Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2338c Report Date: 09-May-96:17:02 Version: ********** Check-in Date: ********** 1.Proposal Title: SPECTROSCOPY OF THE SPECKLE-RESOLVED ETA CARINAE POINT SOURCES ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS GO Sub Category MASSIVE STARS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Kris Davidson MINNESOTA, UNIVERSITY OF USA 612-624-5711 ------------------------------------------------------------------------------------ 7. Abstract Eta carinae is thought to be the most extreme known Luminous Blue Variable (LBV), marking the unstable upper boundary of the HR Diagram. It is crucial for theories of the LBV outburst phenomenon, only recently beginning to be developed. Recently the "central object" in Eta Carinae has been found by speckle techniques to be multiple. Combined with the presence of circumstellar emission and scattering, this multiplicity means that high spatial resolution is needed in order to obtain spectral data specifically on the primary component, the very massive LBV star. The fainter components are also important -- if they are stars, then this is a unique chance to study a truly coeval system of very massive stars of known age (known because the LBV is present), and if they are nebular objects, then we need spectra in order to understand why they are so unexpectedly bright. For these reasons we propose to us the FOS to obtain spectra of the primary star and of its companion objects. The stellar spectra will be used for a quantitative analysis by NLTE methods, aiming for estimates of Teff, g, chemical composition, mass, mass-loss rate, wind velocity field, and luminosity. ------------------------------------------------------------------------------------ 8. Scientific Key Words: EARLY TYPE STARS, ATMOSPHERES, UV SPECTROSCOPY, STELLAR EVOLUTION, NUCLEOSYNTHESIS, ABUNDANCES, LBVS, LUMINOUS STARS, MASSIVE ST ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 6.00 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2338c PI: Dr. Kris Davidson Proposal Title: SPECTROSCOPY OF THE SPECKLE-RESOLVED ETA CARINAE POINT SOURCES ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ P.I. Kris Davidson MINNESOTA, UNIVERSITY OF USA G. Weigelt MAX-PLANCK-INSTITUT F. FRG X RADIOASTRONOMIE Michael Rosa EUROPEAN SOUTHERN OBSERVATORY FRG X B. Wolf HEIDELBERG STATE OBSERVATORY FRG X R. M. Humphreys MINNESOTA, UNIVERSITY OF USA Rolf-Peter Kudritzki MUNICH UNIVERSITY FRG X Nolan R. Walborn STSCI USA Klaus P. Simon MUNICH UNIVERSITY FRG X ------------------------------------------------------------------------------------ 3. Description of proposed observations. (The following text has been revised, April 1991, to describe the post- reassessment modified observing plan. In the original version planned in 1988- 89, each of the 4 known components in Eta Car was to be observed individually with the tiny 0.1" FOS aperture. However, the components cannot be fully separated in this way with the ST's imperfect p.s.f.; hence the following revised plan, which seeks mainly to distinguish between the primary component and its fainter companions.) The 4 speckle-resolved components of Eta Carinae are all within a 0.3" region. Their relative (offset) positions are known to a precision of about 0.03" from several independent and mutually consistent speckle observations during 1983--1989. The primary component A is probably the LBV star, while its companions BCD may be either stars or compact blobs of ejecta. Because all 3 objects BCD are to the northwest of A, we can separate the spectrum of object A from the combined spectrum of B+C+D with the 0.3" FOS aperture. Here is the procedure: (1) The first step is a fairly routine peak-up on the combined object A+B+C+D. This defines a reference location called PKUP, a sort of centroid of ABCD (peak of convolution with the effective p.s.f.). (2) Next, offset about 0.2" southeast from PKUP, to a location called SE. Simulations with a realistic p.s.f. have shown that this offset ----( question 3 continued in next section )---- from the peak-up location gives nearly the maximum ratio of (counts due to A)/(counts due to B+C+D), for a fairly wide range of brightness ratios A/(B+C+D). (The ratio of counts A/(B+C+D) is expected to be of the order of 5 at position SE.) Several FOS gratings are used to obtain a spectrum at position SE. (3) Similarly, an offset location NW, about 0.2" northwest of PKUP, gives the maximum ratio of counts (B+C+D)/A, probably about 3. (4) A few short exposures are also taken at a nearby offset location called NE, and at PKUP too, to roughly indicate the contributions of local diffuse emission-line gas to the spectra taken at SE and NW. ...When all these steps have been done, differences between the spectra obtained in steps 2 and 3 should reveal the qualitative difference between object A and the fainter components B+C+D. Detailed modeling of all the data with the known ST/FOS characteristics should enable us to quantitatively estimate the separate spectra A vs. B+C+D, well enough for good atmospheric analysis of star A and rougher analysis of objects B, C, and D. Obviously these data are also needed for planning any future detailed observations of A, B, C, D individually. ...We will use the blue digicon with 5 FOS gratings to cover wavelengths 1200--5300 A. S/N ratios of the order of 50 per sampling element (1/4 diode) are needed for the detailed analysis. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. (1) High spatial resolution is needed to resolve the multiple system of Eta Carinae. Ground-based speckle observations cannot provide good spectroscopic data on this object. Moreover, the small FOS apertures are better than larger ground-based apertures for minimizing spectral contamination by emission lines from surrounding circumstellar gas. (2) The UV part of the spectrum is indispensable for analysis of the photosphere and stellar wind of each star. If any of the components turn out to be nebular objects, then UV emission lines are critical -- especially since they would probably turn out to be nitrogen-rich. Existing UV data obtained with the IUE include everything within a 3" aperture, heavily contaminated by circumstellar diffuse material. (3) For the proposed NLTE analyses, a sufficiently high spectral resolution and S/N ratio are necessary. ...These requirements are met only by the ST/FOS. Spectroscopic observations have been and are being pursued essentially to the limits attainable from the ground or with IUE. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. UV example, grating G190H with the blue detector: Primary object "A" is expected to have a flux somewhat less than 1.E-12 erg cm-2 s-1 A-1 in the 1600-- 2000 A wavelength region. Using estimates of 0.012 for for the basic instrument efficiency and 0.1 for the 0.3" aperture's throughput, and another factor of 0.6 to correct for the necessary 0.15" off-centering, we estimate roughly 4 counts/s per diode in this wavlength range. Thus a half-hour exposure gives roughly 7000 counts per diode and a S/N of the order of 40 for a 1/4-diode resolution element, except that contamination by the companion objects BCD is likely to reduce the effective S/N. The count rates are considerably higher for the longer- wavelength gratings, and lower for G130H. (S/N's listed in our observing plan may be optimistic.) Numbers for the combined fainter objects B+C+D are comparable to those for object A alone. In most cases we have aimed for S/Ns of 40 or more, to allow disentangling the different linear combinations of A and B+C+D as well as adequate spectral analysis later. ... We are very conscious of the need to carefully avoid excessive count rates with the FOS. Our flux estimates are based on photometry and spectrophotometry cited, e.g., in Ap.J.305, 867, supplemented by measurements of CCD images to determine how much of the light comes from the central core. (The possible count-rate danger is one reason why we are not using the red digicon; the other reason of course is the time needed to switch between BL and RD.) ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. No special scheduling requests. Page 4 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. (This is the original answer to this question, 1988:) The data will be reduced both at the Munich Observatory and also, in parallel, at Minnesota. Two software specialists at the Munich institute are funded by the German research ministry as part of a major soft- and hardware network dedicated to projects in space astronomy. This will be used by Kudritzki's group to reduce the data. At Minnesota the IRAF/SDAS software package will be used with a SUN computer system. Initial classification estimates will be made by Walborn and Humphreys. More detailed analysis by modeling, at Munich, will follow. Effective temperature, gravity, and helium abundance can be determined from photospheric spectra by fitting observed profiles of H, HeI, HeII lines with very detailed NLTE multi- level calculations. The UV part of the spectrum is more important than the visual for abundance analyses of O-type stars. The P-Cygni wind profiles will be fitted by detailed radiative transfer calculations, supplemented by hydrodynamic factors, to derive wind velocities and mass-loss rates. Analyses will be done differentially, relative to galactic O-stars, in order to minimize systematic uncertainties caused by deficiencies in the codes or the atomic parameters. If any of the objects are found to be nebular, or have overlying nebular lines, Davidson and Rosa will attempt interpretation of these. Details cannot be stated in advance because we do not know whether we'll find shock- or photoionization heating, etc. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Basic relative positions of the 4 components are already known from several independent and mutually consistent sets of ground-based speckle data. Additional data on separations of the 4 components may be provided by some short- exposure PC images planned as part of a GTO program by D. Ebbets, in which Davidson and Walborn are assisting. Davidson has done a considerable amount of ground-based astrometric work on the position of the core of Eta Car and also to provide a "special catalog" for ST acquisition in this crowded region. ------------------------------------------------------------------------------------ 9. Description of previous HST work. See question 8 above. Originally it was hoped that short-exposure FOC images made in program 1255 GTO/FOC-86G would also be available, (Weigelt is involved there), but Eta Car was removed from the list of highest-priority targets for that program. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). (This is the original, 1988 answer to this question:) Munich: Drs. K. Butler & S. Becker will assist in NLTE theory and atomic physics. A. Pauldrach and J. Puls will contribute to stellar wind hydrodynamics and diagnostics. NLTE model atmosphere, line formation, and stellar wind codes are implemented on a CDC Cyber 185 and a Cray 1 directly linked to the Institute. Funding of the calculations that are done in Munich will cause no problems. Minnesota: The Graduate School of the University contributed $12000 toward the cost of the SUN purchased by Davidson, Humphreys, and others. Additional equipment and software is continually being added in the usual modern fashion. ------------------------------------------------------------------------------------ 11. Address Information Name: KRIS DAVIDSON Category: PI Institution: UNIVERSITY OF MINNESOTA Address: 116 CHURCH ST. S.E. City: MINNEAPOLIS State: MN Zip Code: 55455 Country: USA Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2338c [ 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 HD93308-PKUP STAR; LBV; MULTIPLE RA = 10H 45M 03.62S +/- 2000 1 V = 7.6 +/- 0.3 -OFFSET ETA- STAR 0.04S , 2 B-V = 0.7 +/- 0.2 CAR-PKUP- DEC = -59D 41' 03.90" +/- 3 F-CONT(4800) = 3.0 +/-.6 E-12 OFFSET 0.30", 4 F-CONT(2000) = 2.5 +/-.6 E-12 PLATE-ID = ZZZQ 5 F-CONT(1400) = 2.0 +/-.6 E-12 6 E(B-V) = 0.9 +/- 0.2 Comments: PEAKUP REF POSITION FOR TARGETS 2-4. ETA CAR HAS FOUR KNOWN COMPONENTS ABCD, SEPARATIONS 0.1 TO 0.3 ARCSEC. TARGET 1 IS A PEAKUP CENTROID LOCATION WITHIN ABCD. FLUXES QUOTED FOR TARGET 1 REPRESENT ROUGH TOTAL OF ALL 4 COMPONENTS. PLATE-ID REFERS TO A SPECIAL CATALOG. ------------------------------------------------------------------------------------------------------------------------------------ 2 HD93308-SE STAR; MASSIVE LBV; HIGH R = 0.179", 2000 1 V = 8.8 +/- 0.4 ETA-CAR-SE LUMINOSITY STAR PA = 142D, 2 B-V = 0.8 +/- 0.2 FROM 1 3 F-CONT(4800) = 1.0 +/-.5 E-12 4 F-CONT(4200) = 0.9 +/-.5 E-12 5 F(2600) = 1.3 +/-2.0 E-12 6 F-CONT(2000) = 0.7 +/-.5 E-12 7 F-CONT(1400) = 0.6 +/-.5 E-12 Comments: TARGET 2 REPRESENTS PRIMARY COMPONENT A. MORE PRECISELY, THIS IS OFFSET WHERE MAX RESPONSE RATIO A/(B+C+D) IS EXPECTED USING 0.3" FOS APER. QUOTED FLUX IS ROUGHLY BRTNESS OF A, DIVIDED BY 1.5 TO CORRECT FOR NECESSARY 0.15" OFF-CENTER POINTING. FE II EMIS ENHANCES FLUX AROUND 2600 A. ------------------------------------------------------------------------------------------------------------------------------------ 3 HD93308-NW STAR; HIGH LUMINOSITY R = 0.240" , 2000 1 V = 9.7 +/- 0.6 ETA-CAR-NW MULTIPLE OBJECT PA = 322D , 2 B-V = 0.6 +/- 0.2 FROM 1 3 F-CONT(4800) = 5.0 +/- 1.5 E-13 4 F-CONT(4200) = 5.0 +/- 1.5 E-13 5 F(2600) = 7.0 +/- 2.0 E-13 6 F-CONT(2000) = 5.0 +/- 1.5 E-13 7 F-CONT(1400) = 5.0 +/- 1.5 E-13 Comments: TARGET 3 REPRESENTS COMPONENTS BCD. MORE PRECISELY, THIS IS OFFSET WHERE MAXIMAL RESPONSE RATIO (B+C+D)/A IS EXPECTED USING THE 0.3" FOS APERTURE. QUOTED FLUX IS VERY ROUGH AND REPRESENTS SUM B+C+D, DIVIDED BY 2 TO CORRECT FOR NECESSARY OFF- CENTER POINTING. OBJECTS BCD MAY BE COMPACT BLOBS, NOT STARS. ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2338c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 4 HD93308-NE STAR; HII REGION; R = 0.36" , 2000 1 V = 10.7 +/- 1.0 ETA-CAR-NE GASEOUS BACKGROUND PA = 45D , 2 B-V = 0.6 +/- 0.3 FROM 1 3 F(4800) = 2.0 +/- 1.0 E-13 4 F(4200) = 2.0 +/- 1.0 E-13 5 F(2600) = 2.0 +/- 1.0 E-13 Comments: TARGET 4 REPRESENTS LOCAL DIFFUSE BACKGROUND, FOR MODELING SPECTRA TAKEN ON MAIN TARGETS 2 AND 3. TARGETS 2-3-4 FORM APPROX EQUILATERAL TRIANGLE, MARGINALLY RESOLVED WITH 0.3" FOS APERTURE. QUOTED FLUX FOR TARGET 4 IS MERELY A PLAUSIBLE GUESS. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2338c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 30 HD93308- FOS/BL ACQ/ 1.0 G570H 4600- SEARCH-SIZE=6 1 0.7S 60 2 1 ONBOARD ACQ FOR 40 PKUP-OFFSET PEAK 4820 SCAN-STEP=0.7 CYCLE 1 Comments: ONLY 4600-4820 RANGE ENABLED TO EXCLUDE H-BETA. S-TO-N RATIOS ASSUME SMALLEST PLAUSIBLE FLUX, BECAUSE THE TRUE BRIGHTNESS OF THE CORE OF ETA CAR IS VERY UNCERTAIN. ------------------------------------------------------------------------------------------------------------------------------------ 40 HD93308- FOS/BL ACQ/ 0.5 G570H 4600- SEARCH-SIZE=5 1 1S 60 2 1 ONBOARD ACQ FOR 50 PKUP-OFFSET PEAK 4820 SCAN-STEP=0.24 CYCLE 1 Comments: ONLY 4600-4820 RANGE ENABLED TO EXCLUDE H-BETA. ------------------------------------------------------------------------------------------------------------------------------------ 50 HD93308- FOS/BL ACQ/ 0.3 G570H 4600- SEARCH-SIZE=6 1 2S 60 2 1 ONBOARD ACQ FOR 60 PKUP-OFFSET PEAK 4820 SCAN-STEP=0.075 CYCLE 1 Comments: ONLY 4600-4820 RANGE ENABLED TO EXCLUDE H-BETA. 6 X 6 MAP FROM THIS STAGE OF PEAKUP MAY BE USEFUL FOR MODELING THE SPECTRAL DATA. ------------------------------------------------------------------------------------------------------------------------------------ 60 HD93308- FOS/BL ACQ/ 0.3 G570H 4600- SEARCH-SIZE=4 1 6S 100 2 1 ONBOARD ACQ FOR PKUP-OFFSET PEAK 4820 SCAN-STEP=0.033 210-530 CYCLE 1 Comments: ONLY 4600-4820 RANGE ENABLED TO EXCLUDE H-BETA. ------------------------------------------------------------------------------------------------------------------------------------ 110 DEFINE # FOS/BL ACCUM 0.3 G570H 4610- 1 500 S 60 3 # MAINOBS 5150 Comments: S/N RATIOS QUOTED FOR ALL SCIENCE EXPOSURES REFER TO A 1/ 4-DIODE RESOLUTION ELEMENT. THESE S/N RATIOS ARE PROBABLY OPTIMISTIC BECAUSE THERE IS CONTAMINATION BY THE COMPANION OBJECTS. ------------------------------------------------------------------------------------------------------------------------------------ 120 DEFINE # FOS/BL ACCUM 0.3 G400H 3250- 1 700 S 70 4 # MAINOBS 4800 ------------------------------------------------------------------------------------------------------------------------------------ 130 DEFINE # FOS/BL ACCUM 0.3 G270H 2240- 1 500 S 70 5 # MAINOBS 3290 ------------------------------------------------------------------------------------------------------------------------------------ 140 DEFINE # FOS/BL ACCUM 0.3 G190H 1590- 1 1800 S 50 6 # MAINOBS 2300 ------------------------------------------------------------------------------------------------------------------------------------ 150 DEFINE # FOS/BL ACCUM 0.3 G130H 1220- 1 2400 S 25 7 # MAINOBS 1600 ------------------------------------------------------------------------------------------------------------------------------------ 210 USE HD93308-SE 2 CYCLE 1 MAINOBS ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2338c [ 8] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 310 USE HD93308-NW 3 CYCLE 1 MAINOBS ------------------------------------------------------------------------------------------------------------------------------------ 410 HD93308-NE FOS/BL ACCUM 0.3 G570H 4610- 1 500 S 40 3 4 CYCLE 1 5150 ------------------------------------------------------------------------------------------------------------------------------------ 420 HD93308-NE FOS/BL ACCUM 0.3 G400H 3250- 1 500 S 40 4 4 CYCLE 1 4810 ------------------------------------------------------------------------------------------------------------------------------------ 430 HD93308-NE FOS/BL ACCUM 0.3 G270H 2240- 1 500 S 40 5 4 CYCLE 1 3290 ------------------------------------------------------------------------------------------------------------------------------------ 510 HD93308- FOS/BL ACCUM 0.5 G570H 4610- 1 120 S 100 3 5 CYCLE 1 PKUP-OFFSET 5150 ------------------------------------------------------------------------------------------------------------------------------------ 520 HD93308- FOS/BL ACCUM 0.5 G400H 3250- 1 120 S 100 4 5 CYCLE 1 PKUP-OFFSET 4810 ------------------------------------------------------------------------------------------------------------------------------------ 530 HD93308- FOS/BL ACCUM 0.5 G270H 2240- 1 120 S 100 5 5 CYCLE 1 PKUP-OFFSET 3290 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2338c [ 9] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=6 SCAN-STEP=0.7 SEARCH-SIZE=5 SCAN-STEP=0.24 SCAN-STEP=0.075 SEARCH-SIZE=4 SCAN-STEP=0.033 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 6.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category MASSIVE STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 40;CYCLE 1; ONBOARD ACQ FOR 50;CYCLE 1; ONBOARD ACQ FOR 60;CYCLE 1; ONBOARD ACQ FOR 210-530;CYCLE 1; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G570H G400H G270H G190H G130H ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD93308-PKUP-OFFSET ETA-CAR-PKUP-OFFSET HD93308-SE ETA-CAR-SE HD93308-NW ETA-CAR-NW HD93308-NE ETA-CAR-NE ------------------------------------------------------------------------------------------------------------------------------------