! $Id: 5390,v 5.1 1994/07/27 17:26:01 pepsa Exp $ coverpage: title_1: OBSERVATIONS OF THE ABLATED COMPANION OF AN ECLIPSING PULSAR sci_cat: HOT STARS sci_subcat: NEUTRON STARS proposal_for: GO pi_fname: ANDREW pi_mi: S pi_lname: FRUCHTER pi_inst: STSCI pi_country: USA pi_phone: 510.643.8142 hours_pri: 3.80 num_pri: 1 wf_pc: Y time_crit: Y off_fname: HERVEY off_lname: STOCKMAN off_title: DEPUTY DIRECTOR off_inst: STSCI off_addr_1: 4700 SAN MARTIN DRIVE off_city: BALTIMORE off_state: MD off_zip: 21218 off_country: USA off_phone: 410-338-2519 ! end of coverpage abstract: line_1: Although the effect of millisecond pulsars on their companions is often line_2: spectacular and the range of observable features great, the means by which these line_3: pulsars ablate their companions, the physics of the pulsar eclipse and the line_4: evolutionary history of these binaries remain poorly understood. Here we propose line_5: to study one of these remarkable systems, the eclipsing pulsar PSR B1957+20 line_6: The companion of this neutron star is heated on one side to nearly line_7: 8000 K by the spin-down radiation of the pulsar; yet the face of the companion line_8: away from the neutron star is astonishingly cool. HST data obtained by us line_9: indicate a temperature less 2600 K. The observations proposed here will allow line_10: us to measure the intensity and colors of this system at minimum. This will line_11: provide valuable information on the size of the companion, and on the line_12: inclination of the binary orbit, both of which are vital for understanding the line_13: nature of pulsar eclipse and constraining the binary evolution. ! ! end of abstract general_form_proposers: lname: FRUCHTER fname: ANDREW inst: 3470 country: USA ! lname: BAILYN fname: CHARLES inst: 3900 country: USA ! lname: BOOKBINDER fname: JAY inst: 2166 country: USA ! lname: CALLANAN fname: PAUL inst: 2166 ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: The observational goal of this project is to obtain R and I band images of line_2: the eclipsing pulsar system PSR 1957+20 near optical minimum (orbital phase line_3: 0.25). The orbital period is 9.16 hours; so we can cover about 0.075 of line_4: a period on a single visit. We will therefore visit the system four times. line_5: The two highest priority visits start at orbital phase 0.198. During one line_6: of these visits we will obtain 4x500s exposures with F814W and during the line_7: other visit we will take 4x500s exposures in F675W. These two filters will line_8: then be used again during two further visits that both begin at orbital line_9: phase 0.232. Together, these two sets of observations will allow us to line_10: cover orbital phases 0.20 -- 0.30 in both R and I. Note that in order to line_11: obtain correct orbital coverage each set of 4x500s exposures must be line_12: uniterrupted. If this is not possible then it would be best to reduce the line_13: exposure time to 3x600s, for example, rather than letting the scheduler line_14: assign one of the 500s exposures to the next HST orbit. ! question: 3 section: 2 line_1: ! question: 4 section: 1 line_1: The presence of a $m_V \approx 20$ star only $0.7''$ from line_2: PSR~1957+20 on the sky has confounded deep imaging from the ground. line_3: In particular, while 4-m class telescopes have been able to obtain line_4: light-curves for the object at various wavebands, so far no ground line_5: based telescope has been able to separate the pulsar system from line_6: this contaminating star at optical minimum. Our previous HST work line_7: has shown that the companion can be detected at minimum, even with line_8: the present aberrated optics. The corrected optical system should line_9: allow us to determine the colors, and thus temperature, of the system line_10: at minimum -- a project which appears to be beyond the best ground-based line_11: telescopes. ! question: 5 section: 1 line_1: The companion to PSR~1957+20 is seen to vary by several magnitudes line_2: with orbital phase. We wish to obtain images of the companion near line_3: optical minimum. As the binary system's orbital period is only line_4: 9.16 hours, the timing of the HST observation is critical. The line_5: observations will be planned so that the center of each session is line_6: slightly before or after optical minimum. This will insure good line_7: coverage of the object at minimum, but will also allow us to observe line_8: a larger fraction of the orbit than if all observations were centered line_9: at minimum. We will provide STScI with an accurate orbital ephemeris. ! question: 6 section: 1 line_1: ! ! question: 8 section: 1 line_1: We will provide the Observatory with an accurate orbital ephemeris. line_2: However, we request that we be given the planned times of observation line_3: well in advance of the actual spacecraft time, so that we may check line_4: the observatory's calculation and make sure that no misunderstanding line_5: has caused the observations to be incorrectly scheduled. ! question: 9 section: 1 line_1: PSR~B1957+20 was observed on three separate occasions using the Plantary line_2: Camera of the Hubble Space Telesecope. During the first observation we line_3: obtained a single 600s exposure of the system at maximum (orbital phase line_4: phi=0.75) using the F569W filter, which corresponds roughly to the line_5: Johnson $V$ band. This image was taken to permit offset postioning line_6: of the slit during spectral line observations. Later, a set of two 500s line_7: exposures were taken, using the F791W, or ``I'', filter. There were line_8: planned for orbital phase $0.25$; however, an error in the scheduling line_9: of the telescope caused these images to be taken at orbital phase $0.4$. line_10: Therefore, a third and final set of images were exposed, this time near line_11: orbital phase $0.25$, corresponding to pulsar eclipse and optical line_12: minimum. These images have allowed us to obtain a three sigma detection line_13: of the system at optical minimum. The gunn_i magnitude of the system line_14: at minimum is approximately 23.4. This limits the temperature of line_15: cool side of the companion to less than about 2700K. ! question: 10 section: 1 line_1: Supplies and computing resources for Bailyn, Bookbinder and Callanan line_2: will be provided by their home institutions. Computer support and line_3: general supplies will be supplied by STScI to Fruchter. ! !end of general form text general_form_address: lname: FRUCHTER fname: ANDREW category: PI inst: 3470 addr_1: DEPARTMENT OF ASTRONOMY addr_2: UNIVERSITY OF CALIFORNIA city: BERKELEY state: CA zip: 94709 country: USA phone: (510)643-8142 telex: asf@orestes.berkeley.edu ! lname: FRUCHTER fname: ANDREW mi: S category: CON inst: UNIVERSITY OF CA addr_1: DEPARTMENT OF ASTRONOMY addr_2: UNIVERSITY OF CALIFORNIA city: BERKELEY state: CA zip: 94709 country: USA phone: (510)643-8142 telex: asf@orestes.berkeley.edu ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: PSR1957+20 descr_1: A, descr_2: 173 pos_1: RA = 19H 59M 36.771S +/- .01S, pos_2: DEC = +20D 48' 15.16" +/- .1" equinox: J2000.0 pos_epoch_bj: J pos_epoch_yr: 1992.00 fluxnum_1: 1 fluxval_1: I=23.5, E(B-V)=0.3 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: PSR1957+20 config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F814W num_exp: 1 time_per_exp: 600S s_to_n: 8 fluxnum_1: 1 priority: 1 param_2: CR-SPLIT = NO req_1: CYCLE 4; req_2: PERIOD 33001.919S +/- 0.001S ; req_3: ZERO-PHASE JD2447700.00693 +/- .00003D ; req_4: PHASE 0.198 +/- 0.008 ; req_5: NON-INT / 1-2 ! linenum: 2.000 targname: PSR1957+20 config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F814W num_exp: 2 time_per_exp: 600S s_to_n: 8 fluxnum_1: 1 priority: 1 param_2: CR-SPLIT = NO req_1: CYCLE 4; ! linenum: 3.000 targname: PSR1957+20 config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F814W num_exp: 1 time_per_exp: 600S s_to_n: 8 fluxnum_1: 1 priority: 2 param_2: CR-SPLIT = NO req_1: CYCLE 4; req_2: PERIOD 33001.919S +/- 0.001S ; req_3: ZERO-PHASE JD2447700.00693 +/- .00003D ; req_4: PHASE 0.232 +/- 0.008 ; req_5: NON-INT / 3-4 ! linenum: 4.000 targname: PSR1957+20 config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F814W num_exp: 2 time_per_exp: 600S s_to_n: 8 fluxnum_1: 1 priority: 2 param_2: CR-SPLIT = NO req_1: CYCLE 4; ! linenum: 11.000 targname: PSR1957+20 config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F675W num_exp: 1 time_per_exp: 600S s_to_n: 8 fluxnum_1: 1 priority: 1 param_2: CR-SPLIT = NO req_1: CYCLE 4; req_2: PERIOD 33001.919S +/- 0.001S ; req_3: ZERO-PHASE JD2447700.00693 +/- .00003D ; req_4: PHASE 0.198 +/- 0.008 ; req_5: NON-INT / 11-12 ! linenum: 12.000 targname: PSR1957+20 config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F675W num_exp: 2 time_per_exp: 600S s_to_n: 8 fluxnum_1: 1 priority: 1 param_2: CR-SPLIT = NO req_1: CYCLE 4; ! linenum: 13.000 targname: PSR1957+20 config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F675W num_exp: 1 time_per_exp: 600S s_to_n: 8 fluxnum_1: 1 priority: 2 param_2: CR-SPLIT = NO req_1: CYCLE 4; req_2: PERIOD 33001.919S +/- 0.001S ; req_3: ZERO-PHASE JD2447700.00693 +/- .00003D ; req_4: PHASE 0.232 +/- 0.008 ; req_5: NON-INT / 13-14 ! linenum: 14.000 targname: PSR1957+20 config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F675W num_exp: 2 time_per_exp: 600S s_to_n: 8 fluxnum_1: 1 priority: 2 param_2: CR-SPLIT = NO req_1: CYCLE 4; ! ! end of exposure logsheet ! No scan data records found