reduced all exps #4 by 180s and adjusted buffer times accordingly. ----- Attempting Submission 5 (Thu Apr 07 19:08:49 GMT 2011) ----- no problems FK Comae is an ultra-fast rotating, single yellow giant, product of a recent W UMa merger. Extraordinary levels of FUV and X-ray emission rate FK Comae a coronal powerhouse on par with the most extreme of the better known activity heavyweights: short-period RS CVn binaries. As a single star, FK Comae has clear advantages as a laboratory for exploring the outer limits of magnetospheric activity among the coronal cool stars. FK Comae has a long history of attention at optical and X-ray wavelengths, thanks to its generously spotted surface, and proclivity to flare regularly at high energies. FUSE discovered ultra-broad, redshifted profiles of O VI and C III, but unfortunately the singular observation could not be repeated, thanks to the satellite's flaky attitude system. The remarkable FUV spectrum was taken just a few months before STIS failed in 2004, so there was no opportunity to turn the more powerful gaze of Hubble to the task. Now, finally, the amazing sensitivity of Cosmic Origins Spectrograph can be brought to bear: a single orbit can capture an FUV spectrum of FK Comae with S/N at instrumental limits for bright lines, and digging down to faint Fe XXI 1354 (bridge to the coordinated Chandra HETGS pointing we also are proposing). We will trace how the bright FUV regions relate spatially to the photospheric dark spots, to inform ideas of coronal structure and heating in these advanced objects. We will probe whether a global magnetosphere exists, and whether the field lines are loaded with hot coronal gas (>10 MK), as well as the cooler 0.3 MK material already suggested by highly broadened FUSE O VI. Further, we will test whether the striking 100 km/s redshifts of the FUV lines, and similar shifts seen in Ne X by Chandra HETGS, are caused by a massive coronal outflow (perhaps implicated in magnetic braking). Our method is to exploit, on the one hand, emission-line "Doppler imaging," whereby bright surface regions are mapped onto specific locations in the global profile, according to the line-of-sight rotational velocity. On the other hand, we compare features of different opacity and excitation (e.g., Si III 1206 and Si IV 1393) to deduce whether, say, a red asymmetry is caused by blueshifted absorption, or alternatively by infall of the entire feature. Multiple epochs spaced over two rotation periods break the degeneracy between profile distortions caused by disk passage of hot patches (Doppler imaging part), and those caused by large-scale flows. Contemporaneous spot maps from the ground will provide a fundamental magnetic context for the coordinated FUV and X-ray "movies."

Overview ------------- The observational objective of the program is to carry out time-domain spectroscopy of the fast-rotating, hyperactive, heavily "spotted" yellow giant FK Comae. We focus on small segments of the NUV and FUV regions where nevertheless numerous important diagnostic emission lines fall. The program calls for eleven COS observations spaced roughly evenly over two spin periods (about 5 days total), the minimum necessary to separate persistent surface features, rotationally mapped onto the very broad line profiles, from transient flares, a common occurrence on this magnetically challenged object. The eleven 1-orbit HST pointings will be coordinated with Chandra transmission grating spectroscopy and Zeeman Doppler Imaging from groundbased telescopes. COS Acquisition & Science Exposures ------------------------------------- The COS observations will be the same in each orbit, and consist of an NUV imaging acquisition with the BOA and MIRROR-A, then a short (51 s) exposure of the 2800 A region with G285M-2676, where the key MgII h & k features fall on stripe "C." The NUV exposure is followed by a pair of G130M-1291 observations, for 900 s each, at FP-POS 3 and 4 and on detector segment "A" only (see below), to fill out the orbit. 1) Imaging ACQ A UV-VIS spectral energy distribution for FK Com was carefully constructed from the extensive IUE low-dispersion SW and LW material available for this object, for wavelengths below about 3200 A; joined at the longer wavelengths to a Kurucz model selected on the basis of the match to the longward end of the IUE SED. Assuming a stellar radius of 8.6 R_sun and the approximate Hipparcos distance of 230 pc, the best fit SED was for log(g)=3.0 and Teff= 4900 K, very reasonable for this mid-G giant with a large surface coverage of cool spots. The COS ETC then indicated that FK Com is a few times brighter than safety limits for the PSA/MIRROR-B combination (NUV imaging acquisition), so we were forced to use the BOA/MIRROR-A combination. The recommended exposure time for S/N=60 is 42 s. Other possible acquisition approaches were investigated, including several types of dispersed light ACQ/SEARCH followed by XD and D peakups, but the NUV imaging acquisition was faster than the other cases considered, and sufficiently robust for this target whose coordinates and proper motions are well known. 2) FUV (& NUV) S/N S/N expectations for the cumulative 1800 s of G130M exposure were estimated by creating a proxy high-resolution FUV spectrum from STIS observations of the hyperactive RS CVn star HR1099. The flux densities of the latter were scaled to FK Com by determining the ratio of the average IUE SW-LO spectrum of FK to that of HR1099, Gaussian smoothed to the same resolution, in bins of 50 A over the full grasp of G130M-1291 (i.e., including both detector segments). The scaled proxy FK spectrum then was smoothed by an appropriate rotational broadening to account for the suppression of the flux densities compared with the more slowly rotating HR1099. Results are given in COS.A322770, which shows that the key FUV lines like CII 1335 and SiIV 1393 will be recorded at peak S/N per resol of around 40 in each single orbit pointing. (The NUV G285M exposure will yield S/N~15 at the peaks of the two MgII features, based on an average IUE LW-HI moderate-resolution spectrum [COS.A322755].) 3) Over-bright Ly-alpha? There is one important caveat to the FUV simulation: the Lyman-alp line of the proxy spectrum likely is much brighter than expected from FK Com itself. Because of geocoronal contamination of the IUE spectra at the HI line, the scaling for the HR1099 spectrum is grossly overestimated at those wavelengths. Furthermore, the FK Com Ly-alp line is expected to be much weaker relative to that of HR1099 because of the large interstellar column (~1E21 per cm^2), including some local HI absorption, which will obliterate the central peak of the line, and impact the surrounding broad wings as well. Thus, the true Ly-alp peak of FK should be below the predictions, which themselves however violate safety limits by a factor of 2, or so. We therefore examined IUE SW-LO spectra of FK Com taken through the large aperture (10"x20") compared with those through the small aperture (3" diameter). If the target was well centered in both apertures, the Ly-alp flux should be mainly stellar in the SMAP but mainly geocoronal in the LAP. Scaling down the LAP geocoronal peak flux by the ratio of SMAP to LAP areas indicates only about a 30% geocoronal correction to the SMAP Ly-ap flux. The residual peak is at about 2E-13 in flux density, which translates to about 2E-12 in integrated flux, when the ~50% throughput of the SMAP and ~5 A resolution are taken into account. The broad FUV emissions of FK Com observed by FUSE have FWHMs of around 500 km/s, or about 2 A at Ly-alp. Thus, a very rough flux density for the peak Ly-alp emission would be around 1E-12. This is a factor of only ~2 below the detector safety threshold. The FUSE observation of FK Com shows a broad feature at Ly-beta, with a peak flux density of 2E-14. The flux density scaling between Ly-alp and -beta is around 20, or more, based on a cursory examination of active stars like HR1099. This also would predict a Ly-alp flux density near 0.5-1E-12, consistent with the IUE scaling within the large uncertainties. Unfortunately, this is about as good as it can get, prediction-wise. The reluctant conclusion is that the FK Com FUV hydrogen emission could be close enough to safety limits to jeopardize the entire sequence, if an overlight condition is triggered. The implication is that the detector side B should be inactivated for the FUV exposures (as was done for the majority of targets in program 11687). They key spectral diagnostics, fortunately, mainly fall on the A side of G130M, so there will be minimal loss of information. (We also included the short NUV exposure of MgII to serve as a proxy for the "lost" HI feature.) The downside is the cost of 300 s for the reconfiguration. Safety Checking ------------------ As far as bright-object safety limits are concerned, FK Com already has been cleared for a Cycle 17 SNAP program (11687), mainly on the basis of an earlier FUSE pointing, through its LSA, which showed no hot star continuum sources in the field of the target. This check will hold for many decades owing to the negligible proper motion of FK Com. In addition, while the hyperactive star is known to flare frequently, it has been observed many time by IUE (and other high-energy experiments) so the flare statistics and amplitude distributions are well known. Typically, the FUV emissions increase in strength by only factors of ~2 during large flares, which is far below the FUV safety limits. It is important to understand, with regard to the flaring behavior, that the FK Comae stars are distinguished by slow, long-duration (~hours) flares of modest amplitude, but large integrated energy; quite unlike the M-dwarf flare stars whose FUV outbursts tend to be very short (~minutes), but larger in amplitude, and very occasionally in the realm of "super flares." The long history of X-ray, UV, and optical observations of FK Com, prototype of a larger class whose members also have been extensively observed, has not captured any behavior analogous to the -- albeit very rare -- dMe super flares, so there is good reason to believe that the flare mechanism on the fast-spinning FK Com yellow giants is quite distinct from that on the tiny, more slowly rotating M dwarfs, although of course strong magnetic fields ultimately are responsible for the events on both types of object. Scheduling ------------- The visibility period in April/May 2011 is optimum for the project because of lack of constraints on the Chandra side, and good access for the groundbased ZDI component. The "BETWEEN" range was selected so that no matter when Visit 01 was scheduled in that range, Visit 11 still will fall within the constraint-free zone for Chandra. The 0.5 D timing of the sequence was accomplished using the "AFTER 01 BY XX D TO YY D" option, with a +/- 0.15 D range (+/- 6% in phase) around each nominal 0.5 D increment to allow for ease of scheduling around SAA passes. COOL STARS 12 false 120 0.0 false false false false SUPPORTED EXT-STAR G III-I FK Comae Berenices; G5II; probably closer to G5III; R~9Rsun; Prot~2.4d; vsini~160km/s FK-COM J2000 13 30 46.7600 +24 13 57.60 J2000 COS/FUV Spectroscopic No No G130M 1291 The scheduling data was generated by CASM 19.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12279 :visit-id "01" :proposal-version -1 :trans-version "20100902" :date "01-Mar-2011 18:24:18.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 243680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12279 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12279 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2906 :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 3249 :pcs-gap 0 ) false 1 0 COS.A321599: optimum exp time for S/N=60 is 42 s; for model SED based on average IUE spectrum for FUV and NUV up to 3100 A, followed by Kurucz log(g)=3, Teff=5000 K scaled to ~4900 K to fit the longward end of IUE composite spectrum (for Rstar= 8.6 Rsun). The scheduling data was generated by CASM 19.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12279 :visit-id "02" :proposal-version -1 :trans-version "20100902" :date "01-Mar-2011 18:24:19.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 243680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12279 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12279 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2906 :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 3249 :pcs-gap 0 ) false 1 0 COS.A321599: optimum exp time for S/N=60 is 42 s; for model SED based on average IUE spectrum for FUV and NUV up to 3100 A, followed by Kurucz log(g)=3, Teff=5000 K scaled to ~4900 K to fit the longward end of IUE composite spectrum (for Rstar= 8.6 Rsun). The scheduling data was generated by CASM 19.0. CASM was run in Phase II mode. 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CASM was run in Phase II mode. (Tic-Visit :proposal-id 12279 :visit-id "04" :proposal-version -1 :trans-version "20100902" :date "01-Mar-2011 18:24:21.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 243680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12279 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12279 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2906 :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 3249 :pcs-gap 0 ) false 1 0 COS.A321599: optimum exp time for S/N=60 is 42 s; for model SED based on average IUE spectrum for FUV and NUV up to 3100 A, followed by Kurucz log(g)=3, Teff=5000 K scaled to ~4900 K to fit the longward end of IUE composite spectrum (for Rstar= 8.6 Rsun). The scheduling data was generated by CASM 19.0. CASM was run in Phase II mode. 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CASM was run in Phase II mode. (Tic-Visit :proposal-id 12279 :visit-id "06" :proposal-version -1 :trans-version "20100902" :date "01-Mar-2011 18:24:24.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 243680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12279 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12279 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2906 :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 3249 :pcs-gap 0 ) false 1 0 COS.A321599: optimum exp time for S/N=60 is 42 s; for model SED based on average IUE spectrum for FUV and NUV up to 3100 A, followed by Kurucz log(g)=3, Teff=5000 K scaled to ~4900 K to fit the longward end of IUE composite spectrum (for Rstar= 8.6 Rsun). The scheduling data was generated by CASM 19.0. CASM was run in Phase II mode. 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CASM was run in Phase II mode. (Tic-Visit :proposal-id 12279 :visit-id "08" :proposal-version -1 :trans-version "20100902" :date "01-Mar-2011 18:24:26.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 243680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12279 :visit-id "08" :obset-id "08" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12279 :visit-id "08" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2906 :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 3249 :pcs-gap 0 ) false 1 0 COS.A321599: optimum exp time for S/N=60 is 42 s; for model SED based on average IUE spectrum for FUV and NUV up to 3100 A, followed by Kurucz log(g)=3, Teff=5000 K scaled to ~4900 K to fit the longward end of IUE composite spectrum (for Rstar= 8.6 Rsun). The scheduling data was generated by CASM 19.0. CASM was run in Phase II mode. 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The scheduling data was generated by CASM 19.0. 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