9078( 7) - 08/13/02 12:59 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9078 Version: 7 Check-in Date: 13-Aug-2002 12:58:26 1.Proposal Title: Flares, Magnetic Reconnections and Accretion Disk Viscosity ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: William Welsh San Diego State University CoI: Prof. Edward Robinson University of Texas at Austin N CoI: Dr. Janet Wood San Diego State University N ------------------------------------------------------------------------------------ 5. Abstract Accretion disks are invoked to explain a host of astrophysical phenomena, from protostellar objects to AGN. And yet the mechanism allowing accretion disks to operate are completely unknown. This proposal seeks to observe the ``smoking gun'' signature of magnetically--driven viscosity in accretion disks. Magnetically-- induced viscosity is a plausible and generally accepted hypothesis (for esthetic reasons), but it is completely untested. Determining the cause of accretion disk viscosity is of major significance to all accretion--disk powered systems (e.g. CVs, X--ray binaries, AGN and protostellar disks). These data will also firmly establish the importance of magnetic fields in accretion disks. Because of its known flaring properites, we will observe the accretion disk in EM Cyg simulataneously with STIS/FUV and CHANDRA. The simultaneous X-rays are absolutely necessary for the unambiguous detection of accretion disk magnetic reconnection flares. ------------------------------------------------------------------------------------ 9078( 7) - 08/13/02 12:59 - [ 2] Observations Description ------------------------ We will observe EM Cyg in quiescence with STIS using the FUV-MAMA detectors and the G140L grating to cover 1150-1730A. This will cover the NV 1240 line, the CIV 1550 doublet, the HeII 1640 line, and possibly the CIII 1174 line. EM Cyg has a V mag ~13.8, and reddening E(B-V) < 0.05. IUE observations give a continuum f_Lambda ~ 6 * 10^-14 erg/s/cm2/A at 1500A, and a maximum flux of f_Lambda ~ 2.5 * 10^-13 erg/s/cm2/A at the peak of the CIV emission line. The STIS ETC gives a predicted peak count rate of 1.6 counts/s/pixel and a S/N (per resolution element) = ~12 in 1 min at 1500A (continuum). The predicted global count rate is 1600 counts/sec.   EM Cyg is a Z-Cam type dwarf nova with irregular outbursts typically occuring every 15-35 days. Outbursts reach a maximum of V=11.8 mag (based on many years of AAVSO data). The MAMA detectors are safe if the target goes into outburst: the peak count rate is 5.0 counts/s/pixel and the global count rate is 6465 counts/s using IUE outburst data. EM Cyg also has shallow eclipses (<0.4 mag in V) that occur every 7 hours. The total amount of necessary observing time is dictated by the need to achieve good statistics on flares, not by the S/N of individual (or grand average) spectra. To get a reasonable number of flare events, we request two visits of 5 orbits each. TIME-TAG mode is necessary to observe the rapid flaring event. The BUFFER-TIME was set as a compromise: it is much lower than necessary for quiescence, but too high if the system is at the peak of an outburst. The value of 450s was determined by the need to allow data acquisition for a full 5 orbits (shorter BUFFER-TIMEs reduce the amount of time we can collect data since the total exposure time cannot exceed 30*BUFFER- TIME). We accept that if the system goes into outburst, there may be occasional data-dropouts because the buffer fills too quickly. EM Cyg was observed with Einstein and ROSAT and has a 0.2-4 keV X-ray flux of roughly 3 * 10^-12 erg/s/cm2. The column density and characteristic brems temperature are very poorly determined: NH~ 5*10^21 cm^-2 and kT~ 2.5 keV. With the CHANDRA back-- illuminated ACIS-S CCD we get spectral coverage of 0.2-10 keV, and a PIMMS predicted count rate of ~0.6 c/s (background is negligible). Significant pile- up is present, so we employ a fast readout of approx 0.4s using only 1/8 of the S3 chip. We also offset 4.5 arcmin to degrade the PSF to about 1".5, to again help with pile-up. Since we need very little X-ray spectral resolution, we can bin substantially in wavelength to increase the S/N. Real Time Justification ----------------------- None. We request simultaneous CHANDRA ACIS observations. We will attempt to get simultaneous observations at 2.1m telescope at McDonald observatory, the 1m telescope at Mt. Laguna Observatory, and elsewhere. Failure to get these optical data will in no way detract from the success of this proposal, but they can add substantially to the overall science goal. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9078( 7) - 08/13/02 12:59 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 EM-CYG STAR, Dwarf Nova, RA=19H 38M 40.12S +/- 0.4", J2000 V = 13.9+/-0.5 Accretion Disk DEC=+30D 30' 28.10" +/- 0.4", B-V = 0.56+/-0.14 PLATE-ID=000J E(B-V) = 0.03 F-CONT(1320)=5+/-2e-14 Coordinate Source: GUIDE_STAR_CATALOG Comments: Observations must be simultaneous with Chandra. Rapid variability (0.1 mag). Shallow eclipse (0.2-0.4 mag) every 7 hours (included in V mag uncertainty). Irregular outbursts every 15-35 days with peak mag of V=11.9, B-V=0.14+/-0.06 and F-CONT(1320)=6+/-1E-13; Though not required, BETWEEN 15-JUN-2002 AND 01-SEP- 2002 (or 2003) is best for the science (allows simultaneous ground-based observations). 9078( 7) - 08/13/02 12:59 - [ 4] Visit: 01 Visit Priority: Visit Requirements: PCS MODE F BETWEEN 26-AUG-2002:00:00 AND 01-SEP-2002:15:30 On Hold Comments: Additional Comments: Visit must be simultaneous with Chandra. Visits 01 and 02 should be as close together as possible. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 EM-CYG STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.5 S CD P Comments: Acq image contains useful science, so exp. time is much longer than 0.3s needed for S/N=40. Exp time ok if in eclipse; Exp time also ok if in outburst (not within 30% of CCD saturation). Accurate photometry is required for this proposal. ------------------------------------------------------------------------------------------------------------------------------------ 2 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 38 M NO SPLIT UV-MAM G A Comments: Buffer-time set short in case of outburst; All exposures must be simultaneous with Chandra. ------------------------------------------------------------------------------------------------------------------------------------ 3 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 48 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 4 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 48 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 5 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 48 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 6 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 48 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9078( 7) - 08/13/02 12:59 - [ 5] Visit: 02 Visit Priority: Visit Requirements: PCS MODE F BETWEEN 26-AUG-2002:00:00 AND 01-SEP-2002:15:30 On Hold Comments: Additional Comments: Visit must be simultaneous with Chandra. Visits 01 and 02 should be as close together as possible. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 EM-CYG STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.5 S CD P Comments: Acq image contains useful science, so exp. time is much longer than 0.3s needed for S/N=40. Exp time ok if in eclipse; Exp time also ok if in outburst (not within 30% of CCD saturation). Accurate photometry is required for this proposal. ------------------------------------------------------------------------------------------------------------------------------------ 2 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 38 M NO SPLIT UV-MAM G A Comments: Buffer-time set short in case of outburst; All exposures must be simultaneous with Chandra. ------------------------------------------------------------------------------------------------------------------------------------ 3 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 48 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 4 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 48 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 5 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 48 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 6 EM-CYG STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=100 1 48 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9078( 7) - 08/13/02 12:59 - [ 6] Summary Form for Proposal 9078 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT BUFFER-TIME=100 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F BETWEEN 26-AUG-2002 00 00 AND 01-SEP-2002 15 30 NO SPLIT PCS MODE F BETWEEN 26-AUG-2002 00 00 AND 01-SEP-2002 15 30 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names EM-CYG ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------