! Proposal 5894, submission 1
! PI: Bart Wakker
! Received Fri Feb 24 17:11:07 EST 1995
! From: wakker@astro.uiuc.edu
! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template
! $Id: 5894,v 13.1 1995/12/18 16:01:25 pepsa Exp $
!
! Refer to the HST Phase II Proposal Instructions to fill this out
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Proposal_Information ! Section 4
Title: The hot gaseous halo of the Large
Magellanic Cloud
Proposal_Category: GO
Scientific_Category: Interstellar Medium
Cycle: 5
Investigators
PI_name: Bart Wakker
PI_Institution: University of Wisconsin
CoI_Name: You-Hua Chu
CoI_Institution: University of Illinois
Contact: Y ! Y or N (designate at most one contact)
CoI_Name: Sean Points
CoI_Institution: University of Illinois
Contact: ! Y or N (designate at most one contact)
CoI_Name: Dominik Bomans
CoI_Institution: Universitaet Bonn
Contact: ! Y or N (designate at most one contact)
Abstract: ! Free format text (please update)
We request observing time with the GHRS on HST to help
determine the structure and physical parameters of the hot
gaseous halo of the Large Magellanic Cloud (LMC). The SMC and
LMC are the only galaxies in which such a determination can be
done in detail, as confusion along the line-of-sight is much
less than in the Milky Way. They are also the only other
galaxies near enough to be able to obtain high-resolution
spectra of individual stars. Gas at 10^5 K can be detected in
the C IV LambdaLambda1548, 1550 UV absorption lines. From such
data it is also possible to obtain information on velocities
and the depth structure of the halo. Previous work with IUE
has shown that 10^5 K gas is present around very hot stars,
in some H II regions, in superbubbles and in supergiant
shells. However, with IUE it is not possible to determine the
existence of a continuous halo surrounding the LMC, since the
required probes are too faint. We request observing time for
eight probes selected to take into account the distribution
10^6 K gas mapped by ROSAT, while avoiding areas known to
produce 10^5 K gas locally. We request a total of ten orbits
and plan to use the G160M grating of GHRS, which allows us to
reach a signal-to-noise ratio of 20 or higher. This
corresponds to a detection limit for N(C IV) of 2x10^13 ,
within the range of values detected in the Milky Way.
Questions ! Free format text (please update)
Observing_Description:
We plan to observe six stars in X-ray dim areas of the LMC,
and two in X-ray bright areas. These targets have been
selected avoid bright H Alpha emission and supergiant
shells. For each target we intend to use the G160M grating
over the wavelength range 1533-1566 Angstrom. Standard comb-
addition and FP-split will be used to reduce the effects of
fixed pattern noise. The spectra will be sampled with 2 sub-
steps per diode (Step Pattern 4). We will use the large
aperture during our observations. The small loss of
resolution relative to the use of the small aperture does not
outweigh the loss of a factor two in light. Exposure times
are estimated using the description in the post-COSTAR HST
GHRS Instrument Handbook (v5.0, May 1994). To determine the
stellar fluxes, we constructed a table of unreddened flux
ratios f(1550)/f(5500) for several different stellar types,
and we determined the reddening for each target. To
determine flux ratios, we used IUE Newsletter No. 22, and
measured reddened flux ratios for stars of spectral types
between O9 and B1, of all luminosity classes. These values
were dereddened using the value of E(B-V) given in the
Newsletter and the UV extinction model described in the GHRS
handbook (Seaton 1979, MNRAS 187, 73p). Since stars of
spectral type B0 and especially B1 also have a broad stellar
absorption, we used half of the continuum flux to obtain the
flux ratios to make sure that we do not underestimate the
flux at the wavelength of interest. The reddening of each
target was found by subtracting the intrinsic color given by
Fitzgerald (1970, AA 4, 234) from the value of \bmv\ given by
Rousseau et al. We used E(B-V)=0.12 for the one target with
unknown color (Sk-70 69). Given the flux ratio, reddening
and visual magnitude, we find the flux at 1550 Angstrom. The
table below gives the result. The count rate then follows
from the sensitivities in the Handbook. Column 7 gives the
resulting integration time to reach a S/N of 20, the minimum
value we need to obtain results that can be unambiguously
interpreted. The acquisition overhead is substantial (12
minutes for the guide star, 11 minutes for the target), and
only 36 out of each 59 minutes in an orbit are available for
the actual integration. In one orbit we can reach the desired
S/N only for Sk-69 59 and Sk-69 110. For Sk-68 28 and Sk-67
46, the missing time is only 4 and 6 minutes, and the
resulting S/N of 19 will still be sufficient. For Sk-67 45
and Sk-69 68 on the other hand, the noise increases by 25%.
Scheduling three consecutive orbits, we can combine the two
longest integrations with the third and fourth longest and we
can achieve the desired S/N for all four stars in two groups
of three consecutive orbits. We would then acquire one of the
objects midway through the second orbit, and we would need
two 6-minute re-acquisitions. The total acquisition overhead
in the three orbits would be 2*(23+6) or 58 minutes, leaving
118 minutes of integration time, just what we need. We
therefore request one orbit each for four probes, and two
combinations of three orbits for the other four probes, for a
grand total of 10 orbits. We note that the right ascension
and declination of the LMC place it within the Continuous
Viewing Zone (CVZ) of HST four times each year. We may use
the CVZ to increase the efficiency of our program from 40% to
91%. The sum of the required integration times is 363 minutes.
The total required overhead for each star is 26 minutes (12 for
guide-star acquisition, 11 for target acquisition, 3 for internal
wavelength calibration) or a total of 208 minutes. Within the
CVZ, the total required time of 571 minutes can fit in 6
orbits.
In the case that our program is scheduled during CVZ time,
we can adjust the description of the observation accordingly.
Name & type & V &E(B-V)& f_1550 &ct/s/d &T(20)&SN(36)
(1) & (2) & (3) & (4) & (5) & (6) &(7) &(8)
Priority-1 probes
Sk-67 46 & B1 & 12.34 & 0.12 & 3.5x10^-13 & 0.173 & 40 & 19
Sk-67 76 & B0 & 12.42 & 0.17 & 3.1x10^-13 & 0.151 & 46 & 18
Sk-69 59 & B0 & 12.13 & 0.18 & 3.8x10^-13 & 0.183 & 38 & 20
Sk-69 110 & B1 & 11.65 & 0.18 & 4.3x10^-13 & 0.210 & 33 & 21
Sk-70 96 & B1 & 12.67 & 0.12 & 3.1x10^-13 & 0.152 & 45 & 18
Priority-2 probes (only if CVZ time scheduled)
Sk-67 28 & B1 & 12.4 & 0.12 & 3.4x10^-13 & 0.164 & 42 & 19
Sk-67 45 & B1 & 12.97 & 0.09 & 2.3x10^-13 & 0.112 & 62 & 15
Sk-69 68 & B0.5 & 12.6 & 0.21 & 2.5x10^-13 & 0.122 & 57 & 16
Real_Time_Justification:
Calibration_Justification: ! Move appropriate text from Real_Time_Justification
Additional_Comments:
If scheduling permits we may increase the efficiency of our
program from 40% to 64%.
IUE observing time has been awarded to re-observe the three
stars for which we found tentative non-detections. These
stars have the following magnitudes and spectral types: 10.6
(a composite spectrum of main type B2Ia), 11.2 (type O9Ib)
and 12.4 (type O7Ib). The IUE proposal also includes the
brightest two stars known that are not obviously connected
with regions containing hot material. These are of magnitude
11.5 (type B0) and 11.9 (type O9). For all five probes we
calculated that at least two IUE shifts (16 hours) are needed
to obtain a useful spectrum. A total of 10 US1 shifts in the
18th episode were awarded to us. Observing time has been
awarded to start a ROSAT HRI survey of the LMC, with Chu as
P.I. The HRI observations are more sensitive to point
sources. The results will help the removal of point sources
from the PSPC images, and improve the diffuse X-ray
measurements.
Fixed_Targets ! Section 5.1
Target_Number: 1
Target_Name: Sk-67.46
Alternate_Names: GSC9161-00960
Description: EXT-STAR, B0-B2 III-I, EXT-MEDIUM, Coronal Gas
! 3/29/95 - Added temporary RA and DEC uncertainties TO ALL 5 TARGETS; deleted Plate IDs
Position: RA = 05H 07M 1.63S +/- 0.03S,
DEC = -67D 37' 29.7" +/- 0.2",
PLATE-ID = 06B0
Equinox: J2000
RV_or_Z:
RA_PM: ! Units are seconds of time per year
Dec_PM: ! Units are seconds of arc per year
Epoch: 1979.193
Annual_Parallax:
Flux: TYPE=B1I, V=12.34, B-V=-0.06, E(B-V)=0.12, F(1550)=3.5E-13
Comments: Coordinates are from GSC
Fixed_Targets ! Section 5.1
Target_Number: 2
Target_Name: Sk-67.76
Alternate_Names: GSC8890-00822
Description: EXT-STAR, B0-B2 III-I, EXT-MEDIUM, Coronal Gas
Position: RA = 05H 20M 5.81S +/- 0.03S,
DEC = -67D 21' 8.9" +/- 0.2",
PLATE-ID = 06B0
Equinox: J2000
RV_or_Z:
RA_PM: ! Units are seconds of time per year
Dec_PM: ! Units are seconds of arc per year
Epoch: 1979.193
Annual_Parallax:
Flux: TYPE=B0I, V=12.42, B-V=-0.13, E(B-V)=0.17, F(1550)=3.1E-13
Comments: Coordinates are from GSC
Fixed_Targets ! Section 5.1
Target_Number: 3
Target_Name: Sk-69.59
Alternate_Names: HDE268960,GSC9161-01130
Description: EXT-STAR, B0-B2 III-I, EXT-MEDIUM, Coronal Gas
Position: RA = 05H 03M 12.79S +/- 0.04S,
DEC = -69D 01' 37.2" +/- 0.2",
PLATE-ID = 05ZW
Equinox: J2000
RV_or_Z:
RA_PM: ! Units are seconds of time per year
Dec_PM: ! Units are seconds of arc per year
Epoch: 1987.064
Annual_Parallax:
Flux: TYPE=B0I, V=12.13, B-V=-0.12, E(B-V)=0.10, F(1550)=6.8E-13
Comments: Coordinates are from GSC
Fixed_Targets ! Section 5.1
Target_Number: 4
Target_Name: Sk-69.110
Alternate_Names: HDE269399, GSC9166-00238
Description: EXT-STAR, B0-B2 III-I, EXT-MEDIUM, Coronal Gas
Position: RA = 05H 20M 33.85S +/- 0.04S,
DEC = -69D 32' 35.5" +/- 0.2",
PLATE-ID = 05ZW
Equinox: J2000
RV_or_Z:
RA_PM: ! Units are seconds of time per year
Dec_PM: ! Units are seconds of arc per year
Epoch: 1987.064
Annual_Parallax:
Flux: TYPE=B1, V=11.65, B-V=0.08, E(B-V)=0.16, F(1550)=5.0E-13
Comments: Coordinates are from GSC
Fixed_Targets ! Section 5.1
Target_Number: 5
Target_Name: Sk-70.96
Alternate_Names: GSC9166-00139
Description: EXT-STAR, B0-B2 III-I, EXT-MEDIUM, Coronal Gas
Position: RA = 05H 29M 23.90S +/- 0.04S,
DEC = -70D 14' 0.9" +/- 0.2",
PLATE-ID = 05ZW
Equinox: J2000
RV_or_Z:
RA_PM: ! Units are seconds of time per year
Dec_PM: ! Units are seconds of arc per year
Epoch: 1987.064
Annual_Parallax:
Flux: TYPE=B1Ib, V=12.67, E(B-V)=0.10, F(1550)=3.6E-13
COMMENTS: Coordinates are from GSC
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Sk-67.46
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Visits ! Section 6
Visit_Number: 1
Visit_Requirements: ! Section 7.1
! CVZ
Exposure_Number: 1
Target_Name: Sk-67.46
Config: HRS
Opmode: ACQ
Aperture: 2.0
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: MAP=DEF, SEARCH-SIZE=3
Number_of_Iterations: 1
Time_Per_Exposure: 1.8S
Special_Requirements: ONBOARD ACQ FOR 2
Comments: STEP-TIME=0.2S
! template kept just in case we decide to change our minds
! Exposure_Number: 2
! Target_Name: WAVE
! Config: HRS
! Opmode: ACCUM
! Aperture: SC2
! Sp_Element: G160M
! Wavelength: 1539
! Optional_Parameters: FP-SPLIT=STD, STEP-PATT=4
!Number_of_Iterations: 1
! Time_Per_Exposure: DEF
!Special_Requirements:
Exposure_Number: 2
Target_Name: Sk-67.46
Config: HRS
Opmode: ACCUM
Aperture: 2.0
Sp_Element: G160M
Wavelength: 1539
Optional_Parameters: STEP-PATT=4, COMB=FOUR, FP-SPLIT=STD, DOPPLER=ON
Number_of_Iterations: 5
Time_Per_Exposure: 403.2s
Special_Requirements: ! Section 7.2
Comments: STEP-TIME=0.2S; Changes required if scheduled in CVZ
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Sk-67.76
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Visits ! Section 6
Visit_Number: 2
Visit_Requirements: ! Section 7.1
! CVZ
Exposure_Number: 1
Target_Name: Sk-67.76
Config: HRS
Opmode: ACQ
Aperture: 2.0
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: MAP=DEF, SEARCH-SIZE=3
Number_of_Iterations: 1
Time_Per_Exposure: 1.8S
Special_Requirements: ONBOARD ACQ FOR 2
Comments: STEP-TIME=0.2S
! template kept just in case we decide to change our minds
! Exposure_Number: 2
! Target_Name: WAVE
! Config: HRS
! Opmode: ACCUM
! Aperture: SC2
! Sp_Element: G160M
! Wavelength: 1539
! Optional_Parameters: FP-SPLIT=STD STEP-PATT=4
!Number_of_Iterations: 1
! Time_Per_Exposure: DEF
!Special_Requirements:
Exposure_Number: 2
Target_Name: Sk-67.76
Config: HRS
Opmode: ACCUM
Aperture: 2.0
Sp_Element: G160M
Wavelength: 1539
Optional_Parameters: STEP-PATT=4, COMB=FOUR, FP-SPLIT=STD, DOPPLER=ON
Number_of_Iterations: 5
Time_Per_Exposure: 403.2s
Special_Requirements: ! Section 7.2
Comments: STEP-TIME=0.2S; Changes required if scheduled in CVZ
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Sk-69.59
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Visits ! Section 6
Visit_Number: 3
Visit_Requirements: ! Section 7.1
! CVZ
Exposure_Number: 1
Target_Name: Sk-69.59
Config: HRS
Opmode: ACQ
Aperture: 2.0
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: MAP=DEF, SEARCH-SIZE=3
Number_of_Iterations: 1
Time_Per_Exposure: 1.8S
Special_Requirements: ONBOARD ACQ FOR 2
Comments: STEP-TIME=0.2S
! template kept just in case we decide to change our minds
! Exposure_Number: 2
! Target_Name: WAVE
! Config: HRS
! Opmode: ACCUM
! Aperture: SC2
! Sp_Element: G160M
! Wavelength: 1539
! Optional_Parameters: FP-SPLIT=STD STEP-PATT=4
!Number_of_Iterations: 1
! Time_Per_Exposure: DEF
!Special_Requirements:
Exposure_Number: 2
Target_Name: Sk-69.59
Config: HRS
Opmode: ACCUM
Aperture: 2.0
Sp_Element: G160M
Wavelength: 1539
Optional_Parameters: STEP-PATT=4, COMB=FOUR, FP-SPLIT=STD, DOPPLER=ON
Number_of_Iterations: 5
Time_Per_Exposure: 403.2s
Special_Requirements: ! Section 7.2
Comments: STEP-TIME=0.2S; Changes required if scheduled in CVZ
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Sk-69.110
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Visits ! Section 6
Visit_Number: 4
Visit_Requirements: ! Section 7.1
! CVZ
Exposure_Number: 1
Target_Name: Sk-69.110
Config: HRS
Opmode: ACQ
Aperture: 2.0
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: MAP=DEF, SEARCH-SIZE=3
Number_of_Iterations: 1
Time_Per_Exposure: 1.8S
Special_Requirements: ONBOARD ACQ FOR 2
Comments: STEP-TIME=0.2S
! template kept just in case we decide to change our minds
! Exposure_Number: 2
! Target_Name: WAVE
! Config: HRS
! Opmode: ACCUM
! Aperture: SC2
! Sp_Element: G160M
! Wavelength: 1539
! Optional_Parameters: FP-SPLIT=STD STEP-PATT=4
!Number_of_Iterations: 1
! Time_Per_Exposure: DEF
!Special_Requirements:
Exposure_Number: 2
Target_Name: Sk-69.110
Config: HRS
Opmode: ACCUM
Aperture: 2.0
Sp_Element: G160M
Wavelength: 1539
Optional_Parameters: STEP-PATT=4, COMB=FOUR, FP-SPLIT=STD, DOPPLER=ON
Number_of_Iterations: 5
Time_Per_Exposure: 403.2s
Special_Requirements: ! Section 7.2
Comments: STEP-TIME=0.2S; Changes required if scheduled in CVZ
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! Sk-70.96
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Visits ! Section 6
Visit_Number: 5
Visit_Requirements: ! Section 7.1
! CVZ
Exposure_Number: 1
Target_Name: Sk-70.96
Config: HRS
Opmode: ACQ
Aperture: 2.0
Sp_Element: MIRROR-N2
Wavelength:
Optional_Parameters: MAP=DEF, SEARCH-SIZE=3
Number_of_Iterations: 1
Time_Per_Exposure: 1.8S
Special_Requirements: ONBOARD ACQ FOR 2
Comments: STEP-TIME=0.2S
! template kept just in case we decide to change our minds
! Exposure_Number: 2
! Target_Name: WAVE
! Config: HRS
! Opmode: ACCUM
! Aperture: SC2
! Sp_Element: G160M
! Wavelength: 1539
! Optional_Parameters: FP-SPLIT=STD STEP-PATT=4
!Number_of_Iterations: 1
! Time_Per_Exposure: DEF
!Special_Requirements:
Exposure_Number: 2
Target_Name: Sk-70.96
Config: HRS
Opmode: ACCUM
Aperture: 2.0
Sp_Element: G160M
Wavelength: 1539
Optional_Parameters: STEP-PATT=4, COMB=FOUR, FP-SPLIT=STD, DOPPLER=ON
Number_of_Iterations: 5
Time_Per_Exposure: 403.2s
Special_Requirements: ! Section 7.2
Comments: STEP-TIME=0.2S; Changes required if scheduled in CVZ
Data_Distribution ! Defaults indicated; change if desired
Medium: 8MM ! 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: Dr. Bart Wakker
University of Wisconsin
Astronomy Department! STSCI or PI_Address or <free-text>
475 N Charter St ! PI Address from Phase I is:
WI 53706 !
!
!
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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