17522( 6) - 22-Oct-2024 20:17:01 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17522 Version: 6 Check-in Time: 22-Oct-2024 20:17:01 STScI Edit Number: 1 Title Betelgeuse: The Great Dimming Redux? ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Andrea Dupree Smithsonian Institution Astrophysical Y Observatory CoI: Thomas Calderwood American Association Of Variable Star N Observers CoI: Dr. Caroline Huang Smithsonian Institution Astrophysical N Observatory CoI: Dr. Thomas Granzer Leibniz-Institut für Astrophysik Potsdam N (AIP) CoI: Dr. Kateryna Kravchenko Max Planck Institute for Extraterrestrial N Physics CoI: Dr. Lynn D Matthews Massachusetts Institute of Technology N CoI: Dr. Miguel Montarges Observatoire de Paris - Section de Meudon N CoI: Prof. Klaus G Strassmeier Leibniz-Institut für Astrophysik Potsdam N (AIP) CoI: Michael Weber Leibniz-Institut für Astrophysik Potsdam N (AIP) CoI: Prof. Pierre Kervella Observatoire de Paris N CoI: Dr. Morgan MacLeod Smithsonian Institution Astrophysical N Observatory CoI: Dr. alain jorissen Universite Libre de Bruxelles N ------------------------------------------------------------------------------------ Abstract The historic Great Dimming of the red supergiant Betelgeuse in 2020 was initiated at a propitious confluence of maximum outflow of the 400-day fundamental mode of pulsation and the 2200-day Long Secondary Period. This condition will occur again sometime between Fall 2024 and Spring 2025. We propose to follow its behavior. Spatially resolved ultraviolet spectra of the star achievable with STIS can provide the connecting link between the convective activity on the stellar surface and the formation of a dust cloud in the outer atmosphere. This campaign will probe the entire atmosphere, from the photosphere to the circumstellar environment, with a combination of ground-based interferometric/AO imaging, radio observations, and optical and UV spectroscopy, creating a comprehensive contemporaneous sampling of the star, its variation with time, and the effects on its extended atmosphere. We should learn whether the event of 2019-2020 was a 'random' 17522( 6) - 22-Oct-2024 20:17:01 - [ 2] occurrence or results from oscillation phase superposition. Two visits are requested during Cycle 31, and 4 visits during Cycle 32 to obtain spatially resolved ultraviolet spectra at this unique time. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to obtain short slit echelle spectra of Betelgeuse with the medium resolution E230M grating in the wavelength range of 2303 to 3111\AA. We will use the small (0.1" x 0.025") slit for maximum spatial resolution. Only with this supported slit can we take full advantage of the STIS/HST resolution. Betelgeuse has no record of flaring and previous STIS observations demonstrate that the STIS detectors are not subject to any danger. For a 4 orbit visit: In order to execute the tomographic studies, we require a S/N of ~50 at 2800A. The S/N will be higher at longer wavelengths. MARCS models demonstrate that there are 615 photospheric lines in the spectral region 2800-3100A that can be used to develop masks selecting features from different photospheric layers. In addition, the chromospheric emission lines reveal dynamics, densities, and emission measures of the chromospheric plasma. We plan to cover the optical diameter of the star (42 mas) with a center pointing, and offsets at +/-25 mas with deep exposures. Then followed by pointing off the optical disk and offset to $\pm$ 50 mas for an exposure yielding S/N ~20. We have used the ETC for STIS, assuming a Castelli/Kurucz model of a M2 supergiant, and normalizing it to the observed STIS flux (from MAST) near 2786A (to avoid Mg II emission) for various pointing offsets on the star at different dates. We used spectra from the 'normal' state of Betelgeuse (not the spectra taken during 2019 Sep-Nov). Ideally a range of exposure times would be used in response to the varying stellar flux. However, we cannot predict the ultraviolet flux level a priori, as it is not related to the optical V-magnitude. We therefore have selected an average value. To achieve the desired S/N, the center exposure requires 34 minutes; the offset at +/-25 mas requires 42 to 50 minutes, and the lower S/N off the optical disk requires 10 minutes. At the declination of Betelgeuse, each HST orbit allows 49-52 minutes on target. These spectra will require guide star acquisition, target acquisition, and two peak ups with the small slit (0.1" x 0.025") in the first orbit of a visit. This takes 31.7 minutes; then we offset to +50 mas for a 9.45 min exposure, followed by offset to -50 m as for a 8.5 minute exp. In the following 3 orbits we will continue the offset points. Orbits following the first require 17522( 6) - 22-Oct-2024 20:17:01 - [ 3] ~6.7 min for reacquisition, leaving 45.2 minutes fo r exposures and readout. Orbit 2: Spectrum at center (45.2 min exp) Orbit 3: spectrum at +25 mas (44.5 mi n exp.) Orbit 4: spectrum at -25 mas (44.5 min exp) ------------------------------------------------------------------------------------ 17522( 6) - 22-Oct-2024 20:17:01 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 -ALF-ORI STAR, M III-I, RA=05H55M10.3054S, J2000 V = +0.42 +/- 0.2 SUPERGIANT O DEC=+07D24'25.43" Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0018514498381218894 0.011300000000000001 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 17522( 6) - 22-Oct-2024 20:17:01 - [ 5] Visit: 01 Visit Requirements: BETWEEN 01-NOV-2024:00:00:00 AND 01-JAN-2025:00:00:00 On Hold Comments: Additional Comments: 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 -ALF-ORI STIS/CCD ACQ F25ND5 MIRROR 1 1 S (1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 -ALF-ORI STIS/CCD ACQ/PEA 0.2X0.09 G230LB 2375 1 1 S (1 S) K Comments: 3 pt linear peakup; telescope returned to central dwell position. ------------------------------------------------------------------------------------------------------------------------------------ 3 -ALF-ORI STIS/CCD ACQ/PEA 0.1X0.03 G230LB 2375 1 1 S (1 S) K Comments: Spiral in 0.1X0.03 aperture. ------------------------------------------------------------------------------------------------------------------------------------ 4 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 567 S POS TARG +0.050, null -MAMA see below (536 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 507 S POS TARG -0.050, null -MAMA see below (476 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 2713 S -MAMA see below (2580 S) Comments: Center point ------------------------------------------------------------------------------------------------------------------------------------ 7 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 2713 S POS TARG +0.025, null -MAMA see below (2580 S) ------------------------------------------------------------------------------------------------------------------------------------ 8 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 2713 S POS TARG -0.025, null -MAMA see below (2580 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ -ALF-ORI 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A -ALF-ORI 2 STIS/CCD ACQ/PEA 0.2X0.09 G230LB 2375 none none none none 1 N/A K 17522( 6) - 22-Oct-2024 20:17:01 - [ 6] 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 | ------------------------------------------------------------------------------------------------------------------------------------ -ALF-ORI 3 STIS/CCD ACQ/PEA 0.1X0.03 G230LB 2375 none none none none 1 N/A K -ALF-ORI 4 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 1 536.0 S -MAMA -ALF-ORI 5 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 1 476.0 S -MAMA -ALF-ORI 6 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 2 2580.0 S -MAMA -ALF-ORI 7 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 3 2580.0 S -MAMA -ALF-ORI 8 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 4 2580.0 S -MAMA 17522( 6) - 22-Oct-2024 20:17:01 - [ 7] Visit: 02 Visit Requirements: AFTER 01 BY 30 D TO 60 D; BEFORE 01-JAN-2025 On Hold Comments: Additional Comments: 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 -ALF-ORI STIS/CCD ACQ F25ND5 MIRROR 1 1 S (1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 -ALF-ORI STIS/CCD ACQ/PEA 0.2X0.09 G230LB 2375 1 1 S (1 S) K Comments: 3 pt linear peakup; telescope returned to central dwell position. ------------------------------------------------------------------------------------------------------------------------------------ 3 -ALF-ORI STIS/CCD ACQ/PEA 0.1X0.03 G230LB 2375 1 1 S (1 S) K Comments: Spiral in 0.1X0.03 aperature. ------------------------------------------------------------------------------------------------------------------------------------ 4 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 567 S POS TARG +0.050, null -MAMA see below (536 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 507 S POS TARG -0.050, null -MAMA see below (476 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 2713 S -MAMA see below (2580 S) Comments: Center point ------------------------------------------------------------------------------------------------------------------------------------ 7 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 2713 S POS TARG +0.025, null -MAMA see below (2580 S) ------------------------------------------------------------------------------------------------------------------------------------ 8 -ALF-ORI STIS/NUV ACCUM 0.1X0.03 E230M 2707 1 2713 S POS TARG -0.025, null -MAMA see below (2580 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ -ALF-ORI 1 STIS/CCD ACQ F25ND5 MIRROR none none none none 1 N/A -ALF-ORI 2 STIS/CCD ACQ/PEA 0.2X0.09 G230LB 2375 none none none none 1 N/A K 17522( 6) - 22-Oct-2024 20:17:01 - [ 8] 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 | ------------------------------------------------------------------------------------------------------------------------------------ -ALF-ORI 3 STIS/CCD ACQ/PEA 0.1X0.03 G230LB 2375 none none none none 1 N/A K -ALF-ORI 4 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 1 536.0 S -MAMA -ALF-ORI 5 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 1 476.0 S -MAMA -ALF-ORI 6 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 2 2580.0 S -MAMA -ALF-ORI 7 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 3 2580.0 S -MAMA -ALF-ORI 8 STIS/NUV ACCUM 0.1X0.03 E230M 2707 none none none none 4 2580.0 S -MAMA 17522( 6) - 22-Oct-2024 20:17:01 - [ 9] Summary Form for Proposal 17522 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.1X0.03, 0.2X0.09, F25ND5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 30 D TO 60 D, BEFORE 01-JAN-2025, BETWEEN 01-NOV-2024:00:00:00 AND 01-JAN-2025:00:00:00, POS TARG +0.025, null, POS TARG +0.050, null, POS TARG -0.025, null, POS TARG -0.050, null ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E230M, G230LB, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names -ALF-ORI ------------------------------------------------------------------------------------------------------------------------------------