Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4487c Report Date: 09-May-96:19:38 Version: ********** Check-in Date: ********** 1.Proposal Title: UV EMISSION LINE FORMATION PROCESSES AROUND THE BRIGHTEST HERBIG AE STAR HD104237 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID COOL STARS GO Sub Category EARLY EVOLUTION ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Alexander Brown U. OF COLORADO USA (303) 492-7810 SENIOR RES ASSOCIATE ------------------------------------------------------------------------------------ 7. Abstract Herbig Ae stars are intermediate mass pre-main sequence (PMS) stars, and the more massive counterparts of the well-known T Tauri stars. Their evolution and atmospheric properties are still poorly understood. We propose to study the profiles of emission lines formed in the outer atmosphere/ circumstellar regions of the brightest and closest Herbig Ae star, HD104237, using GHRS spectra at moderate and high resolution of selected high temperature emission lines. At present it is not clear if these lines form in a classical transition region (TR)/chromosphere, a stellar wind, or an accretion disk (probably the least likely alternative) The emission line profiles will be analyzed to investigate atmospheric (density and temperature structure) and wind (mass loss rate, velocity and density laws) properties of this star. One goal is to discover if the winds from Herbig Ae stars can totally dominate the atmospheric structure of the star with TR plasma forming an integral part of the stellar wind or if physically separate, stationary, confined regions exist at the base of the wind. We shall determine quantitative constraints on the non-radiative heating and mass loss processes in the atmosphere, which will allow a better understanding of the evolution of PMS stars, since the heating and mass loss are driven by processes related to the sub-photospheric stellar structure. ------------------------------------------------------------------------------------ 8. Scientific Key Words: HERBIG AE STAR ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 3.71 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4487c PI: Dr. Alexander Brown Proposal Title: UV EMISSION LINE FORMATION PROCESSES AROUND THE BRIGHTEST HERBIG AE STAR HD104237 ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Alexander Brown COLORADO, UNIVERSITY OF USA Jeffrey L. Linsky COLORADO, UNIVERSITY OF USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. Our proposed observations will provide the first high-quality (S/N = 15- 100) line profiles for emission lines of H I (1216A), Si III (1206A), O V (1218A),O I (1302,4,6 + S I, Si II), C II (1335A), Si IV (1396,1403A) O IV (1402,1407, C IV (1548,1550A) and Mg II (2796,2803A). All of these spectra will be obtained with the G160M grating, except for Mg II which will be obtained with ECH-B. The observations requested are: Central Strong GHRS grating Wavelength(s) Aperture Exposure S/N Features Time G160M 1216 LSA 11 min 30 H I/Si III/O V G160M 1302 LSA 12 min 30 O I/S I G160M 1335 LSA 20 min 15 C II G160M 1400 LSA 45 min 31 Si IV 10 O IV G160M 1550 LSA 34 min 20 C IV ECH -B 2799 LSA 5 min 100 Mg II The quoted signal-to -noise values refer to the peak of the strongest emission line in the particular spectrum. The large dynamic range and low noise of the GHRS ensures that many weak features can be seen in the requested exposures. 1335 EXPOSURE REMOVED TO FIT ALLOCATION. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The data required for this program consists of UV spectra not obtainable from the ground. IUE has been used extensively to study this target to the limits of its capability (including high resolution exposures up to 16 hours), and further observational advances depend on the acquisition of higher S/N spectra with GHRS. The increased sensitivity, wavelength resolution, dynamic range and S/N characteristics of the GHRS over those obtainable with the IUE (Carpenter et al. 1992, Ap.J. Lett., 377, L45.) will allow more accurate and detailed modelling of physical processes occurring in the outer atmosphere of HD104237. Only the GHRS is capable of providing us with the high precision line profiles, fluxes, and absolute velocities required for our program. ONLY GHRS CAN PROVIDE THE LINE PROFILES OF OPTICALLY-THIN, DENSITY-SENSITIVE EMISSION LINES. .. The exposures requested are summarized in section 2. The exposure times have been estimated using absolute fluxes previously measured with the IUE. For the first order and echelle gratings we used sensitivity values given in the GHRS instrument handbook. The LSA is used, because it provides sufficient resolution for our requirements and post-processing of the spectra can recover some of the resolution lost due to the large point spread function filling the LSA. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. No real-time observations or special scheduling is required. Page 3 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. We require the high wavelength accuracy to measure flow velocities in the chromosphere, wind and circumstellar shell of our target star (down to the 1 km/sec level in the medium and echelle observations). We also require the best possible wavelength calibration to aid in the identification of weak features. These requirements mean that we need calibrations good to better than 0.3 diode. Experience with SV and SAO data has demonstrated that the default calibration will produce uncertainties of up to 3 diodes due to magnetic and thermal drifts within the spectrograph. Using internal Pt lamp spectra taken during SPYBALs, we can estimate the amount of drift and can therefore reduce the degree of uncertainty to about 0.5 diodes. To obtain the greatest possible wavelength accuracy, about 0.1 diodes, we require dedicated WAVECAL exposures using the internal Pt lamps to be connected to each GHRS science exposure. The wavelength calibrations must be taken at the same carrousel position and close in time to the science exposures to remove uncertainties caused by the GIMP and thermal drifts which move the image around on the GHRS photocathode. ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. The data will be reduced and analyzed with in-house software developed for analysis of IUE and GHRS data. Software developed by the GHRS IDT will be used to optimize the calibration of the observations. Line widths, profiles, and wavelengths will be carefully measured to extract information on the velocity structure of the outer atmosphere, including both random non-thermal velocities and systematic flows. Relative and absolute fluxes will be measured to estimate densities and temperatures in the outer atmosphere. Methods for analyzing cool star emission line spectra are well established. Emission measure analysis can be used to model chromospheric and transition region structure. A general discussion of the methods is given by Jordan and Brown (1981) and an example of its application to a PMS star is given by Brown,Ferraz and Jordan (1984) in their analysis of T Tau. Other PMS stars that we have modelled with these same methods include HD 283572, a PMS G star studied by Walter et al. (1987), and our analysis of HR5999 and BN Ori (The et al,1985; Brown et al, 1986, 1992). Density- sensitive, O IV and O V lines will provide esimates of the TR electron density and accurate representations of the velocity field in the formation regions, since these lines will be optically thin. If any hot accretion disk line emission is present, it should be very broadened and show stronger shortward flux dure to occulation effects. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. None. ------------------------------------------------------------------------------------ 9. Description of previous HST work. GO Program 3626 - Empirical determination of the wind velocity and density laws for the K supergiant Zeta Aurigae from eclipse ingress Spectra (A. Brown PI, J. Linsky, R. Weyman, D. Reimers, R. Baade, T. Kirsch) ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Software developed by the GHRS IDT and the proposers will be used in the reduction and analysis of these observations. A workstation at JILA connected to the CASA cluster is available for data reduction and analysis. ------------------------------------------------------------------------------------ 11. Address Information Page 4 Name: Alexander Brown Category: PI Institution: Joint Institute for Laboratory As Address: University of Colorado City: Boulder State: CO Zip Code: 803090440 Country: USA Telephone: (303) 492-7810 Telex (or e-mail): 755842 JILA ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4487c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD104237 A,127 RA=11H57M33.47S+/-0.15S, 1950 V=0.0 1 V=6.5 DEC=-77D54'50.5"+/-0.5" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B 1950.00 -0.0162 +/- 0.0010 0.0140 +/- 0.0070 0.0000 +/- 0.0000 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4487c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 HD104237 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=3 1 1.8S 1 ONBOARD ACQ FOR 12 BRIGHT=RETURN CYCLE 3/10-46 GROUP 10-46 NO GAP Comments: STEP TIME = 200 MSEC EXPECTED A2 COUNTS ARE APPROX. 300 PER STEP TIME ------------------------------------------------------------------------------------------------------------------------------------ 12 HD104237 HRS ACQ/ 2.0 MIRROR-A2 1 162.3S 1 2 ONBOARD ACQ FOR PEAKUP 20.0-46.0 Comments: STEP-TIME=1.6 SEC CENTER IN LSA AFTER NEW DEFCAL ------------------------------------------------------------------------------------------------------------------------------------ 20 WAVE HRS ACCUM SC2 G160M 1222.50 STEP-PATT=3 1 54.4S ^ CALIB FOR 21 NO SLEW SEQ 20-21 NO GAP Comments: NO CARROUSEL MOTION BETWEEN 20 AND 21 ------------------------------------------------------------------------------------------------------------------------------------ 21 HD104237 HRS ACCUM 2.0 G160M 1222.5 STEP-PATT=5 2 354.0S ^ ------------------------------------------------------------------------------------------------------------------------------------ 25 WAVE HRS ACCUM SC2 G160M 1302.0 STEP-PATT=3 1 54.4S ^ CALIB FOR 26 NO SLEW SEQ 25-26 NO GAP Comments: NO CARROUSEL MOTION BETWEEN 25 AND 26 ------------------------------------------------------------------------------------------------------------------------------------ 26 HD104237 HRS ACCUM 2.0 G160M 1302.0 STEP-PATT=5 2 354.0S ^ ------------------------------------------------------------------------------------------------------------------------------------ 35 WAVE HRS ACCUM SC2 G160M 1401.0 STEP-PATT=3 1 54.4S ^ CALIB FOR 36 NO SLEW SEQ 35-36 NO GAP Comments: NO CARROUSEL MOTION BETWEEN 35 AND 36 ------------------------------------------------------------------------------------------------------------------------------------ 36 HD104237 HRS ACCUM 2.0 G160M 1401.0 STEP-PATT=5 7 354.0S ^ ------------------------------------------------------------------------------------------------------------------------------------ 40 WAVE HRS ACCUM SC2 G160M 1548.0 STEP-PATT=3 1 54.4S ^ CALIB FOR 41 NO SLEW SEQ 40-41 NO GAP Comments: NO CARROUSEL MOTION BETWEEN 40 AND 41 ------------------------------------------------------------------------------------------------------------------------------------ 41 HD104237 HRS ACCUM 2.0 G160M 1548.0 STEP-PATT=5 6 354.0S 2 ------------------------------------------------------------------------------------------------------------------------------------ 45 WAVE HRS ACCUM SC2 ECH-B20 2800 STEP-PATT=3 1 32S ^ CALIB FOR 46 NO SLEW SEQ 45-46 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ 46 HD104237 HRS ACCUM 2.0 ECH-B20 2800 STEP-PATT=7 1 300S ^ ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4487c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN STEP-PATT=3 STEP-PATT=5 STEP-PATT=7 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 3.71 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COOL STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category EARLY EVOLUTION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 12; CYCLE 3/10-46 ; GROUP 10-46 NO GAP ONBOARD ACQ FOR 20.0-46.0 CALIB FOR 21 NO SLEW; SEQ 20-21 NO GAP CALIB FOR 26 NO SLEW; SEQ 25-26 NO GAP CALIB FOR 36 NO SLEW; SEQ 35-36 NO GAP CALIB FOR 41 NO SLEW; SEQ 40-41 NO GAP CALIB FOR 46 NO SLEW; SEQ 45-46 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-A2 G160M ECH-B20 ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD104237 ------------------------------------------------------------------------------------------------------------------------------------