Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4271c Report Date: 09-May-96:19:30 Version: ********** Check-in Date: ********** 1.Proposal Title: TESTING THE STAR-DISK CONNECTION: CIV AND MGII MAPS OF ACCRETION DISKS CYC3-MED ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category ERUPTIVE BINARIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Keith Horne STSCI USA 410-338-4964 ------------------------------------------------------------------------------------ 7. Abstract Empirical scaling laws among magnetic activity indicators are well established for the sun and other cool stars. Ground-based studies of Balmer and CaII emission suggest that similar relationships may hold for the accretion disks and tidally- locked secondary stars in cataclysmic variables. We propose to test this star-disk connection by using HST to make Doppler maps of MgII and CIV emission in three quiescent dwarf novae. These lines sensitive to chromospheric and transition region temperature regimes are predicted to scale as radius to the -3/2 and -3 respectively in the Keplerian accretion disk. Our experiment tests the hypothesis that dynamo action powers emission lines from accretion disk chromospheres. The disk and secondary star rotate much faster than the stars for which magnetic activity relations have been previously determined. By expanding the study of magnetic activity to higher rotation rates and different geometries, we expect to gain insights into the basic physics that will advance our understanding of dynamos and magnetic activity in a broad context. NOTE: THE TAC CUT THIS PROPOSAL FROM 3 TO 1 OBJECT. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 3.47 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4271c PI: Keith Horne Proposal Title: TESTING THE STAR-DISK CONNECTION: CIV AND MGII MAPS OF ACCRETION DISKS CYC3-MED ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Keith Horne STSCI USA Thomas R Marsh UNIVERSITY OF OXFORD UNITED KING X Rene' Rutten UNIVERSITEIT VAN AMSTERDAM NETHERLANDS X Steven H Saar CENTER FOR ASTROPHYSICS USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We will use the GHRS with the G270M grating to observe MgII 2800A emission line profiles out to +/- 2300 km/s with a resolution of 11 km/s, and with the G160M grating to observe CIV 1550A profiles out to +/- 3300 km/s with a resolution of 16 km/s. These modes are nearly ideal for our experiment. The spectral resolution provides 8-12 resolution elements across the width of the rotationally-broadened lines of the late-type secondary stars, which have a V sin(i) of about 128 km/s. This will permit Doppler imaging of individual active regions should they be present. The velocity range covered is also sufficient to embrace the extended wings of the emission lines from the Keplerian accretion disk. We will perform the Doppler imaging study on three dwarf novae, T Leo,(P=1.4h), IP Peg (P=3.8h), and U Gem (P=4.2h). These dwarf novae have strong cleanly double-peaked Balmer emission lines to ensure that the dominant emission line region is the accretion disk chromosphere and that there is not appreciable contamination of CIV emission from a wind. NOTE: THE TAC CUT OUR STUDY DOWN TO 1 OBJECT. We need phase- resolved spectra covering a range of binary phases in order to use the Doppler mapping technique to separate the disk emission from the late-type star emission. We can achieve this while making efficient use of spacecraft time by taking 8-10 minute exposures alternating between the two gratings (it takes about 1 minute to switch gratings). Since this gives 2 exposures per grating during the visibility window of each HST orbit, 4 HST orbits will provide coverage around 8 different binary phases, adequate for the Doppler mapping studies. The elapsed time between the first and last observations will be 5.6 hours, so we will sample all phases of the 1.41, 3.79 and 4.25 hour binary periods. The gaps in binary phase coverage caused by earth occultations will introduce some ambiguities in our Doppler maps, but we feel they will not be too detrimental to our science goals. In principle the Doppler tomogram of a disk is completely determined by spectra covering only half of the the binary cycle. This is because the disk is flat, so that every element on the disk surface is visible at all binary phases, thus the line profiles in the second half of the cycle are just mirror images of those in the first half. Despite the phase gaps we are confident we can use the data to determine the radial profile of the disk emission lines, and the contribution from several faces of the secondary star. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. From the ground we have obtained phase-resolved spectra for Balmer emission lines and have used them to construct Doppler maps (Marsh and Horne 1990; Marsh, et al. 1990) and we have extended those Doppler mapping studies to include Ca II K (Fig 2). We must now go into the UV to confirm whether the MgII and CIV emission follow the relationships predicted by the star-disk connection. MgII should vary as R**-3/2, while CIV should vary as R**-3. We need the high UV sensitivity of the HST and high spectral resolution of the GHRS to observe the velocity profiles of MgII and CIV emission lines with enough time resolution to follow the changes in the line velocity profiles as the binary system rotates. The time resolution required by the sampling theorem for Doppler tomography is of order DT = P * DV / V, where DT is the time resolution, P is the binary period, DV is the resolution of the map, and V is the maximum velocity in the Doppler map. For DV=20 km/s, V=2000km/s, we need 100 time samples around the binary period, and P=1.5-4.25h that means from 1 to 3 minutes between spectra. We cannot use IUE because not only is its sensitivity too low, but also IUE's time resolution is insufficient because it takes 20 minutes or so to read out its cameras. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The observations of each object must occur on consecutive HST orbits in order to provide samples at different binary phases around the binary orbit. We could alternatively schedule time-critical observations aimed to hit specific binary phases, but the scheduling problems and overheads associated with finding guide stars make that alternative far less efficient than finding the target once and sitting there for consecutive HST orbits. T Leo's binary period is 85m, compared with HST's 96m orbit. Thus 4 HST orbits equals approx. 4.5 T Leo periods. We therefore observe HST orbits 1 and 2 at CIV and MgII, then skip orbits 3 and 4, then repeat CIV and MgII in orbits 5 and 6. This covers the binary phase pretty uniformly. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. None ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. Initial data reduction and calibration will use the standard pipelined software at STScI. We will first make plots of spectral and temporal slices through the data and display the data as trailed spectrograms to check for obvious problems. We will then apply our maximum entropy software which will make Doppler maps of the emission-line regions. We have used this software and published results of analyses of ground-based data on IP Peg and U Gem. By examining the Doppler maps we can see directly the kinematics of the emission line regions, and from that infer what parts of the system emit the lines. For example, disk emission appears as a ring on the Doppler map, while emission from the late-type star appears as a sharp component displaced upward from the center as in Figure 2. We will determine the radial profile of the disk component of the emission by averaging in azimuth around the center of the ring on the map. Then we will subtract the disk component from the data and examine the trailed spectrogram to see if the residual appears to be consistent with emission from the late-type secondary star. We may find that there are active regions on the companion star, in which case we will modify our mapping code to solve for the distribution of flux on the Roche lobe surface of the late-type star as well as on the plane of the accretion disk. Page 4 ------------------------------------------------------------------------------------ 8. Additional comments or special requests. The exposure times planned for this experiment are NOT dictated by signal-to- noise ratio requirements, but rather are required to record velocity profiles at 8 representative phases around full binary cycles. We will attempt to acquire coordinated earth-based observations. ------------------------------------------------------------------------------------ 9. Description of previous HST work. Cycle 1: GO-2334 "Ultraviolet Spectroscopy of the Black Hole AO620-00" McClintock, Remillard, and Horne GO-2380 "Instabilities in Accretion Disks and the Outbursts of Dwarf Novae" Horne and Marsh GO-3232 "Observations of X-Ray Nova Muscae 1991" Panagia, Lund, Gilmozzi, Horne, Paresce, Valle, and Schrader Cycle 2: GO-3578 "Line Eclipse Mapping of an Accretion Disk Wind" Mason, Drew, Marsh, Horne, Cordova, Mauche, Raymond GO-3600 "Oscillations, Flares, and Tomography of AE Aquarii" Horne, Marsh, Robinson, Wood. GO-3683 "Accretion Disk Mapping in Eclipsing Cataclysmic Variables" Horne, Barwig, Long, Marsh, Polidan, Raymond, Robinson, Rutten, Shafter, Szkody, Wade, Wood, and Zhang GO-3824 "A Search for Silicon and Carbon in GO Com" Wood, Marsh, Lambert, and Horne GO-3836 "Spectroscpic Observations of the Exposed WDs in the Dwarf Novae U Gem, WZ Sge, and VW Hyi" Sion, Szkody, Gilland, Long, Pringle, Horne, Wood ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Salary and basic computer facilities are being provided for the P.I. ------------------------------------------------------------------------------------ 11. Address Information Name: KEITH HORNE Category: PI Institution: STScI Address: STSCI 3700 SAN MARTIN DRIVE City: BALTIMORE, MD State: Zip Code: 21218 Country: USA Telephone: 410-338-4964 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4271c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 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 T-LEO A,149,161 RA = 11H 38M 26.954S +/- J2000 1 V=15.5 +/- 0.5 0.07S, 2 F-CONT(1550) = 12 +/- 3 E-15 DEC = +03D 22' 08.05" +/- 3 F-CONT(2800) = 8 +/- 3 E-15 1", PLATE-ID=0592 Comments: V=10 IN RARE DWARF NOVA OUTBURSTS ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4271c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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 T-LEO HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3 1 90S 2 CYCLE 3 / 1-6 BRIGHT=RETURN ONBOARD ACQ FOR 2- 3 SEQ 1-3 NO GAP Comments: EXPECT 700-1000 C/S, THUS USE STEP-TIME = 10S. TO PERMIT COORDINATED OBSERVATIONS, PLEASE NOTIFY P.I. WHEN DATES ARE SCHEDULED OR CHANGED. ------------------------------------------------------------------------------------------------------------------------------------ 2 T-LEO HRS ACCUM 2.0 G160M 1549 STEP-PATT=5 38 54.4S NON-INT COMB=FOUR Comments: FOR TIME-RESOLVED SPECTROSCOPY, NEED SMALL DEADTIME. CHANGE TO COMB=TWO, OR STEP-PATT=3, OR DOUBLE TIME_PER_EXP TO KEEP DEADTIME BELOW 20 PERCENT. THEN SET NUMBER OF EXPOSURES TO FILL AVAILABLE TIME IN HST ORBIT. ------------------------------------------------------------------------------------------------------------------------------------ 3 T-LEO HRS ACCUM 2.0 G270M 2800 STEP-PATT=5 38 54.4S NON-INT COMB=FOUR Comments: FOR TIME-RESOLVED SPECTROSCOPY, NEED SMALL DEADTIME. CHANGE TO COMB=TWO, OR STEP-PATT=3, OR DOUBLE TIME_PER_EXP TO KEEP DEADTIME BELOW 20 PERCENT. THEN SET NUMBER OF EXPOSURES TO FILL AVAILABLE TIME IN HST ORBIT. ------------------------------------------------------------------------------------------------------------------------------------ 4 T-LEO HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3 1 90S 2 ONBOARD ACQ FOR 5- BRIGHT=RETURN 6 SEQ 4-6 NO GAP AFTER 1 BY 384M +/ - 10M Comments: 384M = 4 HST ORBITS, 384M = 4.5 T-LEO PERIODS. THIS DELAY ENSURES COVERAGE OF OPPOSITE HALF OF T-LEO ORBIT. EXPECT 700 -1000 C/S, THUS USE STEP-TIME = 10S. ------------------------------------------------------------------------------------------------------------------------------------ 5 T-LEO HRS ACCUM 2.0 G160M 1549 STEP-PATT=5 38 54.4S NON-INT COMB=FOUR Comments: FOR TIME-RESOLVED SPECTROSCOPY, NEED SMALL DEADTIME. CHANGE TO COMB=TWO, OR STEP-PATT=3, OR DOUBLE TIME_PER_EXP TO KEEP DEADTIME BELOW 20 PERCENT. THEN SET NUMBER OF EXPOSURES TO FILL AVAILABLE TIME IN HST ORBIT. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4271c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 6 T-LEO HRS ACCUM 2.0 G270M 2800 STEP-PATT=5 38 54.4S NON-INT COMB=FOUR Comments: FOR TIME-RESOLVED SPECTROSCOPY, NEED SMALL DEADTIME. CHANGE TO COMB=TWO, OR STEP-PATT=3, OR DOUBLE TIME_PER_EXP TO KEEP DEADTIME BELOW 20 PERCENT. THEN SET NUMBER OF EXPOSURES TO FILL AVAILABLE TIME IN HST ORBIT. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4271c [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN STEP-PATT COMB ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 3.47 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ERUPTIVE BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 3 / 1-6 ; ONBOARD ACQ FOR 2-3 ; SEQ 1-3 NO GAP ; NON-INT ; ONBOARD ACQ FOR 5-6 ; SEQ 4-6 NO GAP ; AFTER 1 BY 384M +/- 10M; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G160M G270M ------------------------------------------------------------------------------------------------------------------------------------ Target Names T-LEO ------------------------------------------------------------------------------------------------------------------------------------