! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 6051,v 18.1 1995/12/27 19:39:45 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Denise Taylor ! Phone: 410 338-4824 , E-mail: dctaylor@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Date generated: Sun Dec 18 11:40:16 EST 1994 ! Proposal_Information ! Section 4 Title: Dynamical Masses for the Stars in the Pre -Main- Sequence Spectroscopic Binary 045251+3016 Proposal_Category: GO Scientific_Category: Cool Stars Cycle: 5 Investigators PI_name: Robert D. Mathieu PI_Institution: University of Wisconsin - Madison CoI_Name: Hans Zinnecker CoI_Institution: Astron. Institut Univ. Wuerzburg Contact: ! Y or N (designate at most one contact) CoI_Name: Mario G. Lattanzi CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to use the Fine Guidance Sensors to measure dynamical masses for the two stars in the pre-main-sequence binary 045251+3016 =GSC2387 535. We have already completed an excellent single-lined spectroscopic orbit, which provides all of the essential orbital elements except inclination angle and mass ratio. We will use the FGS to derive both the apparent relative orbit of the binary (giving the inclination angle) and the absolute orbits of both components (giving the mass ratio). The predicted brightness difference is less than 1 mag and during Cycles 5-7 the predicted separation is greater than 20 mas, so this experiment is well suited for the FGS. These observations will provide the first dynamical mass measurements for stars on their Hayashi tracks. Furthermore, the completed spectroscopic orbital solution makes this a unique opportunity for such measurements independent of any assumptions about the stars or their distance. These measurements are fundamental tests of pre-main-sequence stellar evolution theory. Questions ! Free format text (please update) Observing_Description: We propose to use both astrometric modes of operation of the astrometer FGS (FGS3): TRANS mode and POSitional mode. TRANS is used to map out a highly precise relative orbit of the binary, while POS mode is used in conjunction with TRANS to determine the absolute orbits of the two components. As described in the FGS Instrument Handbook (Version 4.0), and in recently published papers (Bernacca et al. 1993, Lattanzi et al. 1994) TRANS mode samples the interference fringe produced by the Koester's prism interferometer, the "heart" of the Fine Guidance Sensor. There are two Koester's prism interferometers in each FGS. These are fed by a beam-- splitter to give sensitivity in two orthogonal directions, usually referred to as X and Y axes. Therefore, each FGS3 TRANS scan produces two fringes which can then be independently analyzed for signatures other than those characteristic of the FGS3 standard single star UP69. Deviations from the single star fringes provides measures of the projected separations of binary stars. On--sky separation and position angle are easily derived from these measurements and telescope attitude data (Bernacca et al. 1993 and references therein). Experience with TRANS observations very similar to those proposed here (Bernacca et al. 1993, 1994; Lattanzi et al. 1994, and references therein) indicate that the FGS interferometers are capable of measuring separations as small as 10 mas with 1 mas precision and position angles to better than 1 deg between two stars of comparable brightness. The resolution degrades for larger magnitude differences, but even with a difference of 2 mag a resolution of 20 mas is achieved. Even given the uncertainty in inclination angle, the separation of 045251+3016 will exceed 20 mas from the present until at least into Cycle 7 (Figure 3b). In addition, we anticipate the magnitude difference to be less than 1 mag. Thus we should be able to measure an excellent orbital curve at least between points 3 and 6 in Figure 3b, roughly one-quarter of the orbit. POSitional mode is the tool used for relative astrometry within the FGS field of view. It measures the X and Y coordinates of a target averaging over a proper number of elementary observations. The number of these elementary observations and the duration of each of them is set by the target magnitude. High precision is achieved by sensing the linear portion (highest gain) of the interferometric fringe. The typical precision of a POS measurement (under normal spacecraft jitter) is ~eq 1.5 mas per axis. Best results in visual orbit determination are obtained with well distributed observations over 50\ given the spectroscopic orbit we already have excellent measures of all but three of the relative orbital elements (the angular semimajor axis, the inclination angle, and the orientation of the line of nodes Omega). Hence we anticipate being able to obtain very good measures for these quantities with coverage of only a quarter of an orbit. In particular, the present uncertainty in a_prim sin(i) is 3\ improve as radial velocity measurements continue to be acquired. To determine sin(i) to a similar level of precision requires determining the inclination angle to a few degrees. If the other two free parameters were known a priori, examination of Figure 3b shows that this precision could be achieved with several 1- mas-precision measurements obtained in Cycles 6 and 7. Similarly, the orientation of periastron passage Omega is such that observations during Cycle 5 place far more constraint on semimajor axis than inclination (i.e. a node of the apparent orbit falls between points 3 and 4). We anticipate the separation during Cycle 5 to be at least 30 mas (Figure 3b), so with a few Cycle 5 measurements the angular relative semimajor axis can be determined to within a couple percent. In practice, all three unknown orbital elements will be solved for simultaneously, but this discussion shows the importance of observations in all three cycles to obtain a completely defined orbital solution. With such observations, we anticipate measurement errors of no more than a few percent in the relative orbital elements. In addition, the mass ratio must be derived by determining the angular semimajor axes of both absolute orbits. Since the shape of these orbits will be very well determined from both the spectroscopic and relative orbits, this is essentially a matter of establishing size scales. Assuming a measurement error of 1.5 mas on single measurements of absolute positions, 10 measurements, and semimajor axes of order 10 mas, we estimate that relative uncertainties of 5\ axes can be achieved. Hence we anticipate that these measurements will be the limiting factor in our ability to measure the stellar masses. An error of 5\ stellar mass determinations. Given these considerations, we request three visits in each of Cycles 5, 6 and 7 (or 9 measurements between points 3 and 6 in Figure 3b). Each visit comprises TWO orbits. The first orbit is devoted to 20 TRANS scans on the binary, followed by the POS mode observations of three reference stars (RFs). The following orbit (with the spacecraft holding the SAME pointing, i.e. using again the binary as the alignment star) is entirely devoted to POS mode on five RFs. This set includes the POS mode stars done previously, thus allowing the two orbits to be tied together. This combination of POS mode observations provides much better precision than that obtainable using just the guide stars to orient orbit two onto orbit one. This procedure is very similar to that done for parallax work. Fortunately, the star field toward 045251+3016 includes 5 GSC stars brighter than V=14 within ~eq 2' of the target. By observing multiple reference stars we precisely define the reference frame, reduce our astrometric error on the relative position of 045251+3016 to only the contribution from the 045251+3016 measurement, and protect against large peculiar motions or other problems with any one star. Following the procedure for the calculation of the number of orbits given in the Cycle 5 Phase I Proposal Instructions volume, each visit comprises a guide star acquisition (12 min), the set--up time (inlcluding the selected filter) for TRANS mode (3 min), then our first science exposure. This consists of 20 TRANS scans of 2".1 on the sky each (i.e., 1."5 per FGS axis) sampled every 0."0008 (the pixel size per axis is 0."0006). Since each sample takes a fixed 0.025 sec, the 20 scans take 20.8 min, for a total of 12+3+20.8 = 35.8 min. Multiple, consecutive scans are required for three reasons. First, spacecraft jitter can corrupt fringes. With multiple scans one can identify jitter- -corrupted fringes and reject them. Second, multiple scans are the only reliable way to check on the repeatibility of a detection. Finally, multiple scans are co--added to increase the signal--to--noise ratio (S/N). Successful observations should provide co--added fringes with typical S/N ~eq 100. The remainder of the orbit is used for POS mode on three RFs, all of which are brighter than V=14. There are 2 min overhead for each RF of that magnitude. Therefore, there should be (53.0-35.8)-6.0/3 ~eq 3.7 min of POS science exposure per RF available before the end of the visibility period (53 min), more than adequate for best precision on the location of the RFs. For the contiguous orbit, after a 4 min guide stars re- acquisition, we request 15 POS mode exposures on the five RFs selected, arranged in a cyclic fashion. This will provide (53.0-4.0)-30.0/15. ~eq 1.3 min of actual observing time per RF. Again, this is adequate for stars of that magnitude. To conclude, we stress that it is essential to begin this program in Cycle 5 so as to define the maximum relative separation and the rapidly changing orbit curve (between points 3 to 4 in Figure 3). Real_Time_Justification: None Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: STAR-045602+302104 Alternate_Names: GSC2387-535, 045251+3016 Description: STAR, T Tauri Star Position: RA = 04H 56M 02.01S +/- 0.1S, DEC = +30D 21' 04.0" +/- 1.0", ! Most common specification format is ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=02TR Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=11.60 +/- 0.05, B-V=1.28 +/- 0.05 ! Include at least V and B-V Comments: Target_Number: 2 Target_Name: STAR-045600+302206 Alternate_Names: GSC2387-421 Description: STAR Position: RA = 04H 55M 59.86S +/- 0.1S, DEC = +30D 22' 05.7" +/- 1.0", ! Most common specification format is ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=02TR Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=13.6 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 3 Target_Name: STAR-045605+302242 Alternate_Names: GSC2387-527 Description: STAR Position: RA = 04H 56M 04.88S +/- 0.1S, DEC = +30D 22' 41.6" +/- 1.0", ! Most common specification format is ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=02TR Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=11.6 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 4 Target_Name: STAR-045603+302050 Alternate_Names: GSC2387-481 Description: STAR Position: RA = 04H 56M 02.51S +/- 0.1S, DEC = +30D 20' 50.5" +/- 1.0", ! Most common specification format is ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=02TR Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=12.3 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 5 Target_Name: STAR-045606+302144 Alternate_Names: GSC2387-451 Description: STAR Position: RA = 04H 56M 05.92S +/- 0.1S, DEC = +30D 21' 44.0" +/- 1.0", ! Most common specification format is ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=02TR Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=15.3 +/- 0.1 ! Include at least V and B-V Comments: Target_Number: 6 Target_Name: STAR-045623+301937 Alternate_Names: GSC2387-533 Description: STAR Position: RA = 04H 56M 23.33S +/- 0.1S, DEC = +30D 19' 36.8" +/- 1.0", ! Most common specification format is ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", PLATE-ID=02TR Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=14.0 +/- 0.1 ! Include at least V and B-V Comments: !*************************** VISIT 1 ************* ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling PCS MODE F ! GUIDing TOLerance ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN