9800( 4) - 05/16/03 11:15 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9800 Version: 4 Check-in Date: 16-May-2003 11:14:26 1.Proposal Title: Tracking the Evolution of a Knotty, High- Speed Jet in the Carbon Star, V Hydrae ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 12 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Dr. Raghvendra Sahai Jet Propulsion Laboratory CoI: Dr. Mark Morris University of California - Los Angeles N CoI: Dr. Gillian R. Knapp Princeton University N CoI: Dr. Cecilia Barnbaum Valdosta State University N CoI: Dr. Ken Young Smithsonian Institution Astrophysical N Observatory ------------------------------------------------------------------------------------ 5. Abstract The carbon star V Hydrae is experiencing heavy mass loss as it undergoes the transition from AGB star to pre-planetary nebula. This is possibly the earliest object known in this brief phase. Molecular observations reveal that a bipolar nebula has been established even at this early stage. Using STIS on the HST, we have discovered a high-velocity (> 200 km/s) jet or blob of gas which was ejected only ~2 years ago from near the star. A second STIS observation 11 months later clearly showed both its proper motion and the fact that it is being strongly decelerated. We propose STIS monitoring of this remarkable event for an additional 3 years, in order to: 1) obtain a precise dynamical and cooling history of this blob, and 2) determine whether the ejection of such blobs is associated with, or perhaps phased with, the 530-day stellar period. This ejection event is likely to hold the key to understanding why initially spherical mass outflows adopt a bipolar geometry during the post-AGB phase of stellar evolution. We not only have the opportunity to look on as the circumstellar envelope is sculpted by this and perhaps other collimated mass ejections, but we also have an unprecedented chance to constrain the mechanism for mass ejection, and thereby help solve a long-standing puzzle. Finally, molecular line observations and our previous STIS H$\alpha$ observations show that the V Hya system contains a prominent, central disk. We propose a follow-up study in H$\alpha$ in order to better define the disk properties, and thereby to determine whether the disk plays a role in the collimation of the emerging blob. We will use the data to constrain hydrodynamical models of collimated jet interactions with the ambient circumstellar medium in V Hydrae, in order to set quantitative constraints on the physical properties of the blobby outflow. ------------------------------------------------------------------------------------ 9800( 4) - 05/16/03 11:15 - [ 2] Observations Description ------------------------ We will utilise the same observing set-up as in our Dec'02 epoch (GO\, 9632) observations. We will use STIS with G430M (tilt setting of 4194) and the 52''$\times$0\farcs1 to obtain spectra in the $\lambda\lambda$4051-4337{\AA} range. From our previous data, the [SII]$\lambda$4066{\AA} line has a peak intensity of 4$\times10^{-13}$ erg s$^{-1}$ cm$^2$ {\AA}$^{-1}$ arcsec$^{-2}$. We will use the same exposure times as in GO\, 9632 (400 sec total per slit position), using a 3 point dither along the slit, and CR-SPLIT=2, which gives us a S/N$\gsim$60-70 at peak of the [SII]$\lambda$4066{\AA} line, and a S/N$\gsim$15 at the continuum (which is roughly a factor 4 weaker in the - 0\farcs1 slit, where the high-velocity outflow emission is strongest). This high S/N ratio is necessary because it allows us to measure the spatial offset of the peak from the source continuum to sub-pixel accuracy, which is important since the proper motion is about 0\farcs08 per year (and may decrease with time, if deceleration of the blob continues). In addition, we want to continue to be able to detect important fainter lines ([FeII]$\lambda$4241 \& 4285{\AA}) (which we have detected previosly) which provide additional probes of the physical conditions in the outflow. Since our most important objective is to understand the velocity field of the jets in order to study the collimation process, we will obtain spectra with 2 additional slit positions displaced symmetrically on either side of the central star (i.e. with offsets of $\pm$0\farcs1 and $\pm$0\farcs2). The G430M observations will require a total of 3 orbits. We will use a mosaic of 7 adjacent slit positions, using the 52''$\times$0\farcs05 wide slit for the observations of the ``central disk" in H$\alpha$ -- the narrowest slit is used here (in contrast to the G430M observations) in order to obtain the highest spectral resolution because the velocity range covered by the ``disk" emission is much smaller (about 90\kms). The H$\alpha$ disk intensity at the half-power point is about 5$\times10^{-12}$ erg s$^{-1}$ cm$^2$ {\AA}$^{-1}$ arcsec$^{-2}$; we will use exposure times of 300 sec total per slit (CR-SPLIT=2 and a 3-point dither along slit) to obtain a S/N of 40 (after subtraction of the continuum background) -- such a high S/N is necessary to characterise the disk velocity structure with the limited spectral resolution (50\kms). Our slit mosaic will cover a total of 0\farcs35 across the central region -- such a mosaic is necessary because in our previous H$\alpha$ STIS observations, which were done in Jan'02 with a 0\farcs2 slit and 3 positions spaced apart by 0\farcs2, the disk signature was clearly seen only in the offset slits. This was because of the presence of the very strong stellar continuum in the central slit and imperfect rectification, resulting in very strong undulations along the wavelength direction -- making it impossible to subtract the continuum, which is necessary in order to detect the weaker disk signal. Although we will use a better (3-point) dither strategy (than the 2- point used in Jan'02), we do not know {\it a priori} which slit position will best show the disk; hence our conservative choice of 3 offset slits on each side of the center. The 7 slit positions will also enable us to measure the extent of the disk perpendicular to the slit (and outflow) direction. The available windows for observing V Hya given our STIS slit ORIENT constraints (we require an ORIENT within $\pm$4\arcdeg~of the one in first two epochs) occur twice (1) in June/July, and (2) Dec/Jan/Feb each calendar year. We will request observing dates with an attempt to ensure that at least one epoch falls near (i.e. within a month) of maximum light, while a second one fall near minimum light of the 529 day cycle of this object. Such scheduling will allow 9800( 4) - 05/16/03 11:15 - [ 3] us to check if there is any effect of the stellar light cycle on the outflow. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9800( 4) - 05/16/03 11:15 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V-HYDRAE STAR, CARBON STAR RA=10H51M37.25S +/- 0.1", DEC=- J2000 V = 9.7+/-0.0 21D15'0.32" +/- 0.1" B = 14.23 R = 7.8 I = 6 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.00101 0.00272 0.0 9800( 4) - 05/16/03 11:15 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-PERP-TO-SLIT STIS-ALONG-SLIT Pattern_Purpose MOSAIC DITHER Number_Of_Points 4 3 Point_Spacing 0.1 0.225 Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 0.0 90.0 Center_Pattern NO YES ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.225 Coordinate_Frame POS-TARG Pattern_Orient 90.0 Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type STIS-PERP-TO-SLIT STIS-ALONG-SLIT Pattern_Purpose MOSAIC DITHER Number_Of_Points 3 3 Point_Spacing 0.1 0.225 Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 0.0 90.0 Center_Pattern YES YES ------------------------------------------------------------------------------------------------------------------------------------ 9800( 4) - 05/16/03 11:15 - [ 6] Visit: 01 Visit Priority: Visit Requirements: ORIENT 312.0D TO 313.0 D On Hold Comments: Additional Comments: Slit should be oriented along within 1 deg of Epoch 1 data from DD 9632 with +/-10D tolera> Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V-HYDRAE STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.6 S CD Comments: Need to use ND3 filter, S/N=146 in 3x3 box if R=7.8 ------------------------------------------------------------------------------------------------------------------------------------ 2 V-HYDRAE STIS/C ACQ/PEA 52X0.1 G750L 7751 1 1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 V-HYDRAE STIS/C ACCUM 52X0.1 G430M 4194 CR-SPLIT=2,GAIN=1 1 522 S POS TARG -0.1, 0 PATTERN CD 1 3 Comments: mosaic of 4 0.1" slits, spaced 0.1", starting at -0.1 offset ------------------------------------------------------------------------------------------------------------------------------------ 4 V-HYDRAE STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=2,GAIN=4 1 10 S PATTERN 2 4 CD Comments: short exposure 1 central slit ------------------------------------------------------------------------------------------------------------------------------------ 5 V-HYDRAE STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=2,GAIN=4 1 144 S PATTERN 3 5 CD Comments: long exposure, mosaic of 3 0.1" slits, spaced 0.1" ------------------------------------------------------------------------------------------------------------------------------------ 6 CCDFLAT STIS/C ACCUM 52X0.05 G750L 7751 2 DEF CD Comments: fringe flat ------------------------------------------------------------------------------------------------------------------------------------ 9800( 4) - 05/16/03 11:15 - [ 7] Summary Form for Proposal 9800 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25ND3 52X0.1 52X0.05 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT GAIN=1 GAIN=4 CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 312.0D TO 313.0 D POS TARG -0.1, 0 PATTERN 1 3 PATTERN 2 4 PATTERN 3 5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750L G430M G750M ------------------------------------------------------------------------------------------------------------------------------------ Target Names V-HYDRAE CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 7751 4194 6581 ------------------------------------------------------------------------------------------------------------------------------------