I further updated the Alpha Cen A coordinates, and the A to B offsets, based on a recent global solution for proper motions and relative orbital displacements derived from an extensive analysis of Chandra HRC images of Alpha Cen obtained since late 1999. The changes are minor in all cases, less than 1" in the coordinates, and 0.03" in the offsets; but the improvements are important for this system given the high proper motion, and the necessity to perform a "blind" offset to the B component given the presence of brighter A so close by. 1081833318 ----- Attempting Submission 1 (Mon Jun 03 14:19:02 GMT 2013) ----- HST Phase II Proposal 13465 (GO-13465.apt) successfully submitted. ----- Attempting Submission 2 (Thu Jun 27 21:37:16 GMT 2013) ----- ----- Attempting Submission 3 (Tue Aug 20 18:37:34 GMT 2013) ----- The target is a pair of very bright stars, so the TCC provides no useful information (sky images burned out); also, both stars have been observed previously, and will be observed with small apertures spectroscopically; SIMBAD does not indicate any other objects within 2' of the pair, and Chandra HRC-I images do not show any other X-ray sources in the vicinity; thus there is no need to run the BOT either. Nearby Alpha Centauri contains the two best characterized G and K dwarfs, next to the Sun itself, thanks to the accurate orbit, resolved angular diameters, and well understood co-evolutionary state. Alpha Cen A & B also have the best studied stellar X-ray activity cycles, extending back to the 1970's. Present proposal is to continue tracking the evolving multi-decadal high-energy narrative of Alpha Cen with semiannual HRC-I pointings in Cycles 13-15, as solar twin A is expected to be rising to cycle maximum following an extended coronal recession. STIS E140M spectra will support and leverage the broad-band X-ray measurements by probing subcoronal dynamics and providing a low-T boundary condition for DEM modeling, with connection to the X-rays through the FUV Fe XII coronal forbidden line. The STIS observations are straightforward. Alpha Cen falls in the HST Continuous Viewing Zone numerous times during the year, allowing the two stars to be captured in a single visit of just two orbits. Two such visits (four orbits total), about six months apart, are contemplated for Cycle 21, compatible with the semiannual pointings by Chandra. There is no need to strictly coordinate the FUV and X-ray visits, because the FUV Fe XII coronal forbidden line can tie the STIS observation into the X-ray framework. In each HST/STIS visit, the binary companions are observed sequentially, beginning with Alp Cen A, the brighter of the two stars. The target is acquired with the CCD and F25ND5, followed by a 4.3 ks exposure with the E140M-1425 medium-res echelle through the photometric slot (0.2x0.2 ), which delivers R=40,000 and good sensitivity (peak S/N=60 per resol at the tops of the important Si IV and C IV resonance lines). The observation is split into three subexposures to mitigate instrumental drifts. The exposure depth is sufficient to capture the key Fe XII 1242 coronal forbidden line, which as mentioned earlier is used to tie the STIS FUV measurements into the X-ray timeline. Following the E140M exposure, a ~5" offset manuever is performed to Alp Cen B, and a peak-up is performed in dispersed light (G430L) with the 0.3x0.05ND filtered slit to precisely locate the target. This particular slit was chosen because the default peak-up sweeps out a sufficient area (0.3"x0.3") to capture the B component, given that the time-dependent separation of the binary companions is accurately known (to the 0.1" level; based on five years of measurements by Chandra HRC-I). After the peak-up, a second 4.3 ks E140M exposure through the photometric aperture is obtained on B. Given that the AB orbital separation is changing relatively rapidly in the present epoch, Alp Cen B was specified as two separate targets, with different offsets, to reflect the orbital evolution over the six months between the two STIS visits. COOL STARS 12 false false 0.0 0.0 false false false SUPPORTED STAR G V-IV The target coords for epoch 2013.480 were obtained from a global fit to high-precision Chandra HRC images, and includes the parallactic shift at that time. The effective proper motion of Alpha Cen A was determined from the best-fit Center-of-Mass proper motion of the system, based on eight years of Chandra HRC-I measurements, accounting for parallax in each epoch; together with a orbital solution from a recent ephemeris modified slightly to better fit the HRC relative orbit in recent years: Alpha Cen AB are moving toward a close approach (on the sky) in 2016, consequently the orbital motion of A has a significant influence on its apparent proper motion. ALP-CEN-A J2000 J2000 FUV peak fluxes are 5E-12 per Angstrom (excluding Lyman-alpha, which is ~ 8E-11) STAR G V-IV Offset of B relative to A determined from the slightly modified ephemeris, which closely matches the relative orbit as recorded by Chandra HRC in recent years. ALP-CEN-B J2000 STAR G V-IV Offset of B relative to A determined from the slightly modified ephemeris, which closely matches the relative orbit as recorded by Chandra HRC in recent years. ALP-CEN-B J2000 STIS/FUV-MAMA Spectroscopic No No E140M 1425 STIS/FUV-MAMA Spectroscopic No No E140M 1425 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. 1372368876778 This is first CVZ opportunity roughly 6 months after final Visit of program 13060 (of which this is a third year continuation) (Tic-Visit :proposal-id 13465 :visit-id "10" :proposal-version -1 :trans-version "20130502" :date "27-Jun-2013 15:34:35.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 488704 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13465 :visit-id "10" :obset-id "10" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 13465 :visit-id "10" :orbit-number 1 :pcs-time 333 :si-vis-utilization 10773 :al-overhead-at-end 0 :internal-dur-at-end 375 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) false 2 0 Castelli and Kurucz Models:G2V;Time to Saturation (for a single exposure) = 2.3 seconds ; Optimum SNR = 179 input=StarCAT ETC file for ALP-CEN-A; Exposure time= 4.3 ks at wavelength 1393.80 Å gives: SNR = 58 (per resol); Brightest Pixel (at 1215.40 Å)= 1.8 cps; peak S/N~200 at Lyman-alpha dispersed light peak-up assuming Castelli-Kurucz Models K0V, V=1.33 mag: at wavelength 5000 Å in 0.1 s, SNR ~ 15 (per resol); Time to Saturation (for a single exposure) ~ 60 seconds. ETC calculation done with 52x0.05 slit, then scaled to 0.3x0.05ND aperture by factor 0.001 (ND=3), as verified by comparing throughputs indicated by separate ETC TARG ACQ runs (without disperser) with ND ap and clear apertures. ETC run is for ALP-CEN-A, which has very similar spectrum to ALP-CEN-B in observed flux densities The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. 1372368649348 This is next available CVZ opportunity roughly six months after first Visit. (Tic-Visit :proposal-id 13465 :visit-id "11" :proposal-version -1 :trans-version "20130502" :date "27-Jun-2013 15:30:48.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 488704 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13465 :visit-id "11" :obset-id "11" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 13465 :visit-id "11" :orbit-number 1 :pcs-time 333 :si-vis-utilization 10772 :al-overhead-at-end 0 :internal-dur-at-end 375 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) false 2 0 Castelli and Kurucz Models:G2V;Time to Saturation (for a single exposure) = 2.3 seconds ; Optimum SNR = 179 input=StarCAT ETC file for ALP-CEN-A; Exposure time= 4.3 ks at wavelength 1393.80 Å gives: SNR = 58 (per resol); Brightest Pixel (at 1215.40 Å)= 1.8 cps; peak S/N~200 at Lyman-alpha dispersed light peak-up assuming Castelli-Kurucz Models K0V, V=1.33 mag: at wavelength 5000 Å in 0.1 s, SNR ~ 15 (per resol); Time to Saturation (for a single exposure) ~ 60 seconds. ETC calculation done with 52x0.05 slit, then scaled to 0.3x0.05ND aperture by factor 0.001 (ND=3), as verified by comparing throughputs indicated by separate ETC TARG ACQ runs (without disperser) with ND ap and clear apertures. ETC run is for ALP-CEN-A, which has very similar spectrum to ALP-CEN-B in observed flux densities