11116( 3) - 10/23/07 06:27 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11116 Version: 3 Check-in Time: 23-Oct-2007 10:26:47 STScI Edit Number: 0 Title Exploring the Early FUV History of Cool Stars: Transition Regions at 30 Myr ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Steven H. Saar Smithsonian Institution Astrophysical Observatory CoI: Dr. Thomas R. Ayres University of Colorado at Boulder N ------------------------------------------------------------------------------------ Abstract Stellar magnetic activity derives from the so-called "dynamo, " a hydromagnetic interplay between overturning plasma motions and differential rotation in stars cool enough to support significant surface convection zones. The magnetic fields resulting from dynamo action are in turn are responsible for a wide range of high- energy emissions, including the spectacular outbursts called flares. Dynamo powered magnetic activity is not confined solely to stars, but also must occur, for example, in accretion disks of all descriptions, and in some planets. A great deal is known about magnetic activity in middle-aged G dwarfs like our Sun, thanks to its proximity. Less is known, however, about the much younger stars, newly emerged from the T-Tauri stage. Yet, it is during this phase that they reach the peak of their magnetic activity, and subsidiary influences, such as the impact of ionizing radiation and strong coronal winds on developing solar systems, also are maximum. One of the key missing ingredients in our current understanding are measurements of FUV emissions of such stars, to complement the extensive collections of coronal (1- 10 MK) X-ray measurements, particularly from recent ROSAT, Chandra and XMM-Newton surveys. We propose to conduct sensitive ACS/SBC prism ultraviolet spectroscopy of selected fields in two young (30 Myr) Galactic clusters--IC 2391 and IC 2602--to inventory the key C IV emission index (~0.1 MK) over a much larger and more diverse sample of coeval objects than has been possible hitherto. A key question is whether the FUV emissions also suffer the "saturation" and "super-saturation" at short rotation periods seen in coronal X-rays, or whether they continue to rise in the fastest rotating stars. The saturation behavior of the different temperature regimes holds important clues to the organization of the surface active regions on these very young stars, and should allow us to distinguish among several competing models. ------------------------------------------------------------------------------------ 11116( 3) - 10/23/07 06:27 - [ 2] Observations Description ------------------------ There are no previous measurements of our targets in the FUV. The large FOV of GALEX puts too many UV bright OBA stars on the detector, making observations of these clusters impossible (S/N in any case would be much lower). Thus, only HST can make these observations. We choose the SBC PR130L prism (spectra) and F140LP (pre-image) to limit geocoronal Ly alpha. To test the feasibility of our proposed observations, we have estimated fluxes using HST GHRS spectra of three nearby rapid rotators with saturated activity as proxies: EK Dra (G1V, P_{rot} ~ 3 d, D = 33.9 pc, R ~ 1.05 R_sun), LQ Hya (K2V, P_{rot} ~ 1.8 d, D = 18.3 pc, R 0.75 R_sun), and YZ CMi (M4Ve, P_{rot} ~ 2.8 d, D = 5.1 pc, R ~0.40 R_sun). These stars nicely bracket our targets in temperature and radius. The spectra are scaled to the distances of our clusters (IC 2391, 175 pc, redenning 0.008 mag; IC 2602, 160 pc, redenning 0.024 mag). Figure 2 shows the result for IC 2391, rebinned to the resolution of PR130L data, together with the scaled but un-rebinned spectrum of LQ Hya. The major UV lines in this, the highest efficiency section of the PR130L, can be clearly distinguished from the nearby (pseudo)-continuum with little blending of the major lines (except with others of like type, e.g., C IV with C IV). Indeed, we find (remarkably) that we can recover the measured high resolution fluxes for Si IV, C IV, and He II from the PR130L data within ~5%. Target star fluxes are interpolated from these model spectra fluxes (Table 1) by scaling the stellar radius and distance (for IC 2602); SS stars are assumed to have a factor of 2.0 less flux (a bit less than the factor of ~2.5 mean drop in X-rays). For the ETCs we extend the GHRS spectra beyond 1660 A at constant flux (an underestimate) to account for additional continuum, and used average backgrounds. For the SBC direct image we use F140LP to exclude Ly alpha. We aim for S/N = 10 in C IV, and S/N = 5 in the direct image; this gives the exposure times and S/N for other lines given in table 2. With overheads of 6 min per guide star acquisition and 1.7 per exposure, we can fit one preimage and at least 2 spectra with S/N in C IV S/N_CIV ~ 10 of each of our targets, allowing some variation discrimination. For four of the targets, we can fit 5 to 7 spectra iof higher quality (S/N_CIV ~ 14 - 20) into an orbit, permitting 2 sigma detection of 10% and 14% variations on short timescales, respectively, sufficient to detect moderate size flares. Using the NOMAD photometric database through Vizier, we estimated the V and B-V magnitudes and/or spectral types for most of the unknown stars which turned up in the ACS BOT. The ETC shows none of the targets posing any problem for the detector. (In several cases the BOT did not have enough information on our targets, and labeled them O5 stars... with additional photometric data, they prove entirely safe.) Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- 11116( 3) - 10/23/07 06:27 - [ 3] Note that the above description has been modified from the phase one version. Note also that spectra of two stars are obtained in the observation of V372 Vel (see Table 2, owever, V375 Vel will not be possible). The spectra V372 and V373 Vel (a wide binary) will overlap to some extent, but for most roll angles the positional offset (~4") will be sufficient to make at least partial separation possible. In the limited range where overlap is strong, the 4" offset will still displace the emission lines in the merged spectrum, permitting separate measurement against a common (low, M star) continuum. V376 Vel has been added as a substitute for V557 Car, which had nearby B0 star being assertively blue. ------------------------------------------------------------------------------------ 11116( 3) - 10/23/07 06:27 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V372-VEL STAR, CORONA, EMISSION RA=08H43M27.8000S +/- 0.3", J2000 V = 14.21+/-0.3 LINE STAR, M V-IV DEC=-52D57'37.00" +/- 0.3" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. 2 V371-VEL STAR, CORONA, EMISSION RA=08H42M18.4000S +/- 0.3", J2000 V = 13.74+/-0.3 LINE STAR, M V-IV DEC=-53D01'57.00" +/- 0.3" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. 4 V379-VEL STAR, CORONA, EMISSION RA=08H45M27.2000S +/- 0.3", J2000 V = 12.76+/-0.2 LINE STAR, K V-IV DEC=-52D52'8.30" +/- 0.3" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Aimpoint slightly offset from target star to move overbright blue star out of FOV. 5 V552-CAR STAR, CORONA, EMISSION RA=10H40M51.3000S +/- 0.3", J2000 V = 12.19+/-0.2 LINE STAR, K V-IV DEC=-64D42'48.00" +/- 0.3" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. 9 V561-CAR STAR, CORONA, EMISSION RA=10H44M59.6000S +/- 0.3", J2000 V = 10.85+/-0.1 LINE STAR, G V-IV DEC=-65D02'19.00" +/- 0.3" Reference Frame: ICRS 11 V376-VEL STAR, CORONA, EMISSION RA=08H44M5.1863S +/- 0.3", DEC=- J2000 V = 10.85+/-0.2 LINE STAR, G V-IV 52D53'17.22" +/- 0.3" Reference Frame: ICRS 11116( 3) - 10/23/07 06:27 - [ 5] Visit: 01 Visit Priority: Visit Requirements: 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 V372-VEL ACS/SBC ACCUM SBC F140LP 1 118 S Comments: pre-image ------------------------------------------------------------------------------------------------------------------------------------ 2 V372-VEL ACS/SBC ACCUM SBC PR130L 2 1250 S Comments: v372 vel exposure ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V372-VEL 1 ACS/SBC ACCUM SBC F140LP none none none none 1 N/A V372-VEL 2 ACS/SBC ACCUM SBC PR130L none none 1 none 1 N/A V372-VEL 2 ACS/SBC ACCUM SBC PR130L none none 2 none 1 N/A 11116( 3) - 10/23/07 06:27 - [ 6] Visit: 02 Visit Priority: Visit Requirements: 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 V371-VEL ACS/SBC ACCUM SBC F140LP 1 110 S Comments: v371vel preimage ------------------------------------------------------------------------------------------------------------------------------------ 2 V371-VEL ACS/SBC ACCUM SBC PR130L 2 1255 S Comments: v371vel exposure ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V371-VEL 1 ACS/SBC ACCUM SBC F140LP none none none none 1 N/A V371-VEL 2 ACS/SBC ACCUM SBC PR130L none none 1 none 1 N/A V371-VEL 2 ACS/SBC ACCUM SBC PR130L none none 2 none 1 N/A 11116( 3) - 10/23/07 06:27 - [ 7] Visit: 03 Visit Priority: Visit Requirements: 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 V379-VEL ACS/SBC ACCUM SBC F165LP 1 210 S Comments: v379vel preimage ------------------------------------------------------------------------------------------------------------------------------------ 2 V379-VEL ACS/SBC ACCUM SBC PR130L 5 460 S Comments: v379 exposure ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V379-VEL 1 ACS/SBC ACCUM SBC F165LP none none none none 1 N/A V379-VEL 2 ACS/SBC ACCUM SBC PR130L none none 1 none 1 N/A V379-VEL 2 ACS/SBC ACCUM SBC PR130L none none 2 none 1 N/A V379-VEL 2 ACS/SBC ACCUM SBC PR130L none none 3 none 1 N/A V379-VEL 2 ACS/SBC ACCUM SBC PR130L none none 4 none 1 N/A V379-VEL 2 ACS/SBC ACCUM SBC PR130L none none 5 none 1 N/A 11116( 3) - 10/23/07 06:27 - [ 8] Visit: 04 Visit Priority: Visit Requirements: 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 V552-CAR ACS/SBC ACCUM SBC F165LP 1 175 S Comments: v552car (rsp) preimage ------------------------------------------------------------------------------------------------------------------------------------ 2 V552-CAR ACS/SBC ACCUM SBC PR130L 6 390 S Comments: v552car (rsp) exposure ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V552-CAR 1 ACS/SBC ACCUM SBC F165LP none none none none 1 N/A V552-CAR 2 ACS/SBC ACCUM SBC PR130L none none 1 none 1 N/A V552-CAR 2 ACS/SBC ACCUM SBC PR130L none none 2 none 1 N/A V552-CAR 2 ACS/SBC ACCUM SBC PR130L none none 3 none 1 N/A V552-CAR 2 ACS/SBC ACCUM SBC PR130L none none 4 none 1 N/A V552-CAR 2 ACS/SBC ACCUM SBC PR130L none none 5 none 1 N/A V552-CAR 2 ACS/SBC ACCUM SBC PR130L none none 6 none 1 N/A 11116( 3) - 10/23/07 06:27 - [ 9] Visit: 06 Visit Priority: Visit Requirements: 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 V561-CAR ACS/SBC ACCUM SBC F165LP 1 30 S Comments: v561car preimage ------------------------------------------------------------------------------------------------------------------------------------ 2 V561-CAR ACS/SBC ACCUM SBC PR130L 7 355 S Comments: v561car exposures (flare study) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V561-CAR 1 ACS/SBC ACCUM SBC F165LP none none none none 1 N/A V561-CAR 2 ACS/SBC ACCUM SBC PR130L none none 1 none 1 N/A V561-CAR 2 ACS/SBC ACCUM SBC PR130L none none 2 none 1 N/A V561-CAR 2 ACS/SBC ACCUM SBC PR130L none none 3 none 1 N/A V561-CAR 2 ACS/SBC ACCUM SBC PR130L none none 4 none 1 N/A V561-CAR 2 ACS/SBC ACCUM SBC PR130L none none 5 none 1 N/A V561-CAR 2 ACS/SBC ACCUM SBC PR130L none none 6 none 1 N/A V561-CAR 2 ACS/SBC ACCUM SBC PR130L none none 7 none 1 N/A 11116( 3) - 10/23/07 06:27 - [ 10] Visit: 07 Visit Priority: Visit Requirements: 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 V376-VEL ACS/SBC ACCUM SBC F140LP 1 28 S see below Comments: v376vel preimage (temp) ------------------------------------------------------------------------------------------------------------------------------------ 2 V376-VEL ACS/SBC ACCUM SBC PR130L 5 470 S see below Comments: v376vel exposure (temp) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V376-VEL 1 ACS/SBC ACCUM SBC F140LP none none none none 1 48.0 S V376-VEL 2 ACS/SBC ACCUM SBC PR130L none none 1 none 1 490.0 S V376-VEL 2 ACS/SBC ACCUM SBC PR130L none none 2 none 1 490.0 S V376-VEL 2 ACS/SBC ACCUM SBC PR130L none none 3 none 1 490.0 S V376-VEL 2 ACS/SBC ACCUM SBC PR130L none none 4 none 1 490.0 S V376-VEL 2 ACS/SBC ACCUM SBC PR130L none none 5 none 1 490.0 S 11116( 3) - 10/23/07 06:27 - [ 11] Summary Form for Proposal 11116 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures SBC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/SBC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F140LP PR130L F165LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names V372-VEL V371-VEL V379-VEL V552-CAR V561-CAR V376-VEL ------------------------------------------------------------------------------------------------------------------------------------