! 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 ! MAXimum DURation [