Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 3095c Report Date: 09-May-96:17:58 Version: ********** Check-in Date: ********** 1.Proposal Title: WHITE DWARF PULSATIONS AND DIFFUSION--INDUCED CN BURNING ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS EROS Sub Category ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Joseph Dolan STANFORD UNIVERSITY USA (415)723-2464 ------------------------------------------------------------------------------------ 7. Abstract We propose to observe the DA-type white dwarf Sirius B to search for non- radial pulsations which have been predicted and recently found in other classes of white dwarfs. Theory predicts that pulsations caused by diffusion-induced CN burning should exist in this class of white dwarf. Such pulsations would constitute useful probes of the internal structure of these stars, and may reveal the importance of nucleosynthesis in the white dwarf stage of stellar evolution. Pulsational activity, if found, may also be related to the controversial but possibly real color change of Sirius, from a recorded color of red in Ptolemy's time to its present blue - white color. In one scenario, a thermonuclear runaway would temporarily expand Sirius B to a red giant, followed by a return to the white dwarf stage. Regardless of the interpretation of its historical record, Sirius B is an ideal candidate in which to search for pulsations driven by diffusion-induced CN burning. REVISION HISTORY: Created base line version--BJW 9/11/90; ------------------------------------------------------------------------------------ 8. Scientific Key Words: WHITE DWARFS: PULSATIONS ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 1.00 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 3095c PI: Joseph Dolan Proposal Title: WHITE DWARF PULSATIONS AND DIFFUSION--INDUCED CN BURNING ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Joseph F. Dolan STANFORD UNIVERSITY USA Robert C. Bless WISCONSIN, UNIVERSITY OF USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. The DA-type white dwarf Sirius B is proposed as a target. A 0.5 hour exposure will be taken with the HSP using the UV2 prism. Two filter bandpasses are used quasi-simultaneously: F145M, close to the wavelength of peak flux in the star (but longward of the broad Lyman alpha absorption line), and F262M, to allow us to derive color temperatures of the star through any pulsation. Integration time will be one second in one filter, then one second in the other, repeating throughout the observation. Multiple mode pulsations often interfere destructively, leading to intervals of very low amplitude variability. Each star will be observed twice to determine whether the amplitude of any pulsation is variable in time. ------------------------------------------------------------------------------------ 11. Address Information Name: JOSEPH DOLAN Category: PI Institution: STANFORD UNIVERSITY Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ Name: JOSEPH F. DOLAN Category: PI Institution: STANFORD UNIVERSITY Address: DEPT. OF PHYSICS City: STANFORD State: CA Zip Code: 94305 Country: USA Telephone: (415)723-2464 Telex (or e-mail): ------------------------------------------------------------------------------------ Name: ROBERT C BLESS Category: CON Institution: UNIVERSITY OF WISCONSIN Address: SPACE ASTRONOMY LAB 1150 UNIVERSITY AVE. City: MADISON State: WI Zip Code: 53706 Country: USA Telephone: (608)262-1715 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 3095c [ 3] ------------------------------------------------------------------------------------------------------------------------------------ 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 SIRIUS-B RA = 06H 42M 56.7S +/- 0.2S, 1950 1 V=8.5 DEC = -16D 38' 46.4" +/- 0.3" ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3095c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 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 SIRIUS-B HSP/ ACQ 1 4S 1 1 INT ACQ FOR 2 UV2 ------------------------------------------------------------------------------------------------------------------------------------ 2 ^ HSP/ PRISM 1.0 F262M/ 2 30M ^ UV2 F145M Comments: CLOSE BINARY. USE MAXIMUM AMOUNT OF TIME POSSIBLE IN TWO ORBITS. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 3095c [ 5] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HSP/UV2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ PRISM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Proposal for EROS ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 1.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements INT ACQ FOR 2; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F262M/F145M ------------------------------------------------------------------------------------------------------------------------------------ Target Names SIRIUS-B ------------------------------------------------------------------------------------------------------------------------------------