6769( 3) - 02/05/96 12:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6769 Version: 3 Check-in Date: 05-Feb-1996 11:50:36 1.Proposal Title: The Eclipsing Binary Pulsar PSR B1718-19: A Clean RS CVn System? ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: V. M. Kaspi IPAC/Caltech/JPL CoI: M. H. van Kerkwijk California Institute of Technology N CoI: S. Kulkarni California Institute of Technology N CoI: D. Van Buren IPAC/Caltech/JPL N CoI: A. G. Lyne University of Manchester/Jodrell Bank N CoI: A. R. Klemola Lick Observatory N ------------------------------------------------------------------------------------ 6. Abstract We request WFPC2 observations of the eclipsing binary pulsar PSR B1718-19. This slowly-rotating pulsar lies in the direction of the globular cluster NGC 6342, and defies standard binary pulsar formation models in which the pulsar is ``spun-up'' via mass accretion. Furthermore, the observed eclipses cannot be explained with standard models. This pulsar's unusual properties can be explained elegantly if its companion is an active, non-degenerate star like those observed in RS CVn systems, but in this case, subject only to gravity. Following Keck observations of the field, we propose HST observations of PSR B1718-19 to detect and study variability in the companion, in order to answer the following questions. 1- Are the eclipses seen in PSR B1718-19 indeed a result of RS CVn-type activity in the companion, and what is the evolutionary history of the binary? 2- Is the activity in RS CVn systems purely a tidal effect? 3- How are mass loss, rotation, and surface activity related in RS CVn stars? 4- Is PSR B1718-19 in NGC 6342? ------------------------------------------------------------------------------------ 6769( 3) - 02/05/96 12:13 - [ 2] Observations Description ------------------------ The proposed observations are straightforward. We will make a continuous series of exposures over the course of a single 6.2 hr orbit of \\psr, or 4 HST orbits. Per orbit, we have 40 minutes of exposure time, which will give us adequate sensitivity to measure 10\\% light variations of an I=24 optical counterpart at the 3Sigma level. Note that given the small number of stars with such brightnesses expected in the error box, a 3Sigma deviation will be truly significant. Each orbit, we will take three 800 second exposures through F702W. This will minimize the effect of cosmic-ray hits. Combining these images per orbit, we will obtain an SNR of 25--30 for an I=24 object. For all orbits combined, we expect to reach a 3Sigma limiting magnitude of I=27.4. We note that the F702W filter provides us with 10\\% more SNR than F814W, which is better matched to the expected source spectrum, but less well matched to the CCD sensitivity roll-off at long wavelengths. This assumes an M0 spectrum. At later spectral types F814W becomes marginally better, but a counterpart for which this is true will be too faint to detect photometric variations. Since the SNR limit on detection is less stringent than the limit on modulations of the light, F702W covers the bases better. These numbers were derived from the WWW exposure estimator online at STScI. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6769( 3) - 02/05/96 12:13 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR-172102- STAR, PULSAR, BINARY RA=17H 21M 01.54S +/- 0.02S, 2000 I = 24.5+/-1.5 193637 PULSAR, RS CVN STAR, DEC=-19D 36' 36.6" +/- 0.2" R-I = 1+/-0.5 NEUTRON STAR Comments: We are trying to find the pulsar companion and do not know its flux in advance. We have put a best guess. 6769( 3) - 02/05/96 12:13 - [ 4] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR-172102 WFPC2 IMAGE PC1 F702W CR- 1 700S -193637 SPLIT=NO,CLOCKS =YES,DITHER- TYPE=LINE,DITHE R-LINE- Comments: STEPS=3,DITHER- LINE- SPACING=0.1928 ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-172102 WFPC2 IMAGE PC1 F702W CR- 1 700S -193637 SPLIT=NO,CLOCKS =YES,DITHER- TYPE=LINE,DITHE R-LINE- Comments: STEPS=3,DITHER- LINE- SPACING=0.1928 ------------------------------------------------------------------------------------------------------------------------------------ 3 STAR-172102 WFPC2 IMAGE PC1 F702W CR- 1 700S -193637 SPLIT=NO,CLOCKS =YES,DITHER- TYPE=LINE,DITHE R-LINE- Comments: STEPS=3,DITHER- LINE- SPACING=0.1928 ------------------------------------------------------------------------------------------------------------------------------------ 4 STAR-172102 WFPC2 IMAGE PC1 F702W CR- 1 700S -193637 SPLIT=NO,CLOCKS =YES,DITHER- TYPE=LINE,DITHE R-LINE- Comments: STEPS=3,DITHER- LINE- SPACING=0.1928 ------------------------------------------------------------------------------------------------------------------------------------ 6769( 3) - 02/05/96 12:13 - [ 5] Summary Form for Proposal 6769 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO CLOCKS=YES DITHER-TYPE=LINE DITHER-LINE-STEPS=3 DITHER-LINE-SPACING=0.1928 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F702W ------------------------------------------------------------------------------------------------------------------------------------ Target Names STAR-172102-193637 ------------------------------------------------------------------------------------------------------------------------------------