13060( 2) - 10-Jul-2012 15:21:11 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13060 Version: 2 Check-in Time: 10-Jul-2012 15:21:11 STScI Edit Number: 1 Title Alpha Cen: Climbing out of a Coronal Recession? (year 2 continuation) ------------------------------------------------------------------------------------ Type Cycle GO 20 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Thomas R. Ayres University of Colorado at Boulder Y ------------------------------------------------------------------------------------ Abstract 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 from 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 HRC through the FUV Fe XII coronal forbidden line. ------------------------------------------------------------------------------------ Observations Description ------------------------ 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 20, 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 (0.2′′ ×0.2′′ ), 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 λ1242 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 13060( 2) - 10-Jul-2012 15:21:11 - [ 2] 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. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 13060( 2) - 10-Jul-2012 15:21:11 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD128620 STAR, G V-IV RA=14H39M30.2940S +/- 0.5", J2000 V = 24 V = -0.1 +/- 0.1 FUV peak fluxes are DEC=-60D49'58.86" +/- 0.5" 5E-12 per Angstrom (excluding Lyman-alpha, which is ~ 8E-11) Reference Frame: ICRS Comments: The target coords for epoch 2011.997 were measured directly from a high-precision Chandra HRC-I image, and include the parallactic shift at that time. The effective proper motion of Alpha Cen A was determined from the best-fit track of that component, based on most recent two years of HRC-I measurements (the orbit is near periaston, where the apparent proper motion of both companions is most affected by the orbital component). The coords (advanced slightly to epoch 2012.0) and PMs differ minimally from those cited in SIMBAD, even though the catelogue values were measured in an earlier epoch when the relative orbital motion was different. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2012.0 -0.49792428781721304 +0.11 0.747 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD128621-1 STAR, G V-IV RA-OFF=-0.6417S +/- 0.015S, J2000 V = 1.33 +/- 0.1 DEC-OFF=-0.127" +/- 0.1", FROM 1 Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2010 0.00 0.00 0.00 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD128621-2 STAR, G V-IV RA-OFF=-0.6128S +/- 0.015S, J2000 V = 1.33 +/- 0.1 DEC-OFF=+0.253" +/- 0.1", FROM 1 Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2010 0.00 0.00 0.00 ------------------------------------------------------------------------------------------------------------------------------------ 13060( 2) - 10-Jul-2012 15:21:11 - [ 4] Visit: 10 Visit Requirements: CVZ; BETWEEN 20-MAR-2013:12:00:00 AND 22-MAR-2013:11:59:59 On Hold Comments: Additional Comments: This is first CVZ opportunity roughly 6 months after visit 2 of program 12758 (of which this is second year continuation) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD128620 STIS/CCD ACQ F25ND5 MIRROR 1 0.1 S GS ACQ SCENARIO BASE1B3 Comments: Castelli and Kurucz Models:G2V; Time to Saturation (for a single exposure) = 2.3 seconds ; Optimum SNR = 179 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD128620 STIS/FUV ACCUM 0.2X0.2 E140M 1425 3 1425 S -MAMA Comments: 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 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD128621-1 STIS/CCD ACQ/PEA 0.3X0.05N G430L 4300 1 0.1 S K D Comments: 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. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD128621-1 STIS/FUV ACCUM 0.2X0.2 E140M 1425 3 1425 S -MAMA Comments: ETC run is for ALP-CEN-A, which has very similar spectrum to ALP-CEN-B in observed flux densities ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD128620 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD128620 2 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 1 none 1 N/A -MAMA 13060( 2) - 10-Jul-2012 15:21:11 - [ 5] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD128620 2 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 2 none 1 N/A -MAMA HD128620 2 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 3 none 1 N/A -MAMA HD128621-1 3 STIS/CCD ACQ/PEA 0.3X0.05 G430L 4300 none none none none 1 N/A K ND HD128621-1 4 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 1 none 2 N/A -MAMA HD128621-1 4 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 2 none 2 N/A -MAMA HD128621-1 4 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 3 none 2 N/A -MAMA 13060( 2) - 10-Jul-2012 15:21:11 - [ 6] Visit: 11 Visit Requirements: CVZ; BETWEEN 01-SEP-2013:12:00:00 AND 03-SEP-2013:11:59:59 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD128620 STIS/CCD ACQ F25ND5 MIRROR 1 0.1 S GS ACQ SCENARIO BASE1B3 Comments: Castelli and Kurucz Models:G2V; Time to Saturation (for a single exposure) = 2.3 seconds ; Optimum SNR = 179 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD128620 STIS/FUV ACCUM 0.2X0.2 E140M 1425 3 1425 S -MAMA Comments: 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 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD128621-2 STIS/CCD ACQ/PEA 0.3X0.05N G430L 4300 1 0.1 S K D Comments: 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. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD128621-2 STIS/FUV ACCUM 0.2X0.2 E140M 1425 3 1425 S -MAMA Comments: ETC run is for ALP-CEN-A, which has very similar spectrum to ALP-CEN-B in observed flux densities ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD128620 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A HD128620 2 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 1 none 1 N/A -MAMA 13060( 2) - 10-Jul-2012 15:21:11 - [ 7] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD128620 2 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 2 none 1 N/A -MAMA HD128620 2 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 3 none 1 N/A -MAMA HD128621-2 3 STIS/CCD ACQ/PEA 0.3X0.05 G430L 4300 none none none none 1 N/A K ND HD128621-2 4 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 1 none 2 N/A -MAMA HD128621-2 4 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 2 none 2 N/A -MAMA HD128621-2 4 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none 3 none 2 N/A -MAMA 13060( 2) - 10-Jul-2012 15:21:11 - [ 8] Summary Form for Proposal 13060 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.2, 0.3X0.05ND, F25ND5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-SEP-2013:12:00:00 AND 03-SEP-2013:11:59:59, BETWEEN 20-MAR-2013:12:00:00 AND 22-MAR-2013:11:59:59, CVZ, GS ACQ SCENARIO BASE1B3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140M, G430L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD128620, HD128621-1, HD128621-2 ------------------------------------------------------------------------------------------------------------------------------------