5870( 0) - 07/18/95 18:23 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5870 Version: ********** Check-in Date: ********** 1.Proposal Title: Dead Or Just Sleeping? Status of Magnetic Dynamos in ``Maunder Minumum" Stars ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Cool Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Steven Saar Smithsonian Astrophysical Observatory CoI: Dr. Sallie Baliunas Smithsonian Astrophysical Observatory N CoI: Dr. Robert Donahue Smithsonian Astrophysical Observatory N ------------------------------------------------------------------------------------ 6. Abstract The Maunder minimum (and similar episodes occurring every few centuries) is a poorly understood 75 year period in which the normal solar magnetic dynamo cycle was temporarily interrupted. Its study is important for understanding the generation and evolution of solar/stellar magnetic fields, and for the possible influence of magnetic flux on the Sun's luminosity and hence on earth's climate. We propose to study the Maunder mimimum state by obtaining HRS spectra of a sample of solar-like stars which appear to be in the stellar analog of the Maunder minimum: i.e., stars with weak, nonvariable Ca II emission and long periods of rotation. Using transition region line emission as a proxy for magnetic fields, we will determine the residual magnetic activity levels of Maunder stars, the magnetic contribution to the total energy budget of their outer atmospheres, and explore the relations between Maunder activity levels and stellar mass and rotation. Only HST has the sensitivity to detect or usefully constrain the very weak emission seen in these stars. The results will be used to explore the evolution of dynamos with time, define the dependence of Maunder minimum activity on mass and rotation rate, test non-linear dynamo models, and estimate what solar conditions are like during a Maunder episode. ------------------------------------------------------------------------------------ 5870( 0) - 07/18/95 18:23 - [ 2] Observations Description ------------------------ We propose to take deep, far UV HRS spectra of all known late F, G and early K dwarfs which appear to be in a ``Maunder minimum-like" state: i.e., stars which are old (large P_ rot, low Li I abundance) and show weak, non- variable Ca II H+K emission. These spectra will be used to search for signs of high temperature T >= 10^5 K plasma, such as emission in Si IV (1400 Angstrom) and C IV (1550 Angstrom). Presence of these lines will indicate the existence of magnetic fields. Comaprison of their ratios to cooler chromospheric lines (e.g., C II 1335 Angstrom, O I 1305 Angstrom) relative to ratios seen in ``normal" cool stars will imply the fractional contribution of magnetic heating to the energy balance in the outer atmosphere. To obtain the necessary lines at adequate resolution, we will use the HRS with the G140L grating (LSA). This combination is much more sensitive than the FOS + G130H shortward of C IV and has a much lower scattered light. We can estimate the exposure time needed by scaling from the C IV flux of a MM star detected with IUE (HD 10700). This star has f_C IV = 5 * 10^-14 ergs cm^-2 s^-1 AA^-1, equivalent to a surface flux of F_C IV ~ 0.5 F_C IV(\odot). Few stars will be much older than HD 10700 (it is an old disk subdwarf), but we would like to be able to make 4 Sigma detections of C IV in stars with 5 times less surface flux - this would allow for a range of possible MM F_C IV values as a function of mass or age. (We relax this constraint to a 3 Sigma detection for our three faintest targets.) This exposure level also allows stringent limits to be placed on the existence of stars in the sample with no magnetic dynamos operating, and allows detection of fainter lines at somewhat lower significance (e.g., Si IV at ~ 2.5 Sigma). With an efficiency of 67* 10^11 counts s^-1 diode^-1 per incident erg cm^-2 s^- 1 at C IV, HD 10700 would require an t_ exp ~ 2 minutes to obtain the required S/N. Values for the other stars were scaled from this value, including corrections for dark counts in the fainter stars (Table 1). Note that due to the length of the HST orbit, we will typically observe each star longer than the minimum t_ exp given in Table 1, yielding even more accurate detections or lower limits to the line fluxes. Real Time Justification ----------------------- None. We will attempt contemporaneous observations of our target stars in Ca II H+K emission flux from Mt. Wilson observatory and otehr chromospheric diagnostics (e.g., H-Alpha, He I D3) from Kitt Peak. Ongoing time-flexible observational programs at both sites will make this plan easy to schedule. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 5870( 0) - 07/18/95 18:23 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5870( 0) - 07/18/95 18:23 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD3651 STAR,K V-IV RA = 00H 39M 21.72S +/- 0.01S, J2000 V=-34 V=5.86 +/- 0.02 B-V=0.85 +/- 0.02 DEC = 21D 15' 2.1" +/- 0.1" Comments: Coordinates are from Hipparcos INCA Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.000 -0.0331 -0.366 0.095 2 HD9562 STAR,G V-IV RA = 01H 33M 42.85S +/- 0.01S, J2000 V=-15 V=5.74 +/- 0.02 B-V=0.64 +/- 0.02 DEC = -07D 01' 31.4" +/- 0.1" Comments: Coordinates are from Hipparcos INCA Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.000 0.0118 -0.077 0.095 3 HD29645 STAR,G V-IV RA = 04H 41M 50.26S +/- 0.01S, J2000 V=47 V=5.99 +/- 0.02 B-V=0.57 +/- 0.02 DEC = 38D 16' 48.8" +/- 0.1" Comments: Coordinates are from Hipparcos INCA Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.000 0.0201 -0.096 0.022 4 HD142373 STAR,F3-F9 RA = 15H 52M 40.53S +/- 0.01S, J2000 V=-55 V=4.62 +/- 0.02 B-V=0.56 +/- 0.02 DEC = 42D 27' 5.6" +/- 0.1" Comments: Coordinates are from Hipparcos INCA Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.000 0.0396 0.628 0.056 5 HD143761 STAR,G V-IV RA = 16H 01M 2.57S +/- 0.01S, J2000 V=18 V=5.41 +/- 0.02 B-V=0.60 +/- 0.02 DEC = 33D 18' 12.5" +/- 0.1" Comments: Coordinates are from Hipparcos INCA Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.000 -0.0159 -0.768 0.095 5870( 0) - 07/18/95 18:23 - [ 5] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 HD3651 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN, 1 1.8S ONBOARD ACQ FOR 20 SEARCH-SIZE=3 Comments: PLEASE NOTIFY P.I. WHEN DATES ARE SCHEDULED OR CHANGED (FOR COORDINATED OBSERVATIONS) IN ACQ EXPECT ABOUT 62000 CTS/S, HENCE STEP-TIME 0.2 SEC ------------------------------------------------------------------------------------------------------------------------------------ 15 HD3651 HRS ACCUM 2.0 G270M 2800 COMB=FOUR, STEP 2 761.6S -PATT=DEF, DOPPLER=DEF, FP -SPLIT=STD Comments: Line added to use up side 2 orbit ------------------------------------------------------------------------------------------------------------------------------------ 20 HD3651 HRS ACCUM 2.0 G140L 1433.0 COMB=FOUR, STEP 7 353.6S -PATT=DEF, DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 5870( 0) - 07/18/95 18:23 - [ 6] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 HD9562 HRS ACQ 2.0 MIRROR-N1 BRIGHT=RETURN, 1 45S ONBOARD ACQ FOR 20 SEARCH-SIZE=3 Comments: PLEASE NOTIFY P.I. WHEN DATES ARE SCHEDULED OR CHANGED (FOR COORDINATED OBSERVATIONS) IN ACQ EXPECT ABOUT 25 CTS/S, HENCE STEP-TIME 5 SEC ------------------------------------------------------------------------------------------------------------------------------------ 20 HD9562 HRS ACCUM 2.0 G140L 1433.0 COMB=FOUR, STEP 6 625.6S -PATT=DEF, DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 5870( 0) - 07/18/95 18:23 - [ 7] Visit: 03 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 HD29645 HRS ACQ 2.0 MIRROR-N1 BRIGHT=RETURN, 1 36S ONBOARD ACQ FOR 20 SEARCH-SIZE=3 Comments: PLEASE NOTIFY P.I. WHEN DATES ARE SCHEDULED OR CHANGED (FOR COORDINATED OBSERVATIONS) IN ACQ EXPECT ABOUT 40 CTS/S, HENCE STEP-TIME 4 SEC ------------------------------------------------------------------------------------------------------------------------------------ 20 HD29645 HRS ACCUM 2.0 G140L 1433.0 COMB=FOUR, STEP 7 571.2S -PATT=DEF, DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 5870( 0) - 07/18/95 18:23 - [ 8] Visit: 04 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 HD142373 HRS ACQ 2.0 MIRROR-N1 BRIGHT=RETURN, 1 7.2S ONBOARD ACQ FOR 20 SEARCH-SIZE=3 Comments: PLEASE NOTIFY P.I. WHEN DATES ARE SCHEDULED OR CHANGED (FOR COORDINATED OBSERVATIONS) IN ACQ EXPECT ABOUT 170 CTS/S, HENCE STEP-TIME 0.8 SEC ------------------------------------------------------------------------------------------------------------------------------------ 20 HD142373 HRS ACCUM 2.0 G140L 1433.0 COMB=FOUR, STEP 7 217.8S -PATT=DEF, DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 5870( 0) - 07/18/95 18:23 - [ 9] Visit: 05 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 HD143761 HRS ACQ 2.0 MIRROR-N1 BRIGHT=RETURN, 1 18S ONBOARD ACQ FOR 20 SEARCH-SIZE=3 Comments: PLEASE NOTIFY P.I. WHEN DATES ARE SCHEDULED OR CHANGED (FOR COORDINATED OBSERVATIONS) IN ACQ EXPECT ABOUT 70 CTS/S, HENCE STEP-TIME 2 SEC ------------------------------------------------------------------------------------------------------------------------------------ 20 HD143761 HRS ACCUM 2.0 G140L 1433.0 COMB=FOUR, STEP 5 272S -PATT=DEF, DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 5870( 0) - 07/18/95 18:23 - [ 10] Summary Form for Proposal 5870 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=3 FP-SPLIT=STD DOPPLER=DEF STEP-PATT=DEF COMB=FOUR ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Cool Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 20 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G270M G140L MIRROR-N1 ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD3651 HD9562 HD29645 HD142373 HD143761 ------------------------------------------------------------------------------------------------------------------------------------