========================================================================
*TITLE_1! WR 22, the most massive star known in a binary system: assessing
TITLE_2! its wind characteristics through phase resolved spectroscopy.
========================================================================
*OM_CONTACT! J.-M. Vreux
*OM_CONTACT_EMAIL! Panoptix@astro.ulg.ac.be
========================================================================
*SCIENCE_OBJECTIVES!
WR 22 is an eclipsing binary (Gosset et al, 1991) of
spectral type WN7+abs + O in the Carina OB1 association. The photometric
eclipse corresponds to the occultation of the secondary by the WR primary and
its dense wind around the periastron passage. Recently, Rauw et al. (1996a)
used an extensive set of high resolution spectra of WR 22 to investigate the
orbit of this eccentric binary (e = 0.56 , P = 80.3 days). From the radial
velocities of the secondary's absorption lines, Rauw et al. derive a minimum
mass of the WN7+abs primary of 72 solar masses, making it the most massive
star known so far in a binary system. This high mass together with a hydrogen
mass-fraction of +/- 0.4 determined from the visible spectrum (Crowther et
al., 1995a) suggest that WR 22 is at the very beginning of its Wolf-Rayet
evolution and is probably still a core hydrogen burning object which has
evolved from a progenitor of at least 90-110 solar masses (Rauw et al.,
1996a). EINSTEIN observations of WR 22 obtained around the upper conjunction,
i.e. near apastron when the O star is in front, indicate a bright X-ray source,
whereas the system appears much fainter around the periastron passage, when the
WR primary with its denser wind is in front (Pollock, 1987). These observations
are in line with the picture of a colliding winds binary system where a copious
X-ray emission is generated near the interface between the winds of the two
stars. The X-ray modulation observed in the case of WR22 results from the
variable column density along the line of sight. Observations of this system
with a better S/N ratio and a better phase coverage (ideally with a roughly
7-days interval between two successive pointings over about half an orbital
cycle starting on apastron) will allow to use the X-ray emission as a probe to
study the properties of the winds, taking advantage of the varying separation
between the two stars. Furthermore these observations will put constraints on
the mass loss rate of the WN7 + abs star and on the chemical composition of
its wind.

This proposal is part of a comprehensive program aimed at the study of stars in
different evolutionary stages.

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*TOTAL_NO_POINTINGS! 7 ;one, but 7 times, at different orbital phases.
*TOTAL_TIME! 70
*PRIME_INSTRUMENT! EPIC
SPECIAL! Time constrained observations
==========================================================================
*TECHNICAL_INFO!

There are four visibility windows for WR 22 over the first two years of
XMM operations. Each window covers about 40 spacecraft orbits i.e. 80
days. During a visibility window, the duration of visibility is 145 ksec
per orbit.
The first observation should be centered on the apastron passage of
WR 22 i.e. Ti = H.J.D. 2451452.782 + n * 80.325 days and the last one
on periastron i.e. 40.15 days later.
The other observations should be distributed as evenly as possible on
the orbital cycle i.e. separated by about 6.7 days.
A margin error of 2 days on these separations is acceptable, provided that
this "error" is not introduced systematically with the same sign. For the
observation around periastron however the error should ideally be less than
half a day.
For the August, 2 1999 launch date and a 48 hours orbit, the best suited
windows are the first one and the fourth one. During the first observing
window the apastron passage occurs during s/c orbit 71 (= first observation)
and the periastron passage occurs during s/c orbit 92 (= last observation).
During the fourth window, apastron occurs during s/c orbit 354 and peri-
astron during orbit 375. Observations during one of the two other visi-
bility windows are also possible, but they require a revision of the
observing strategy.
The X-ray luminosity derived from EINSTEIN observations is 8e32 erg s-1.
We estimated the count rates using the PIMMS software. For a column density
of 5e20 cm-2, the count rates are 0.57 cts s-1 for EPIC and 0.041 cts s-1
for the RGS. Given the optical brightness of WR 22, the thick filter is
required for the EPIC observations (TBC).
We suggest to use the pn EPIC instrument in full frame imaging mode with
a TBD value of w. For the EPIC MOS detectors the partial window imaging
mode is probably required to avoid pile-up at least at those orbital
phases when the maximum luminosity is expected (TBC).

Data are requested on the whole FOV in particular to study the possible
diffuse background emission from the Carina nebula.

===========================================================================
*TARGET_NAME_01! WR 22
TARGET_ALT_NAME_01! HD 92740
*TARGET_RA_01! 10 41 18
*TARGET_DEC_01! -59 40 37
*TARGET_EXPOSURE_01! 10 ; ksec (1 of 7; see technical information)
*TARGET_PRIORITY_01! A
TARGET_MODE_EPIC_MOS1_01! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_MOS2_01! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_PN_01! full field imaging (TBC)
TARGET_FILTER_EPIC_MOS1_01! [Thick]
TARGET_FILTER_EPIC_MOS2_01! [Thick]
TARGET_FILTER_EPIC_PN_01! [Thick]
TARGET_MODE_RGS1_01!
TARGET_MODE_RGS2_01!
TARGET_MODE_OM_01! ;U filter with obscuration bar or safety (TBD)
TARGET_FILTER_OM_01! [Bar, Closed] ;U filter with obscuration bar or safety (TBD)
TARGET_OBS_DATE_01! [constrained]
TARGET_COMMENT_01! time constrained observations
The first observation should be centered on the apastron passage of
WR 22 i.e. Ti = H.J.D. 2451452.782 + n * 80.325 days and the last one
on periastron i.e. 40.15 days later.
The other observations should be distributed as evenly as possible on
the orbital cycle i.e. separated by about 6.7 days.
A margin error of 2 days on these separations is acceptable, provided this
"error" is not introduced systematically with the same sign and provided
the first and last pointings are done at the requested dates as precisely
as possible (i.e. better than 0.5 d).
Data are requested on the whole FOV in particular to study the possible
diffuse background emission from the Carina nebula.
===========================================================================
===========================================================================
*TARGET_NAME_02! WR 22
TARGET_ALT_NAME_02! HD 92740
*TARGET_RA_02! 10 41 18
*TARGET_DEC_02! -59 40 37
*TARGET_EXPOSURE_02! 10 ; ksec (1 of 7; see technical information)
*TARGET_PRIORITY_02! A
TARGET_MODE_EPIC_MOS1_02! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_MOS2_02! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_PN_02! full field imaging (TBC)
TARGET_FILTER_EPIC_MOS1_02! [Thick]
TARGET_FILTER_EPIC_MOS2_02! [Thick]
TARGET_FILTER_EPIC_PN_02! [Thick]
TARGET_MODE_RGS1_02!
TARGET_MODE_RGS2_02!
TARGET_MODE_OM_02! ; U filter with obscuration bar or safety (TBD)
TARGET_FILTER_OM_02! [Bar, Closed] ; U filter with obscuration bar or safety (TBD)
TARGET_OBS_DATE_02! [constrained]
TARGET_COMMENT_02! time constrained observations
The first observation should be centered on the apastron passage of
WR 22 i.e. Ti = H.J.D. 2451452.782 + n * 80.325 days and the last one
on periastron i.e. 40.15 days later.
The other observations should be distributed as evenly as possible on
the orbital cycle i.e. separated by about 6.7 days.
A margin error of 2 days on these separations is acceptable, provided this
"error" is not introduced systematically with the same sign and provided
the first and last pointings are done at the requested dates as precisely
as possible (i.e. better than 0.5 d).
Data are requested on the whole FOV in particular to study the possible
diffuse background emission from the Carina nebula.
===========================================================================
===========================================================================
*TARGET_NAME_03! WR 22
TARGET_ALT_NAME_03! HD 92740
*TARGET_RA_03! 10 41 18
*TARGET_DEC_03! -59 40 37
*TARGET_EXPOSURE_03! 10 ; ksec (1 of 7; see technical information)
*TARGET_PRIORITY_03! A
TARGET_MODE_EPIC_MOS1_03! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_MOS2_03! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_PN_03! full field imaging (TBC)
TARGET_FILTER_EPIC_MOS1_03! [Thick]
TARGET_FILTER_EPIC_MOS2_03! [Thick]
TARGET_FILTER_EPIC_PN_03! [Thick]
TARGET_MODE_RGS1_03!
TARGET_MODE_RGS2_03!
TARGET_MODE_OM_03! ;U filter with obscuration bar or safety (TBD)
TARGET_FILTER_OM_03! [Bar, Closed] ;U filter with obscuration bar or safety (TBD)
TARGET_OBS_DATE_03! [constrained]
TARGET_COMMENT_03! time constrained observations
The first observation should be centered on the apastron passage of
WR 22 i.e. Ti = H.J.D. 2451452.782 + n * 80.325 days and the last one
on periastron i.e. 40.15 days later.
The other observations should be distributed as evenly as possible on
the orbital cycle i.e. separated by about 6.7 days.
A margin error of 2 days on these separations is acceptable, provided this
"error" is not introduced systematically with the same sign and provided
the first and last pointings are done at the requested dates as precisely
as possible (i.e. better than 0.5 d).
Data are requested on the whole FOV in particular to study the possible
diffuse background emission from the Carina nebula.
===========================================================================
===========================================================================
*TARGET_NAME_04! WR 22
TARGET_ALT_NAME_04! HD 92740
*TARGET_RA_04! 10 41 18
*TARGET_DEC_04! -59 40 37
*TARGET_EXPOSURE_04! 10 ; ksec (1 of 7; see technical information)
*TARGET_PRIORITY_04! A
TARGET_MODE_EPIC_MOS1_04! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_MOS2_04! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_PN_04! full field imaging (TBC)
TARGET_FILTER_EPIC_MOS1_04! [Thick]
TARGET_FILTER_EPIC_MOS2_04! [Thick]
TARGET_FILTER_EPIC_PN_04! [Thick]
TARGET_MODE_RGS1_04!
TARGET_MODE_RGS2_04!
TARGET_MODE_OM_04! ;U filter with obscuration bar or safety (TBD)
TARGET_FILTER_OM_04! [Bar, Closed] ;U filter with obscuration bar or safety (TBD)
TARGET_OBS_DATE_04! [constrained]
TARGET_COMMENT_04! time constrained observations
The first observation should be centered on the apastron passage of
WR 22 i.e. Ti = H.J.D. 2451452.782 + n * 80.325 days and the last one
on periastron i.e. 40.15 days later.
The other observations should be distributed as evenly as possible on
the orbital cycle i.e. separated by about 6.7 days.
A margin error of 2 days on these separations is acceptable, provided this
"error" is not introduced systematically with the same sign and provided
the first and last pointings are done at the requested dates as precisely
as possible (i.e. better than 0.5 d).
Data are requested on the whole FOV in particular to study the possible
diffuse background emission from the Carina nebula.
===========================================================================
===========================================================================
*TARGET_NAME_05! WR 22
TARGET_ALT_NAME_05! HD 92740
*TARGET_RA_05! 10 41 18
*TARGET_DEC_05! -59 40 37
*TARGET_EXPOSURE_05! 10 ; ksec (1 of 7; see technical information)
*TARGET_PRIORITY_05! A
TARGET_MODE_EPIC_MOS1_05! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_MOS2_05! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_PN_05! full field imaging (TBC)
TARGET_FILTER_EPIC_MOS1_05! [Thick]
TARGET_FILTER_EPIC_MOS2_05! [Thick]
TARGET_FILTER_EPIC_PN_05! [Thick]
TARGET_MODE_RGS1_05!
TARGET_MODE_RGS2_05!
TARGET_MODE_OM_05! ;U filter with obscuration bar or safety (TBD)
TARGET_FILTER_OM_05! [Bar, Closed] ;U filter with obscuration bar or safety (TBD)
TARGET_OBS_DATE_05! [constrained]
TARGET_COMMENT_05! time constrained observations
The first observation should be centered on the apastron passage of
WR 22 i.e. Ti = H.J.D. 2451452.782 + n * 80.325 days and the last one
on periastron i.e. 40.15 days later.
The other observations should be distributed as evenly as possible on
the orbital cycle i.e. separated by about 6.7 days.
A margin error of 2 days on these separations is acceptable, provided this
"error" is not introduced systematically with the same sign and provided
the first and last pointings are done at the requested dates as precisely
as possible (i.e. better than 0.5 d).
Data are requested on the whole FOV in particular to study the possible
diffuse background emission from the Carina nebula.
===========================================================================
===========================================================================
*TARGET_NAME_06! WR 22
TARGET_ALT_NAME_06! HD 92740
*TARGET_RA_06! 10 41 18
*TARGET_DEC_06! -59 40 37
*TARGET_EXPOSURE_06! 10 ; ksec (1 of 7; see technical information)
*TARGET_PRIORITY_06! A
TARGET_MODE_EPIC_MOS1_06! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_MOS2_06! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_PN_06! full field imaging (TBC)
TARGET_FILTER_EPIC_MOS1_06! [Thick]
TARGET_FILTER_EPIC_MOS2_06! [Thick]
TARGET_FILTER_EPIC_PN_06! [Thick]
TARGET_MODE_RGS1_06!
TARGET_MODE_RGS2_06!
TARGET_MODE_OM_06! ;U filter with obscuration bar or safety (TBD)
TARGET_FILTER_OM_06! [Bar, Closed] ;U filter with obscuration bar or safety (TBD)
TARGET_OBS_DATE_06! [constrained]
TARGET_COMMENT_06! time constrained observations
The first observation should be centered on the apastron passage of
WR 22 i.e. Ti = H.J.D. 2451452.782 + n * 80.325 days and the last one
on periastron i.e. 40.15 days later.
The other observations should be distributed as evenly as possible on
the orbital cycle i.e. separated by about 6.7 days.
A margin error of 2 days on these separations is acceptable, provided this
"error" is not introduced systematically with the same sign and provided
the first and last pointings are done at the requested dates as precisely
as possible (i.e. better than 0.5 d).
Data are requested on the whole FOV in particular to study the possible
diffuse background emission from the Carina nebula.
===========================================================================
===========================================================================
*TARGET_NAME_07! WR 22
TARGET_ALT_NAME_07! HD 92740
*TARGET_RA_07! 10 41 18
*TARGET_DEC_07! -59 40 37
*TARGET_EXPOSURE_07! 10 ; ksec (1 of 7; see technical information)
*TARGET_PRIORITY_07! A
TARGET_MODE_EPIC_MOS1_07! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_MOS2_07! [Prime Partial Window] ;partial window imaging (TBC)
TARGET_MODE_EPIC_PN_07! full field imaging (TBC)
TARGET_FILTER_EPIC_MOS1_07! [Thick]
TARGET_FILTER_EPIC_MOS2_07! [Thick]
TARGET_FILTER_EPIC_PN_07! [Thick]
TARGET_MODE_RGS1_07!
TARGET_MODE_RGS2_07!
TARGET_MODE_OM_07! ;U filter with obscuration bar or safety (TBD)
TARGET_FILTER_OM_07! [Bar, Closed] ;U filter with obscuration bar or safety (TBD)
TARGET_OBS_DATE_07! [constrained]
TARGET_COMMENT_07! time constrained observations
The first observation should be centered on the apastron passage of
WR 22 i.e. Ti = H.J.D. 2451452.782 + n * 80.325 days and the last one
on periastron i.e. 40.15 days later.
The other observations should be distributed as evenly as possible on
the orbital cycle i.e. separated by about 6.7 days.
A margin error of 2 days on these separations is acceptable, provided this
"error" is not introduced systematically with the same sign and provided
the first and last pointings are done at the requested dates as precisely
as possible (i.e. better than 0.5 d).
Data are requested on the whole FOV in particular to study the possible
diffuse background emission from the Carina nebula.
===========================================================================