Changed schedulability flag for Visit 11 to 100%. This opened up additional scheduling
opportunities compared to the default. (An ORIENT constraint for PSA protection limited
scheduling possibilities under 1-G mode). Not necessary to make same change for Visit 10
because there were already sufficiently many scheduling opportunities.1057832232----- Attempting Submission 1 (Fri Jul 12 17:42:20 GMT 2024) -----
----- Attempting Submission 2 (Thu Aug 15 23:09:22 GMT 2024) -----Already run for previous versions of this program in Cycles 30 & 31.The Beat Goes On(This is a joint Chandra/HST program: the Chandra proposal abstract follows.)
Chandra has been following magnetic heartbeats of late-type stars via high-contrast coronal X-rays. Goal is to provide fundamental observational constraints for contemporary and future studies of the underlying magnetic dynamo, whose internal workings remain elusive. The Sun's high-energy modulations play an important space weather role in our heliosphere, as do stellar counterparts for their exoplanets. A 3-year continuation (joint with HST) is proposed for current cycles targets Xi Boo (G8V+K4) and 70 Oph (K0V+K5V). Key questions: (1) origin of diverging branches in rotational period vs. cycle duration, where Sun sits isolated in the middle, possibly in a transitional state; (2) extent of high-energy variability bias, which can affect interpretations of large surveys.**Impact of Reduced Gyro Mode**
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The two targets, Xi Boo and 70 Oph, would be minimally affected by RGM, because there is only a minor orientation constraint on the observations (having to do with protecting the PSA for the NUV/BOA target acquisition). Further, the Visits are only 2 orbits, minimizing the possibility of re-acquisition failures. However, if target acquisition times are increased by RGM, then one or more of the exposures would have to be shortened. This can be done with minimal loss of science.
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Phase II Observing Description (for normal 3-gyro operations)
Observational goal is to obtain FUV moderate-resolution spectra of both components of Xi Boo and 70 Oph using Cosmic Origins Spectrograph (COS) . The primaries, Xi Boo A and 70 Oph A, are nearly identical in FUV flux levels, about a tenth of well-studied (by STIS) Alpha Cen A. Normally, high-sensitivity COS would be off-limits for these primaries, because their strong Lyman-alpha features would violate FUV detector bright limits. However, the COS G130M-1222 setting places Lyman-alpha in the gap between detector sides A and B, so can be used for cool stars, as long as their other strong emissions (e.g., C II 133 nm) are "safe" (as is the case for Xi Boo A and 70 Oph A). When combined with COS G160M-1533, the spectral range 107-171 nm can be covered, with only two small gaps: 120.7-122.3 nm (Lyman-alpha) and 151.5-153.3 nm (devoid of important lines). COS's 15 km/s resolution is fully adequate for the relatively broad FUV emission features of these cool stars, especially the "hot" lines like Si III 120.6 nm (T~30,000 K), Si IV 139.3 nm (80,000 K), and C IV 154.8 nm (100,000 K). The COS FUV channel is so sensitive that a mere 1000 s exposure obtains S/N~100 (line peak) at Si III, 80 at Si IV, and 65 at C IV, for both primary stars. Each grating setting requires 4 "FP-Splits" to mitigate fixed pattern noise.
The pair of FUV settings plus FP-SPLITs can be done in a single orbit for the primary of each system, including the initial Guide Star and NUV imaging target acquisitions.
At the beginning of the second orbit, the secondary star would be centered by a small offset manuever from the primary, given the accurate orbital ephemeris. The same dual-setting FUV sequence then would be carried out, extending over the remaining unocculted part of the second orbit.
The COS visits would be once a year for each system (4 HST orbits per year, total): experience with Alpha Cen AB has shown that the FUV variability, while significant, is not as pronounced as that of the X-rays (which are observed twice a year for each system). Helpfully, key coronal forbidden lines Fe XII 134.9 nm (T~2 MK) and Fe XXI 135.4 nm (10 MK) are available in the FUV to assess the stellar coronal states at the times of the COS pointings. For this reason, the HST and Chandra observations need not be simultaneous. In fact, it is better to have them separated, since the FUV coronal forbidden lines would then provide an additional point on the high-energy time line. Given the very deep COS exposures proposed here (especially at 134.9 nm and 135.4 nm, which receive double coverage in the 2 nm overlap between G130M and G160M), the Fe XII coronal forbidden line will be easily detected in the primary stars (based on the previous COS visits), and probably also in the UV-fainter secondaries.T. Ayres is a highly experienced HST observer, especially with the STIS and COS spectrographs, with dozens of successful programs as PI.Stellar Physics6falsefalsefalsefalsefalsefalsefalsefalseAVAILABLESTARCORONAG V-IVNOTarget coords for epoch 2000 from SIMBAD, based on Gaia measurements for a mean epoch of 2015.5 corrected for Gaia proper motionsXI-BOO-AJ2000J2000STARCORONAK V-IVNOTarget offset based on ephemeris from 6th Orbit Catalog, for 2025.5XI-BOO-BJ2000STARCORONAK V-IVNOTarget coords for epoch 2000 from SIMBAD, based on Gaia measurements for a mean epoch of 2015.5 corrected for Gaia proper motions70-OPH-AJ2000J2000STARCORONAK V-IVNOTarget offset based on ephemeris from 6th Orbit Catalog, for 2025.570-OPH-BJ2000STIS/FUV-MAMASpectroscopicNoNoE140M1425STIS/FUV-MAMASpectroscopicNoNoE140M1425STIS/FUV-MAMASpectroscopicNoNoE140M1425STIS/FUV-MAMASpectroscopicNoNoE140M1425STIS/FUV-MAMASpectroscopicNoNoE140M1425STIS/FUV-MAMASpectroscopicNoNoE140M1425The scheduling data was generated by CASM 32.1.1.CASM was run in Phase II mode.(Tic-Visit
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:date "12-Jul-2024 13:34:38.0"
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)false20Castelli-Kurucz Models G8V, renormalized to vegamag = 4.68 in filter Johnson/Vh_hd131156_uvsum_1m_51163_etc.dat from StarCAT (STIS E140M-1425)h_hd131156_uvsum_1m_51163_etc.dat from StarCAT (STIS E140M-1425)B fluxes scaled by 0.14 from A [h_hd131156_uvsum_1m_51163_etc.dat from StarCAT (STIS E140M-1425)]B fluxes scaled by 0.14 from A [h_hd131156_uvsum_1m_51163_etc.dat from StarCAT (STIS E140M-1425)]The scheduling data was generated by CASM 32.1.1.CASM was run in Phase II mode./private/var/folders/g8/sfxwph3d1y78xbb04wh45v0c0000gn/T/OPVisit3594336566056239090.xml(Tic-Visit
:proposal-id 17839
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:trans-version "20240604"
:date "15-Aug-2024 17:02:50.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
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(Tic-Orbit
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)true20Castelli-Kurucz Models K0V, renormalized to vegamag = 4.22 in filter Johnson/V (from BSC and WDS)