A New Opportunity to Detect Iron in the Most Iron-Poor Star Known

0 Assigned ID: 126 ----- Attempting Submission 1 (Wed Apr 09 20:33:47 GMT 2014) ----- When running the BOT, one star in the field is flagged as a "health/safety" concern. This star is actually the target star, of type G III, not O5V as assumed by the BOT for lack of information. Thus it should not pose a threat to the detectors. Resubmitted 09/28/2015 with minor corrections to the ACQ/IMAGE exposure estimates. -iur 1391151413 ----- Attempting Submission 1 (Wed Jul 09 12:57:32 GMT 2014) ----- ----- Attempting Submission 2 (Mon Sep 28 16:15:29 GMT 2015) ----- A New Opportunity to Detect Iron in the Most Iron-Poor Star Known At present, there are three stars known in the Milky Way with Fe/H ratios less than 1/100,000 times the Solar Fe/H ratio. These stars were almost certainly formed during the earliest epochs of star formation in the Milky Way, and their metals were formed from the yields of just one zero-metallicity Population III supernova. High-quality optical spectroscopy reveals the presence of C, Mg, Ca, Fe, and other metals in two of these stars. In the most iron-poor star, SMSS J031300-670839, only Li, C, Mg, and Ca are detected. Not a single iron line can be detected in the optical spectral range. The Fe/H ratio of this star is currently estimated to be less than 1/13,000,000 times the Solar Fe/H ratio. I propose to obtain a high-resolution COS spectrum of this star to attempt to detect Fe II lines in the NUV near 2400 Angstroms. These Fe II lines are the strongest of any iron-group element, and they present the best opportunity to detect iron in this star. My proposed observations would tighten the constraint on the Fe/H ratio by a factor of 50, and a detection would be possible if the Fe/H ratio in this star is 1/1,000,000,000 times the Solar Fe/H ratio or greater. NUV observations with COS provide the only opportunity to perform this study. This program will obtain R~22,000 COS spectra around several Fe II absorption lines near 2400 Angstroms in a very metal-poor late-G-type star. The goal is to obtain the highest S/N possible (target: S/N ~ 20/1) in this one setup within the 10 orbits allocated. COOL STARS 12 false true false false SUPPORTED STAR G III-I HALO POPULATION II NO The coordinates are taken from the USNO-B catalog accessed through IRSA on 07 July 2014. The proper motions derived by the PPMXL catalog (USNO-B plus 2MASS) are PMRA = -0.000002 +/- 0.000003 deg/yr and PMDEC = 0.000002 +/- 0.000003 deg/yr. Neither one is significant, so I have entered 0.0 for both values in the APT table. The coordinate uncertainties are given as 0.000018 deg (*cos(DEC)), which I convert to 0.17 arcsec. J2000 J2000 E(B-V) = 0.04; B = 15.36 (USNO-B); R = 14.10 (USNO-B); J = 13.181 (2MASS); H = 12.692 (2MASS); K = 12.661 (2MASS) COS/NUV Spectroscopic No No G225M 2390 COS/NUV Spectroscopic No No G225M 2390 1443456736818 /private/var/folders/ly/dz_8k_s14_qbfx0j25d8qbjc0000gn/T/OPVisit8382576630874377353.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13827 :visit-id "01" :proposal-version -1 :trans-version "20150609" :date "28-Sep-2015 12:12:16.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "32" :si-bright-earth-limb-angle 20.0 :data-volume 1226496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13827 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13827 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3223 :al-overhead-at-end 0 :internal-dur-at-end 114 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3556 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13827 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3334 :al-overhead-at-end 0 :internal-dur-at-end 38 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3556 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13827 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3334 :al-overhead-at-end 0 :internal-dur-at-end 38 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3556 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13827 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 3334 :al-overhead-at-end 0 :internal-dur-at-end 38 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3556 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13827 :visit-id "01" :orbit-number 5 :pcs-time 222 :si-vis-utilization 3334 :al-overhead-at-end 0 :internal-dur-at-end 331 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3556 :pcs-gap 0 ) true 5 0 1443456717402 /private/var/folders/ly/dz_8k_s14_qbfx0j25d8qbjc0000gn/T/OPVisit8960892258182553842.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. 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