18113( 7) - 09-Feb-2026 20:59:50 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18113 Version: 7 Check-in Time: 09-Feb-2026 20:59:50 STScI Edit Number: 4 Title UV Exo-Aurorae: Multi-Wavelength Observations of a Radio Emitting T-dwarf to confirm Auroral Activity in the Ultraviolet. ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Mr. Cian O'Toole Trinity College Dublin Y CoI: Dr. Johanna Vos Trinity College Dublin N CoI: Dr. Evert Nasedkin Trinity College Dublin N CoI: Dr. Melodie Kao Lowell Observatory N CoI: Anna D. Zuckerman University of Colorado at Boulder N CoI: Dr. Michael P. Fitzgerald University of California - Los Angeles N CoI: Mr. Aidan Gibbs University of California - Los Angeles N CoI: Dr. John Sebastian Pineda University of Colorado at Boulder N CoI: Dr. Yifan Zhou The University of Virginia N CoI: Dr. Robert Kavanagh Stichting Astronomisch Onderzoek in N Nederland (ASTRON) CoI: Dr. Allison McCarthy Boston University N ------------------------------------------------------------------------------------ Abstract We propose simultaneous UV and radio observations with HST/STIS and the VLA of 2M1047+21, a cool, radio-emitting brown dwarf, to measure the first UV auroral emission from an extrasolar world. Over the last two decades, brown dwarfs have been discovered to emit powerful radio signatures indicative of aurorae. However, a conclusive detection of auroral UV emission on a brown dwarf has remained elusive. This program will constrain electron precipitation energies, resolve the magnetosphere structure and verify if auroral processes in brown dwarfs follow similar scaling relations to planetary aurorae. Detecting auroral emission in the UV would bridge the gap between the stellar and planetary regimes and complete picture of extrasolar auroral emission. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe the first ultraviolet aurora outside the solar system by stacking observations of 6 consecutive orbits with HST STIS G140L. Whiile previous attempts to observe UV exo-aurorae have been tentative o far, this will provide the longest observations yet of a brown dwarf in the UV. We aim to obtain a S/N >5 by stacking these observations over the 6 orbits between 1400-1600 Angstroms. This along with simultaneous VLA observations will allow us to confirm that the UV detection is auroral in nature. ------------------------------------------------------------------------------------ 18113( 7) - 09-Feb-2026 20:59:50 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 2MASSW-J1047 STAR, BROWN DWARF RA=10H47M51.7874S, J2000 V = 25 Spectral Type: T6.5; 2MASS J 539+212423 DEC=+21D24'14.92" :15.819 [0.059], 2MASS H: 15.797 [0.120] , 2MASS K: 16.20 [0.03] (Flux values in order of: filter-name: flux-value [error]; reference: SIMBAD) Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.405 -0.12061132614232731 -0.495854149 0.09473 ------------------------------------------------------------------------------------------------------------------------------------ 18113( 7) - 09-Feb-2026 20:59:50 - [ 3] Visit: 01 (Orbit Visit 1) Visit Requirements: 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 2MASSW-J104 STIS/CCD ACQ 50CCD MIRROR 1 200 S (200 7539+212423 S) Comments: I used the T2 Phoenix 1200K model for the target acquisition. This is approx 300K hotter than this object, however, I normalised it to realistic T6.5 dwarf values. An exposiure time of 200 seconds should be ok, and is greater than the exposure time for the previous UV auroral observation of 2M1237 by HST PID 15870 (150 seconds). This should be ok. ------------------------------------------------------------------------------------------------------------------------------------ 2 2MASSW-J104 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 BUFFER-TIME=1000 1 1215 S 7539+212423 -MAMA G (1215 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 2MASSW-J104 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 BUFFER-TIME=1000 1 2571 S 7539+212423 -MAMA G (2571 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 2MASSW-J104 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 BUFFER-TIME=1000 1 2529 S 7539+212423 -MAMA G (2529 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2MASSW-J1047539+212 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A 423 2MASSW-J1047539+212 2 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 none none none none 1 N/A 423 -MAMA G 2MASSW-J1047539+212 3 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 none none none none 2 N/A 423 -MAMA G 2MASSW-J1047539+212 4 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 none none none none 3 N/A 423 -MAMA G 18113( 7) - 09-Feb-2026 20:59:50 - [ 4] Visit: 02 (Visit 2) Visit Requirements: AFTER 01 BY 17 Orbits TO 19 Orbits 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 2MASSW-J104 STIS/CCD ACQ 50CCD MIRROR 1 200 S (200 7539+212423 S) Comments: I used the T2 Phoenix 1200K model for the target acquisition. This is approx 300K hotter than this object, however, I normalised it to realistic T6.5 dwarf values. An exposiure time of 200 seconds should be ok, and is greater than the exposure time for the previous UV auroral observation of 2M1237 by HST PID 15870 (150 seconds). This should be ok. ------------------------------------------------------------------------------------------------------------------------------------ 2 2MASSW-J104 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 BUFFER-TIME=1000 1 1215 S 7539+212423 -MAMA G (1215 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 2MASSW-J104 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 BUFFER-TIME=1000 1 2571 S 7539+212423 -MAMA G (2571 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 2MASSW-J104 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 BUFFER-TIME=8000 1 2529 S 7539+212423 -MAMA G (2529 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2MASSW-J1047539+212 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A 423 2MASSW-J1047539+212 2 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 none none none none 1 N/A 423 -MAMA G 2MASSW-J1047539+212 3 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 none none none none 2 N/A 423 -MAMA G 2MASSW-J1047539+212 4 STIS/FUV TIME-TA 52X0.5D1 G140L 1425 none none none none 3 N/A 423 -MAMA G 18113( 7) - 09-Feb-2026 20:59:50 - [ 5] Summary Form for Proposal 18113 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD, 52X0.5D1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1000, BUFFER-TIME=8000 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 17 Orbits TO 19 Orbits ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names 2MASSW-J1047539+212423 ------------------------------------------------------------------------------------------------------------------------------------