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J/ApJ/683/433           Polaris monitoring                       (Bruntt+, 2008)

Polaris the Cepheid returns: 4.5 years of monitoring from ground and space. Bruntt H., Evans N.R., Stello D., Penny A.J., Eaton J.A., Buzasi D.L., Sasselov D.D., Preston H.L., Miller-Ricci E. <Astrophys. J., 683, 433-440 (2008)> =2008ApJ...683..433B
ADC_Keywords: Stars, variable ; Photometry Keywords: Cepheids - stars: individual (HD 8890, Polaris) Abstract: We present the analysis of 4.5 years of nearly continuous observations of the classical Cepheid Polaris, which comprise the most precise data available for this star. We have made spectroscopic measurements from ground and photometric measurements from the WIRE star tracker and the SMEI instrument on the Coriolis satellite. Measurements of the amplitude of the dominant oscillation (P=4days), which go back more than a century, show a decrease from AV=120 to 30mmag around the turn of the millennium. It has been speculated that the reason for the decrease in amplitude is the evolution of Polaris toward the edge of the instability strip. However, our new data reveal an increase in the amplitude by ∼30% from 2003 to 2006. It now appears that the amplitude change is cyclic rather than monotonic and most likely the result of a pulsation phenomenon. In addition, previous radial velocity campaigns have claimed the detection of long-period variation in Polaris (P>40days). Our radial velocity data are more precise than previous data sets, and we find no evidence for additional variation for periods in the range 3-50days with an upper limit of 100m/s. However, in the WIRE data we find evidence of variation on timescales of 2-6days, which we interpret as being due to granulation. Description: Polaris (α Ursae Minoris) was observed with the star tracker on the Wide-field InfraRed Explorer (WIRE) satellite in 2004 January and February, 2004 July, and 2005 February. These runs lasted about 4, 3, and 2 weeks, respectively. In addition, Polaris was monitored using 3.8 years of nearly continuous photometry from the SMEI instrument on the Coriolis satellite. These observations were obtained between 2003 April and the end of 2006. We further used the 2m Tennessee State University Automatic Spectroscopic Telescope (AST) to collect 517 high-dispersion spectra of Polaris over a period of 3.8 years, from late 2003 to late 2007. Objects: ------------------------------------------------------------ RA (2000) DE Designation(s) ------------------------------------------------------------ 02 31 49.1 +89 15 51 HD 8890 = NAME POLARIS = V* alf UMi ------------------------------------------------------------ File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 18 239 Times of maximum light in the SMEI and WIRE data sets
See also: J/A+A/281/465 : Chemical Composition of alf UMi and V473 Lyr (Andrievsky+ 1994) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 8 F8.3 d HJD-2453000 Heliocentric Julian date (-2453000) of maximum 10- 13 I4 --- E Epoch of maximum (cycle number) 15- 18 A4 --- Source Observation source ("SMEI" on Coriolis, or "WIRE" satellite)
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 01-Dec-2010
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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