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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
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: -------------------------------------------------------------------- RA (2000) DE Designation(s) (files) -------------------------------------------------------------------- 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) -------------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 57 100 Summary of 60 Cyg data table2.dat 57 141 Summary of π Aqr data
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
Bytes Format Units Label Explanations
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)
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, Cat. II/220); 2 = data are from McDavid (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, 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.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Mar-2012
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