14897( 2) - 13-Dec-2016 19:55:40 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14897 Version: 2 Check-in Time: 13-Dec-2016 19:55:40 STScI Edit Number: 0 Title Quantifying the Impact of High-Energy Electrons on Low-Temperature Dwarfs ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Peter K. G. Williams Harvard University Y CoI: Prof. Edo Berger Harvard University N CoI: Dr. Trent J. Dupuy University of Texas at Austin N CoI: Dr. Quinn Konopacky University of California - Los Angeles N CoI: Dr. Jan Forbrich University of Vienna N CoI: Dr. Jonathan Irwin Smithsonian Institution Astrophysical N Observatory CoI: Prof. David Charbonneau Harvard University N ------------------------------------------------------------------------------------ Abstract Radio studies show that, despite their low temperatures, very low-mass stars and brown dwarfs can generate strong magnetic fields and accelerate ~MeV electrons. Strikingly, the resulting phenomenology resembles that of a scaled- up planet more than a scaled-down star, with aurorae and radiation belts thousands of times brighter than those of Jupiter. In both Jupiter and the "ultracool dwarfs, " radio emission traces energetic magnetospheric electrons. In Jupiter, many of these electrons eventually crash into the upper atmosphere, their energy driving haze production and vertical mixing. We do not know how efficiently magnetic energy is deposited in ultracool dwarf atmospheres, or the chemistry that this drives. This deposition leads to FUV emission, however, and we have recently calculated that the most radio-active ultracool dwarf, NLTT33370B, should produce enough FUV to be detectable with Hubble. We propose a 4-hour simultaneous VLA/HST observation to measure the impact of this deposition process. Using a novel VLA sub-arraying tactic, we will leverage well-vetted planetary radiation belt models to obtain an unprecendently detailed view of how electrons migrate through this dwarfs's inner magnetosphere. Hubble will probe their ultimate fate. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose an HST UV imaging observation aiming to achieve S/N = 5 in our fiducial model of the auroral UV emission of NLTT 33370 B (described in the VLA proposal text). This observation is to be conducted simultaneously with a Very Large Array observation. The Solar Blind Channel of the ACS provides the highest raw sensitivity. Using a realistic model of the auroral emission spectrum (Gustin+, 2013JMoSp.291..108G), we find that observations with the SHADOW constraint provide the most efficient use of HST time. Given the system's known NUV emission (see Williams+, 2015ApJ...799..192W), we propose dithered exposures in both the F115LP and F165LP filters to allow "red leak" subtraction. Using the ACS instrument handbook and the HST exposure time calculator, we find that the desired S/N can be achieved in 2 orbits, with 2470 s (226 s) of on-target exposure in the F115LP (F165LP) filters, after 14897( 2) - 13-Dec-2016 19:55:40 - [ 2] accounting for overheads; the achieved S/N is 6.1 (6.2). [NOTE: these numbers have not been updated to match the precise values derived from use of the orbit planner.] We have checked that the proposed observations do not exceed ACS/SBC count limits, and both the HST Bright Object Tool and GALEX catalogs confirm that there are no sources in a 70'' diameter that threaten instrument safety. The SHADOW constraint means that NLTT 33370 B is visible to HST for a relatively brief window, from 2017 Apr 9 to 2017 Jul 5 with some gaps. This window overlaps a VLA configuration change (D -> C; 2017 May 15--25), but the configuration change fortuitously mostly overlaps a gap in HST visit schedulability. ------------------------------------------------------------------------------------ 14897( 2) - 13-Dec-2016 19:55:40 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NLTT33370 STAR, M V-IV RA=13H14M20.1850S +/- 0.0004", J2000 V = 15.83 +/- 0.05 spectral type M7, DEC=+13D19'58.96" +/- 0.0009" GALEX NUV magnitude 21.0 +- 0.2, not detected in GALEX FUV Reference Frame: ICRS Extended: NO Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Astrometry has been updated from Dupuy et al 2016. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2010.0 -0.016990631583788857 -0.18358000000000002 0.057975 ------------------------------------------------------------------------------------------------------------------------------------ 14897( 2) - 13-Dec-2016 19:55:40 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type ACS-SBC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.472 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 44.4 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 14897( 2) - 13-Dec-2016 19:55:40 - [ 5] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: This visit is to be conducted simultaneously with an observation on the Very Large Array. It also has a SHADOW constraint which constrains the time of its execution to a few-month window. 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 NLTT33370 ACS/SBC ACCUM SBC F115LP 1 734 S SHADOW; PATTERN 2 1 (1468 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NLTT33370 ACS/SBC ACCUM SBC F165LP 1 74 S (148 SHADOW; PATTERN 2 2 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 NLTT33370 ACS/SBC ACCUM SBC F115LP 1 734 S SHADOW; PATTERN 2 3 (1468 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 NLTT33370 ACS/SBC ACCUM SBC F165LP 1 74 S (148 SHADOW; PATTERN 2 4 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 | ------------------------------------------------------------------------------------------------------------------------------------ NLTT33370 1 ACS/SBC ACCUM SBC F115LP 1 none none none 1 N/A NLTT33370 1 ACS/SBC ACCUM SBC F115LP 2 none none none 1 N/A NLTT33370 2 ACS/SBC ACCUM SBC F165LP 1 none none none 1 N/A NLTT33370 2 ACS/SBC ACCUM SBC F165LP 2 none none none 1 N/A NLTT33370 3 ACS/SBC ACCUM SBC F115LP 1 none none none 2 N/A NLTT33370 3 ACS/SBC ACCUM SBC F115LP 2 none none none 2 N/A NLTT33370 4 ACS/SBC ACCUM SBC F165LP 1 none none none 2 N/A NLTT33370 4 ACS/SBC ACCUM SBC F165LP 2 none none none 2 N/A 14897( 2) - 13-Dec-2016 19:55:40 - [ 6] Summary Form for Proposal 14897 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures SBC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/SBC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 2 1, PATTERN 2 2, PATTERN 2 3, PATTERN 2 4, SHADOW ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F115LP, F165LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names NLTT33370 ------------------------------------------------------------------------------------------------------------------------------------