Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5390 Report Date: 18-Jul-95:17:16 Version: ********** Check-in Date: ********** 1.Proposal Title: OBSERVATIONS OF THE ABLATED COMPANION OF AN ECLIPSING PULSAR ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category NEUTRON STARS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Andrew S Fruchter STSCI USA 510.643.8142 ------------------------------------------------------------------------------------ 7. Abstract Although the effect of millisecond pulsars on their companions is often spectacular and the range of observable features great, the means by which these pulsars ablate their companions, the physics of the pulsar eclipse and the evolutionary history of these binaries remain poorly understood. Here we propose to study one of these remarkable systems, the eclipsing pulsar PSR B1957+20 The companion of this neutron star is heated on one side to nearly 8000 K by the spin-down radiation of the pulsar; yet the face of the companion away from the neutron star is astonishingly cool. HST data obtained by us indicate a temperature less 2600 K. The observations proposed here will allow us to measure the intensity and colors of this system at minimum. This will provide valuable information on the size of the companion, and on the inclination of the binary orbit, both of which are vital for understanding the nature of pulsar eclipse and constraining the binary evolution. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 3.80 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5390 PI: Andrew S Fruchter Proposal Title: OBSERVATIONS OF THE ABLATED COMPANION OF AN ECLIPSING PULSAR ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Andrew Fruchter 3470 USA Charles Bailyn 3900 USA Jay Bookbinder 2166 USA Paul Callanan 2166 ------------------------------------------------------------------------------------ 3. Description of proposed observations. The observational goal of this project is to obtain R and I band images of the eclipsing pulsar system PSR 1957+20 near optical minimum (orbital phase 0.25). The orbital period is 9.16 hours; so we can cover about 0.075 of a period on a single visit. We will therefore visit the system four times. The two highest priority visits start at orbital phase 0.198. During one of these visits we will obtain 4x500s exposures with F814W and during the other visit we will take 4x500s exposures in F675W. These two filters will then be used again during two further visits that both begin at orbital phase 0.232. Together, these two sets of observations will allow us to cover orbital phases 0.20 -- 0.30 in both R and I. Note that in order to obtain correct orbital coverage each set of 4x500s exposures must be uniterrupted. If this is not possible then it would be best to reduce the exposure time to 3x600s, for example, rather than letting the scheduler assign one of the 500s exposures to the next HST orbit. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The presence of a $m_V \approx 20$ star only $0.7''$ from PSR~1957+20 on the sky has confounded deep imaging from the ground. In particular, while 4-m class telescopes have been able to obtain light-curves for the object at various wavebands, so far no ground based telescope has been able to separate the pulsar system from this contaminating star at optical minimum. Our previous HST work has shown that the companion can be detected at minimum, even with the present aberrated optics. The corrected optical system should allow us to determine the colors, and thus temperature, of the system at minimum -- a project which appears to be beyond the best ground-based telescopes. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The companion to PSR~1957+20 is seen to vary by several magnitudes with orbital phase. We wish to obtain images of the companion near optical minimum. As the binary system's orbital period is only 9.16 hours, the timing of the HST observation is critical. The observations will be planned so that the center of each session is slightly before or after optical minimum. This will insure good coverage of the object at minimum, but will also allow us to observe a larger fraction of the orbit than if all observations were centered at minimum. We will provide STScI with an accurate orbital ephemeris. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. We will provide the Observatory with an accurate orbital ephemeris. However, we request that we be given the planned times of observation well in advance of the actual spacecraft time, so that we may check the observatory's calculation and make sure that no misunderstanding has caused the observations to be incorrectly scheduled. Page 3 ------------------------------------------------------------------------------------ 9. Description of previous HST work. PSR~B1957+20 was observed on three separate occasions using the Plantary Camera of the Hubble Space Telesecope. During the first observation we obtained a single 600s exposure of the system at maximum (orbital phase phi=0.75) using the F569W filter, which corresponds roughly to the Johnson $V$ band. This image was taken to permit offset postioning of the slit during spectral line observations. Later, a set of two 500s exposures were taken, using the F791W, or ``I'', filter. There were planned for orbital phase $0.25$; however, an error in the scheduling of the telescope caused these images to be taken at orbital phase $0.4$. Therefore, a third and final set of images were exposed, this time near orbital phase $0.25$, corresponding to pulsar eclipse and optical minimum. These images have allowed us to obtain a three sigma detection of the system at optical minimum. The gunn_i magnitude of the system at minimum is approximately 23.4. This limits the temperature of cool side of the companion to less than about 2700K. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Supplies and computing resources for Bailyn, Bookbinder and Callanan will be provided by their home institutions. Computer support and general supplies will be supplied by STScI to Fruchter. ------------------------------------------------------------------------------------ 11. Address Information Name: ANDREW FRUCHTER Category: PI Institution: 3470 Address: DEPARTMENT OF ASTRONOMY UNIVERSITY OF CALIFORNIA City: BERKELEY State: CA Zip Code: 94709 Country: USA Telephone: (510)643-8142 Telex (or e-mail): asf@orestes.berkeley.edu ------------------------------------------------------------------------------------ Name: ANDREW S FRUCHTER Category: CON Institution: UNIVERSITY OF CA Address: DEPARTMENT OF ASTRONOMY UNIVERSITY OF CALIFORNIA City: BERKELEY State: CA Zip Code: 94709 Country: USA Telephone: (510)643-8142 Telex (or e-mail): asf@orestes.berkeley.edu ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5390 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 PSR1957+20 A, RA = 19H 59M 36.771S +/- J2000.0 1 I=23.5, E(B-V)=0.3 173 .01S, DEC = +20D 48' 15.16" +/- .1" ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5390 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PSR1957+20 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 600S 8 1 1 CYCLE 4 PERIOD 33001.919S +/- 0.001S ZERO-PHASE JD2447700.00693 +/ - .00003D PHASE 0.198 +/- 0.008 NON-INT / 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 PSR1957+20 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 600S 8 1 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 3 PSR1957+20 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 600S 8 1 2 CYCLE 4 PERIOD 33001.919S +/- 0.001S ZERO-PHASE JD2447700.00693 +/ - .00003D PHASE 0.232 +/- 0.008 NON-INT / 3-4 ------------------------------------------------------------------------------------------------------------------------------------ 4 PSR1957+20 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 2 600S 8 1 2 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 11 PSR1957+20 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO 1 600S 8 1 1 CYCLE 4 PERIOD 33001.919S +/- 0.001S ZERO-PHASE JD2447700.00693 +/ - .00003D PHASE 0.198 +/- 0.008 NON-INT / 11-12 ------------------------------------------------------------------------------------------------------------------------------------ 12 PSR1957+20 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO 2 600S 8 1 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 13 PSR1957+20 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO 1 600S 8 1 2 CYCLE 4 PERIOD 33001.919S +/- 0.001S ZERO-PHASE JD2447700.00693 +/ - .00003D PHASE 0.232 +/- 0.008 NON-INT / 13-14 ------------------------------------------------------------------------------------------------------------------------------------ 14 PSR1957+20 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO 2 600S 8 1 2 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5390 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 3.80 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category NEUTRON STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; PERIOD 33001.919S +/- 0.001S ; ZERO-PHASE JD2447700.00693 +/- .00003D ; PHASE 0.198 +/- 0.008 ; NON-INT / 1-2 PHASE 0.232 +/- 0.008 ; NON-INT / 3-4 NON-INT / 11-12 NON-INT / 13-14 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F675W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PSR1957+20 ------------------------------------------------------------------------------------------------------------------------------------