9109( 13) - 01/22/02 12:52 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9109 Version: 13 Check-in Date: 22-Jan-2002 12:51:39 1.Proposal Title: Mapping the Chromosphere of the K Supergiant in the Eclipsing Binary 31 Cygni ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Philip Bennett University of Colorado at Boulder CoI: Dr. Alexander Brown University of Colorado CASA N CoI: Dr. Wendy Hagen Bauer Wellesley College N CoI: Dr. Graham Harper University of Colorado CASA N CoI: Dr. Jeffrey Linsky University of Colorado JILA N CoI: Prof. Dieter Reimers University of Hamburg N CoI: Dr. Robert Baade University of Hamburg N CoI: Dr. Edward Guinan Villanova University N ------------------------------------------------------------------------------------ 5. Abstract Red supergiants (RSGs) are responsible for returning the greatest contribution of mass to the ISM, but this mass loss process, can not be modeled in a fundamental way because the physical mechanism responsible remains uncertain. This difficulty has profound implications for stellar population sythesis and galactic evolution. We propose to address this problem by observing the chromosphere and wind of the supergiant primary in the long-period (10.36 yr) eclipsing binary 31 Cygni. This binary has the largest orbital separation relative to primary size (and the least interaction) of the known Zeta Aur binaries. The next eclipse in 2003 will be the last available during the lifetime of HST; if this project is to be done at all, it must be started now. We will obtain STIS NUV and FUV observations of 31 Cyg (K4 Ib + B4 V), using the hot companion to probe the thermodynamic state of the supergiant's chromosphere and wind. Our objective is to construct an empirical model of the outer atmosphere to constrain theoretical mechanisms of wind acceleration. A major secondary goal is to determine accurate stellar and orbital parameters for the 31 Cyg binary. These data will permit direct comparison of the individual stars' positions in the H- R diagram with evolutionary model tracks and will constrain the physics of mass loss and core mixing in RSGs. ------------------------------------------------------------------------------------ 9109( 13) - 01/22/02 12:52 - [ 2] Observations Description ------------------------ sectionObservational Requirements for Eclipse Coverage Earlier Zeta Aur observing programs define the key requirements: beginitemize em Consistent coverage of the eclipse phases is essential, with adjacent lines of sight separated by no more than ~ H_Rho (density scale height). If observations are too far apart in orbital phase, then it can be very difficult to meaningfully interpolate between them, and the continuity of the entire eclipse sequence is compromised. The proposed observation program was chosen so that the projected separation of consecutive lines-of-sight is 1.35H_Rho. The orbital phases of the proposed 34 visits are shown on Figure ref31cyg. Our program -- unavoidably -- places most of the observations in Cycles 11 & 12, but we emphasize the importance of the early out-of-eclipse Cycle 10 observations. Here, the hot star photosphere is observed (nearly) free of overlying chromospheric absorption lines. We will use these out-of-eclipse spectra to rectify the continuum during the eclipse phases, so it is crucial that they be observed. They also provide optimal phase coverage for radial velocity measurements of the secondary (see below). em Complete spectral coverage is important so that as many diagnostics from different ionization stages are observed (neutrals, singly- and doubly-ionized species). We will observe the entire UV region accessible to STIS at high- resolution (E140H & E230H). The source is bright (typical UV continuum fluxes are ~ 10^-10 ergs cm^-2 s^-1 AA^-1 (see note about MAMA bright limits below) allowing full UV coverage to be obtained in 2 orbits. em Observation of the total eclipse spectrum is absolutely crucial because this gives the emission line spectrum due to hot star photons scattered by the supergiant wind, which is always present. This spectrum should be removed from all other out-of-eclipse observations (by subtraction of the eclipse spectrum) before any analysis is done. We have proposed three eclipse observations: one just after 2nd contact, one just prior to 3rd contact, and a longer exposure (3 orbits) at mid-eclipse in order to obtain especially good S/N (since this spectrum will be subtracted from all other out of eclipse observations). em We will use the E140H FUV region near Ly-Alpha to determine the differential radial velocities of the secondary by cross- correlating observations taken at widely separated phases. Ideally, we would like to observe at least one quadrature (where the stellar radial velocity reaches an extremum). We have proposed such an observation early in Cycle 10. Note that we already have been observing the supergiant primary of 31 Cyg for ~6 years on the PI's precise radial velocity program being conducted at the Dominion Astrophysical Observatory near Victoria, Canada. We will have essentially complete orbital coverage by the end of the proposed multi- cycle program. We expect to determine the primary's radial velocity amplitude, K_1, to within 50 m s^-1. With the primary orbit determined, we need only two well separated radial velocity observations of the secondary star to fully determine its orbit, and the masses of each star. In fact, the proposed program will provide considerable redundancy beyond the minimum two observations which will substantially reduce the uncertainty in our determination of K_2. We expect to determine the masses of the 31 Cyg stars accurate to 2%. We are proposing repeated time-critical observations of the eclipse and nearby phases of the binary 31 Cyg for Cycles 10, 11 & 12. We have selected orbital phases that ensure optimal spectroscopic monitoring of the supergiant's chromosphere and wind. The permissible windows around the selected observation phases are not, in general, stringent. These range from 2 weeks for observations far from eclipse to less than a day near 2nd and 3rd contacts. The typical window is ~5 days or so. There are no beta angle constraints for 31 Cyg that would interfere with the proposed program of observations. The long duration of this event makes a multi-cycle proposal the only way to ensure consistent spectral coverage over the entire eclipse period. Because mid-eclipse is in July 2003 (near the end of Cycle 11 and the beginning of Cycle 12), most of the observations will occur in Cycles 11 & 12. However, it is essential (for reasons detailed in the previous section) that the fairly small number of observations proposed for Cycle 10 be obtained. From a scientific perspective, the best way of doing this is to propose for a multi-cycle program spanning the entire eclipse period, i.e., Cycles 10--12. Because of the heavy end-loading of this program, though, we suggest that the total orbit request for Cycles 10 & 11 (37 orbits) be considered together as the key orbit allocation, rather than the small Cycle 10 request (4 orbits). 31 Cyg is UV bright, and approaches the MAMA bright limits: therefore we will use the Jenkins slit (0.1 * 0.03) at high resolution to reduce the light on the detector. Exposure times are short: 30-- 300s, and the entire observation sequence can be done in 2 orbits per visit. However, the Spectroscopic ETC tool using an actual IUE out-of-eclipse spectrum (SWP10923 + LWR09605) makes two E230H grating tilts problematic: c2263 slightly exceeds, and c2513 is just below the MAMA global count rate bright limits. We will carefully discuss this with STScI at Phase II time; options include using the ND2 filtered slit with E230M, or just dropping these two exposures (resulting in a 175 Angstrom\ spectrum gap). This will not seriously affect the proposed science return. vspace0.08in We propose to observe 31 Cyg at 2 visits, and a total of 4 orbits in Cycle 10. An additional 33 orbits will be requested for Cycle 11 and 32 orbits for Cycle 12. Real Time Justification ----------------------- We are requesting repeated, time-critical observations of the eclipsing binary 31 Cyg at selected orbital phases chosen to optimize the sampling of the supergiant's chromosphere. The justification for the choice of orbital phases is described in the Scientific Justification section. Three total eclipse observations are also requested, as these observations are crucial to the overall success of the analysis. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9109( 13) - 01/22/02 12:52 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD192577 STAR, COMPOSITE RA=20H 13M 37.90S +/- 0.00175", J2000 V = -7.7 V = 3.80+/-0.02 SPECTRAL TYPE, K III-I, DEC=46D 44' 28.8" +/- 0.00140" B = 5.08+/-0.02 B3-B5 V-IV TYPE=K4IB+B3V U = 5.50+/-0.03 F-CONT(3000)=3.0+/-0.5e-11 F-CONT(2400)=4.5+/-0.5e-11 F-CONT(2000)=7+/-1e-11 F-CONT(1400)=1.6+/-0.1e-10 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: Coordinates are from the Hipparcos/Tycho Catalog (HD192577=31CYG=HIP99675). UV continuum fluxes are from IUE images SWP10923 and LWR09605, which were observed far from eclipse in 1980. The UV spectrum is due to the stellar continuum of the B-type secondary, with some absorption from the wind of the K supergiant superimposed, and does not appear to vary. The UV flux is large, and is at, or slightly exceeds, the MAMA global count rate limit of 2.0e5 counts/s using E230H and the 0.01X0.03 slit at grating settings c2263 and c2513, based upon the above IUE fluxes. Elsewhere, the spectrum has a global count rate below 1.7e5 counts/s. The STIS instrument group has granted a bright object protection (BOP) exception in this case, and has authorized us to observe 31 Cyg in the E230H/2263 and E230H/2513 settings. As a precaution, we will first observe 31 Cyg with the G230LB grating, and NOT with E230H/2263 or E230H/2513. If the Visit 1 G230LB fluxes are as expected, we w ill proceed to observe with E230H/2263 and E230H/2513 in Visit 2. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.00041 0.00187 0.0 9109( 13) - 01/22/02 12:52 - [ 4] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 01-Jun-2001 AND 02-Sep-2001 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 HD192577 STIS/C ACQ F25ND5 MIRROR 1 1.5 S CD ------------------------------------------------------------------------------------------------------------------------------------ 20 HD192577 STIS/C ACCUM 52X0.5 G430L 4300 1 0.2 S CD ------------------------------------------------------------------------------------------------------------------------------------ 30 HD192577 STIS/C ACCUM 52X0.5 G230LB 2375 1 2 S CD ------------------------------------------------------------------------------------------------------------------------------------ 40 HD192577 STIS/C ACQ/PEA 0.2X0.0 G230LB 2375 1 2 S CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 50 HD192577 STIS/N ACCUM 0.1X0.0 E230H 2762 WAVECAL=NO 1 180 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 60 WAVE STIS/N ACCUM 0.1X0.0 E230H 2762 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 70 HD192577 STIS/N ACCUM 0.1X0.0 E230H 2013 1 220 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 80 WAVE STIS/N ACCUM 0.1X0.0 E230H 2013 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 90 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1416 1 215 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 100 WAVE STIS/F ACCUM 0.1X0.0 E140H 1416 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 110 WAVE STIS/F ACCUM 0.1X0.0 E140H 1234 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 120 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1234 1 500 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 9109( 13) - 01/22/02 12:52 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 130 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1598 1 540 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 140 WAVE STIS/F ACCUM 0.1X0.0 E140H 1598 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 150 HD192577 STIS/N ACCUM 0.1X0.0 E230H 3012 1 400 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 160 WAVE STIS/N ACCUM 0.1X0.0 E230H 3012 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 170 HD192577 STIS/N ACCUM 0.1X0.0 E230H 1763 1 490 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 180 WAVE STIS/N ACCUM 0.1X0.0 E230H 1763 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 9109( 13) - 01/22/02 12:52 - [ 6] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 01-Aug-2002 AND 01-Oct-2002 ON HOLD FOR 11 On Hold Comments: For SITS MAMA safety, the target flux in G230LB must be verified in visit 11 before E230H/2263 and E230H/2513 observation in visit 2 may proceed. 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 HD192577 STIS/C ACQ F25ND5 MIRROR 1 1.5 S CD ------------------------------------------------------------------------------------------------------------------------------------ 20 HD192577 STIS/C ACCUM 52X0.5 G230LB 2375 1 2 S CD ------------------------------------------------------------------------------------------------------------------------------------ 30 HD192577 STIS/C ACQ/PEA 0.2X0.0 G230LB 2375 1 2 S CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 40 HD192577 STIS/N ACCUM 0.1X0.0 E230H 2013 WAVECAL=NO 1 200 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 50 WAVE STIS/N ACCUM 0.1X0.0 E230H 2013 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 60 HD192577 STIS/N ACCUM 0.1X0.0 E230H 2762 1 160 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 70 WAVE STIS/N ACCUM 0.1X0.0 E230H 2762 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 80 HD192577 STIS/N ACCUM 0.1X0.0 E230H 2513 1 120 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 90 WAVE STIS/N ACCUM 0.1X0.0 E230H 2513 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 100 HD192577 STIS/N ACCUM 0.1X0.0 E230H 2263 1 145 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 110 WAVE STIS/N ACCUM 0.1X0.0 E230H 2263 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 120 WAVE STIS/N ACCUM 0.1X0.0 E230H 3012 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 9109( 13) - 01/22/02 12:52 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 130 HD192577 STIS/N ACCUM 0.1X0.0 E230H 3012 1 300 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 140 HD192577 STIS/N ACCUM 0.1X0.0 E230H 1763 1 400 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 150 WAVE STIS/N ACCUM 0.1X0.0 E230H 1763 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 160 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1234 1 250 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 170 WAVE STIS/F ACCUM 0.1X0.0 E140H 1234 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 180 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1416 1 200 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 190 WAVE STIS/F ACCUM 0.1X0.0 E140H 1416 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 200 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1598 1 350 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 210 WAVE STIS/F ACCUM 0.1X0.0 E140H 1598 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 9109( 13) - 01/22/02 12:52 - [ 8] Visit: 11 Visit Priority: Visit Requirements: BETWEEN 15-Nov-2001 AND 15-Dec-2001 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 HD192577 STIS/C ACQ F25ND5 MIRROR 1 1.5 S CD ------------------------------------------------------------------------------------------------------------------------------------ 20 HD192577 STIS/C ACCUM 52X0.5 G430L 4300 1 0.2 S CD ------------------------------------------------------------------------------------------------------------------------------------ 30 HD192577 STIS/C ACCUM 52X0.5 G230LB 2375 1 2 S CD ------------------------------------------------------------------------------------------------------------------------------------ 40 HD192577 STIS/C ACQ/PEA 0.2X0.0 G230LB 2375 1 2 S CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 50 HD192577 STIS/N ACCUM 0.1X0.0 E230H 2762 WAVECAL=NO 1 180 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 60 WAVE STIS/N ACCUM 0.1X0.0 E230H 2762 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 70 HD192577 STIS/N ACCUM 0.1X0.0 E230H 2013 1 220 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 80 WAVE STIS/N ACCUM 0.1X0.0 E230H 2013 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 90 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1416 1 215 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 100 WAVE STIS/F ACCUM 0.1X0.0 E140H 1416 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 110 WAVE STIS/F ACCUM 0.1X0.0 E140H 1234 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 120 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1234 1 500 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 9109( 13) - 01/22/02 12:52 - [ 9] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 130 HD192577 STIS/F ACCUM 0.1X0.0 E140H 1598 1 540 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 140 WAVE STIS/F ACCUM 0.1X0.0 E140H 1598 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 150 HD192577 STIS/N ACCUM 0.1X0.0 E230H 3012 1 400 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 160 WAVE STIS/N ACCUM 0.1X0.0 E230H 3012 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 170 HD192577 STIS/N ACCUM 0.1X0.0 E230H 1763 1 490 S UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 180 WAVE STIS/N ACCUM 0.1X0.0 E230H 1763 1 DEF UV-MAM 3 A ------------------------------------------------------------------------------------------------------------------------------------ 9109( 13) - 01/22/02 12:52 - [ 10] Summary Form for Proposal 9109 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25ND5 52X0.5 0.2X0.06 0.1X0.03 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-Jun-2001 AND 02-Sep-2001 BETWEEN 01-Aug-2002 AND 01-Oct-2002 ON HOLD FOR 11 BETWEEN 15-Nov-2001 AND 15-Dec-2001 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G230LB E230H E140H ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD192577 WAVE ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 2375 2762 2013 1416 1234 1598 3012 1763 2513 2263 ------------------------------------------------------------------------------------------------------------------------------------