10116( 5) - 01/07/05 07:51 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10116 Version: 5 Check-in Date: 07-Jan-2005 12:48:01 1.Proposal Title: Towards an Accurate Calibration of the Galactic Cepheid P-L Zero Point ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance GO 13 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Prof. Edward F. Guinan Villanova University CoI: Dr. Ignasi Ribas Institut d'Estudis Espacials de Catalunya N CoI: Dr. Edward L. Fitzpatrick Villanova University N CoI: Dr. Staszek Zola Uniwersytetu Jagiellonskiego Krakow N CoI: Dr. Thomas G. Barnes III University of Texas at Austin N ------------------------------------------------------------------------------------ 6. Abstract The young open cluster NGC 7790 is unique and astrophysically important because it contains three classical Cepheid variables (CF Cas, CE Cas A, and CE Cas B). If the distance of NGC 7790 were known with certainty, these Cepheids would define the zero point for the galactic Cepheid Period-Luminosity (P-L) relationship. By a stroke of good luck, NGC 7790 also contains a 10th-mag eclipsing binary located near the turnoff of the main-sequence of the color-magnitude diagram of the cluster. This important eclipsing binary has been little studied until now and contains two B1IV- V+B3V stars with an orbital period of P=6.005 days. With HST we propose to secure the accurate distance and reddening of QX Cas (and thus of the Cepheids) by using eclipsing binaries as precise standard candles, as we have demonstrated in our work on the Large Magellanic Cloud. With absolute radii, temperatures, and luminosities of the stars known from ground-based and HST observations, the method is essentially geometric and free from many of the uncertainties that plague other less direct methods. Light and radial velocity curve data will be combined with the proposed HST/STIS spectrophotometry (1150-8000 A) to determine the physical properties of the eclipsing binary and thus to secure an accurate distance and reddening for NGC 7790. The determination of the stars' temperatures, reddenings and chemical abundances, and therefore the cluster's distance, with the necessary accuracy can only be accomplished with HST. According to our previous experience, we expect a resulting distance determination with an accuracy of about 2-3%. HST/STIS spectrophotometry will be carried out also for the three Cepheids to determine their properties and individual reddenings. Thus, the proposed HST observations could help eliminate the current nagging uncertainty of the galactic Cepheid zero point and provide the key for a firm calibration of the P-L relationship. ------------------------------------------------------------------------------------ 10116( 5) - 01/07/05 07:51 - [ 2] Observations Description ------------------------ With declinations of +61 deg, all targets lie within the Continuous Viewing Zone (CVZ) of HST. This permits the entire 96 min of the orbit to be utilized for science and various overheads. We wish to obtain complete low resolution UV/optical/NIR spectral coverage for QX Cas. In our calculations, we have used the V magnitude at quadrature and spectral type of QX Cas and an estimated cluster reddening of E(B-V)=0.52 mag. Taking into account acquisition times plus all instrument overheads, the proposed observations can be obtained within one CVZ orbit. Our strategy for the observation of the Cepheids will consist of two pointed observations using small angle maneuvers within a single CVZ orbit. This is achievable because the angular separation between CF Cas and CE Cas AB is 77", and CE Cas A and CE Cas B are 2.6" apart. The three Cepheids have nearly the same brightness (V~11 mag) and spectral types (~F8 I). In calculating their exposure times, we adopt an estimated cluster reddening of E(B-V)=0.52 mag. The requested program requires a total of two orbits to fulfill the scientific goals and, most importantly, to nail down the zero point of the Cepheid P-L relationship. Real Time Justification ----------------------- TIME CONSTRAINTS It is important to the success of the program that the proposed visit to QX Cas is executed outside the eclipses (near quadrature; phases 0.10-0.30 or 0.50-0.90), when both components are fully visible and no light variations occur over the exposure time. This is a mild time constrain since the allowed observation windows cover about 60% of the time. The orbital ephemeris of QX Cas is: Min I=HJD2435682.938 + 6.00471 E; MinII=0.38 phase. The exact pulsation phases of the Cepheids during the actual HST observations will be known from our ground-based photometry and updated ephemerides. CVZ ORBIT REQUEST All four targets have declinations of +61 deg and lie within the CVZ of Cycle 13. To make the most efficient use of HST, we plan to execute the proposed visits during CVZ orbits, thus reducing the time requirements by about a factor of two. All targets will be available in the CVZ on 4 opportunities for a total of 150 orbits. This large number of possible visit windows and their duration (up to 70 orbits), combined with the mild time constrain described above, guarantees easy schedulability of the proposed observations. Calibration Justification ------------------------- It is critical to this program that the low-resolution HRC/ACS modes are well flux calibrated. We expect this to be done during routine calibrations by the ACS team. Additional Comments ------------------- ------------------------------------------------------------------------------------ 10116( 5) - 01/07/05 07:51 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 QXCAS STAR, B0-B2 V-IV RA=23H58M43.1600S +/- 0.1", J2000 V = 10.3+/-0.2 DEC=+61D09'39.60" +/- 0.1" Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0014 -0.0108 0.000300000 2 CECASA STAR, CEPHEID, F3-F9 RA=23H58M9.4400S +/- 0.1", J2000 V = 10.9+/-0.3 DEC=+61D12'49.40" +/- 0.1" Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.000300000 -0.0041 0.000300000 3 CFCAS STAR, CEPHEID, F3-F9 RA=23H58M17.9800S +/- 0.1", J2000 V = 11.1+/-0.3 DEC=+61D13'15.80" +/- 0.1" Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.000960000 -0.0027 0.000300000 10116( 5) - 01/07/05 07:51 - [ 4] Visit: 10 Visit Priority: Visit Requirements: CVZ; Period 6.00471 D AND ZERO-PHASE JD2435682.938 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 QXCAS ACS/HRC ACCUM HRC F330W 1 5.6 S PHASE 0.5 TO 0.9 ------------------------------------------------------------------------------------------------------------------------------------ 2 QXCAS ACS/HRC ACCUM HRC PR200L AUTOIMAGE=NO 1 2 S ------------------------------------------------------------------------------------------------------------------------------------ 3 QXCAS ACS/HRC ACCUM HRC F330W 1 5.6 S ------------------------------------------------------------------------------------------------------------------------------------ 4 QXCAS ACS/HRC ACCUM HRC PR200L AUTOIMAGE=NO 1 12 S ------------------------------------------------------------------------------------------------------------------------------------ 5 QXCAS ACS/HRC ACCUM HRC F220W 1 32 S ------------------------------------------------------------------------------------------------------------------------------------ 6 QXCAS ACS/HRC ACCUM HRC F250W 1 12 S ------------------------------------------------------------------------------------------------------------------------------------ 7 QXCAS ACS/HRC ACCUM HRC F435W 1 1.6 S ------------------------------------------------------------------------------------------------------------------------------------ 8 QXCAS ACS/HRC ACCUM HRC F475W 1 1 S ------------------------------------------------------------------------------------------------------------------------------------ 9 QXCAS ACS/HRC ACCUM HRC G800L AUTOIMAGE=NO 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 10 QXCAS ACS/WFC ACCUM WFC F475W 1 8 S ------------------------------------------------------------------------------------------------------------------------------------ 11 QXCAS ACS/WFC ACCUM WFC F625W 1 8 S ------------------------------------------------------------------------------------------------------------------------------------ 12 QXCAS ACS/WFC ACCUM WFC F775W CR-SPLIT=NO 1 8 S ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ QXCAS 1 ACS/HRC ACCUM HRC F330W none none none 1 tbd N/A QXCAS 1 ACS/HRC ACCUM HRC F330W none none none 2 tbd N/A QXCAS 2 ACS/HRC ACCUM HRC PR200L none none none 1 tbd N/A QXCAS 2 ACS/HRC ACCUM HRC PR200L none none none 2 tbd N/A QXCAS 3 ACS/HRC ACCUM HRC F330W none none none 1 tbd N/A QXCAS 3 ACS/HRC ACCUM HRC F330W none none none 2 tbd N/A QXCAS 4 ACS/HRC ACCUM HRC PR200L none none none 1 tbd N/A QXCAS 4 ACS/HRC ACCUM HRC PR200L none none none 2 tbd N/A QXCAS 5 ACS/HRC ACCUM HRC F220W none none none 1 tbd N/A QXCAS 5 ACS/HRC ACCUM HRC F220W none none none 2 tbd N/A QXCAS 6 ACS/HRC ACCUM HRC F250W none none none 1 tbd N/A 10116( 5) - 01/07/05 07:51 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ QXCAS 6 ACS/HRC ACCUM HRC F250W none none none 2 tbd N/A QXCAS 7 ACS/HRC ACCUM HRC F435W none none none 1 tbd N/A QXCAS 7 ACS/HRC ACCUM HRC F435W none none none 2 tbd N/A QXCAS 8 ACS/HRC ACCUM HRC F475W none none none 1 tbd N/A QXCAS 8 ACS/HRC ACCUM HRC F475W none none none 2 tbd N/A QXCAS 9 ACS/HRC ACCUM HRC G800L none none none 1 tbd N/A QXCAS 9 ACS/HRC ACCUM HRC G800L none none none 2 tbd N/A QXCAS 10 ACS/WFC ACCUM WFC F475W none none none 1 tbd N/A QXCAS 10 ACS/WFC ACCUM WFC F475W none none none 2 tbd N/A QXCAS 11 ACS/WFC ACCUM WFC F625W none none none 1 tbd N/A QXCAS 11 ACS/WFC ACCUM WFC F625W none none none 2 tbd N/A 10116( 5) - 01/07/05 07:51 - [ 6] Visit: 20 Visit Priority: Visit Requirements: CVZ; ORIENT 90.0D TO 150.0 D; ORIENT 270.0D TO 330.0 D 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 CFCAS ACS/HRC ACCUM HRC F330W 1 30 S ------------------------------------------------------------------------------------------------------------------------------------ 2 CFCAS ACS/HRC ACCUM HRC PR200L AUTOIMAGE=NO 1 6 S ------------------------------------------------------------------------------------------------------------------------------------ 3 CFCAS ACS/HRC ACCUM HRC PR200L AUTOIMAGE=NO 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 4 CFCAS ACS/HRC ACCUM HRC F330W 1 30 S ------------------------------------------------------------------------------------------------------------------------------------ 5 CFCAS ACS/HRC ACCUM HRC PR200L AUTOIMAGE=NO 1 220 S ------------------------------------------------------------------------------------------------------------------------------------ 6 CFCAS ACS/HRC ACCUM HRC F220W 1 220 S ------------------------------------------------------------------------------------------------------------------------------------ 7 CFCAS ACS/HRC ACCUM HRC F250W 1 120 S ------------------------------------------------------------------------------------------------------------------------------------ 8 CFCAS ACS/HRC ACCUM HRC F435W 1 4 S ------------------------------------------------------------------------------------------------------------------------------------ 9 CFCAS ACS/HRC ACCUM HRC F475W 1 2 S ------------------------------------------------------------------------------------------------------------------------------------ 10 CFCAS ACS/HRC ACCUM HRC G800L AUTOIMAGE=NO 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 11 CECASA ACS/HRC ACCUM HRC F330W 1 25 S ------------------------------------------------------------------------------------------------------------------------------------ 12 CECASA ACS/HRC ACCUM HRC PR200L AUTOIMAGE=NO 1 5 S ------------------------------------------------------------------------------------------------------------------------------------ 13 CECASA ACS/HRC ACCUM HRC F330W 1 25 S ------------------------------------------------------------------------------------------------------------------------------------ 14 CECASA ACS/HRC ACCUM HRC PR200L AUTOIMAGE=NO 1 32 S ------------------------------------------------------------------------------------------------------------------------------------ 15 CECASA ACS/HRC ACCUM HRC F330W 1 25 S ------------------------------------------------------------------------------------------------------------------------------------ 16 CECASA ACS/HRC ACCUM HRC PR200L AUTOIMAGE=NO 1 190 S ------------------------------------------------------------------------------------------------------------------------------------ 17 CECASA ACS/HRC ACCUM HRC F220W 1 200 S ------------------------------------------------------------------------------------------------------------------------------------ 18 CECASA ACS/HRC ACCUM HRC F250W 1 110 S ------------------------------------------------------------------------------------------------------------------------------------ 19 CECASA ACS/HRC ACCUM HRC F435W 1 3 S ------------------------------------------------------------------------------------------------------------------------------------ 20 CECASA ACS/HRC ACCUM HRC F475W 1 1.6 S ------------------------------------------------------------------------------------------------------------------------------------ 10116( 5) - 01/07/05 07:51 - [ 7] Exposures ----------------------------------------------------------------------------------------------------------------------------------- Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ----------------------------------------------------------------------------------------------------------------------------------- 21 CECASA ACS/HRC ACCUM HRC G800L AUTOIMAGE=NO 1 50 S ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ CFCAS 1 ACS/HRC ACCUM HRC F330W none none none 1 tbd N/A CFCAS 1 ACS/HRC ACCUM HRC F330W none none none 2 tbd N/A CFCAS 2 ACS/HRC ACCUM HRC PR200L none none none 1 tbd N/A CFCAS 2 ACS/HRC ACCUM HRC PR200L none none none 2 tbd N/A CFCAS 3 ACS/HRC ACCUM HRC PR200L none none none 1 tbd N/A CFCAS 3 ACS/HRC ACCUM HRC PR200L none none none 2 tbd N/A CFCAS 4 ACS/HRC ACCUM HRC F330W none none none 1 tbd N/A CFCAS 4 ACS/HRC ACCUM HRC F330W none none none 2 tbd N/A CFCAS 5 ACS/HRC ACCUM HRC PR200L none none none 1 tbd N/A CFCAS 5 ACS/HRC ACCUM HRC PR200L none none none 2 tbd N/A CFCAS 6 ACS/HRC ACCUM HRC F220W none none none 1 tbd N/A CFCAS 6 ACS/HRC ACCUM HRC F220W none none none 2 tbd N/A CFCAS 7 ACS/HRC ACCUM HRC F250W none none none 1 tbd N/A CFCAS 7 ACS/HRC ACCUM HRC F250W none none none 2 tbd N/A CFCAS 8 ACS/HRC ACCUM HRC F435W none none none 1 tbd N/A CFCAS 8 ACS/HRC ACCUM HRC F435W none none none 2 tbd N/A CFCAS 9 ACS/HRC ACCUM HRC F475W none none none 1 tbd N/A CFCAS 9 ACS/HRC ACCUM HRC F475W none none none 2 tbd N/A CFCAS 10 ACS/HRC ACCUM HRC G800L none none none 1 tbd N/A CFCAS 10 ACS/HRC ACCUM HRC G800L none none none 2 tbd N/A CECASA 11 ACS/HRC ACCUM HRC F330W none none none 1 tbd N/A CECASA 11 ACS/HRC ACCUM HRC F330W none none none 2 tbd N/A CECASA 12 ACS/HRC ACCUM HRC PR200L none none none 1 tbd N/A CECASA 12 ACS/HRC ACCUM HRC PR200L none none none 2 tbd N/A CECASA 13 ACS/HRC ACCUM HRC F330W none none none 1 tbd N/A CECASA 13 ACS/HRC ACCUM HRC F330W none none none 2 tbd N/A CECASA 14 ACS/HRC ACCUM HRC PR200L none none none 1 tbd N/A CECASA 14 ACS/HRC ACCUM HRC PR200L none none none 2 tbd N/A CECASA 15 ACS/HRC ACCUM HRC F330W none none none 1 tbd N/A CECASA 15 ACS/HRC ACCUM HRC F330W none none none 2 tbd N/A CECASA 16 ACS/HRC ACCUM HRC PR200L none none none 1 tbd N/A CECASA 16 ACS/HRC ACCUM HRC PR200L none none none 2 tbd N/A CECASA 17 ACS/HRC ACCUM HRC F220W none none none 1 tbd N/A CECASA 17 ACS/HRC ACCUM HRC F220W none none none 2 tbd N/A CECASA 18 ACS/HRC ACCUM HRC F250W none none none 1 tbd N/A CECASA 18 ACS/HRC ACCUM HRC F250W none none none 2 tbd N/A CECASA 19 ACS/HRC ACCUM HRC F435W none none none 1 tbd N/A CECASA 19 ACS/HRC ACCUM HRC F435W none none none 2 tbd N/A CECASA 20 ACS/HRC ACCUM HRC F475W none none none 1 tbd N/A CECASA 20 ACS/HRC ACCUM HRC F475W none none none 2 tbd N/A 10116( 5) - 01/07/05 07:51 - [ 8] 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 | ------------------------------------------------------------------------------------------------------------------------------------ CECASA 21 ACS/HRC ACCUM HRC G800L none none none 1 tbd N/A CECASA 21 ACS/HRC ACCUM HRC G800L none none none 2 tbd N/A 10116( 5) - 01/07/05 07:51 - [ 9] Summary Form for Proposal 10116 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures HRC WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/HRC ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters AUTOIMAGE=NO CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ; Period 6.00471 D AND ZERO-PHASE JD2435682.938 PHASE 0.5 TO 0.9 CVZ; ORIENT 90.0D TO 150.0 D; ORIENT 270.0D TO 330.0 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F330W PR200L F220W F250W F435W F475W G800L F625W F775W ------------------------------------------------------------------------------------------------------------------------------------ Target Names QXCAS CFCAS CECASA ------------------------------------------------------------------------------------------------------------------------------------