! File: 3851C.PROP ! Database: PEPDB ! Date: 19-FEB-1994:21:45:01 coverpage: title_1: DEEP SEARCH FOR CVS AND COMPACT BINARIES IN THE COLLAPSED title_2: CLOSE GLOBULAR NGC6397 sci_cat: STELLAR POPULATIONS sci_subcat: GLOBULAR CLUSTERS proposal_for: GO longterm: 1 cont_id: 3851 pi_title: PROF pi_fname: JONATHAN pi_mi: E. pi_lname: GRINDLAY pi_inst: HARVARD UNIVERSITY pi_country: USA pi_phone: 617-495-7204 keywords_1: GLOBULAR CLUSTERS hours_pri: 5.43 num_pri: 3 wf_pc: Y funds_amount: 41180 funds_length: 12 funds_date: JUL-92 pi_position: PROF off_fname: MERRILY off_mi: D. off_lname: STERNS off_title: ASSOC DIR AWARDS MGT off_inst: HARVARD UNIVERSITY off_addr_1: OFFICE FOR SPONSORED RESEARCH off_addr_2: HOLYOKE CENTER 441 off_city: CAMBRIDGE off_state: MA off_zip: 02138 off_country: USA off_phone: 617-495-5501 off_telex: 921428 ! end of coverpage abstract: line_1: We propose to obtain deep H-ALPHA and R exposures with the PC on the closest line_2: core-collapsed globular cluster, NGC 6397. This will allow the most line_3: sensitive search to date for cataclysmic variables (CVs) and other line_4: compact binaries in the core of this dynamically evolved cluster. The line_5: search is sensitive to CVs with increasingly faint luminosities, which are line_6: distinguished by increasingly strong H-ALPHA emission, and thus will provide the line_7: most definitive test yet for the possible deficit of CVs in globulars. line_8: Comparison of these images with archived HST uv images that we have recently line_9: received, with our ground-based H-ALPHA and uv images (for regions line_10: outside the core), and with our ROSAT x-ray images will allow line_11: the long-standing question of the nature of the population of line_12: low luminosity x-ray sources in globulars (CVs \?) to be probed in line_13: unprecedented detail. The search will also be sensitive to the line_14: populations and distributions of blue subdwarfs (H-ALPHA absorbers, and line_15: possibly WD-stellar merger products) and millisecond pulsar emission nebulae, line_16: so that models of binary formation and evolution in globulars will be tested. ! ! end of abstract general_form_proposers: lname: GRINDLAY fname: JONATHAN title: PROF mi: E. inst: HARVARD UNIVERSITY country: U.S.A. ! lname: BAILYN fname: CHARLES mi: D. inst: YALE UNIVERSITY country: U.S.A. ! lname: CALLANAN fname: PAUL mi: J. inst: HARVARD UNIVERSITY country: U.S.A. ! lname: COHN fname: HALDAN mi: N. inst: INDIANA UNIVERSITY country: U.S.A. ! lname: COOL fname: ADRIENNE mi: M. inst: HARVARD UNIVERSITY country: U.S.A. ! lname: LUGGER fname: PHYLLIS mi: M. inst: INDIANA UNIVERSITY country: U.S.A. ! ! end of general_form_proposers block general_form_text: question: 3 section: 0 line_1: The proposed observations are direct imaging with the Planetary Camera (PC) of line_2: the core of the nearby globular cluster NGC 6397. The entire observation will be line_3: centered on the cluster core center for maximum sensitivity. Two filters will line_4: be used: the F656N filter for images in H-ALPHA and the F675W filter for line_5: comparison continuum images in the (approximate) R band. Based on our line_6: preliminary program on the more distant cluster NGC 6752, we need a ratio of at line_7: least 10:1 in favor of the narrow band H-ALPHA filter. The total H-ALPHA line_8: exposure time to achieve the desired sensitivity limit of absolute line_9: magnitude Mv = 11 in the cluster is about 18 ksec. In order to line_10: keep cosmic rays manageable, and to minimize stellar saturation, this total line_11: exposure will be obtained in 1000 sec integrations. The R integration times line_12: will be 100 sec, with several 10 sec exposures to remove saturated line_13: stars. The narrow band-pass of the F656N filter means that short exposures line_14: will not be necessary. Thus the total program will need about 19 ksec of total line_15: integration time, or just under 10 hours of spacecraft time. To minimize line_16: uncertainties due to flat fielding in the H-ALPHA filter as well as imperfect line_17: bias subtraction we shall divide our total number of exposures into 3 groups. line_18: For each group, we shall offset point the telescope by about 4 arcsec, so that line_19: the total observation is distributed over three distinct regions on the CCD: line_20: thus differences in flat fielding or residual Newton's rings in the stacked line_21: H-ALPHA images will be removable. ! question: 4 section: 0 line_1: HST is absolutely essential for this project. Even with the degraded psf of line_2: the telescope and conditions of crowded-field stellar photometry (the NGC 1850 line_3: tests of Holtzman et al 1991), the 0.1 arcsec (radius) cores of the stellar line_4: images contain enough of the total light (15%) that they can be photometered line_5: to about 0.1 mag down to 21st mag (cf. Holtzman et al 1991). This is the line_6: apparent magnitude limit needed to reach absolute mag Mv = 9 in NGC 6397. Even line_7: at Mv = 11 in NGC 6397, the NGC 1850 photometry results of Holtzman et al line_8: would suggest errors of less than 0.3 mag, or enough for a threshold line_9: "detection" (3-4 sigma) of a CV with equivalent width of about 30 angstroms. line_10: Thus HST can carry out the color-excess photometry to sufficient accuracy to line_11: detect CVs with Mv = 9-11 and H-ALPHA equivalent width below 30 angstroms in line_12: the core of NGC 6397 in the exposure times requested. line_13: For comparison, the extensive ground-based H-ALPHA vs. narrow band R line_14: photometry (as well as UBV) we have carried out with the 4m-PFCCD at CTIO (cf. line_15: Grindlay et al 1991) will only reach limits of Mv = 9 (for the same H-ALPHA line_16: equivalent width) and this only beyond 3-4 core radii where stellar crowding line_17: does not severely affect our deep 1 arcsec seeing images. line_19: The proposed program for NGC 6397 will be 5 magnitudes deeper (i.e. from Mv = line_20: 6 to Mv = 11) than our similar observations obtained on the globular line_21: cluster NGC 6752 in Cycle 1 (Program P2555). The proximity of NGC 6397 (factor line_22: of 2 closer than NGC 6752) makes it the very best globular for a very deep CV line_23: search. ! question: 5 section: 0 line_1: In order to ensure that the multiple ROSAT error circles are well placed on line_2: two of the CCDs in the HST/PC, we are requesting a specific detector orientation line_3: (with a +/- 10 degree tolerance). ! question: 6 section: 0 line_1: In order to limit the effect of read noise on our H-ALPHA images, we are line_2: requesting that our 1000s exposures not be divided into shorter exposures. line_3: We are confident that with the 3 sets of 6 exposures we are planning, line_4: we will be able to remove cosmic rays effectively. Our experience with our line_5: 1300s H-ALPHA exposures of NGC6752 with the HST/PC support this view. ! question: 7 section: 0 line_1: We propose to reduce these frames using standard reduction techniques and line_2: STScI tools and packages. We shall employ standard IRAF tools and packages we line_3: have used extensively in analysis of our gound-based CTIO H-ALPHA vs. R data line_4: on globulars. line_6: We shall analyze our data by a variety of techniques. First, we shall employ line_7: the ratio or colormap techniques we have developed (Bailyn et al 1988, line_8: Cederbloom et al 1991) on our CTIO and CFHT data. Second, we shall use DAOPHOT line_9: for stellar photometry. Again, we have considerable experience with this and line_10: will coordinate our efforts with both P. Stetson and STScI (e.g. the line_11: modifications mentioned by Holtzman et al 1991) for optimum choices of psf line_12: parameter fitting. Further, we shall develop new techniques of analysis of line_13: stellar image shape and sharpness to be combined with DAOPHOT analysis. line_14: Finally, we have developed techniques to simulate HST PC images of clusters line_15: in order to test and refine our analysis procedures. line_17: We have recently received archived FOC frames (uv filters) on NGC 6397. line_18: These data will be extremely important for final analysis of the line_19: proposed investigation (cf. question 8) since uv excess colors line_20: and H-ALPHA emission are the hallmark of CVs vs. other H-ALPHA objects likely line_21: to be found (e.g. planetaries or possibly millisecond pulsar nebulae). ! question: 8 section: 0 line_1: This proposed observation will be supported by our continuing analysis of our line_2: ground-based H-ALPHA vs. narrow-band R images (CTIO/PF-CCD) of NGC 6397. As line_3: mentioned in question 4 above, these data are sensitive to about Mv = 9 and line_4: H-ALPHA equivalent width 30-40 angstrom at radii OUTSIDE about 3-4 core line_5: radii in the cluster, or at about 30 arcsec (i.e. the edge of the PC field) line_6: given the approximate core radius recently derived by Auriere et al (1991). line_7: Thus the CTIO data will complement (though not be as sensitive as) the HST line_8: data, particularly at the edge of the field. By using the HST data to derive line_9: stellar positions (e.g. with DAOPHOT's FIND routine), however, the CTIO data line_10: can be searched deeper than the overlapping stellar images would otherwise line_11: allow. This was pointed out in our proposal by Bailyn et al line_12: for use of archival HST/FOC images on NGC 6397. By comparing the HST/PC line_13: H-ALPHA images with the CTIO H-ALPHA images, we can not only gain additional line_14: sensitivity (at least in the outer parts of the core) for the CTIO data, but line_15: also search for large amplitude variability such as could be expected if dwarf line_16: novae are present in the cluster CV population. ! question: 9 section: 0 line_1: The PI and the Co-I's for this proposal are currently recalibrating the data line_2: from their Cycle 1 observation of the globular cluster NGC 6752. These data were line_3: obtained in Program P2555 entitled "Cataclysmic Variables and Millisecond line_4: Pulsars in Globular Cluster Cusps". The initial calibration suffered from line_5: the use of an incorrect bias frame. Our recalibration is using a new bias frame line_6: together with the latest flat available. line_8: Preliminary colormap and DAOPHOT analysis of the data, prior to recalibration, line_9: revealed no obvious CV candidates down to an approximate limiting magnitude line_10: of about Mv = 6. However this result is extremely preliminary and requires line_11: considerable and careful full analysis, which we will perform following the line_12: recalibration. ! question: 10 section: 0 line_1: Each institution will supply already-obtained computing and data handling line_2: facilities to process these extensive data. Sun Workstations will be used at line_3: Harvard and at Indiana, and VAX workstations at Yale. Each instituion has full line_4: IRAF and DAOPHOT capabilities. line_6: Graduate students will work with the PI and Co-I's on reducing and analyzing line_7: fully these data. These students will be partially supported by other research line_8: funds. ! !end of general form text general_form_address: lname: GRINDLAY fname: JONATHAN mi: E. title: PROF category: PI inst: HARVARD COLLEGE OBSERVATORY addr_1: CENTER FOR ASTROPHYSICS addr_2: 60 GARDEN STREET city: CAMBRIDGE state: MA zip: 02138 country: U.S.A. phone: 617-495-7204 telex: 921428 from_date: 01-JUL-92 to_date: 30-JUN-93 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: NGC6397-POS1 descr_1: C,201 pos_1: RA = 17H 40M 41.74S +/- 0.06S, pos_2: DEC = -53D 40' 24.94" +/- 0.50" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 fluxnum_1: 1 fluxval_1: V = 21 ! targnum: 2 name_1: NGC6397-POS2 descr_1: C,201 pos_1: RA = 17H 40M 41.51S +/- 0.06S, pos_2: DEC = -53D 40' 24.94" +/- 0.50" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 fluxnum_1: 1 fluxval_1: V = 21 ! targnum: 3 name_1: NGC6397-POS3 descr_1: C,201 pos_1: RA = 17H 40M 41.74S +/- 0.06S, pos_2: DEC = -53D 40' 28.94" +/- 0.50" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 fluxnum_1: 1 fluxval_1: V = 21 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: NGC6397-POS1 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F656N num_exp: 6 time_per_exp: 1000S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES param_2: CR-SPLIT = NO req_1: ORIENT 80.0D +/- 10.0D; req_2: CYCLE 2 /1-9 ! linenum: 2.000 targname: NGC6397-POS1 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F675W num_exp: 2 time_per_exp: 10S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES req_1: ORIENT 80.0D +/- 10.0D ! linenum: 3.000 targname: NGC6397-POS1 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F675W num_exp: 5 time_per_exp: 100S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES req_1: ORIENT 80.0D +/- 10.0D ! linenum: 4.000 targname: NGC6397-POS2 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F656N num_exp: 6 time_per_exp: 1000S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES param_2: CR-SPLIT = NO req_1: ORIENT 80.0D +/- 10.0D ! linenum: 5.000 targname: NGC6397-POS2 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F675W num_exp: 2 time_per_exp: 10S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES req_1: ORIENT 80.0D +/- 10.0D ! linenum: 6.000 targname: NGC6397-POS2 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F675W num_exp: 5 time_per_exp: 100S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES req_1: ORIENT 80.0D +/- 10.0D ! linenum: 7.000 targname: NGC6397-POS3 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F656N num_exp: 6 time_per_exp: 1000S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES param_2: CR-SPLIT = NO req_1: ORIENT 80.0D +/- 10.0D ! linenum: 8.000 targname: NGC6397-POS3 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F675W num_exp: 1 time_per_exp: 10S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES req_1: ORIENT 80.0D +/- 10.0D ! linenum: 9.000 targname: NGC6397-POS3 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F675W num_exp: 5 time_per_exp: 100S fluxnum_1: 1 priority: 1 param_1: PRE-FLASH = YES req_1: ORIENT 80.0D +/- 10.0D ! ! end of exposure logsheet ! No scan data records found