6620( 7) - 05/23/96 18:23 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6620 Version: 7 Check-in Date: 23-May-1996 18:19:55 1.Proposal Title: Density Diagnostics for the Dynamic Atmospheres of LPV Stars ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle COOL STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Donald G. Luttermoser East Tennessee State University CoI: Dr. George H. Bowen Iowa State University N ------------------------------------------------------------------------------------ 6. Abstract We propose to use the GHRS onboard HST to probe the temperature--density structure of the shocked atmospheres of long-period variable (LPV, Mira--type) stars. At 3 selected phases, we wish to obtain GHRS spectra of the C II multiplet near Lambda2325 and the Mg II h & k lines near Lambda2800 for 2 bright Mira stars, R Leo and R Hya. With these spectra, we will make comparisons (1) with previous GHRS and IUE spectra of the semiregular variable g Her, in order to investigate the differences in the atmospheric structures of these 2 variable types, and (2) to synthetic spectra from representative dynamic models we have generated. These NLTE radiative transfer calculations have shown that the radiation field of the inner shocks dominate the ionization throughout the entire atmosphere. The calculations also have shown the C II intersystem lines are the best diagnostic to supply electron density information of the inner shock region, the first time such a diagnostic has been measured for these stars. Finally, it is imperative to obtain high--dispersion spectra of the C II and Mg II lines in Miras before GHRS is decommissioned, since comparisons of such spectra to similar spectra obtained for semiregulars are fundamental in the understanding of mass loss in this critical stage of a star's evolution. ------------------------------------------------------------------------------------ 6620( 7) - 05/23/96 18:23 - [ 2] Observations Description ------------------------ Due to the limited GHRS life in Cycle 6, and in order to achieve proper phase coverage of a pulsation cycle, we have selected 2 separate, but similar Miras for our study, R Leo and R Hya. We have selected to observe R Leo near light-- curve phase 0.15 (15 Jan 1997, V = 5.2) and R Hya near 0.35 (15 Jul 1996, V = 6.5) and 0.75 (15 Dec 1996, V = 5.8). Miras are at their brightest luminosities near phase 0.0 and at minima near 0.5-0.6. From comparisons to the dynamic models, phase 0.9 corresponds to the emergence of a strong inner shock from the photosphere. Mg II is typically not seen with IUE at this phase. Phase 0.1 corresponds to this shock residing between the photosphere and chromosphere in the models, and Mg II first becoming visible in IUE spectra. Mg II is typically at its brightest at phase 0.4, when this shock arrives and heats the chromosphere. Finally at phase 0.7, Mg II disappears as this shock continues to travel outward. The observing dates mentioned above do not have to be followed exactly, we can still get the same science out of the data with a +/-1 week window from these dates. Please note that R Leo will be unobservable from HST from 28 June 1996 until 12 Oct 1996, and R Hya from 30 Aug 1996 until 12 Dec 1996, due to these targets being within 50^degrees of the Sun. R Leo is visible from HST for 52 minutes per orbit, while R Hya is visible for 53 minutes per orbit. The total exposure times required to detect the emission lines will depend on phase as is shown in the table Table 1 (note that these numbers have been revised from the Phase I version of this proposal). In this table, we list (1) the peak flux in a given feature as determined by either IUE observations (e.g., Mg II) or scaled NLTE synthetic spectra (e.g., C II), (2) the counts per second per diode, based upon these fluxes and the sensitivity function of the wavelength in question, and (3) the total exposure time in minutes. This table also lists the line in question and its wavelength. The total exposure time is estimated to achieve a signal--to--noise of approximately 50 in the Mg II features and near 10 for the C II features. We expect all of the count rates, even when the emission line flux is at its weakest, to be greater than the GHRS diode dark counts (0.008 and 0.011 counts/sec/diode for the D_1 and D_2 detectors, respectively). We will be using the G270M grating and the N_2 mirror for the 2 wavelength regimes exclusively. Three visits will be made, two for R Hya (phases 0.35 and 0.75) and one for R Leo (phase 0.15), with a total exposure time for each visit of 163.2 minutes over 4 orbits. This gives a grand total of 8.2 hours in total exposure time in 12 orbits, which was granted by the TAC for this proposal. There are 2 targets with 3 visits and the total number of wavelength settings is 2. The number of exposures is 57 (including acquisition exposures), since we plan to break each long exposure into a series of approximately 10 minute--long sub--exposures to allow correction of thermal and geomagnetic drifts during the course of the long exposures. Standard calibrations will be adequate and we anticipate using only the LSA for the science data, since we are mainly interested in line--flux measurements. We have allowed 1 minute for subsequent science readouts at the same identical wavelength setting, and the 11 minute target acquisition overheads. We plan to use the N_2 mirror for aquisition. For R Leo near maximum light (V = 4.5), the detection rate should be 72,100 counts/sec based upon the aquisition count rate data (i.e. Table 7--1) in the GHRS Handbook. This gives a 14,400 counts in 0.2 sec (i.e. STEP-TIME = 0.2 sec). Near minimum light for R Hya (V = 6.5), 11,400 counts/sec should be seen. At this brightness, a STEP-TIME = 1.0 sec would produce 10,000 counts. -------------------------------------------------------- ----- Table 1: Estimated UV Emission Line Fluxes and Exposure Times ============================================================= Star: R Leo R Hya R Hya Phase: 0.15 0.35 0.75 --------------------------------------------------- ---------- 0.8(a) 0.8 0.8 C II (UV 0.01) 0.017(b) 0.017 0.017 2325 Angstrom 136.(c) 145. 136. 9.2(d) 9.5 9.2 ---------------------------------------------- --------------- 30. 75. 30. Mg II (k & h) 1.26 3.15 1.26 2800 Angstrom 27.2 18.1 27.2 45 58 45 ------------------------------------------------------------ - Total Orbits: 4 4 4 --------------------------------------------------------- ---- (a) Peak fluxes in units of 10^-14 erg/s/cm^2/Angstrom. (b) Photon counts per second per diode. (c) Exposure times in units of minutes. (d) Signal-to- Noise Real Time Justification ----------------------- Observations made within 1 week of the dates suggested in the Description of Observations section. These stars are Mira-type variables. The brightness and line flux strengths change over a cycle period, which last on the order of a year for these stars. The estimated fluxes and exposure time were deduced for specific phases which is why the observations have to be obtained on the dates requested. However, since these star's spectra change slowly on a weekly time scale, the observing window can be +/-1 week of the request dates. Calibration Justification ------------------------- None. Standard wavecals will be sufficient for these observations, since we are primarily concerned with line fluxes and secondly with velocity measurements. Additional Comments ------------------- The exposures for the C II lines (2344A) may have to be modified, since I will probably be need longer exposures to record these faint lines, instead of the 9 minute segments that are listed. ------------------------------------------------------------------------------------ 6620( 7) - 05/23/96 18:23 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6620( 7) - 05/23/96 18:23 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 STAR,LONG PERIOD RA=9H 47M 33.44S +/- J2000 V = 13. V = 5.2+/-0.5 VARIABLE,AGB STAR,M III 0.10S,DEC=11D 25' 43.6" +/- B-V = +1.68+/-0.20 -I, 1.0", PLATE-ID=01X2 E(B-V) = 0.0 TYPE=M8III F(2800)=3+/-1e-13 F(2325)=9+/-4e-15 F-CONT(2800)=3+/-2e-14 F-CONT(2325)=2+/-1e-15 Comments: The fluxes correspond to phase 0.15 (312 day period) on 15-JAN-1997. The UV line flux strengths can vary from one cycle to the next at a given phase. The above flux numbers are averaged values based upon past IUE observations and NLTE synthetic spectra. Coords obtained from PLATE-ID=01X2. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1985.05 -0.0004 -0.0440 0.020 2 HD117287 STAR,LONG PERIOD RA=13H 29M 42.89S +/- 0.10S,DEC= J2000 V = -10. V = 6.5+/-0.5 VARIABLE,AGB STAR,M III -23D 16' 53.2" +/- 0.6", PLATE- B-V = +1.67+/-0.20 -I, ID=04LM E(B-V) = 0.0 TYPE=M7III F(2800)=8+/-5e-13 F(2325)=8+/-5e-15 F-CONT(2800)=5+/-3e-15 F-CONT(2325)=6+/-3e-16 Comments: Fluxes corresponds to phase 0.35 (390 day period) on 15-JUL-1996. A 2nd set of obs will be made at phase 0.75 (15-DEC-1996), with F(2800)=3+/-1e-13, F(2325)=8+/-5e-15, F-CONT(2800)=5+/-3e-15, F- CONT(2325) =6+/-3e-16, and V=5.8+/-0.5. Coords from PLATE-ID=04LM. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1976.417 -0.0041 -0.0150 0.0 6620( 7) - 05/23/96 18:23 - [ 5] Visit: 01 Visit Requirements: BETWEEN 05-Jul-1996 AND 25-Jul-1996 On Hold Comments: Additional Comments: R Hya is near visual light variability phase 0.35. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD117287 HRS ACQ 2.0 MIRROR-N2 1 9.0 S ONBOARD ACQ FOR 2-4 Comments: Time_Per_Exposure: N(MAP) = 0, SEARCH-SIZE = 3 (the default value), STEP-TIME = 1.0 (to achieve 10,000 counts for V=6.5) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD117287 HRS ACCUM 2.0 G270M 2810 STEP-PATT=DEF,FP-SPLIT=STD, 1 1088 S COMB=FOUR,STEP-TIME=0.2 Comments: Min_Exposure_Time = 108.8S: SP-SPLIT=4, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 3 HD117287 HRS ACCUM 2.0 G270M 2344 6 544 S Comments: Min_Exposure_Time = 27.2S: SP-SPLIT=NO, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD117287 HRS ACCUM 2.0 G270M 2344 SPYBAL=YES 10 544 S Comments: Min_Exposure_Time = 27.2S: SP-SPLIT=NO, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 6620( 7) - 05/23/96 18:23 - [ 6] Visit: 02 Visit Requirements: BETWEEN 15-Dec-1996 AND 22-Dec-1996 On Hold Comments: Additional Comments: R Hya is near visual light variability phase 0.75. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD117287 HRS ACQ 2.0 MIRROR-N2 1 3.6 S ONBOARD ACQ FOR 2-4 Comments: Time_Per_Exposure: N(MAP) = 0, SEARCH-SIZE = 3, STEP-TIME = 0.4 (to achieve 8500 counts for V=5.8) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD117287 HRS ACCUM 2.0 G270M 2810 STEP-PATT=DEF,FP-SPLIT=STD, 1 1632 S COMB=FOUR,STEP-TIME=0.2 Comments: Min Exposure Time = 108.8S: SP-SPLIT=4, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 3 HD117287 HRS ACCUM 2.0 G270M 2344 5 544 S Comments: Min Exposure Time = 27.2S: SP-SPLIT=NO, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD117287 HRS ACCUM 2.0 G270M 2344 SPYBAL=YES 10 544 S Comments: Min Exposure Time = 27.2S: SP-SPLIT=NO, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 6620( 7) - 05/23/96 18:23 - [ 7] Visit: 03 Visit Requirements: BETWEEN 13-Jan-1997 AND 24-Jan-1997 On Hold Comments: Additional Comments: R Leo is near visual light variability phase 0.15. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 HRS ACQ 2.0 MIRROR-N2 1 1.8 S ONBOARD ACQ FOR 2-4 Comments: Time_Per_Exposure: N(MAP) = 0, SEARCH-SIZE = 3, STEP-TIME = 0.2 (to achieve 7400 counts for V=5.2) ------------------------------------------------------------------------------------------------------------------------------------ 2 HD84748 HRS ACCUM 2.0 G270M 2810 STEP-PATT=DEF,FP-SPLIT=STD, 1 1632 S COMB=FOUR,STEP-TIME=0.2 Comments: Min Exposure Time = 108.8S: SP-SPLIT=4, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 3 HD84748 HRS ACCUM 2.0 G270M 2344 5 544 S Comments: Min Exposure Time = 27.2S: SP-SPLIT=NO, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD84748 HRS ACCUM 2.0 G270M 2344 SPYBAL=YES 10 544 S Comments: Min Exposure Time = 27.2S: SP-SPLIT=NO, STEP-TIME=0.2, COMB=4, STEP-PATT=5, which gives N(back)=2, N(spec)=4, ratio=8. ------------------------------------------------------------------------------------------------------------------------------------ 6620( 7) - 05/23/96 18:23 - [ 8] Summary Form for Proposal 6620 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters STEP-PATT=DEF FP-SPLIT=STD COMB=FOUR STEP-TIME=0.2 SPYBAL=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COOL STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 05-Jul-1996 AND 25-Jul-1996 ONBOARD ACQ FOR 2-4 BETWEEN 15-Dec-1996 AND 22-Dec-1996 BETWEEN 13-Jan-1997 AND 24-Jan-1997 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G270M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD117287 HD84748 ------------------------------------------------------------------------------------------------------------------------------------