<=== observer ===> "MBARLOW",\ "Barlow, M.J.",\ "Department of Physics & Astronomy",\ "University College London",\ "Gower Street",\ "",\ "WC1E 6BT",\ "London",\ "United Kingdom",\ " 44 713807160",\ " 44 713807145",\ "mjb@star.ucl.ac.uk" <=== proposal ===> "HIRES",1,3,\ {"circumstellar envelopes","abundances","AGB stars"},\ {"LWS consortium","Baluteau, J.","Emery, R.","Glencross, W.","Habing, H.",\ "Omont, A.","Rieu, N-Q.","Cohen, R.","Skinner, C.","van Dishoeck, E."} <=== title ===> High spectral resolution observations of molecules and atoms in outflows from evolved stars <=== abstract ===> SCIENTIFIC ABSTRACT We propose to carry out high spectral resolution observations of atomic and molecular lines from the outflows around a number of cool evolved objects. These observations will address the following questions: (a) Can direct observational evidence be provided for the first time showing the operation of the proposed IR radiative pump mechanism for OH maser emission? (b) What is the abundance of H2O in O-rich winds? It has been proposed that OH originates mainly from H2O dissociation and, further, that H2O can be an important coolant in such winds. OBSERVATION SUMMARY We will use the SWS Fabry-Perot to observe the 34.6um doublet, which should be in absorption, as it is believed to pump the observed OH maser lines in the microwave region. The LWS Fabry-Perots will be used to observe seven OH doublets at 48.76um, 53.31um, 79.15um, 96.34um, 98.73um, 119.34um and 163.26um which are predicted to be part of the resulting emission cascade which leads to the inversion of the OH ground state. The SWS and LWS observations will be tied as closely together in time as possible for each target, due to the known strong variability of the OH masers. LWS FP observations will also be obtained at the wavelengths of three H2O rotational lines, at 108.07um, 136.50um and 179.53um, whose fluxes are predicted to be detectable from a number of objects, in an effort to diagnose how important H2O is as a coolant in the outflows. If targets in the Orion-hole should be observable (i.e. a Spring launch), the total amount of LWS Guaranteed (spacecraft) time allocated will be 19.86 hours, of which 7.51 hours will be for Priority 1 targets. For an Autumn launch (Sagittarius-hole observable), 19.38 hours of LWS Guaranteed (spacecraft) time will be allocated, of which 7.31 hours will be for Priority 1 targets. 3.5 hours of Mission Scientist (H.J. Habing) Guaranteed time is being used for this project, with the remainder coming from LWS Consortium Guaranteed time. <=== scientific_justification ===> Two particular problems in the field of cool evolved stars will be studied with the LWS. These are : (a) the excitation mechanism for the 18cm OH maser emission observed from Mira and OH/IR stars; (b) the abundance of H2O in O-rich stellar winds. (a) OBSERVATIONS OF IR TRANSITIONS ASSOCIATED WITH THE OH MASER PUMP Many late type stars are sources of microwave maser emission from OH, H2O and SiO molecules. The OH sources exhbit maser emission from transitions within the J = 3/2 2Pi(3/2) ground state. It has been proposed that the upper sublevel of the 1612 MHz transition is inverted by 34.6um photons, emitted by dust in the wind, which are absorbed from the ground state up to the J=5/2 2Pi(1/2) rotational level, followed by a cascade back to the ground state, involving the emission of 98.7um, 163.2um and 79.1um photons; 48.7um, 96.3um and 119.4um photons; and 53.3um photons (Elitzur, Goldreich and Scoville, Ap.J., 205, 384, 1976). There are three OH maser lines detected in circumstellar envelopes. The `mainlines' (1665 and 1667 MHz) are dominant in optically thin envelopes, whereas the 1612 MHz satellite line dominates in optically thick envelopes. To obtain 1612 MHz masing, the expected pathway is as follows: the ground 2Pi(3/2) J=3/2 state is excited to the 2Pi(1/2) J=5/2 state by 34.6um line absorption - the preferred decay from there is to the 2Pi(1/2) J=3/2 state, with emission at 98.7um. The next preferred stage is decay to the 2Pi(1/2) J=1/2 state, with emission at 163.2um, and finally there is a decay back to the 2Pi(3/2) J=3/2 ground state, with emission at 79.1um. This scheme, with sufficient 34.6um flux available, causes an inversion of the F=2/F=1 levels of the ground state, leading to 1612 MHz maser action. Under slightly different conditions, much the same scheme can lead to inversion between the lambda-doubled F=2 and F=1 levels in the ground state, which are separated by transitions at 1665 and 1667 MHz (the `main-lines'), which can thus also mase. Observations of the far-IR transitions represent the obvious way to test the radiative pumping scheme, since the line strengths will reveal the number of photons making each transition and thus enable a trivial check on the degree of inversion of the ground state F levels of the OH molecules (some other decay pathways can be followed after absorption of 34.6um photons - the degree of inversion of each masing transition will depend on the number of molecules which follow each pathway. All the decay pathways are observable using the LWS). Elitzur et al. estimated that, for a typical red giant maser, about four 34.6um photons will be absorbed for every one 1612 MHz maser photon emitted. The upward 34.6um absorption can be observed by the SWS, while all the resulting cascade photons can be observed by the LWS. Thus ISO observations can critically test theory and will certainly throw light on the excitation properties of the OH radical. OH TARGETS: COOL STARS IRAS (Jy) Name Sp. Type RA(1950) DEC(1950) 12 25 60 100 IK Tau M6-M10e 03 50 46.0 +11 15 42 4634 2377 332 103 VY Cma M5Ia 07 20 54.8 -25 40 12 9919 6651 1453 331 W Hya M8IIIe 13 46 12.2 -28 07 05 4200 1189 195 72.2 VX Sgr M4-9Ia 18 05 03.0 -22 13 56 2738 1385 263 82.3 IRC+10420 F8Ia 19 24 27.0 +11 15 11 1346 2314 718 186 OH/IR STARS IRAS (Jy) Name Sp. Type RA(1950) DEC(1950) 12 25 60 100 WX Psc OH/IR 01 03 48.0 +12 19 45 1155 967 215 72 OH127.8+0.0 OH/IR 01 30 27.7 +62 11 30 289 456 194 50 AFGL 5379 OH/IR 17 41 08.2 -31 54 33 1262 2723 1365 406 OH26.5+0.6 OH/IR 18 34 51.6 -05 27 24 360 634 463 <310 OH104.9+2.4 OH/IR 22 17 43.1 +59 36 16 123 229 91 35 POST-AGB OBJECT IRAS (Jy) Name Sp. Type RA(1950) DEC(1950) 12 25 60 100 OH231.8+4.2 OH/IR/PPN 07 39 58.9 -14 35 44 19.0 226 548 294 Our sample is chosen to include objects with mass loss rates at the low end of the range, with the 1665 and 1667 MHz mainlines dominant (e.g. W Hya) and optically thick objects (higher mass loss rates) with the 1612 MHz maser dominant. We propose to observe with the LWS FP's the OH transitions listed below, and to observe with the SWS FP the 34.6um OH pumping transition. Wavelengths of the OH doublets to be observed with the LWS: 48.704, 48.817um 53.262, 53.351um 79.117, 79.182um 96.312, 96.367um 98.725, 98.737um 119.234, 119.441um 163.121, 163.396um Wavelengths of the OH pumping doublet to be observed with the SWS: 34.6035, 34.6294um AOT's: The LWS High Resolution Line Spectrum AOT, LWS04, will be used with four sample points per FP resolution element, scanned +-4 resolution elements on either side of the central wavelength of each doublet component (except for the 98.7um doublet, where the components are so close to each other that a scan centred at their mean wavelength of 98.731um will suffice). An integration time of 5 seconds per sample point will be used, which will yield, per resolution element, 5sigma line flux detection limits of 1.7x10(-15), 1.05x10(-15), 6.4x10(-16) and 8.1x10(-16) W m-2 at 48um, 98um, 119um and 163um, respectively. The total spacecraft time required to obtain the LWS FP scans at the thirteen separate wavelengths settings will be 75.43 minutes per star. We will observe the OH 34.6um doublet, expected to be in absorption, with the SWS FP at R = 30,000, using the SWS07 AOT. The velocity separation of the doublet components is 225 km/s, so we will scan +-200 km/s on either side of the mean wavelength of the doublet of 34.6165um. The total spacecraft time needed for the SWS observations of each target is listed in Table 2 below, along with the continuum S/N ratios that are expected for these integration times. As the SWS time estimates include the spacecraft slew-time overhead of 180 seconds, this overhead has not been included in the spacecraft time estimates for the LWS observations. ** The LWS and SWS FP observations must be obtained as close together in time as possible, due to the known strong variability of the OH masers.** (b) SPECTRAL LINE OBSERVATIONS OF H2O The photodissociation of H2O by the interstellar or chromospheric radiation fields is thought to be the main production mechanism for OH in late-type stellar winds. In addition, H2O can act as a heat source in the inner dense regions (via collisional de-excitation following absorption of trapped IR line photons), while acting as a coolant in the outer lower-density regions. The goal of our observations is to determine the abundance of H2O in late-type stellar winds, via LWS FP observations of a selected number of diagnostic lines. Deguchi and Rieu (Ap.J., 360, L27, 1990) have predicted the fluxes in various ortho and para H2O lines, based on a thermal excitation model and we have used these predictions to select the lines to be observed. S/N estimates for the stars listed in Table 1 (below) were based upon H2O line fluxes predicted by N-Q-Rieu, based on the thermal excitation model of Deguchi and Rieu (Ap.J., 360, L27, 1990). The line fluxes have been derived by performing radiative transfer calculations based on the most recent collisional cross sections. The line flux depends on the mass loss rate, the shell expansion velocity, and the distance of the source. A fractional H2O abundance (relative to molecular hydrogen) of 4x10(-4) was assumed. The characteristics of the envelopes were taken from Knapp (Ap.J., 293, 273, 1985), Knapp and Morris (Ap.J., 292, 640, 1985) and Knapp et al. (Ap.J., 336, 822, 1989). AOT's: The LWS High Resolution Line Spectrum AOT, LWS04, will be used, with 4 sample elements per resolution element, and a total scan range of +-4 resolution elements about line centre, giving 32 sample elements per line. An integration time of 10 seconds per point will be used. Table 1 lists the H2O lines that will be observed towards each star. For five of the targets, the 414-303 line at 113.538um is being observed as part of the Mission Scientist proposal mharwit_mharwit, and so will not be observed here. For the two sources not in the OH target list, O Ceti and Alpha Ori, the spacecraft slew time overhead of 180 seconds per target is included in the total observing time estimates given in Table 2. TABLE 1: H2O Line Observations Line 221-110 212-101 330-321 414-303 616-505 108.073um 179.527um 136.496um 113.538um 82.030um NAME IK Tau X X X X X VY CMa X X X X W Hya X X X X VX Sgr X X X X X IRC+10420 X X X X X O Ceti X X X X Alf Ori X X X X X WX Psc X X X X OH127.8+0.0 X X X X AFGL 5379 X X X X X OH26.5+0.6 X X X X X OH104.9+2.4 X X X X X OH231.8+4.2 X X X X Table 2: Summary of OH and H2O observations SWS OH LWS OH LWS H2O Total Prior. Hole NAME S/C Time S/C Time S/C Time S/C Time (secs) (secs) (secs) (hours) 3 IK Tau 967 4526 2464 2.210 1 O VY CMa 967 4526 1948 2.067 1 W Hya 1956 4526 1948 2.342 1 S VX Sgr 1956 4526 2464 2.485 2 IRC+10420 967 4526 2464 2.210 2 WX Psc 1956 4526 1948 2.342 3 O OH127.8+0.0 1956 4526 2464 2.485 3 S GL 5379 967 4526 2464 2.210 1 S OH26.5+0.6 1956 4526 2464 2.485 3 OH104.9+2.4 1956 4526 2464 2.485 1 O OH231.8+4.2 1956 4526 1948 2.342 3 O Cet 2230 0.619 1 O Alf Ori 2746 0.763 SPACECRAFT TIME SUMMARY: Orion-hole observable (Spring launch) Sgr-hole observable (Autumn launch) Priority 1 time = 7.51 hrs (37.8%) Priority 1 time = 7.31 hrs (37.7%) Priority 2 time = 6.76 hrs (34.0%) Priority 2 time = 6.76 hrs (34.9%) Priority 3 time = 5.59 hrs (28.2%) Priority 3 time = 5.31 hrs (27.4%) Total S/C time = 19.86 hrs Total S/C time = 19.38 hrs Time distribution for autumn launch targets: Team top 40% second 30% last 30% LWS : 21282 20564 15353 HJH : 5040 3780 3780 total : 26322 24344 19133 Time distribution for spring launch targets: Team top 40% second 30% last 30% LWS : 22007 20564 16342 HJH : 5040 3780 3780 total : 27047 24344 20122 <=== autumn_launch_targets ===> 1, "LWS04", 3.0, "N", "O Ceti", 2.28028, -3.20333, 1950, 0.,0.,2230,0 2, "LWS04", 2.0, "N", "IK Tau", 3.84611, +11.26167, 1950, 0.,0.,1764,3 3, "LWS04", 2.0, "N", "IK Tau", 3.84611, +11.26167, 1950, 0.,0.,5226,4 4, "SWS07", 2.0, "N", "IK Tau", 3.84611, +11.26167, 1950, 0.,0.,967,0 5, "LWS04", 1.0, "N", "W Hya", 13.77006, -28.11806, 1950, 0.,0.,1248,6 6, "LWS04", 1.0, "N", "W Hya", 13.77006, -28.11806, 1950, 0.,0.,5226,7 7, "SWS07", 1.0, "N", "W Hya", 13.77006, -28.11806, 1950, 0.,0.,1956,0 8, "LWS04", 1.0, "N", "VX Sgr", 18.08417, -22.23222, 1950, 0.,0.,1764,9 9, "LWS04", 1.0, "N", "VX Sgr", 18.08417, -22.23222, 1950, 0.,0.,5226,10 10, "SWS07", 1.0, "N", "VX Sgr", 18.08417, -22.23222, 1950, 0.,0.,1956,0 11, "LWS04", 2.0, "N", "IRC+10420",19.40750, +11.25306, 1950, 0.,0.,1764,12 12, "LWS04", 2.0, "N", "IRC+10420",19.40750, +11.25306, 1950, 0.,0.,5226,13 13, "SWS07", 2.0, "N", "IRC+10420",19.40750, +11.25306, 1950, 0.,0.,967,0 14, "LWS04", 3.0, "N", "AFGL 5379",17.68561, -31.90917, 1950, 0.,0.,1764,15 15, "LWS04", 3.0, "N", "AFGL 5379",17.68561, -31.90917, 1950, 0.,0.,5226,16 16, "SWS07", 3.0, "N", "AFGL 5379",17.68561, -31.90917, 1950, 0.,0.,967,0 17, "LWS04", 1.0, "N", "26.5+0.6", 18.58100, -5.45667, 1950, 0.,0.,1764,18 18, "LWS04", 1.0, "N", "26.5+0.6", 18.58100, -5.45667, 1950, 0.,0.,5226,19 19, "SWS07", 1.0, "N", "26.5+0.6", 18.58100, -5.45667, 1950, 0.,0.,1956,0 20, "LWS04", 2.0, "N", "WX Psc", 1.06333, +12.32917, 1950, 0.,0.,1248,21 21, "LWS04", 2.0, "N", "WX Psc", 1.06333, +12.32917, 1950, 0.,0.,5226,22 22, "SWS07", 2.0, "N", "WX Psc", 1.06333, +12.32917, 1950, 0.,0.,1956,0 23, "LWS04", 3.0, "N", "104.9+2.4",22.29531, +59.60444, 1950, 0.,0.,1764,24 24, "LWS04", 3.0, "N", "104.9+2.4",22.29531, +59.60444, 1950, 0.,0.,5226,25 25, "SWS07", 3.0, "N", "104.9+2.4",22.29531, +59.60444, 1950, 0.,0.,1956,0 <=== spring_launch_targets ===> 1, "LWS04", 3.0, "N", "O Ceti", 2.28028, -3.20333, 1950, 0.,0.,2230,0 2, "LWS04", 2.0, "N", "IK Tau", 3.84611, +11.26167, 1950, 0.,0.,1764,3 3, "LWS04", 2.0, "N", "IK Tau", 3.84611, +11.26167, 1950, 0.,0.,5226,4 4, "SWS07", 2.0, "N", "IK Tau", 3.84611, +11.26167, 1950, 0.,0.,967,0 5, "LWS04", 1.0, "N", "Alf Ori", 5.87436, +7.39889, 1950, 0.,0.,2746,0 6, "LWS04", 1.0, "N", "VY CMa", 7.34856, -25.67000, 1950, 0.,0.,1248,7 7, "LWS04", 1.0, "N", "VY CMa", 7.34856, -25.67000, 1950, 0.,0.,5226,8 8, "SWS07", 1.0, "N", "VY CMa", 7.34856, -25.67000, 1950, 0.,0.,967,0 9, "LWS04", 1.0, "N", "W Hya", 13.77006, -28.11806, 1950, 0.,0.,1248,10 10, "LWS04", 1.0, "N", "W Hya", 13.77006, -28.11806, 1950, 0.,0.,5226,11 11, "SWS07", 1.0, "N", "W Hya", 13.77006, -28.11806, 1950, 0.,0.,1956,0 12, "LWS04", 2.0, "N", "IRC+10420",19.40750, +11.25306, 1950, 0.,0.,1764,13 13, "LWS04", 2.0, "N", "IRC+10420",19.40750, +11.25306, 1950, 0.,0.,5226,14 14, "SWS07", 2.0, "N", "IRC+10420",19.40750, +11.25306, 1950, 0.,0.,967,0 15, "LWS04", 1.0, "N", "231.8+4.2", 7.66636, -14.59556, 1950, 0.,0.,1248,16 16, "LWS04", 1.0, "N", "231.8+4.2", 7.66636, -14.59556, 1950, 0.,0.,5226,17 17, "SWS07", 1.0, "N", "231.8+4.2", 7.66636, -14.59556, 1950, 0.,0.,1956,0 18, "LWS04", 2.0, "N", "WX Psc", 1.06333, +12.32917, 1950, 0.,0.,1248,19 19, "LWS04", 2.0, "N", "WX Psc", 1.06333, +12.32917, 1950, 0.,0.,5226,20 20, "SWS07", 2.0, "N", "WX Psc", 1.06333, +12.32917, 1950, 0.,0.,1956,0 21, "LWS04", 3.0, "N", "104.9+2.4",22.29531, +59.60444, 1950, 0.,0.,1764,22 22, "LWS04", 3.0, "N", "104.9+2.4",22.29531, +59.60444, 1950, 0.,0.,5226,23 23, "SWS07", 3.0, "N", "104.9+2.4",22.29531, +59.60444, 1950, 0.,0.,1956,0 24, "LWS04", 3.0, "N", "127.8+0.0", 1.50769, +62.19167, 1950, 0.,0.,1764,25 25, "LWS04", 3.0, "N", "127.8+0.0", 1.50769, +62.19167, 1950, 0.,0.,5226,26 26, "SWS07", 3.0, "N", "127.8+0.0", 1.50769, +62.19167, 1950, 0.,0.,1956,0