J/ApJ/835/152 HST FGS-1r parallaxes for 8 metal-poor stars (Chaboyer+, 2017)
Testing metal-poor stellar models and isochrones with HST parallaxes of
metal-poor stars.
Chaboyer B., McArthur B.E., O'Malley E., Benedict G.F., Feiden G.A.,
Harrison T.E., McWilliam A., Nelan E.P., Patterson R.J., Sarajedini A.
<Astrophys. J., 835, 152-152 (2017)>
=2017ApJ...835..152C 2017ApJ...835..152C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Parallaxes, trigonometric ;
Proper motions ; Photometry, HST ; Interferometry ;
Positional data
Keywords: globular clusters: general; parallaxes; stars: distances;
stars: interiors; stars: Population II
Abstract:
Hubble Space Telescope (HST) fine guidance sensor observations were
used to obtain parallaxes of eight metal-poor ([Fe/H]< -1.4) stars.
The parallaxes of these stars determined by the new Hipparcos
reduction average 17% accuracy, in contrast to our new HST parallaxes,
which average 1% accuracy and have errors on the individual parallaxes
ranging from 85 to 144µas. These parallax data were combined with
HST Advanced Camera for Surveys photometry in the F606W and F814W
filters to obtain the absolute magnitudes of the stars with an
accuracy of 0.02-0.03 mag. Six of these stars are on the main sequence
(MS) (with -2.7<[Fe/H]< -1.8) and are suitable for testing metal-poor
stellar evolution models and determining the distances to metal-poor
globular clusters (GCs). Using the abundances obtained by O'Malley+
(2017ApJ...838...90O 2017ApJ...838...90O), we find that standard stellar models using the
VandenBerg & Clem (2003AJ....126..778V 2003AJ....126..778V) color transformation do a
reasonable job of matching five of the MS stars, with HD 54639
([Fe/H]=-2.5) being anomalous in its location in the color-magnitude
diagram. Stellar models and isochrones were generated using a Monte
Carlo analysis to take into account uncertainties in the models.
Isochrones that fit the parallax stars were used to determine the
distances and ages of nine GCs (with -2.4≤[Fe/H]≤-1.9).
Averaging together the age of all nine clusters led to an absolute age
of the oldest, most metal-poor GCs of 12.7±1.0Gyr, where the quoted
uncertainty takes into account the known uncertainties in the stellar
models and isochrones, along with the uncertainty in the distance and
reddening of the clusters.
Description:
Each program star was observed with the HST Advanced Camera for
Surveys-Wide Field Camera (ACS/WFC) in the F606W and F814W filters.
The CTE-corrected ACS/WFC images for the program stars were retrieved
from MAST. These instrumental magnitudes were corrected for exposure
time, matched to form colors, and calibrated to the VEGAMag and
ground-based VI systems using the Sirianni+ (2005PASP..117.1049S 2005PASP..117.1049S)
photometric transformations. Ground based photometry for all of our
program stars were obtained using the New Mexico State University
(NMSU) 1m telescope, the MDM 1.3m telescope, and the SMARTS 0.9m
telescope. See appendix A1 for further details.
We used HST FGS-1r, a two-axis interferometer, to make the astrometric
observations. Eighty-nine orbits of HST astrometric observations were
made between 2008 December and 2013 June. Every orbit contained
several observations of the target and surrounding reference stars.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 43 8 Metal-poor target star parallaxes
table3.dat 84 8 Metal-poor target star proper motions
table4.dat 55 8 Summary of parallax star properties
table11.dat 765 2345 Astrometric data for the 8 targets and
reference stars
--------------------------------------------------------------------------------
See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
I/254 : The HST Guide Star Catalog, Version 1.2 (Lasker+ 1996)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
I/317 : The PPMXL Catalog (Roeser+ 2010)
I/320 : SPM 4.0 Catalog (Girard+, 2011)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
J/AJ/107/2240 : Proper motion stars survey. XII. (Carney+, 1994)
J/A+A/359/347 : Reddening in open and globular clusters (Dutra+, 2000)
J/A+A/445/939 : Metal-poor stars uvby-beta photometry. XI. (Schuster+, 2006)
J/ApJ/715/1203 : υ Andromedae system with HST (McArthur+, 2010)
J/AJ/142/187 : HST observations of 7 Pop.II variable stars (Benedict+, 2011)
J/A+A/575/A26 : Properties of Population II star HD 140283 (Creevey+, 2015)
J/ApJ/812/149 : HSTPROMO. III. Dynamical distances (Watkins+, 2015)
J/AJ/151/160 : 1103 parallaxes and proper motions from URAT (Finch+, 2016)
J/ApJ/831/L6 : Eclipsing binary parallaxes with Gaia data (Stassun+, 2016)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP [46120/108200] HIP number
8- 13 F6.3 mas Plx [3.4/15.1] HST parallax
15- 19 F5.3 mas e_Plx [0.08/0.2] Plx uncertainty
21- 25 F5.2 mas PlxH07 [9.5/16] HIP parallax (Cat. I/311)
27- 30 F4.2 mas e_PlxH07 [0.9/3] PlxH07 uncertainty
32- 37 F6.3 mas PlxT17 [2.4/15]? TGAS parallax (Cat. I/337/tgas)
39- 43 F5.3 mas e_PlxT17 [0.2/0.9]? PlxT17 uncertainty
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP [46120/108200] HIP number
8- 15 F8.3 mas/yr pmRA [-567.1/760.7] µR.A. from HST
17- 21 F5.3 mas/yr e_pmRA [0.07/0.2] pmRA uncertainty
23- 30 F8.3 mas/yr pmDE [-625.6/1236.4] µDecl. from HST
32- 36 F5.3 mas/yr e_pmDE [0.08/0.2] pmDE uncertainty
38- 44 F7.2 mas/yr pmRAH07 [-568/763] HIP proper motion along RA
46- 49 F4.2 mas/yr e_pmRAH07 [1/4] pmRAH07 uncertainty
51- 57 F7.2 mas/yr pmDEH07 [-627/1237] HIP proper motion along DEC
59- 62 F4.2 mas/yr e_pmDEH07 [1/3] pmDEH07 uncertainty
64- 69 F6.1 mas/yr pmRAPP [-382/762] PPMXL µR.A. (Cat. I/317)
71- 73 F3.1 mas/yr e_pmRAPP [1/9] pmRAPP uncertainty
75- 80 F6.1 mas/yr pmDEPP [-630/1238] PPMXL µDecl.
82- 84 F3.1 mas/yr e_pmDEPP [1/7] pmDEPP uncertainty
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP [46120/108200] HIP number
8- 12 F5.2 mag Vmag [10/11.6] V-band magnitude (Vega system)
14- 18 F5.3 mag V-I [0.7/1] (V-I) color index
20- 23 F4.2 mag E(B-V) [0/0.2] Color excess (1)
25- 29 F5.3 --- (V-I)0 [0.6/1] Dereddened (V-I) color index
31- 34 F4.2 mag VMag [3.9/6.7] Absolute V-band magnitude (MV)
36- 39 F4.2 mag e_VMag [0.01/0.1] VMag uncertainty
41- 44 F4.2 mag F606W [3.7/6.4] F606W absolute magnitude (MF606W) (2)
46- 50 F5.2 [-] [Fe/H] [-2.7/-1.4] [Fe/H] abundance (1)
52- 55 F4.2 [-] [a/Fe] [0.01/0.7] [α/Fe] abundance (1)(3)
--------------------------------------------------------------------------------
Note (1): High-resolution spectroscopic abundances and reddening estimates are
from O'Malley+ (2017ApJ...838...90O 2017ApJ...838...90O). The reddening estimates are
based upon the strength of the interstellar NaI line in the
high-resolution spectra of the target stars. See section 3.
Note (2): Uncertainty is the same as the VMag values.
Note (3): Based upon the abundance of calcium, an α-capture element.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table11.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- obsID HST Observation ID (Dataset)
11- 18 A8 --- Mode HST observing mode; POSITION or TRANSFER
20- 28 I9 --- PID Raw target ID from proposal (Proposal ID)
30- 34 I5 --- Plate Proposal number of observations
36- 38 I3 --- Star [1/580] Star number of observation from proposal
40- 44 F5.2 mag pVmag [10/16] Predicted V band magnitude
46- 50 F5.2 mag Vmag [9.5/16.2] Actual V band magnitude
52- 60 F9.5 deg RApdeg Predicted Right Ascension (J2000)
62- 70 F9.5 deg DEpdeg Predicted Declination (J2000)
72- 79 F8.4 deg RAdeg Right Ascension of V1 telescope axis (J2000)
81- 90 F10.6 deg DEdeg Declination of V1 telescope axis (J2000)
92-100 F9.5 deg rollV3 Roll about V3 of telescope
102-113 F12.6 km Xpos X position of telescope
115-126 F12.6 km Ypos Y position of telescope
128-139 F12.6 km Zpos Z position of telescope
141-149 F9.6 km/s Xvel X velocity of telescope
151-159 F9.6 km/s Yvel Y velocity of telescope
161-169 F9.6 km/s Zvel Z velocity of telescope
171-181 F11.3 d JD Observation Julian Date; corrected
183-193 F11.5 d MJD Modified Julian observation time
195-198 I4 yr Obs.Y [2008/2011] Year of observation
200-202 I3 d Obs.D [2/356] Day of observation
210-211 I2 h Obs.h [0/23] The hour of observation
213 I1 --- Astro [1] FGS used as the astrometer (always "1")
215-219 A5 --- Filt [F583W] Filter used for observation
(always F583W)
221-222 I2 --- Set [1/12] Set number of observation group
224 I1 km/s E+Xvel [0] Earth plus HST X velocity
226 I1 km/s E+Yvel [0] Earth plus HST Y velocity
228 I1 km/s E+Zvel [0] Earth plus HST Z velocity
230-239 F10.5 arcsec Xave Uncorrected X position calculated by average
241-249 F9.5 arcsec Yave Uncorrected Y position calculated by average
251-257 F7.5 arcsec e_Xave [0.001/0.6] Standard deviation in Xave
259-265 F7.5 arcsec e_Yave [0.001/0.02] Standard deviation in Yave
267-275 E9.2 arcsec XYcor XY correlation
277-285 E9.2 arcsec XYcov XY covariance
287-300 F14.9 arcsec Xmed Uncorrected X position calculated by median
302-312 F11.7 arcsec Ymed Uncorrected Y position calculated by median
314-320 F7.5 arcsec Xmad [0.001/0.2] X median average deviation
322-328 F7.5 arcsec Ymad [0.0009/0.007] Y median average deviation
330-337 E8.2 s exptm [20/124] Seconds of FINELOCK data
339-342 I4 --- npix [829/4969] Number of samples
from FINELOCK interval
344-348 A5 --- VLabSi Instrument velocity aberration measured from
HST/FGS-1r (always FGS1r)
350 I1 --- VLabFGS [1] FGS velocity aberration measured from
352-365 F14.9 arcsec XVLab X position of velocity aberration
367-377 F11.7 arcsec YVLab Y position of velocity aberration
379 I1 --- Dom-GS [2/3] Dominant FGS guider
381-390 F10.4 --- pmtsum [40/11825] Sum of pmts
392-400 F9.4 --- pmtxa pmt from channel xa
402-410 F9.4 --- pmtxb pmt from channel xb
412-420 F9.4 --- pmtya pmt from channel ya
422-430 F9.4 --- pmtyb pmt from channel yb
432-434 I3 --- S-bckgd [100] Number of samples for background
436-439 I4 --- NSamX [0/1733] Number of samples for walkdown
pmt diff/sum in X axis
441-447 F7.4 --- xfld/s [-0.6/0.3] X pmt diff/sum from fine lock dv
interval
449-455 F7.4 --- xwdd/s [-1/0.2] X pmt diff/sum from walkdown interval
457-462 F6.4 --- k1x [0.01/0.04] Reference X axis S_curve inverse
slope of Upgren69
464-472 F9.6 arcsec xdiff [-1/0.004] X centroid shift in arcseconds;
add to Xmed
474-477 I4 --- NSamY [87/4322] Number of samples for walkdown
pmt diff/sum in Y axis
479-485 F7.4 --- yfld/s [-0.4/0.02] Y pmt diff/sum from fine lock dv
interval
487-493 F7.4 --- ywdd/s [-1/-0.08] Y pmt diff/sum from walkdown interval
495-500 F6.4 --- k1y [0.01/0.05] Reference Y axis S_curve inverse
slope of Upgren69
502-510 F9.6 arcsec ydiff [-1/0.005] Y centroid shift in arcseconds;
add to Ymed
512-519 F8.3 arcsec ctX Course track X position
521-527 F7.3 arcsec ctY Course track Y position
529-534 I6 arcsec ssAmed Star selector position; theta A
536-541 I6 arcsec ssBmed Star selector position; theta B
543-553 E11.4 arcsec Xvar Variance of X
555-565 E11.4 arcsec Yvar Variance of Y
567-577 E11.4 arcsec Xmvar [/0.02] Median average deviation variance of X
579-589 E11.4 arcsec Ymvar Median average deviation variance of Y
591-601 F11.4 --- ssA1 Predicted star selector position; theta A
603-613 F11.4 --- ssB1 Predicted star selector position; theta B
615-625 F11.9 --- intrhoA Interpolated rhoA lever arm
627-637 F11.9 --- intkA Interpolated kA lever arm
639-650 F12.9 --- Q1 Spacecraft quaternion
652-663 F12.9 --- Q2 Spacecraft quaternion
665-676 F12.9 --- Q3 Spacecraft quaternion
678-689 F12.9 --- Q4 Spacecraft quaternion
691-702 F12.9 --- Palpha [-3.5/2.3] Parallax factor α
704-715 F12.9 --- Pdelta [-1/1.1] Parallax factor δ
717-728 E12.5 arcsec Xsinfit [-0.003/0.002] Sinfit position correction for X
730-743 F14.9 arcsec Xfcqc Final X corrected position
with polynomial drift correction
745-755 F11.7 arcsec Yfcqc Final Y corrected position
757-759 A3 --- --- [HIP]
760-765 I6 --- HIP Target name (HIP number)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Aug-2017