Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5689 Report Date: 18-Jul-95:17:51 Version: ********** Check-in Date: ********** 1.Proposal Title: A SEARCH FOR SILICON AND CARBON IN GP COM - CYCLE 4 CARRYOVER ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS GO/CAR 3824 Sub Category PECULIAR BINARIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Janet H Wood KEELE UNIVERSITY UK 011-44-782-583 LECTURER ------------------------------------------------------------------------------------ 7. Abstract The spectra of the 46 minute period binary white dwarf GP Com show emission lines from an accretion disk supplied from the hydrogen-exhausted core of a star, providing us with an opportunity to see the products of nucleosynthesis directly. The optical and ultraviolet data taken to date show evidence for CNO processing, but the abundances of elements such as silicon, calcium and iron appear anomalously low. The only plausible explanation for this involves the transfer of nitrogen-rich material from the progenitor of the accreting white dwarf to its companion in a common envelope stage. Confirmation of the low abundance of the heavier elements is a critical test of this model. We will take high signal-to-noise ultraviolet spectra of GP Com to search for emission from the SiIV 1400 doublet, CIV 1550 and other Si and C ions. We will measure the emission from NV 1239, 1243. This will allow us to determine the extent of CNO equilibrium and enhancement of nitrogen. These data will constrain both the evolution of GP Com and the poorly understood common envelope phase of binary evolution. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 2.74 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5689 PI: Dr. Janet H Wood Proposal Title: A SEARCH FOR SILICON AND CARBON IN GP COM - CYCLE 4 CARRYOVER ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Dr. Janet H Wood KEELE UNIVERSITY UK X Dr. Thomas R Marsh UNIVERSITY OF SOUTHAMPTON UK X Prof. David L Lambert UNIVERSITY OF TEXAS USA Dr. Keith Horne UNIVERSITY OF UTRECHT NETHERLANDS X ------------------------------------------------------------------------------------ 3. Description of proposed observations. We will take GHRS spectra of GP Com through the LSA. with the G140L grating. We will observe the range 1150-1430A in order to cover the SiIV 1394, 1403, and NV 1239, 1243 doublets with the highest sensitivity. We will also cover CIII 1175 and the SiIII complex at 1300. Observation of NV will allow us to compare the strength of the line with those of Si and C and also allow us to determine whether the accretion disc contributes to the ultraviolet lines through its characteristic double peaked profile. This has not been clearly determined for any cataclysmic variable. The exposures will cover more than two orbits of GP Com and by reading out the detector every 400 seconds we will obtain information on orbital variations in the NV line and continuum. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The nitrogen abundance in GP Com has clearly been enhanced by CNO processing. Our aim is to determine whether another mechanism (e.g. mass transfer from the star now accreting) has enhanced it still further. Observationally we aim to detect silicon to pin down the heavy element abundance. Optical data are already limited by the presence of many weak blended lines (possibly of neon) which makes reliable estimation of the continuum impossible. Higher spectral resolution will not resolve these lines since they are intrinsically broad because of Doppler shifting in the accretion disk. By analogy with normal CVs, in which silicon is easily detected in the ultraviolet, it is the best region to look in GP Com. We also gain sensitivity to a different ion species, SiIV in addition to SiII which will greatly decrease the uncertainties of the model of the disk's atmosphere. The IUE spectrum of figure 1 represents a 15,000 sec exposure which has a signal- to-noise roughly a factor of 5 - 10, too low for our requirements (see the exposure time computation in the next section). Thus, even if there was no fixed pattern noise to worry about, our experiment would require a prohibitively long IUE exposure. HST is the only instrument available that can solve this problem. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. ------------------------------------------------------------------------------------ 9. Description of previous HST work. Program GTO-1064 "Boron in Main Sequence Stars": Lambert. Lambert has received and analysed this data. Program GO-2380 "Instabilities in Accretion Disks and the Outbursts of Dwarf Novae": Horne and Marsh. Data under analysis. Program GO-2334 "Ultraviolet Spectroscopy of the Black Hole A0620-00": McClintock, Remillard and Horne. Data under analysis. Program GO-3232 "Observations of X-ray Nova Muscae 1991": Panagia, Lund, Gilmozzi, Horne, Paresce, Valle, Schrader. paper submitted to Ap. J. Lambert has other GTO proposals for which no data has been received as yet. These projects are not related to the current proposal. Page 3 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Data analysis will be done using workstations at STSci, on a SUN Sparcstation at the University of Texas and on the STARLINK nodes at the Universities of Keele and Oxford. ------------------------------------------------------------------------------------ 11. Address Information Name: JANET H WOOD Category: PI Institution: KEELE UNIVERSITY Address: DEPARTMENT OF PHYSICS City: KEELE State: Zip Code: Country: UK Telephone: 011-44-782-583341 Telex (or e-mail): 36113 UNKLIB G ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5689 [ 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 GP-COM G61- A,151,161,906,909 PLATE-ID=01PP, J2000 Z=0.0 1 V=15.8+/-0.2, E(B-V)=0.0+/-0.05 29 RA = 13H 5M 42.84S +/- 2 F-CONT(13961396)=5.0+/-0.5E-15 WD1303+182 0.027S, 3 F-LINE(1240)=5.0+/-0.05E-14 DEC = +18D 1' 2.6" +/- 0.4" 4 W-LINE(1240)=20+/-1 Comments: THE CRITICAL S/N IS THAT IN THE CONTINUUM AT 1396A, NOT THAT IN THE 1240 LINE. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B 1982.16 -0.0239 +/- 0.0000 0.0160 +/- 0.0000 0.0000 +/- 0.0000 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5689 [ 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 GP-COM HRS ACQ 2.0 MIRROR-N1 1 135S 1 1 ONBOARD ACQ FOR 2 GROUP 1-3 NO GAP CYCLE 4 / 1-3 Comments: step-time=15S expect 1000 counts ------------------------------------------------------------------------------------------------------------------------------------ 2 GP-COM HRS ACQ/ 2.0 MIRROR-N1 1 714S 1 1 ONBOARD ACQ FOR 3 PEAKUP Comments: step-time=7S ------------------------------------------------------------------------------------------------------------------------------------ 3 GP-COM HRS ACCUM 2.0 G140L 1290 13 411S 19 2 1 5343S Comments: THE CRITICAL S/N IS THAT IN THE CONTINUUM AT 1396A, NOT THAT IN THE 1240 LINE. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5689 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO/CAR ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 2.74 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category PECULIAR BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2; GROUP 1-3 NO GAP; CYCLE 4 / 1-3 ONBOARD ACQ FOR 3; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N1 G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names GP-COM G61-29 WD1303+182 ------------------------------------------------------------------------------------------------------------------------------------