6721( 5) - 05/03/96 14:52 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6721 Version: 5 Check-in Date: 03-May-1996 14:49:49 1.Proposal Title: Ultra--Rapid UV Continuum Variability as a Probe of AGN Physics ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle AGN GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: William F. Welsh Keele University CoI: Kirk Korista University of Kentucky N CoI: Anuradha Koratkar Space Telescope Science Institute N CoI: Bradley Peterson Ohio State University N ------------------------------------------------------------------------------------ 6. Abstract We will use the FOS in RAPID mode with the G160L and PRISM dispersers to obtain high --speed (90s time resolution), exactly simultaneous UV through optical spectrophotometry of the rapid variations in the Seyfert galaxy NGC7469. Our goals are to determine the time delay between the UV & optical continua, to detect a high- -frequency cutoff in the power spectrum, to determine the wavelength dependency of the rapid variations, and to determine if the spectrum of the flickering is timescale--dependent. AGN continuum models make different predictions about the correlation between the UV & optical variations and therefore are easily distinguished, provided the variations are resolved. Previous observations of Seyferts show variability on very short timescales (<<1 day), but their time resolution was too poor to fully resolve the fluctuations and place tight limits on the UV--optical delay. Because our time resolution will extend beyond the limit of the fastest theoretically expected variations, we will be able to place extremely powerful constraints on the physical conditions in the AGN continuum--producing region. We will coordinate our observations with the AGN Watch IUE+XTE Campaign already scheduled to observe NGC7469, giving simultaneous X-ray coverage. This will allow us to extend our UV--optical analysis into the hard X-rays. We will have two orders of magnitude finer time resolution than IUE. ------------------------------------------------------------------------------------ 6721( 5) - 05/03/96 14:52 - [ 2] Observations Description ------------------------ Observing strategy: We will use the FOS/BLUE camera and the G160L grating in RAPID mode with READ-TIME=45 seconds. RAPID mode gives us maximum flexibility and control over the time sampling, and since the FOS has practically zero readout noise it is to our advantage to go to as high a sampling rate as feasible. The G160L grating is the primary choice since it covers the widest UV spectral range (1140-2500 Ang) and simultaneously measures the optical U band (Eracleous, et al. 1994). We will also use the PRISM with the FOS/RED camera, which gives the largest simultaneous UV through optical coverage of any HST configuration (~2000-8000Ang). We anticipate devoting ~85% of the allocated orbits to the G160L disperser and the remainder to the PRISM. Because of the overlap between the PRISM and G160L observations, we effectively have coverage from ~1200 to 8000Ang. We note that the FOS/RD+PRISM configuration offers a far wider wavelength range than could be obtained with STIS. We will use the 1.0" upper square aperture, a compromise between keeping maximum flux reliability and minimizing contamination from the host galaxy (and to avoid the ``CIV'' blemish). As recommendeed by the TAC, we will use a very careful target acquisition strategy (a 4-stage critical peak-up, ACQ/PEAK sequence A+B2+P1+P3). We will switch from the FOS BLUE to RED cameras during earth occultation to minimize the dead time. NGC 7469 is a bright, variable Seyfert galaxy with V=13-14 mag and F_Lambda(1330 Ang)= 3-6 E-14 erg/s/cm^2/Ang. With the FOS/BL G160L configuration, at 1350 Ang we expect to get >50 counts/diode/exposure. Binning 10 diodes (40 pix) together into 70 Ang sections gives 20 independent windows with a typical S/N ratio of ~23 per exposure. The PRISM has a higher efficiency still. The nature of this experiment plus the large wavelength coverage allows us to comfortably bin larger sections together, should the S/N need more boosting. Real Time Justification ----------------------- The scheduling of observations is time critical --- for optimum science we must be as simultaneous as possible with XTE. There is a very wide window within which to schedule: 1996 June 10 through 1996 July 15 (*FINAL TIMES NEED TO BE CONFIRMED*). To maximize the science value of the data, the observations should occur about 2/3 of the way through the Campaign, approximately 1996 July 3-5. The TAC stressed this point - the correlation between the X-ray, UV, and optical is a critical part of this proposal. Only if there is significant overlap between the XTE and HST observastions is this possible. The XTE 45min observing window must not be in anti-phase with the HST observing window. These observations will be part of a huge multi-observatory, multi-wavelength NGC 7469 Campaign. The Campaign has been awarded 700ksec of XTE priority time, 720 hours of IUE high priority time, and 180 hours of lower priority time. Extensive ground based observations are planned. The Campaign will span 75 days, with 30 days of continuous IUE coverage. Calibration Justification ------------------------- Additional Comments ------------------- We ask that the schedulers please coordinate the observations with XTE, as this is far too difficult to do as a GO. The XTE proposal P.I. is Paul Nandra, and the schedulers are Sandy Antunes (301) 286 6419 and Robin Corbet (301) 286 2851. The email address for XTE schedulers is: xteplan@athena.gsfc.nasa.gov The XTE schedulers are fully aware of this HST program. For maximum efficiency, the schedulers may want to consider having this proposal execute immediately after proposal id#6747 (P.I., Kriss) which is on exactly the same object - the active nucleus of NGC 7469. ------------------------------------------------------------------------------------ 6721( 5) - 05/03/96 14:52 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Dr. William Welsh*Department of Physics*Keele University*Keele, Staffordshire*ST5 5BG*UK Ship Via: UPS Email: wfw@astro.keele.ac.uk , ------------------------------------------------------------------------------------ 6721( 5) - 05/03/96 14:52 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7469 GALAXY,SEYFERT,NUCLEUS RA=23H 03M 15.63S +/- 0.2", 2000 Z=0.016 V = 13.5 DEC=08D 52' 25.69" +/- 0.2", B-V = -1 PLATE-ID=028Z U-B = -0.7 F(1330)=4.5+/-1.5e-14 Comments: variable source: V can vary by 1 mag; minimum F(1260)=4E-14 6721( 5) - 05/03/96 14:52 - [ 5] Visit: 01 Visit Requirements: SCHED 100% BETWEEN 15-JUN-1996 AND 10-JUL-1996 On Hold Comments: Additional Comments: This proposal must be very carefully scheduled to be as simultaneous as possible with XTE. XTE scheduling information is given in the phase II text, and the schedulers should contact with the P.I. for last-minute adjustments. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7469 FOS/BL ACQ/PEA 4.3 MIRROR SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3, 1 4.0S ONBOARD ACQ FOR 2-6 K SCAN-STEP-Y=1.23 SEQUENCE 1-3 NON-INT Comments: 1st of 4-stage critical peak up; pattern "A"; nb: the SEQ 1-3 NON-INT is to avoid the RPS2 bug ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7469 FOS/BL ACQ/PEA 1.0-PAI MIRROR SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2, 1 4.0S ONBOARD ACQ FOR 3-6 K R-A SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 Comments: 2nd of 4-stage critical peak up; pattern "B2" ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC7469 FOS/BL ACQ/PEA 0.25-PA MIRROR SEARCH-SIZE-X=5,SEARCH-SIZE-Y=5, 1 5.0S ONBOARD ACQ FOR 4-6 K IR-A SCAN-STEP-X=0.17,SCAN-STEP-Y=0.17 Comments: 3rd of 4-stage critical peak up; pattern "P1" ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC7469 FOS/BL ACQ/PEA 0.25-PA MIRROR SEARCH-SIZE-X=5,SEARCH-SIZE-Y=5, 1 5.0S ONBOARD ACQ FOR 5-6 K IR-A SCAN-STEP-X=0.052, SCAN-STEP-Y=0.052 Comments: 4th of 4-stage critical peak up; pattern "P3"; ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC7469 FOS/BL RAPID 1.0-PAI G160L READ-TIME=45,STEP-PATT=SINGLE 1 15930S R-A Comments: These orbits MUST be coordinated with XTE ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC7469 FOS/RD RAPID 1.0-PAI PRISM READ-TIME=45,STEP-PATT=SINGLE 1 2160S NO SPLIT R-A Comments: switch to red camera during earth occultation ------------------------------------------------------------------------------------------------------------------------------------ 6721( 5) - 05/03/96 14:52 - [ 6] Summary Form for Proposal 6721 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-Y=1.23 SCAN-STEP-Y=0.61 SCAN-STEP-Y=0.17 SCAN-STEP-Y=0.052 STEP-PATT=SINGLE READ-TIME=45 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category AGN ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SCHED 100% BETWEEN 15-JUN-1996 AND 10-JUL-1996 ONBOARD ACQ FOR 2-6 SEQUENCE 1-3 NON-INT ONBOARD ACQ FOR 3-6 ONBOARD ACQ FOR 4-6 ONBOARD ACQ FOR 5-6 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G160L PRISM ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC7469 ------------------------------------------------------------------------------------------------------------------------------------