β Lyr B taken with the same
instrument as this data set (FCO). Therefore, we used the Serkowski
fit to the HPOL β Lyr B observations (see Section 2.1) to
calculate the ISP contributions at the central wavelengths of the BVR
bands and subtracted these estimated values from the observations in
this data set.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- --- [HPOL Synthetic] Instrument
16 A1 --- Filt [BVR] Filter used in the observation
18- 24 A7 --- Syst "Reticon" or "CCD" based system
26- 30 F5.3 --- Phase Phase of observation (G1)
32- 39 F8.2 d HJD Heliocentric Julian Date (HJD-2400000)
41- 47 F7.4 % Q [-0.4/0.8] Polarization percentage in Q
49- 55 F7.4 % U [-1/-0.2] Polarization percentage in U
57- 63 F7.4 % ISP-Q [-0.5/0.6] Interstellar polarization
subtracted Q value
65- 71 F7.4 % ISP-U [-0.7/0.05] Interstellar polarization
subtracted U value
73- 78 F6.4 % e_Q [0.0008/0.07] Internal error in Q & U (1)
80- 85 F6.4 % s_Q [0.004/0.03] Systematic error in Q & U (1)
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Note (1): The filter routine produces broadband values and associated
internal errors for each observation; however, we must still take into
account systematic variations in the instrumental polarization between
nights. Systematic errors for HPOL at PBO were evaluated by
periodically analyzing observations of unpolarized standard stars.
This table lists broadband polarization values and internal errors
determined by the filter routine along with the systematic errors. In
the case of the Reticon data, the systematic errors are less well
determined; based on our previous experience with these data, we have
estimated the uncertainties in the Stokes parameters for the Reticon
data to be 0.02% in all bands.
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Global Notes:
Note (G1): the phase is computed with the ephemeris
T1 = 2408247.966 + 12.91378E + 3.87196x10-6E2
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Dec-2013