J/AJ/142/187 HST observations of 7 Pop.II variable stars (Benedict+, 2011)
Distance scale zero points from galactic RR Lyrae star parallaxes.
Benedict G.F., McArthur B.E., Feast M.W., Barnes T.G., Harrison T.E.,
Bean J.L., Menzies J.W., Chaboyer B., Fossati L., Nesvacil N., Smith H.A.,
Kolenberg K., Laney C.D., Kochukhov O., Nelan E.P., Shulyak D.V.,
Taylor D., Freedman W.L.
<Astron. J., 142, 187 (2011)>
=2011AJ....142..187B 2011AJ....142..187B
ADC_Keywords: Stars, variable ; Photometry, HST ; Stars, population II
Keywords: astrometry - stars: distances - stars: variables: RR Lyrae
Abstract:
We present new absolute trigonometric parallaxes and proper motions
for seven Population II variable stars - five RR Lyr variables: RZ
Cep, XZ Cyg, SU Dra, RR Lyr, and UV Oct; and two type 2 Cepheids: VY
Pyx and κ Pav. We obtained these results with astrometric data
from Fine Guidance Sensors, white-light interferometers on Hubble
Space Telescope. We find absolute parallaxes in milliseconds of arc:
RZ Cep, 2.12±0.16mas; XZ Cyg, 1.67±0.17mas; SU Dra,
1.42±0.16mas; RR Lyr, 3.77±0.13mas; UV Oct, 1.71±0.10mas; VY
Pyx, 6.44±0.23mas; and κ Pav, 5.57±0.28mas; an average
σπ/π=5.4%. With these parallaxes, we compute absolute
magnitudes in V and K bandpasses corrected for interstellar extinction
and Lutz-Kelker-Hanson bias. Using these RR Lyrae variable star
absolute magnitudes, we then derive zero points for MV-[Fe/H] and
MK-[Fe/H]-logP relations. The technique of reduced parallaxes
corroborates these results. We employ our new results to determine
distances and ages of several Galactic globular clusters and the
distance of the Large Magellanic Cloud. The latter is close to that
previously derived from Classical Cepheids uncorrected for any
metallicity effect, indicating that any such effect is small. We also
discuss the somewhat puzzling results obtained for our two type 2
Cepheids.
Description:
Between 13 and 23 sets of astrometric data were acquired with HST FGS
(Fine Guidance Sensor; a two-axis shearing interferometer) 1r for each
of our 7 science targets. The various complete data aggregates span
from 2.37 to 13.14 years (49984.2 to 55351.4, MJD). Each individual
HST data set required approximately 33 minutes of spacecraft time.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 70 7 Target Properties
table2.dat 45 569 Log of observations, apparent magnitude,
estimated B-V, and pulsational phase
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2012)
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2013)
B/hst : HST Archived Exposures Catalog (STScI, 2007)
I/254 : The HST Guide Star Catalog, Version 1.2 (Lasker+ 1996)
J/A+A/330/515 : RR Lyrae parallaxes + proper motions (Fernley+, 1998)
J/MNRAS/386/2115 : Type II Cepheid and RR Lyrae variables (Feast+, 2008)
J/MNRAS/396/553 : Galactic RR Lyrae data (Dambis, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Sources (RRLs or type 2 Cepheids)
13- 17 A5 --- Type Variable type (ab/c for RR Lyr or BLHer, WVir)
19 A1 --- Ref [c-i] References and notes (1)
21- 28 F8.5 [-] logP [-0.51052/0.95815] Log of the pulsational
period
30- 39 F10.4 d T0 [50749.2/54793.01] Epoch of observation
41- 44 F4.2 mag <Vmag> [4.35/9.78] Mean HST V band magnitude
46- 49 F4.2 mag <Ksmag> [2.78/8.72] Mean Ks band magnitude (2)
51- 55 F5.2 [-] [Fe/H] [-1.8/0] Metallicity (3)
57- 60 F4.2 [-] e_[Fe/H] Fe/H abundance uncertainty
62- 65 F4.2 mag Av [0.03/0.78] V-band absorption
67- 70 F4.2 mag Ak ? K-band absorption
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Note (1): Flags as follows:
c = RZ Cep: T0 determined for this paper using
Smith (1995obas.book.....S 1995obas.book.....S);
[Fe/H], Av from Fernley et al. (1998MNRAS.293L..61F 1998MNRAS.293L..61F).
d = XZ Cyg: Fernley et al. (1998MNRAS.293L..61F 1998MNRAS.293L..61F),
Feast et al. (2008, Cat. J/MNRAS/386/2115);
logP, T0 from LaCluyze et al. (2004AJ....127.1653L 2004AJ....127.1653L).
e = SU Dra: Fernley et al. (1998MNRAS.293L..61F 1998MNRAS.293L..61F),
Feast et al. (2008, Cat. J/MNRAS/386/2115).
f = RR Lyr: Fernley et al. (1998MNRAS.293L..61F 1998MNRAS.293L..61F),
Feast et al. (2008, Cat. J/MNRAS/386/2115);
[Fe/H], Av from Kolenberg et al. (2010A&A...519A..64K 2010A&A...519A..64K).
g = UV Oct: Fernley et al. (1998MNRAS.293L..61F 1998MNRAS.293L..61F),
Feast et al. (2008, Cat. J/MNRAS/386/2115);
logP, T0 from FGS photometry;
[Fe/H] determined for this paper, using the approach described
in Kolenberg et al. (2010A&A...519A..64K 2010A&A...519A..64K).
h = VY Pyx: Feast et al. (2008, Cat. J/MNRAS/386/2115);
Ks determined for this paper, using
Laney (2009AIPC.1170...34L 2009AIPC.1170...34L);
T0 from FGS photometry;
[Fe/H] determined for this paper, using the approach described
Kolenberg et al. (2010A&A...519A..64K 2010A&A...519A..64K).
i = κ Pav: Feast et al. (2008, Cat. J/MNRAS/386/2115);
T0 from FGS photometry;
[Fe/H] from Luck & Bond (1989ApJ...342..476L 1989ApJ...342..476L).
Note (2): Ks from Feast et al. (2008, Cat. J/MNRAS/386/2115),
except where noted in Note (1).
Note (3): [Fe/H] on the Zinn & West (1984ApJS...55...45Z 1984ApJS...55...45Z) scale.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Sources (RRLs or type 2 Cepheids)
13- 14 I2 --- Set [1/23] Set (1)
16- 26 F11.5 --- MJD [49984.2/55351.4] Modified Julian Date
(JD-2400000.5)
28- 33 F6.3 mag Vmag [3.961/10.214] HST V band magnitude
35- 38 F4.2 mag B-V Estimated B-V color index (2)
40- 45 F6.4 --- Phase Pulsational phase
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Note (1): Between 13 and 23 sets of astrometric data were acquired with HST FGS
1r for each of our 7 science targets.
Note (2): The B-V colors are inferred from phased color curves constructed
from various sources:
* Galactic RRLs:
RZ Cyg = Sturch (1966ApJ...143..774S 1966ApJ...143..774S)
RZ Cep = Epps & Sinclair (1973Obs....93...78E 1973Obs....93...78E)
SU Dra = Barcza (2002A&A...384..460B 2002A&A...384..460B)
RR Lyr = Hardie (1955ApJ...122..256H 1955ApJ...122..256H)
UV Oct = Kolenberg et al. (2010, priv. com.)
* Type 2 Cepheids:
VY Pyx = Sanwal & Sarma (1991JApA...12..119S 1991JApA...12..119S)
κ Pav = Shobbrook (1992MNRAS.255..486S 1992MNRAS.255..486S)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 21-Mar-2013