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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 (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), we find that standard stellar models using the VandenBerg & Clem (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) 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). 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
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