17705( 4) - 25-Apr-2025 13:16:33 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17705 Version: 4 Check-in Time: 25-Apr-2025 13:16:33 STScI Edit Number: 0 Title UV STIS Spectroscopy of the MgII nebula around Eta Carinae ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Nathan Smith University of Arizona Y CoI: Dr. Jon A. Morse California Institute of Technology N ------------------------------------------------------------------------------------ Abstract This proposal seeks to obtain deep STIS spectra of the extended ultraviolet Mg II emission recently discovered around the supermassive star Eta Carinae, with the longslit oriented across the flow direction, in both poles of the bipolar Homunculus Nebula. This will measure the expansion speed and velocity dispersion of this warm neutral gas, which will be combined with published proper-motion measurements to determine its tilt angle and deprojected outflow speed, and thus the 3D outflow structure. While density and mass-loss rate from Mg II emission alone are uncertain, spatially resolved velocity structure can be translated to approximate relative density and outflow speed as a function of latitude. These provide a unique probe of the radius, surface gravity, temperature, and rotation rate of the star that launched this wind. This is critical information for piecing together the physical properties of the unstable LBV star in the decades leading up to its eruption, and vital for constraining the physical interaction if it was a stellar merger event. LBVs more generally are hypothesized to be the products of mass transfer and mergers, but Eta Car is the only one for which this detailed pre-eruption information can be derived observationally. Understanding outer material into which ejecta expand is critical for the extended Eta Car system and hydrodynamics of bipolar nebulae more generally. ------------------------------------------------------------------------------------ Observations Description ------------------------ Observational goal is to obtain long-slit STIS spectra of the Mg II 2800 AA line from ejecta immediately outside the bipolar Homunculus nebula in order to measure radial velocities along the slit, and hence, 3D kinematics in combination with proper motions already punlished. The STIS spectra use 4 CVZ orbits at each of two positions, 8 orbits total. Each position ois a separate visit. The slit centers are offset to the SE and NW (in the two polar directions) and the slit orientation is roughly perpendicular to the polar axis of the nebula, cutting across the polar axis. For each visit, we acquire on the central star, and then offset to the NW or SE. We do not perform a peakup, since the targets are nebulous and spread over a few arcsec. ------------------------------------------------------------------------------------ 17705( 4) - 25-Apr-2025 13:16:33 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ETA-CAR-NWOF ISM, BIPOLAR OUTFLOW RA-OFF=-0.00250D, DEC-OFF=8.20", J2000 V = 6.21 F FROM 3 Reference Frame: ICRS Extended: YES Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 2 ETA-CAR-SEOF ISM, BIPOLAR OUTFLOW RA-OFF=0.00250D, DEC-OFF=-8.60", J2000 V = 6.21 F FROM 3 Reference Frame: ICRS Extended: YES Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 3 ETA-CAR STAR, CIRCUMSTELLAR RA=10H45M3.5460S, J2000 V = 6.21 MATTER, ETA CARINAE DEC=-59D41'3.95" STAR Reference Frame: ICRS Extended: YES Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 17705( 4) - 25-Apr-2025 13:16:33 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.1 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 90.0 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17705( 4) - 25-Apr-2025 13:16:33 - [ 4] Visit: 01 (STIS NWOFF) Visit Requirements: CVZ; ORIENT 84D TO 89 D On Hold Comments: Additional Comments: STIS spectrum with slit oriented roughly perpendicular to the polar axis, offset to NW Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ETA-CAR STIS/CCD ACQ F25ND3 MIRROR 1 0.2 S (0.2 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ETA-CAR-NWO STIS/CCD ACCUM 52X0.5 G230MB 2794 CR-SPLIT=5 1 10080 S POS TARG 0.0, 0.0; FF (20160 S) PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ ETA-CAR 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 1 1 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 2 1 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 3 1 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 4 2 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 5 2 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 1 3 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 2 3 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 3 3 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 4 4 N/A ETA-CAR-NWOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 5 4 N/A 17705( 4) - 25-Apr-2025 13:16:33 - [ 5] Visit: 02 (STIS NWOFF) Visit Requirements: CVZ; ORIENT 84D TO 89 D On Hold Comments: Additional Comments: STIS spectrum with slit oriented roughly perpendicular to the polar axis, offset to NW Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ETA-CAR STIS/CCD ACQ F25ND3 MIRROR 1 0.2 S (0.2 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ETA-CAR-SEO STIS/CCD ACCUM 52X0.5 G230MB 2794 CR-SPLIT=5 1 10080 S POS TARG 0.0, 0.0; FF (20160 S) PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ ETA-CAR 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 1 1 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 2 1 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 3 1 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 4 2 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 1 none none 5 2 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 1 3 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 2 3 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 3 3 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 4 4 N/A ETA-CAR-SEOFF 2 STIS/CCD ACCUM 52X0.5 G230MB 2794 2 none none 5 4 N/A 17705( 4) - 25-Apr-2025 13:16:33 - [ 6] Summary Form for Proposal 17705 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.5, F25ND3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=5 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ, ORIENT 84D TO 89 D, PATTERN 1 2, POS TARG 0.0, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G230MB, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names ETA-CAR, ETA-CAR-NWOFF, ETA-CAR-SEOFF ------------------------------------------------------------------------------------------------------------------------------------