The shaping of planetary and protoplanetary nebulae (PNe and PPNe) is probably the most exciting yet least understood problem in the late evolution of ~1-8 solar mass stars. An increasing number of astronomers believe that fast jet-like winds ejected in the PPN phase are responsible for carving out the diverse shapes in the dense envelopes of the Asymptotic Giant Branch (AGB) stars. To date, the properties of these post-AGB jets have not been characterized and, indeed, their launching/collimation mechanism is still subject to controversial debate. This is due to the lack of the direct observations probing the spatio-kinematic structure of post-AGB winds in the stellar vicinity (~10e16cm), which is only possible with HST+STIS. Recently, STIS observations have allowed us for the first time the DIRECT study of the structure and kinematics of the elusive post-AGB winds in one PPN, He3-1475 (Sanchez Contreras & Sahai 2001). Those winds have been discovered through H-alpha blue-shifted absorption features in the inner 0.3"-0.7" of the nebula. These STIS observations have revealed an ultra-fast collimated outflow relatively unaffected by the interaction with the AGB wind that is totally hidden in ground-based spectroscopic observations and HST images. The discovery of the pristine ultra-fast (~2300km/s) jet in He3-1475 is the first observational confirmation of the presence of collimated outflows as close as ~10e16cm from the central star. Most importantly, the spatio-kinematic structure of the ultra-fast jet clearly rules out hydrodynamical collimation alone and favors magnetic wind collimation. Therefore, STIS observations provide a unique method of probing the structure, kinematics, and collimation mechanism of the elusive post-AGB winds. We now propose similar observations for a sample of bipolar PPNe with ongoing post-AGB ejections in order to investigate the frequency of jets like those in He3-1475 in other PPNe and elucidate their nature and collimation mechanism. The observational characterization of these winds is indispensable for understanding this violent and important phase of post-AGB evolution.

We will perform optical long-slit spectroscopy with medium spectral resolution in 8 bi- and multi-polar PPNe. These objects show intense Halpha emission near the center (within 1") with broad wings and P Cygni profiles indicating presently active pAGB ejections. 52×0.2 slits will be used for all the sources except for IRAS 08005. For IRAS 08005, the brightest and most compact nebula in our sample, a 52×0.1 slit is more appropriate. The large brightness of this source compensates the extra time required for narrower slits. The number and position of the slits have been carefully chosen according to the extent and peculiarities for each source (see below). For each object, we will observe the Halpha line emission using several slits parallel to the nebular axis in order to properly study the spatio-kinematic structure of the fast wind. Since the slits cover a relatively wide region along the equator and the whole nebulae in the axial direction, these observations will provide a very complete view of the properties of a) the pristine jets in the innermost regions and b) the outer shock-excited gas (e.g. the emission knots). In addition, for the brightest sources (M1-92, IRAS 08005, and IRAS 20462) we will obtain Hbeta spectra for the central slit, i.e. passing through the central star. This would be done without any extra orbit cost due to the large intensities of these objects and would allow us to constrain the physical conditions of pAGB winds. Gratings. We will use the first-order grating G750M centered at 6768A to obtain Halpha spectra with spectral resolution ~70 km/s, which is appropriate to study the expansive kinematics of the inner nebular regions. For the brightest objects we will use the first-order grating G430L to obtain Hbeta spectra. Given the spectral range covered by the selected gratings we will be able to simultaneously obtain (in a single exposure), spectra of many other important nebular lines (e.g. the [N II] 6548,6583 A and [S II] 6716,6731 A doublets), which are necessary to diagnose the excitation and physical conditions in the gas. Exposure time and orbit time determination. Exposure times have been estimated using the STIS Exposure Time Calculator, given the brightness of the sources in the continuum and line wings (we are interested in observing absorption features that may go below the continuum). The brightness surface in the region of interest for each source has been estimated combining the information on the continuum and line wing intensities given by spectroscopic ground-based observations and HST images. In all cases, we expect most the line and continuum emission to arise in a small, central region ( 0.3"×0.3"). We have checked that this procedure gives good intensity estimates when applied to He 3-1475 (for which ground-based and STIS spectra exist). The requested time will provide a S/N> 5 in the continuum around Halpha and Hbeta for regions at < 0.5" from the central star. CCD exposures are split into two separated images (CR-SPLIT=2 or 3 depending on the source) in order to allow removal of cosmic rays. Also, for the central slit, the position of the source relative to the CCD will be displaced by a non-integer number of pixels along the slit in each individual exposure in order to remove the effects produced by undersampling of compact sources on the rectified spectra. The spatial undersampling of the central star is apparent in the STIS spectra of He 3-1475 (analysed by us), which shows a remarkable flux undulation towards the position of the (unresolved) central star. We expect similar effects in these observations for most tragets (all except for IRAS 22036 and Roberts 22) unless we perform spatial dithering as proposed. We have checked that the intense peak of the line emission does not saturate the STIS/CCD in any of the cases. We have also estimated that the spread of the core emisson (due to the wings of the PSF) is negligible in regions where we intend to study pAGB ejections. For most of the objects we have chosen a 0.2 slit, therefore we only need target-acquisition to center the target in the scientific aperture. For IRAS 08005, which will be observed with the 0.1-wide slit, additional peakup exposures are required. In all cases we have checked that ACQ and ACQ/PEAK exposures can be done in a time shorter than the maximum allowed. The total number of orbits has been calculated considering the scientific exposure times, and time for acquisition (of the guide stars and the scientific targets), peakups (for IRAS 08005), and other overheads (time to move the slits and grating wheel, additional wavecal every 40min, time for dumping the buffer and return mechanism to normal for CVZs, etc). For Roberts 22, for which CVZ observations are requested, the total number of CVZ opportunities is 3 and the maximum duration (in days) of any single CVZ opportunity is 4. We have checked using the visit planner that the desired orientation of the slit is possible within the CVZ. ISM AND CIRCUMSTELLAR MATTER 12 false 0.0 0.0 false false false false false false SUPPORTED STAR POST-AGB STAR CIRCUMSTELLAR MATTER EMISSION LINE NEBULA EJECTA S8Q4014967 J2000 17 03 9.7000 -47 00 28.00 J2000 R=12.2 STAR CIRCUMSTELLAR MATTER EJECTA EMISSION LINE NEBULA POST-AGB STAR N277049412 J2000 19 32 55.0000 +14 13 35.00 J2000 R=13.3 STAR CIRCUMSTELLAR MATTER EJECTA EMISSION LINE NEBULA POST-AGB STAR N2TO020842 J2000 21 29 58.4800 +51 04 0.30 J2000 STAR CIRCUMSTELLAR MATTER EJECTA EMISSION LINE NEBULA POST-AGB STAR N2UE106560 00 00 0.0000 +00 00 0.00 J2000 STAR CIRCUMSTELLAR MATTER EJECTA EMISSION LINE NEBULA POST-AGB STAR ROBERTS22 S47O000556 00 00 0.0000 +00 00 0.00 J2000 STAR POST-AGB STAR CIRCUMSTELLAR MATTER EJECTA EMISSION LINE NEBULA N35N001016 J2000 20 48 16.6400 +34 27 24.30 J2000 STAR CIRCUMSTELLAR MATTER EJECTA EMISSION LINE NEBULA POST-AGB STAR M1-92 N2FF000650 00 00 0.0000 +00 00 0.00 J2000 STAR POST-AGB STAR CIRCUMSTELLAR MATTER EMISSION LINE NEBULA EJECTA S5S1001027 J2000 08 02 40.8000 -24 04 44.00 J2000 CALIBRATION APERTURE LOCATION N2UE106559 1433-0422251 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION APERTURE LOCATION S47O016447 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION APERTURE LOCATION N2FF000649 1195-0380996 J2000 00 00 0.0000 +00 00 0.00 J2000 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G430L 4300 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G430L 4300 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G430L 4300 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G750M 6768 POS-TARG DITHER 0.225 2 sub-pixel dither for the central slit LINE false false 2 90.0 STIS-ALONG-SLIT 1 false POS-TARG MOSAIC DITHER 0.2 2 slits, step=0.2 arcsec - to be placed adjacent to the central slit with NO DITHER. STIS-ALONG-SLIT false false 2 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 2 false POS-TARG MOSAIC DITHER 0.2 Pattern for 5 0.2 slits accross the srcs with no DITHER - for iras22036 and Rob22 STIS-ALONG-SLIT false false 5 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 3 false POS-TARG MOSAIC DITHER 0.1 2 slits separated by 0.1arcsec to be placed adjacent to the central slit - pattern for iras08005, which will be observed with the 52x0.1 slit. STIS-ALONG-SLIT false false 2 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 4 false POS-TARG DITHER 0.225 2 sub-pixel dither for the central slit LINE false false 2 90.0 STIS-ALONG-SLIT 5 false POS-TARG MOSAIC DITHER 0.2 2 slits, step=0.2 arcsec - to be placed adjacent to the central slit with NO DITHER. STIS-ALONG-SLIT false false 2 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 6 false The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1287197330000 113.0 (Tic-Visit :proposal-id 11634 :visit-id "01" :proposal-version -1 :trans-version "20080609" :date "03-Jul-2008 09:08:32.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 258096 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11634 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11634 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3065 :al-overhead-at-end 75 :internal-dur-at-end 342 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3398 :pcs-gap 0 ) false 1 0 The bright, compact nucleus is surrounded by a faint reflection nebulosity. central slit - 2 point sub-pixel DITHER + CR-SPLIT=2 Adjacent slits at positive offsets - NO DITHER adjacent slits at negative offsets - NO DITHER (Tic-Visit :proposal-id 11634 :visit-id "02" :proposal-version -1 :trans-version "20091209" :date "02-Nov-2010 16:25:46.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 276496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11634 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11634 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2912 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11634 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3023 :al-overhead-at-end 75 :internal-dur-at-end 362 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) false 2 0 The bright, compact nucleus is surrounded by a fainter reflection nebulosity. Central slit - 2 point sub-pixel dither + CR-SPLIT=2. Adjacent slits starting at positive offsets Adjacent slits starting at negative offset (Tic-Visit :proposal-id 11634 :visit-id "03" :proposal-version -1 :trans-version "20091209" :date "02-Nov-2010 16:30:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 386880 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11634 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11634 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3112 :al-overhead-at-end 72 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11634 :visit-id "03" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3223 :al-overhead-at-end 0 :internal-dur-at-end 381 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) false 2 0 The bright, compact nucleus is surrounded by a fainter reflection nebulosity. central slit - 2 point sub-pixel dither + CR-SPLIT=2 adjacent slits at positive offsets adjacent slits at negative offsets The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1288227907000 110.0 (Tic-Visit :proposal-id 11634 :visit-id "04" :proposal-version -1 :trans-version "20080609" :date "03-Jul-2008 09:08:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 350080 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11634 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11634 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3120 :al-overhead-at-end 72 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3453 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11634 :visit-id "04" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3258 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3453 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11634 :visit-id "04" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3258 :al-overhead-at-end 0 :internal-dur-at-end 381 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3453 :pcs-gap 0 ) false 3 0 5 adjacent slits spaced every 0.2arcsec; NO DITHER The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1273391294000 85.0 (Tic-Visit :proposal-id 11634 :visit-id "05" :proposal-version -1 :trans-version "20080609" :date "03-Jul-2008 09:08:43.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 313264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11634 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 11634 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 5011 :al-overhead-at-end 0 :internal-dur-at-end 401 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1282367423000 170.0 (Tic-Visit :proposal-id 11634 :visit-id "06" :proposal-version -1 :trans-version "20080609" :date "03-Jul-2008 09:08:46.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 368512 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11634 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11634 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2950 :al-overhead-at-end 0 :internal-dur-at-end 421 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3283 :pcs-gap 0 ) false 1 0 The bright, compact nucleus is surrounded by a much fainter reflection nebulosity. adjacent slits at positive offsets The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1246554702000 178.0 (Tic-Visit :proposal-id 11634 :visit-id "07" :proposal-version -1 :trans-version "20080609" :date "03-Jul-2008 09:08:49.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 331696 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11634 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11634 :visit-id "07" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2934 :al-overhead-at-end 0 :internal-dur-at-end 421 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1264584708000 1.0 (Tic-Visit :proposal-id 11634 :visit-id "08" :proposal-version -1 :trans-version "20080609" :date "03-Jul-2008 09:08:53.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 331792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11634 :visit-id "08" :obset-id "08" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11634 :visit-id "08" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2907 :al-overhead-at-end 0 :internal-dur-at-end 441 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3258 :pcs-gap 0 ) false 1 0