! Proposal 6688, submission 1
! PI: Thomas Marsh
! Received Mon Feb 12 14:48:12 EST 1996
! From: trm@astro.soton.ac.uk
! +====================+
! | PED OUTPUT PRODUCT |
! +====================+
!
! /pool7/trm/hst_phaseII/6688.prop
! Generated by PREPROCESSOR, version 6.0e
! Date: Mon Feb 12 18:23:29 GMT 1996
Proposal_Information
Title: The accretion disk and white dwarf in the dwarf nova HS1804+6753
Proposal_Category: GO
Scientific_Category: BINARIES AND STAR FORMATION
Cycle: 6
Investigators
PI_Name: Thomas Marsh
PI_Institution: Southampton University
CoI_Name: Keith Horne
CoI_Institution: St. Andrews University
Contact:
Abstract:
We will take high-speed UV spectroscopy of the dwarf nova
HS1804+6753 to find and measure the role of supersonic turbulence
in its outer accretion disk. With HST observations of the
eclipsing dwarf nova OY Car we have discovered a sensitive
probe of physical conditions in its accretion disk. This is
based upon model atmosphere fits to strong veiling of the
white dwarf by a mass of FeII lines at ultraviolet
wavelengths. Suprisingly we found supersonic microturblence at
Mach ~ 6 in the absorbing gas. While this would normally be
expected to dissipate in shocks, recent theoretical work
suggests that the disk can become strongly magnetic in which
case it is the Alfven rather than sound speed which is
relevant. The result needs to be confirmed on other targets.
Other systems are also needed to study vertical stratification
in the disk as a single object only gives us one line of
sight. Eclipsing dwarf novae are of particular interest as the
eclipse allows the component spectra to be separated and
because the line-of-sight is likely to pass through the disk.
Therefore we propose to observe a newly discovered and
relatively bright eclipsing dwarf nova named HS1804+6753. At 5
hours HS1804+6753 has a much longer period than any other suitable
target and there are signs that it has a particularly high
inclination and therefore it will provide an extreme test of
our model.
Questions
Observing_Description:
The absorption curtain occurs over a wide range of
wavelengths from Ly-alpha up to around 3000 Angstrom, and
therefore as we have used on OY Car we will use the G160L (1140 to
2510 Angstrom) which has the important benefit of providing
zeroth order light weighted to longer and less obscured
wavelengths. We need high time resolution, because the
ingress and egress of the white dwarf take only 40 seconds.
To fully resolve this we need to observe with the FOS RAPID mode
with READ-TIME=4. At the same time continuous coverage of
the eclipses is vital as dwarf novae do not repeat precisely from
cycle to cycle. This requires long exposures and therefore the
low telemetry rate. Therefore we have chosen SUB-STEP=2;
the mild under-sampling incurred with the use of SUB-STEP=2
is of no significance to our program. The orbital period of HS 1804+6753
is 5.038 hours and so to obtain continuous coverage of entire orbits
we need CVZ scheduling. After a 4-stage peak-up into the 1.0-PAIR-A
aperture we can observe for 11.75 hour within the 8 orbit uninterrupted
period. This covers more than 2 whole orbits of HS1804+6753 and therefore
guarantees coverage of at least 2 eclipses without a phase constraint. If
possible, the exposure should be started 30-60 minutes before an eclipse
to give coverage of 3 eclipses. However we have not required this in order
not to constrain the program any more than already implied by the CVZ
restriction. HS1804+6753 is variable so we will use ACQ/PEAK.
We have lengthened the acquisition exposures to allow for the eclipses
(1.7 mags deep from the usual magnitude around 15), and we have also used
a 4-stage peak-up so that even if variability during an eclipse causes
the wrong peak to be selected, the star will not be too far from the centre
of the aperture. However, if possible, the acquisition exposures should avoid
phases within +/-0.08 of the eclipses; again we have not enforced this for
flexibility.
Real_Time_Justification:
Continuous coverage is most important scientifically as pieces of
different eclipses cannot be spliced together. Therefore we have
requested CVZ scheduling.
Calibration_Justification:
Additional_Comments:
Fixed_Targets
Target_Number: 1
Target_Name: HS1804+6753
Alternate_Names: GSC4429.01070
Description: STAR,DWARF NOVA,INTERACTING BINARY,
Position: RA=18H 04M 14.11S +/- 0.4",DEC=67D 54' 12.2" +/- 0.4",PLATE-ID=00T0
Equinox: J2000
RV_or_Z:
RA_PM: 0.0
Dec_PM: 0.0
Epoch:
Annual_Parallax: 0.0
Flux:
V = 14.0+/-1.0
B-V = 0.2+/-0.2
E(B-V) = 0.0+/-0.05
U-B = -1.0+/-0.3
Comments: Eclipsing binary, rapidly variable.
Solar_System_Targets
Generic_Targets
Scan_Data
Visits
Visit_Number: 01
Visit_Requirements:
CVZ;
PERIOD 0.2099372667D AND ZERO-PHASE JD2448398.45250
On_Hold_Comments:
Visit_Comments:
Exposure_Number: 10
Target_Name: HS1804+6753
Config: FOS/BL
Opmode: ACQ/PEAK
Aperture: 4.3
Sp_Element: MIRROR
Wavelength:
Optional_Parameters: SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3,SCAN-STEP-Y=1.23
Number_of_Iterations: 1
Time_Per_Exposure: 5S
Special_Requirements:
ONBOARD ACQ FOR 20;
PHASE 0.09 TO 0.60
Comments: HS1804+6753 shows eclipses on the HELIOCENTRIC ephemeris
HJD = 2448398.45250 + 0.2099372667 E. Acquisition preferable in phase range
0.08 to 0.92.
Exposure_Number: 20
Target_Name: HS1804+6753
Config: FOS/BL
Opmode: ACQ/PEAK
Aperture: 1.0-PAIR-A
Sp_Element: MIRROR
Wavelength:
Optional_Parameters: SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2,SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61
Number_of_Iterations: 1
Time_Per_Exposure: 6S
Special_Requirements:
ONBOARD ACQ FOR 30
Comments: HS1804+6753 shows eclipses on the HELIOCENTRIC ephemeris
HJD = 2448398.45250 + 0.2099372667 E. Acquisition preferable in phase range
0.08 to 0.92.
Exposure_Number: 30
Target_Name: HS1804+6753
Config: FOS/BL
Opmode: ACQ/PEAK
Aperture: 0.5-PAIR-A
Sp_Element: MIRROR
Wavelength:
Optional_Parameters: SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29,SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3
Number_of_Iterations: 1
Time_Per_Exposure: 6S
Special_Requirements:
ONBOARD ACQ FOR 40
Comments: HS1804+6753 shows eclipses on the HELIOCENTRIC ephemeris
HJD = 2448398.45250 + 0.2099372667 E. Acquisition preferable in phase range
0.08 to 0.92.
Exposure_Number: 40
Target_Name: HS1804+6753
Config: FOS/BL
Opmode: ACQ/PEAK
Aperture: 0.25-PAIR-A
Sp_Element: MIRROR
Wavelength:
Optional_Parameters: SCAN-STEP-X=0.11,SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4,SCAN-STEP-Y=0.11
Number_of_Iterations: 1
Time_Per_Exposure: 6S
Special_Requirements:
ONBOARD ACQ FOR 100
Comments: HS1804+6753 shows eclipses on the HELIOCENTRIC ephemeris
HJD = 2448398.45250 + 0.2099372667 E. Acquisition preferable in phase range
0.08 to 0.92.
Exposure_Number: 100
Target_Name: HS1804+6753
Config: FOS/BL
Opmode: RAPID
Aperture: 1.0-PAIR-A
Sp_Element: G160L
Wavelength:
Optional_Parameters: READ-TIME=4,SUB-STEP=2,STEP-PATT=SINGLE
Number_of_Iterations: 1
Time_Per_Exposure: 10.0H
Special_Requirements:
NO SPLIT
Comments: READ-TIME must be kept at 4 seconds; SUB-STEP=2 for low
telemetry.
Exposure_Number: 200
Target_Name: HS1804+6753
Config: FOS/BL
Opmode: RAPID
Aperture: 1.0-PAIR-A
Sp_Element: G160L
Wavelength:
Optional_Parameters: READ-TIME=4,SUB-STEP=2,STEP-PATT=SINGLE
Number_of_Iterations: 1
Time_Per_Exposure: 1.57H
Special_Requirements:
NO SPLIT
Comments: READ-TIME must be kept at 4 seconds; SUB-STEP=2 for low
telemetry.
Data_Distribution ! Defaults indicated; change if desired
Medium: 8MM
Blocking_Factor: 10
Ship_To: PI_Address
Ship_Via: UPS
Recipient_Email:
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