The TW Hya association (age ~ 9 Myr, distances ~ 50 pc) is the nearest group of young stars with ages < 10 Myr and has stars with both actively accreting and debris disks. Consequently, this association offers special opportunities for studying protoplanetary system evolution. We propose to study low mass TWA members using Chandra ACIS-S to obtain CCD resolution X-ray spectra and the HST COS+STIS spectrographs to obtain medium resolution FUV and NUV spectra. Using these spectra we will study the temperature/EM distributions of the hot (log T = 4-7 K) plasma, examine the flows and turbulence in the hot plasma, and construct the full X-ray/EUV/FUV radiation fields to allow modeling their influence on protoplanetary system physics and chemistry. [ Chandra and HST time awarded to observe the common proper motion pair TWA 13 A + 13B.]

Two TWA Association members are to be observed using COS G130M/G160M and the brighter will also be observed using STIS G230L and E230M. These stars are a common proper motion pair separated by ~ 5 arcseconds. Both are M1 dwarfs and have V magnitudes of 11.5 (TWA13A) and 12.0 (TWA13B). No UV spectra exist for TWA 13 A+B. Therefore, we have constructed our Phase II observing sequence to match successfully implemented COS/STIS observations for young stars with similar properties and brightness by Cycle 17 program 11616. N.B. we are using exposure times and settings matching those for stars that have ALREADY been observed by 11616, such as GM Aur (V=12.2), RECX-11 (V=11.2), and RECX-1 (V=10.5), that span a magnitude range encompassing the TWA 13 stars. TWA 13 is old enough that the stars are no longer accreting and do not have circumstellar disks; thus their UV continuum will not show variability due to variable accretion. The coordinates given in this Phase II proposal are from the 2MASS Catalog and are already corrected for proper motion to 2000.0. The proper motions are relatively small and are the most accurate currently available from the as yet unpublished work of Mamajek. The positions and proper motions are accurate enough that the positional error for TWA 13A will be far less than 1 arcsecond and there should be no chance of acquiring TWA 13B by mistake. We acquire TWA 13A using a COS ACQ/IMAGE with MIRRORB and the PSA, and then obtain four G130M exposures in the rest of Orbit 1.Orbit 2 is used for three G160M exposures. Orbit 3 starts with an offset to TWA 13B and then contains four G130M exposures, while orbit 4 is used for three G160M exposures. Orbit 5 starts with a STIS acquisition of TWA 13A and then obtains G230L and E230M spectra with the NUV-MAMA. COOL STARS 12 false 0.0 0.0 false false false false false false SUPPORTED STAR M V-IV PRE-MAIN SEQUENCE STAR Common proper motion companion to TWA13A. TWA13B 10 28 4.0210 +48 47 10.74 J2000 STAR M V-IV PRE-MAIN SEQUENCE STAR J2000 10 28 3.8823 +48 47 5.64 J2000 COS/FUV Spectroscopic No No G140L 1230 COS/FUV Spectroscopic No No G140L 1230 COS/FUV Spectroscopic No No G140L 1230 COS/FUV Spectroscopic No No G140L 1230 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12361 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "01-Oct-2010 18:02:15.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1653360 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12361 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 12361 :visit-id "01" :obset-id "A1" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12361 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2873 :al-overhead-at-end 0 :internal-dur-at-end 59 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12361 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3020 :al-overhead-at-end 0 :internal-dur-at-end 50 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12361 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3030 :al-overhead-at-end 0 :internal-dur-at-end 50 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12361 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 3040 :al-overhead-at-end 0 :internal-dur-at-end 362 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12361 :visit-id "01" :orbit-number 5 :pcs-time 333 :si-vis-utilization 2914 :al-overhead-at-end 0 :internal-dur-at-end 587 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) false 5 0