6549( 13) - 12/08/97 11:37 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6549 Version: 13 Check-in Date: 08-Dec-1997 11:35:25 1.Proposal Title: Calibration of Nearby Type Ia Supernovae as Standard Candles: NGC 3627 and SN 1989B ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 6 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Allan Sandage OBSERVATORIES OF THE CARNEGIE INSTITUTION OF WASHINGTON CoI: Gustav Tammann University of Basel N CoI: Lukas Labhardt University of Basel N CoI: Duccio Macchetto Space Telescope Science Institute N CoI: Nino Panagia Space Telescope Science Institute N CoI: Abhijit Saha Space Telescope Science Institute Y ------------------------------------------------------------------------------------ 5. Abstract We propose to continue our calibration experiment for M(max) of type Ia supernovae (SNe Ia) by determining Cepheid distances to their parent galaxies. To date we have completed the calibration for 5 SNe Ia, and have found Cepheids in the parent galaxy of a sixth. The resulting absolute magnitudes of SN 1937C (in IC4182 from Cycle 1) and SN 1895B and SN 1972E (both in NGC 5253 from Cycle 3) have been published; those of SN 1960F (in NGC 4496A) and SN 1981B (in NGC4536, both from Cycle 4) are completed and the archive papers will be submitted by Nov. 1, 1995. Data from Cycle 5 for SN 1990N (in NGC 4639) have yielded Cepheids and a preliminary distance from a partial reduction. The experiment is designed to determine the mean absolute magnitude M(max) in B and V of SNe Ia, and how large the dispersion is about this mean. To adequately do this we need the calibration of about 10 such SNe Ia. We request 34 orbits (two orbits each for 12 epochs in F555W and two orbits each for 5 epochs in F814W) for the two-color photometry of the Cepheids in NGC 3627, parent of SN 1989B, a prototype of a type Ia SN. The SN will provide M(max) in UBV and with somewhat lower weight also in JHK. From our previous experience we are convinced that the project is feasible. The galaxy is nearer than NGC 4496A and NGC 4536, yet being dust-rich it is not trivial. ------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 2] Observations Description ------------------------ Observations will be carried out with the WFPC2. Properly time spaced observations spanning a period of about 2 months in the V band (F555W) will be required. A special timing scheme is to be specified, which provides maximum detection completeness and phase coverage for Cepheids with periods from 15 to 70 days, and minimizes aliassing problems with period determination. In particular we request 12 epochs in the V band spaced by varying amounts within an approximately 70 day observing window, to provide optimal phase coverage over the widest possible relevant range of periods. In addition, five I band (F814W) exposures are to be taken at selected epochs to allow computation of , in order to determine the reddening in NGC 3627. Each epoch in F555W (or F814W) is a pair of back to back exposures, utilizing the orbit duration to the fullest, which results in effective exposure times of 4000 s or a little more. The limiting magnitude is thus 28 in V (F555W), and Cepheids with mean magnitudes V < 27.5 can be detected. These numbers are empirical determinations from Cycle 4 data. This makes a total of 12 visits to the galaxy. This is an extremely minimalist approach: reducing the number of epochs from this level or altering the timing scheme significantly will introduce aliassing, and incur the risk of obtaining incorrect periods. Thus there are 12 epochs in V, each 2 orbits long, plus 5 epochs in I that are also each 2 orbits long, making a total of 34 orbits. Adopting (m-M)^0 = 30.2 (i.e. 0.9 mag nearer than NGC 4539 and NGC 4496A) as a working hypothesis for the distance of NGC 3627, we estimate to find approx 50 useful Cepheids with P > 5 days in the field of the WFPC2. Real Time Justification ----------------------- 1) Timing - Observations need to be conducted at the planned time intervals to ensure adequate coverage of the Cepheids' light curves. par 2) Orientation - it is highly desirable (all but absolutely essential) to keep the field orientation the same over most of the observing period. The natural telescope roll angle for a given target changes with observation epoch. Hence the time of year for observations should be chosen to provide the maximum range for off- nominal roll angles so that the field orientation is kept the same over the maximum permissible span of dates. Such accommodation has been possible in previous cycles. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Abi Saha*NOAO*P.O. BOX 26732*950 N. CHERRY AVE*TUCSON, AZ 85726 Ship Via: UPS Email: saha@noao.edu ------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 GALAXY, SPIRAL RA=11H 20M 14.5S +/- 0.5S, DEC = 2000.0 V = 700 V = 27.0 12D 57' 42.0" +/- 5.0" SURF-BKG(V) = 24.0 Comments: Repeated visits to find Cepheids Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1990.0 0 0 0.0 6549( 13) - 12/08/97 11:37 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 293.5D to 294.5D; BETWEEN 08-NOV-97 AND 26-NOV-97 SCHED 100% On Hold Comments: Additional Comments: this 1st epoch visit must happen within specified dates and at specified roll angle for sequence to work Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 6] Visit: 02 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 8.3D TO 8.7D SCHED 100% On Hold Comments: Additional Comments: Same pointing as visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 7] Visit: 03 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 15.4D TO 15.8D SCHED 100% On Hold Comments: Additional Comments: Same position as Visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 8] Visit: 04 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 21.3D TO 21.7D SCHED 100% On Hold Comments: Additional Comments: Same pointing position as Visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 9] Visit: 05 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 26.1D TO 26.5D SCHED 100% On Hold Comments: Additional Comments: Same pointing position as Visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 10] Visit: 06 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 31.4D TO 31.8D SCHED 100% On Hold Comments: Additional Comments: Same pointing as visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 11] Visit: 07 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 34D TO 37D SCHED 100% On Hold Comments: Additional Comments: Same pointing as visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 12] Visit: 08 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 39.3D TO 39.9D SCHED 100% On Hold Comments: Additional Comments: Same pointing as visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 13] Visit: 09 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 45.0D TO 45.6D SCHED 100% On Hold Comments: Additional Comments: Same pointing as visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 14] Visit: 10 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 51.4D TO 52.0D SCHED 100% On Hold Comments: Additional Comments: Same pointing as visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 15] Visit: 11 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 58.3D TO 58.9D SCHED 100% On Hold Comments: Additional Comments: Same pointing as visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3627 WFPC2 IMAGE WFALL-F F814W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 16] Visit: 12 Visit Priority: Visit Requirements: SAME ORIENT as 1; AFTER 1 BY 3.8D TO 4.2D SCHED 100% On Hold Comments: Additional Comments: Same pointing as visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2000 S EXPAND; END ORBIT IX Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3627 WFPC2 IMAGE WFALL-F F555W ATD-GAIN = 7,CR-SPLIT = NO 1 2500 S SAME POS AS 1; EXPAND; IX END ORBIT Comments: Exposure should fill the orbit visibility ------------------------------------------------------------------------------------------------------------------------------------ 6549( 13) - 12/08/97 11:37 - [ 17] Summary Form for Proposal 6549 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN = 7 CR-SPLIT = NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 293.5D to 294.5D; BETWEEN 08-NOV-97 AND 26-NOV-97 SCHED 100% EXPAND; END ORBIT SAME POS AS 1; EXPAND; END ORBIT SAME ORIENT as 1; AFTER 1 BY 8.3D TO 8.7D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 15.4D TO 15.8D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 21.3D TO 21.7D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 26.1D TO 26.5D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 31.4D TO 31.8D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 34D TO 37D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 39.3D TO 39.9D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 45.0D TO 45.6D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 51.4D TO 52.0D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 58.3D TO 58.9D SCHED 100% SAME ORIENT as 1; AFTER 1 BY 3.8D TO 4.2D SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC3627 ------------------------------------------------------------------------------------------------------------------------------------