J/ApJ/709/1306 Spectropolarimetry of 60 Cyg and π Aqr (Wisniewski+, 2010)
Disk-loss and disk-renewal phases in classical Be stars.
I. Analysis of long-term spectropolarimetric data.
Wisniewski J.P., Draper Z.H., Bjorkman K.S., Meade M.R., Bjorkman J.E.,
Kowalski A.F.
<Astrophys. J., 709, 1306-1320 (2010)>
=2010ApJ...709.1306W 2010ApJ...709.1306W
ADC_Keywords: Stars, Be ; Equivalent widths ; Polarization
Keywords: circumstellar matter - stars: individual (π Aquarii, 60 Cygni)
Abstract:
Classical Be stars are known to occasionally transition from having a
gaseous circumstellar disk ("Be phase") to a state in which all
observational evidence for the presence of these disks disappears
("normal B-star phase"). We present one of the most comprehensive
spectropolarimetric views to date of such a transition for two Be
stars, π Aquarii and 60 Cygni. The disk-loss episode of 60 Cyg was
characterized by a generally monotonic decrease in emission strength
over a timescale of ∼1000 days from the maximum V-band polarization to
the minimum Hα equivalent width, consistent with the viscous
timescale of the disk, assuming α∼0.14. π Aqr's disk loss was
episodic in nature and occurred over a timescale of ∼2440 days.
Description:
The spectropolarimetric data analyzed in this study were obtained by
the University of Wisconsin's (UW's) HPOL spectropolarimeter, mounted
on UW's 0.9m Pine Bluff Observatory (PBO) telescope. π Aquarii was
observed on 127 nights between 1989 August 8 and 2004 October 10 while
60 Cygni was observed on 35 nights between 1992 August 3 and 2004
September 26 (see Tables 1 and 2). We supplement our HPOL
spectroscopic observations of 60 Cyg with 65 nights of spectra
obtained from 1998 August 26 to 2006 December 9 using the fiber-fed
echelle spectrograph of the 1.0m Ritter Observatory at the University
of Toledo.
Objects:
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RA (2000) DE Designation(s) (files)
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21 01 10.93 +46 09 20.8 60 Cyg = TYC 3588-12112-1 (table1.dat)
22 25 16.62 +01 22 38.6 pi. Aqr = TYC 560-1818-1 (table2.dat)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 100 Summary of 60 Cyg data
table2.dat 57 141 Summary of π Aqr data
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See also:
II/226 : Stellar polarization catalogs agglomeration (Heiles, 2000)
II/220 : Polarisation of Be stars (McDavid, 1986-1999)
J/ApJS/187/228 : Hα profiles of Be stars (Silaj+, 2010)
J/A+A/368/912 : Polarization and rotational velocities of Be stars (Yudin,
2001)
J/A+A/378/861 : Spectroscopy of Be stars (Chauville+, 2001)
J/PASP/106/949 : Multicolor polarimetry of Be stars (McDavid, 1994)
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 10 A10 "YYYY/MM/DD" Date UT date of the observation
12- 18 I7 d JD Julian Date of the observation
20- 22 A3 --- Obs Facility code (1)
24 I1 --- f_Obs [1,4]? Flag on Obs (2)
26- 31 F6.2 0.1nm EW.Ha ? Hα equivalent width; in Angstroms
33- 37 F5.3 0.1nm e_EW.Ha ? Uncertainty in EW.Ha
39- 43 F5.3 % VPol ? V band polarization
45- 49 F5.3 % e_VPol ? Uncertainty in VPol
51- 55 F5.1 deg PA ? Polarization position angle
57 A1 --- State [H/L]? Polarization state (3)
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Note (1): Observatory code as follows:
PBO = Pine Bluff Observatory;
RIT = Ritter Observatory.
McD = HPOL polarimetric observations of π Aqr from literature V-band
polarization measurements (McDavid, Cat. II/220, or J/PASP/106/949).
Note (2): Flag on observation (only for table 2) as follows:
1 = data are from McDavid (1986PASP...98..572M 1986PASP...98..572M, Cat. II/220);
2 = data are from McDavid (1990PASP..102..773M 1990PASP..102..773M, Cat. II/220);
3 = data are from McDavid (1994, Cat. J/PASP/106/949);
4 = data are from McDavid (1999PASP..111..494M 1999PASP..111..494M, Cat. II/220).
Note (3): A qualitative assessment of whether 60 Cyg (table 1) or π Aqr
(table 2) is in a polarimetrically high state (H), indicative of the
presence of strong disk, or in a polarimetrically low state (L), in
which evidence of the presence of a disk is absent (see Section 3.3.3
for further discussion of these designations). Note that we have
labeled the two observations in 1992 August (in table 1) as being
"high state", primarily because they are isolated from subsequent
observations by ∼5 years.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Mar-2012