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! | PED OUTPUT PRODUCT |
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! /spectre/data1/aroman/proposals/6010.prop
! Generated by PREPROCESSOR, version 6.3g
! Date: Tue Jul 23 15:13:10 EDT 1996
Proposal_Information
Title: Lyman Alpha Observations of High Radial Velocity Stars
Proposal_Category: GO
Scientific_Category: Cool Stars
Cycle: 5
Investigators
PI_Name: Dr. Jay Bookbinder
PI_Institution: Eureka Scientific
CoI_Name: Dr. Ken Gayley
CoI_Institution: Bartol Reseach Institute
Contact:
CoI_Name: Dr. Wayne Landsman
CoI_Institution:
Contact:
CoI_Name: Dr. James E. Neff
CoI_Institution: Pennsylvania State University
Contact:
CoI_Name: Dr. David Soderblom
CoI_Institution: STScI
Contact:
Abstract:
The H I Lyman-Alpha line is probably the most important cooling channel for transition regions in late-type stars, and it directly or indirectly influences the formation of numerous other UV lines, yet it is the least studied line in the far UV. Accurate intrinsic stellar line profiles would be of immense use both as a diagnostic of stellar transition regions and for studies of the local interstellar medium (LISM), including determining the D/H ratio. An additional use is to determine the intrinsic stellar Ly-Alpha flux from low-dispersion observations. However, the absorption of most of the stellar flux by interstellar material and the high geocoronal background in IUE has seriously complicated the analysis of this line. It is possible to circumvent, to a large extent, the influence of the LISM on the intrinsic stellar profile by observing stars with radial velocities high enough to Doppler shift a significant fraction of the emission line out of the LISM absorption core. Motivated by the success of our previous IUE and HST programs that focussed on giant stars, we have selected 7 dwarf stars covering a range of spectral types, with radial velocities from 150 to over 300 km/sec for detailed studies of their Ly-Alpha profiles.
Questions
Observing_Description:
Target Selection
----------------
We propose to obtain medium dispersion Ly-Alpha line profiles from dwarf stars covering a wide range of spectral types (from late-F to early-M are included) -- see Table I. Individual target selection for this program is based primarily on the radial velocity of the star, since it is the ISM absorption due to hydrogen that is the primary uncertainty and limitation in obtaining accurate intrinsic stellar Ly-Alpha fluxes and line profiles. The stellar radial velocities listed in Table I are relative to the predicted ISM flow velocity (Crutcher 1982). A radial velocity of 150 km/sec corresponds (at Ly-Alpha) to 0.6 Angstrom. Since the stellar line width for typical dwarf stars is on the order of 1 Angstrom (see Figure 1; Landsman and Simon (1993), it is clear that for the selected targets the ISM absorption is effectively removed from at least one side of the line core. The increased flux made available by avoiding the ISM absorption aids in making these moderate dispersion observations feasible. Our previous IUE programs (CSJJB and LGKJB) on giant stars ( e.g., Delta Lep) showed that acceptable results can be obtained even when the radial velocity is as low as 99 km/sec (see Figure 2) the star, since the total ISM absorption depends upon the column density towards the target, though for some of targets, ( e.g., HD 14439) the stellar radial velocity sufficiently high to shift the entire Ly-Alpha profile off of the ISM absorption. Tertiary selection criteria were for stars that do not lie near the ecliptic, and stars that lie in directions known to have a low column density of intervening hydrogen (e.g., the IIIrd galactic quadrant). The brightest stars meeting these criteria were selected.
Instrument Configuration
------------------------
We will employ the G160M grating and the Small Science Aperture of the GHRS for the Ly-Alpha observations. This configuration ensures that the geocoronal emission will only affect about 1 Angstrom of the spectrum, and that the Ly-Alpha features of our target stars will be well in the wings of the geocoronal feature. In addition to the Lyman-Alpha observation, we will obtain a short observation of the Mg II lines using the G270M grating (centered at 2800 Angstrom) and the LSA. The Mg II profiles will permit us to measure independently the characteristics of the LISM in each line of sight, as well as aid in modeling the atmospheres.
Exposure Time Estimates
-----------------------
The exposure times for moderate resolution (R = 12,500 at Ly-Alpha) GHRS spectra have estimated on the basis of low-S/N, low- and high-dispersion IUE spectrum of the Ly-Alpha line for a variety of dwarf stars of similar spectral types (Landsman and Simon 1993). The time estimates assumed the use of the small science aperture, and the sensitivities quoted (GHRS Handbook V. 5.0, May 1994) for the G160M grating (neither scattered light nor dark counts are important in this experiment). These observations will be of sufficient duration to produce a spectrum with a S/N > 15 at the half-power point, which is adequate for modeling. The typical exposure time is about 100 minutes. The Mg II lines (at R=20,000) can be obtained 15 minute exposures (S/N ~ 15 near the half-power point), based on IUE spectra and the GHRS handbook sensitivities (5.0, May 1994) of the G270M grating using the large science aperture.
Other Considerations
--------------------
We are necessarily requesting that all of the stars in the target list be observed in the current cycle, given the large number of orbits requested. This list represents a complete sample of the high velocity dwarf stars brighter than m_v=10 meeting our selection criteria. The outlook of this program is long-term, and stars not observed in this round will be requested in future cycles. Our list, from highest to lowest, is: HD6755, HD6833, GL630.1, HD191408, HD14439, and HD167740. For studies of the LISM, GL278C and GL630.1 are most important, as they accurately reflect the Pop I stars of the solar neighborhood. Unfortunately, they also require the longest observations.
Real_Time_Justification:
Two of the targets (Gl278C, Gl630.1) in our program are binary systems with a very high radial velocity swing that is used to remove the Ly-Alpha emission from the ISM absorption. For these two systems, we will require time observations to ensure that the observations are made at orbital quadratures.
Calibration_Justification:
None.
Additional_Comments:
Fixed_Targets
Target_Number: 1
Target_Name: HD6755
Alternate_Names:
Description: STAR,F3-F9,
Position: RA=01H 9M 43.068S +/- 0.1S,DEC=61D 32' 50.2" +/- 1.0"
Equinox: J2000
RV_or_Z: V = -320
RA_PM: 0.0889
Dec_PM: 0.07
Epoch: J2000
Annual_Parallax: 0.0
Flux:
V = 7.73+/-0.5
B-V = 0.72
Comments: Coordinates from Hipparchos catalog
Target_Number: 2
Target_Name: HD6833
Alternate_Names:
Description: STAR,K III-I,
Position: RA=01H 9M 52.261S +/- 0.1S,DEC=54D 44' 20" +/- 1"
Equinox: J2000
RV_or_Z: V = -245
RA_PM: 0.002
Dec_PM: 0.03
Epoch: J2000
Annual_Parallax: 0.0
Flux:
V = 7.1+/-0.5
B-V = 1.17
Comments: Coordinates from Hipparchos catalog
Solar_System_Targets
Generic_Targets
Scan_Data
Visits
Visit_Number: 01
Visit_Requirements:
On_Hold_Comments:
Visit_Comments:
Exposure_Number: 10
Target_Name: HD6833
Config: HRS
Opmode: ACQ
Aperture: 2.0
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: BRIGHT=RETURN,SEARCH-SIZE=5
Number_of_Iterations: 1
Time_Per_Exposure: 5 S
Special_Requirements:
ONBOARD ACQ FOR 15-30
Comments: STEP-TIME = 0.2s
Exposure_Number: 15
Target_Name: WAVE
Config: HRS
Opmode: ACCUM
Aperture: SC2
Sp_Element: G160M
Wavelength: 1205-1243
Optional_Parameters:
Number_of_Iterations: 1
Time_Per_Exposure: DEF
Special_Requirements:
Comments:
Exposure_Number: 20
Target_Name: HD6833
Config: HRS
Opmode: ACCUM
Aperture: 2.0
Sp_Element: G270M
Wavelength: 2780-2820
Optional_Parameters: STEP-PATT=5
Number_of_Iterations: 3
Time_Per_Exposure: 244.8 S
Special_Requirements:
Comments: Check on S/N for use of FP-SPLIT
Exposure_Number: 30
Target_Name: HD6833
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: 7.5 S
Special_Requirements:
ONBOARD ACQ FOR 40-50
Comments: STEP-TIME = 0.3s
Exposure_Number: 40
Target_Name: HD6833
Config: HRS
Opmode: ACCUM
Aperture: 0.25
Sp_Element: G160M
Wavelength: 1205-1243
Optional_Parameters: STEP-PATT=5
Number_of_Iterations: 11
Time_Per_Exposure: 299.2 S
Special_Requirements:
SHADOW
Comments:
Exposure_Number: 45
Target_Name: WAVE
Config: HRS
Opmode: ACCUM
Aperture: SC2
Sp_Element: G160M
Wavelength: 1205-1243
Optional_Parameters:
Number_of_Iterations: 1
Time_Per_Exposure: DEF
Special_Requirements:
Comments:
Exposure_Number: 50
Target_Name: HD6833
Config: HRS
Opmode: ACCUM
Aperture: 0.25
Sp_Element: G160M
Wavelength: 1205-1243
Optional_Parameters: STEP-PATT=5
Number_of_Iterations: 10
Time_Per_Exposure: 299.2 S
Special_Requirements:
SHADOW
Comments:
Visit_Number: 02
Visit_Requirements:
On_Hold_Comments:
Visit_Comments:
Exposure_Number: 10
Target_Name: HD6755
Config: HRS
Opmode: ACQ
Aperture: 2.0
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: BRIGHT=RETURN,SEARCH-SIZE=5
Number_of_Iterations: 1
Time_Per_Exposure: 10 S
Special_Requirements:
ONBOARD ACQ FOR 15-30
Comments: STEP-TIME = 0.4s
Exposure_Number: 15
Target_Name: WAVE
Config: HRS
Opmode: ACCUM
Aperture: SC2
Sp_Element: G160M
Wavelength: 1205-1243
Optional_Parameters: STEP-PATT=4
Number_of_Iterations: 1
Time_Per_Exposure: DEF
Special_Requirements:
Comments:
Exposure_Number: 20
Target_Name: HD6755
Config: HRS
Opmode: ACCUM
Aperture: 2.0
Sp_Element: G270M
Wavelength: 2780-2820
Optional_Parameters: STEP-PATT=5
Number_of_Iterations: 3
Time_Per_Exposure: 244.8 S
Special_Requirements:
Comments: Check on S/N for use of FP-SPLIT
Exposure_Number: 30
Target_Name: HD6755
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: 12.5 S
Special_Requirements:
ONBOARD ACQ FOR 40-50
Comments: STEP-TIME = 0.5s
Exposure_Number: 40
Target_Name: HD6755
Config: HRS
Opmode: ACCUM
Aperture: 0.25
Sp_Element: G160M
Wavelength: 1205-1243
Optional_Parameters: STEP-PATT=5
Number_of_Iterations: 11
Time_Per_Exposure: 299.2 S
Special_Requirements:
SHADOW
Comments:
Exposure_Number: 45
Target_Name: WAVE
Config: HRS
Opmode: ACCUM
Aperture: SC2
Sp_Element: G160M
Wavelength: 1205-1243
Optional_Parameters: STEP-PATT=4
Number_of_Iterations: 1
Time_Per_Exposure: DEF
Special_Requirements:
Comments:
Exposure_Number: 50
Target_Name: HD6755
Config: HRS
Opmode: ACCUM
Aperture: 0.25
Sp_Element: G160M
Wavelength: 1205-1243
Optional_Parameters: STEP-PATT=5
Number_of_Iterations: 10
Time_Per_Exposure: 299.2 S
Special_Requirements:
SHADOW
Comments:
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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