! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template
! $Id: 6466,v 5.1 1996/08/19 22:30:54 pepsa Exp $
!
! Refer to the HST Phase II Proposal Instructions to fill this out
!
! Anything after a "!" is ignored, and may be deleted
!
! All keywords with multiple entries are comma delimited except the
! Visit_Requirements and Special_Requirements keywords which can be
! delimited with carriage returns or semi-colons, but not commas
!
! For help call your Program Coordinator: Karla Peterson
! Phone: 410-338-4774 , E-mail: peterson@stsci.edu
!
! This partially completed template was generated from a Phase I proposal.
Proposal_Information ! Section 4
Title: Fundamental properties of a DA-dM
detached eclipsing binary with
Porb=3h37m
Proposal_Category: GO
Scientific_Category: BINARIES AND STAR FORMATION
Cycle: 6
Investigators
PI_name: Dr. Darragh O'Donoghue
PI_Institution: University of Cape Town
CoI_Name: Dr. David Kilkenny
CoI_Institution: South African Astronomical Observatory
Contact: N ! Y or N (designate at most one contact)
CoI_Name: Dr. Chris Koen
CoI_Institution: South African Astronomical Observatory
Contact: N ! Y or N (designate at most one contact)
CoI_Name: Dr. Bob Stobie
CoI_Institution: South African Astronomical Observatory
Contact: N ! Y or N (designate at most one contact)
Abstract: ! Free format text (please update)
EC13471-1258 is a detached DA-dMe eclipsing binary with an
orbital period of 3h37m. It is important because monitoring
its orbital period from eclipse timings, which can be made
with a precision of 5 s or better, will show how rapidly the
binary is losing angular momentum, a key issue in the
evolution of semi-detached binaries. In addition, the
secondary is close to filling its Roche lobe and is
chromospherically active (showing occasional flares). In
contrast to the cataclysmic variables, the secondary of
EC13471-1258 can be easily studied in the optical. Indeed, its
light swamps that of the white dwarf and has prevented the
radial velocity curve of the latter from being measured from
optical data. We therefore propose to use GHRS to measure the
white dwarf's radial velocity curve and effective temperature
from its Ly-Alpha absorption line, yielding vital information
(e.g. the mass ratio and white dwarf's gravitational redshift)
which will permit a solution for the masses, radii and other
key parameters of the component stars. This knowledge will
then permit full exploitation of the insight into semi-
detached binaries which this system will provide. Secondary
goals are: (i) to measure the temperature of the white dwarf
using both the Ly-Alpha profile, and spectrophotometry from
the UV to the optical region; (ii) a search for circumstellar
material using a FOS G160L spectrum.
Questions ! Free format text (please update)
Observing_Description:
We are requesting 3 orbits for this target. The primary
scientific goal is to measure the radial velocity curve of
the white dwarf in EC13471 using the Ly-Alpha absorption
line. The observations should yield an error in the semi-
amplitude no larger than 13 km/s. The Ly-Alpha absorption
line is typically 100 Angstrom wide (FWZI). Assuming typical
values for the masses of the M dwarf (0.3 Msun) and the
white dwarf (0.7 Msun), the white dwarf's orbital velocity
is 120 sin i km/s, corresponding to a periodic shift of semi-
amplitude 0.5 Angstrom (sin i~1) in the wavelength of the Ly
-Alpha line. Thus, the best instrumental configuration is
GHRS with the G140L grating. This provides 286 Angstrom
coverage, sufficient to encompass the line profile. G140L has
a dispersion of 0.57 Angstrom per diode, adequate resolution
to detect the velocity variations. Note that none of the
other GHRS dispersers provides sufficient wavelength
coverage, and the highest resolution FOS grating provides
only 1 Angstrom per diode. Each 96-min HST orbit spans 0.44
binary cycles of EC13471 (Porb=217 min). Therefore, 2
consecutive HST orbits would be required to cover half the
binary orbital period, enabling spectra to be obtained at
orbital phases 0.25 and 0.75, the maximum blue-shift and
red-shift of the white dwarf's radial velocity curve. These
data will be acquired in orbits 2 and 3. RPS2 modelling of
orbits 2 and 3 show that 5m16s and 6m23s are needed for
Guide Star re-acquisition, 5m21s are needed for wavelength
calibration, leaving 43 min available to obtain 4 spectra
with exposure times of 598.4 s in each of orbits 2 and 3.
In order to estimate the exposure time required to measure
the white dwarf's radial velocity semi-amplitude with an error
of 13 km/s or less, the following simulation was performed:
The Ly-Alpha profile from Koester's (private communication)
20000 K, log g=8, DA model atmosphere (this is the best
current estimate for the Teff of the white dwarf) was used.
Eight spectra were generated from this profile and each had
varying amounts of (Poissonian) noise added (no sources of
noise other than photon shot noise are expected to contribute
significantly to the spectra). Finally, the wavelength scale
for each spectrum was shifted from the rest wavelength using
a radial velocity ephemeris with Porb=217 min and K1=120
km/s. The time of the first spectrum was chosen so that it
corresponded to maximum velocity of approach of the white
dwarf. Radial velocities by cross-correlation with the model
Ly-Alpha profile were measured, and fitted with a sinusoidal
curve of the appropriate period. As expected, the uncertainty
in the semi-amplitude of the velocity curve increased with
the amount of noise added. It was found that at least 100
photons per Angstrom in the continuum were needed to measure
the radial velocity curve with the required precision. With
the contribution from the M dwarf subtracted, the apparent B
magnitude (lambda(eff) ~ 4400 Angstrom) of the DA white dwarf
is 15.25, corresponding to 5.3x10^-15 erg/s/cm^2/Angstrom. The
DA, log g = 8 model atmosphere of Wesemael (1981, ApJS, 43,
159, Table 74-5) list fluxes, H(lambda), (for Teff=20000 K):
T=20000 K
Lambda H(lambda)
1150 9.3x10^8
1250 4.0x10^8
4400 2.8x10^7
These values were used, along with the white dwarf's B-band
flux, to estimate the flux at 1150 and 1250 Angstrom. From the
sensitivity of GHRS (scaling the values in Table 8-2 by 50 % for
the Small Science Aperture), the count rates listed below were
obtained. The count rates on both sides of the Ly-Alpha line
are listed because of the steep increase in sensitivity of
the instrument at the shortest wavelengths.
Quantity T=20000 K units
F(lambda)(1150) 1.75x10^-13 erg/s/cm^2/Angstrom
F(lambda)(1250) 7.54x10^-14 erg/s/cm^2/Angstrom
Cnt/s/diode(1150) 0.19
Cnt/s/diode(1250) 0.56
(Note: the number in the last line was incorrect in Phase
I but this has no impact as the penultimate line is the
critical one).
Thus, even on the short wavelength side of Ly-Alpha, in 600 s
of exposure, 120 photons per diode will be accumulated, or 210
photons per Angstrom. This exceeds the minimum count rate in
the simulations required to achieve the scientific goal by a
factor of two. The extra counts will guarantee that the presence
of geocoronal Ly-Alpha (and any residual emission from the M
dwarf in EC13471) will not compromise the scientific goals.
The best estimate for the white dwarf temperature is 20000 K.
However, this is based on optical data and may not be very
accurate. Whereas the Phase I proposal envisaged acquiring
the target in orbit 1 and obtaining 2 science exposures with
HRS G140L, the uncertainty in the temperature, and consequently
the UV flux, has caused a different acquisition strategy to be
proposed: (i) a FOS/BL ACQ/BIN acquisition will be used; (ii) a
FOS G160L spectrum will be obtained; (iii) an offset to the
HRS LSA will be done followed by an HRS ACQ/PEAKUP in the
HRS SSA using side 2 of HRS to guarantee good centering.
Reconfiguring HRS from side 2 to side 1 will follow in the
occultation at the end of the first orbit, ready for HRS side
1 data in orbits 2 and 3. This acquisition strategy has been
chosen because: (i) it is a conservative strategy to guarantee
acquisition; (ii) no useful science can be done with HRS side
2 on its own; (iii) a FOS G160L spectrum will assist in the
secondary scientific goals of white dwarf temperature estimation
and the search for circumstellar material around the white dwarf.
The following count rate estimations were made for the G140L
grating which, with a 780-s exposure, will yield a good quality
spectrum:
Wavelength 2400 2000 1600 1300
Cnt/s/diode 10.9 4.5 5.8 4.1
Real_Time_Justification:
The observations must be scheduled so that the first science
exposure takes place near binary orbital phase 0.25 or 0.75:
the 8 spectra acquired will then coincide with maximum blue
or red shift of the white dwarf. An orbital ephemeris of
sufficient accuracy has been provided. Scheduling the
observations at orbital phases 0.0 or 0.5 will yield a
useless radial velocity curve.
Coordinated observations at the time of those by HST are not
needed. A large database of optical observations are
currently being, or already have been, acquired: (i)
photometry of the eclipses to establish the orbital
ephemeris, detect any period change, and obtain the best
possible measurement of the eclipse to establish the
relationship between the inclination and stellar radii; (ii)
VRI photometry to establish the red dwarf's mean colour,
yielding its Boeshaar spectral type, and thus its luminosity,
radius and mass. In addition, the amplitude and shape of its
ellipsoidal modulation are variable and these are being
monitored; (iii) time-resolved spectra, centred on HAlpha, to
measure the red dwarf's radial velocity curve from the Na D
lines, the TiO bands and the HAlpha chromospheric emission.
These spectra will also yield the spectral classification of
the secondary; (iv) time-resolved spectra, centred on HGamma,
which was intended, but unable, to establish the white
dwarf's radial velocity curve. Instead, in conjunction with
Teff determined by HST, model profiles will be fitted to the
Balmer lines to yield the log g of the white dwarf. The
analysis of these data is in progress.
Calibration_Justification: ! Move appropriate text from Real_Time_Justification
Additional_Comments:
Fixed_Targets ! Section 5.1
Target_Number: 1
Target_Name: EC13471-1258
Alternate_Names: GSC5559:0143
Description: STAR,DA,Interacting Binary,Composite Spectral Type
Position: RA=13H49M51.97S+/-0.03S,! Most common specification format is
DEC=-13D13'38.0"+/-0.4",! RA=0H 0M 0.00S +/- 0S,
PLATE-ID=00OK ! DEC=0D 0' 0.0" +/- 0",
! PLATE-ID=0000
Equinox: J2000
RV_or_Z:
RA_PM: ! Units are seconds of time per year
Dec_PM: ! Units are seconds of arc per year
Epoch:
Annual_Parallax:
Flux: V=14.4+/-0.1 ! Include at least V and B-V
B-V=0.6+/-0.1
U-B=-0.7+/-0.1
Comments: HRS spectra near phases 0.25 and 0.75 of the 217 min
orbital period are needed. HRS spectra at other phases
are much less useful. Best current estimate for white
dwarf Teff is 20000 K but this may be uncertain.
! This is a template for a single visit containing a single exposure
! Repeat exposure and visit blocks as needed
Visits ! Section 6
Visit_Number: 1
Visit_Requirements: PERIOD 0.15075751D AND ZERO-PHASE JD2449779.61758
Visit_Comments:
Exposure_Number: 1 ! Section 6.5
Target_Name: EC13471-1258
Config: FOS/BL
Opmode: ACQ/BINARY
Aperture: 4.3
Sp_Element: MIRROR
Wavelength:
Optional_Parameters:
Number_of_Iterations: 1
Time_Per_Exposure: 2.2S
Special_Requirements: ONBOARD ACQ FOR 2-3
SEQ 1-4 NON-INT
Comments:
Exposure_Number: 2 ! Section 6.5
Target_Name: EC13471-1258
Config: FOS/BL
Opmode: ACCUM
Aperture: 1.0-PAIR
Sp_Element: G160L
Wavelength:
Optional_Parameters: STEP-PATT=SINGLE
Number_of_Iterations: 1
Time_Per_Exposure: 3.5M
Special_Requirements:
Comments:
Exposure_Number: 3
Target_Name: EC13471-1258
Config: HRS
Opmode: ACQ
Aperture: 2.0
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: BRIGHT=RETURN
Number_of_Iterations: 1
Time_Per_Exposure: 9S
Special_Requirements: ONBOARD ACQ FOR 4
Exposure_Number: 4 ! Section 6.5
Target_Name: EC13471-1258
Config: HRS
Opmode: ACQ/PEAKUP
Aperture: 0.25
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: SEARCH-SIZE=5
Number_of_Iterations: 1
Time_Per_Exposure: 25.0S
Special_Requirements: ONBOARD ACQ FOR 5-8
Comments:
Exposure_Number: 5 ! Section 6.5
Target_Name: WAVE
Config: HRS
Opmode: ACCUM
Aperture: SC2
Sp_Element: G140L
Wavelength: 1215
Optional_Parameters:
Number_of_Iterations: 1
Time_Per_Exposure: DEF
Special_Requirements: PHASE 0.145 TO 0.175; SEQ 5-6 NON-INT
Comments:
Exposure_Number: 6 ! Section 6.5
Target_Name: EC13471-1258
Config: HRS
Opmode: ACCUM
Aperture: 0.25
Sp_Element: G140L
Wavelength: 1215
Optional_Parameters:
Number_of_Iterations: 4
Time_Per_Exposure: 598.4S
Special_Requirements:
Comments: 80s free at end of this orbit - please expand last
exposure to fill it
Exposure_Number: 7 ! Section 6.5
Target_Name: WAVE
Config: HRS
Opmode: ACCUM
Aperture: SC2
Sp_Element: G140L
Wavelength: 1215
Optional_Parameters:
Number_of_Iterations: 1
Time_Per_Exposure: DEF
Special_Requirements: SEQ 7-8 NON-INT
! ONBOARD ACQuisition FOR <exp-list>
! MAXimum DURation [<time> | <%>]
! MINimum DURation [<time> | <%>]
! PHASE <number1[0,1]> TO <number2[0,1]>
Comments:
Exposure_Number: 8 ! Section 6.5
Target_Name: EC13471-1258
Config: HRS
Opmode: ACCUM
Aperture: 0.25
Sp_Element: G140L
Wavelength: 1215
Optional_Parameters:
Number_of_Iterations: 4
Time_Per_Exposure: 598.4S
Special_Requirements:
Comments:
Data_Distribution ! Defaults indicated; change if desired
Medium: 6250BPI ! 8MM or 6250BPI or 1600BPI
Blocking_Factor: 10 ! 10 or 1
! Only astronomers with very old 9-
! track tape drives should consider
! a blocking factor of 1
Ship_To: PI_Address ! STSCI or PI_Address or <free-text>
! PI Address from Phase I is:
!
! Department of Astronomy
! Rondebosch
! Cape Town
! 7700
!
!
Ship_Via: UPS ! UPS (2-day) or OVERNIGHT
! Overnight shipping done at PI expense
Recipient_Email: ! Needed if Ship_To: is not PI_Address
! <free-text>
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! Please send a list of your likes and dislikes to your Program Coordinator