0 Assigned ID: 380 ----- Attempting Submission 1 (Fri Mar 06 03:19:15 GMT 2020) ----- FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser hi Amy i did the STIS ACQ/PK ETC using the 52 x 0.05 slit, however, ETC didn't give me an option to set the filter to G750L, so I am not sure if it is correct, raghvendra Hi I have revised the STIS exposures: (i) used 52 x 0.1 slit (as per Phase 1 proposal), (ii) improved the packing of the 2 orbits for STIS, (iii) increased ACQ/PEAK to 30 sec to be on the safe side, as central source may be a bit extended. raghvendra 1685548266 ----- Attempting Submission 1 (Wed Jul 08 16:38:38 GMT 2020) ----- HST Phase II Proposal 16232 successfully submitted. Receipt: # 16232-1 ----- Attempting Submission 2 (Tue Nov 17 21:10:45 GMT 2020) ----- ----- Attempting Submission 3 (Fri Dec 18 21:06:55 GMT 2020) ----- these are wranings that I am supposed to ignore An exciting development in the understanding of the early evolutionary stages of massive stars, based on a new study of the Orion BN/KL region, is that the disruption of a massive young stellar system can lead to an explosive event producing a wide-angle outflow - an entirely different phenomenon from the classical bipolar flows driven by YSO accretion disks. We have discovered an object, IRAS05506+2414, which may be the 2nd clear-cut example of this phenomenon. Our HST optical and near-IR images show a fan-like spray of high-velocity (up to 350 km/s) elongated knots which appear to emanate from a bright compact central source; we find that the physical properties (opening angle, outflow speeds, knot masses, Herbig-Haro-object like optical line emission) of the IRAS05506 wide-angle outflow are very similar to those seen in Orion. We propose to determine IRAS05506's distance from a measurement of the knot proper motions using WFC3 to obtain a 2nd epoch F606W image. Only then will we be able to robustly constrain the central star's luminosity and mass and the dynamical time-scale, mass, velocity, and kinetic energy distributions of its outflows -- needed to test possible mechanisms for the explosive disintegration model for such sources. Deep emission-line imaging with WFC3 will be used to probe the full size and structure of the bullet spray. We will use STIS to confirm the presence of a second outflow engine in IRAS05506: an intriguing linear feature that looks like a classical YSO collimated jet can be seen emanating from the central source, but only a long-slit spectrum of the line emission with sufficient angular resolution can confirm it to be a high-velocity jet. \noindent$\bullet$ {\bf WFC3/UVIS} -- We will obtain a deep 2nd-epoch image of IRAS\,05506 using WFC3/UVIS (since ACS/HRC is no longer functional), but with longer exposure times than the the 1st epoch (discovery) observations -- covering one orbit (in which the HRC was used with 2$\times$400\,s exposures). This observation will enable proper motion determination with an accuracy better than 15\,\kms$\times$(D/2.8\,kpc). The longer exposure time will enable a more accurate comparison with the WFC3 emission line imaging, which is needed in order to distinguish emission-line knots from dusty substructure. For the deep optical emission-line imaging needed to probe the full azimuthal and radial extent of the knotty outflow, we will use the WFC3/UVIS camera and the H$\alpha$+[NII] (F657N) filter. It is better suited for sampling the knots than ACS/WFC because of its smaller pixels (0.04${''}$ compared to 0.05${''}$ ). \noindent$\bullet$ {\bf WFC3/IR} -- We will carry out high S/N imaging with WFC3/IR in the [FeII]\,1.64\micron~emission-line and related continuum filters (F164N, F167N) in order to look for high-velocity knots with shocked gas near the central source, where the extinction is high and therefore not well-probed by the optical emission-line imaging. Shock models (Hartigan et al.\,2004) show that the [FeII]\,1.64\micron~emission is comparable or stronger than the optical forbidden line emission (e.g. in [OI]6300) for a variety of shock conditions (shock velocity, preshock density and ionization fraction etc.). Hence, the average [FeII] 1.64\micron~brightness in knot $K1$ is expected to be about $9\times10^{-15}$ erg s$^{-1}$ cm$^2$ arcsec$^{-2}$. We will therefore use exposure times of about 15 minutes for each of the F164N\,\&\,F167N filters, allowing us to detect knots which are fainter by a factor $\gtrsim$5 than $K1$. We are requesting the F167N narrow filter for continuum subtraction, because using the broad-band filter (see below) for subtraction in a region of large and variable extinction gives very poor results. We will use the F110W and F160W filters to distinguish faints stars from compact knots seen in the [FeII]\,1.64\micron~image. Integration times of about 200 and 80\,s with WFC3 provide S/N of about 40 each in the F110W and F160W images. This high S/N will also improve the characterisation of many faint filamentary structures seen in the vicinity of the central source. \noindent$\bullet$ {\bf STIS} -- We will use STIS with G750M and the 52''$\times$0\farcs1 slit to obtain spectra in the $\lambda\lambda$6295-6867{\AA} range with $\sim$50\,\kms~spectral and 0.05 arcsec spatial resolution. The slit will be aligned along the jet, i.e. PA=238\arcdeg. We will thus cover the H$\alpha$, [NII]\,6548,6583 and [SII]\,6717,6731 lines; the [OI]6300 line will be near the edge, but still visible. The jet {\it Sa-jet(?)} is roughly 0.05 arcsec wide and about 0.2 arcsec long in the F606W ACS image. The H$\alpha$ average line intensity is 4.8$\times10^{-15}$ erg s$^{-1}$ cm$^2$ arcsec$^{-2}$ over a velocity width of about 130\,\kms, and a factor of 3.5 larger at the peak. The [SII]\,6717,6731 lines are 61\%,\,94\% of the H$\alpha$ brightness. We will need an exposure time of about 70 minutes (i.e. 2 orbits) which gives us a S/N$\gsim$12 at the peak, and about 5 at a velocity offset of 130\,\kms. This S/N ratio is adequate to allow us to centroid the line peak to significantly better than 10\,\kms. From the observed PA of {\it Sa-jet(?)}, 50\arcdeg, we compute an $ORIENT=PA+46.3\arcdeg\sim96\arcdeg$ or $PA+226.3\arcdeg\sim276\arcdeg$ (as per the STIS handbook). We therefore request a slit ORIENT in the range 92\arcdeg--100\arcdeg, or 272\arcdeg-280\arcdeg, in order to probe the emission from the highly-collimated jet precisely. This ORIENT range, although restricted, allows many available windows for scheduling. We have also checked with the Help desk that we can use $Sa$ for registering the slit. Several brighter stars are also available for offset imaging, if in case during Phase II, we determine that the latter is the better option. We will use the STScI recommended dithering patterns for all data taken with the WFC3 and STIS in order to optimally sample the PSF. Dr. Sahai is Principal Research Scientist at JPL. His research in the last 25 years has focused on the physics and chemistry of circumstellar matter (including AGB stars, pre-planetary and planetary nebulae, young stars), using both spectroscopic and continuum observations (at all major wavelength bands from the X-ray to the radio), and interferometric techniques. He has over 100 refereed articles in these areas. Sahai has been using NASA's Great Observatories (HST, Chandra, Spitzer & Galex) for two decades in support of his research. He is an expert on modeling of multiwavelength data using molecular-line and dust radiative transfer codes, and numerical hydrodynamical simulations of interacting stellar winds and jets. Claussen has worked and published on the physics and chemistry of the winds from dying stars, low-mass star-forming regions, and high angular resolution and polarization observations of masers found not only in dying stars and low-mass star forming regions, but also in high-mass star forming regions, supernova remnants, extragalactic nuclei, and in nearby galaxies (e.g. the LMC) for more than 30 years, using the VLA, VLBA, and millimeter-wave telescopes and interferometers. Morris has worked and published extensively on the physics and chemistry of the strong winds from dying stars, and the Galactic Center (GC) region for more than 40 years, using millimeter-wave telescopes, the VLA, VLBA, Keck Telescopes, Spitzer, SOFIA and HST. He has carried out theoretical investigations of the dynamics, the photochemistry, molecular excitation mechanisms, and the transfer of line and continuum radiation through circumstellar envelopes. Sanchez Contreras worked on the physics and chemistry of circumstellar envelopes resulting from mass-loss during the latest stages of the stellar evolution of intermediate mass stars, namely, Asymptotic Giant Branch (AGB) stars, pre-planetary nebulae (PPNe) and planetary nebulae (PNe). She has carried out extensive observations of such systems at different wavelengths, from radio to X-ray wavelengths, using a variety of techniques. Lee is an expert on the kinematic analysis of outflowing gas from evolved stars and protostars. Bally is an expert on massive star formation, molecular outflows, and Herbig-Haro jets. Patel is an expert on using interferometric observations to study the chemistry of circumstellar and interstellar matter. Sahai will lead the scientific effort, being responsible for the overall management of the study, major scientific analyses and final publication of the results. 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