0 Assigned ID: 1719 ----- Attempting Submission 1 (Fri Mar 01 20:09:20 GMT 2013) ----- HST Phase I Proposal 1719 (hst_apt.pdf.apt) successfully submitted. ----- Attempting Submission 2 (Fri Mar 01 22:24:02 GMT 2013) ----- HST Phase I Proposal 1719 (hst_apt.pdf.apt) successfully submitted. ----- Attempting Submission 3 (Sat Mar 02 00:05:17 GMT 2013) ----- HST Phase I Proposal 1719 (hst_apt.pdf.apt) successfully submitted. ----- Attempting Submission 4 (Sat Mar 02 00:35:04 GMT 2013) ----- HST Phase I Proposal 1719 (hst_apt.pdf.apt) successfully submitted. ----- Attempting Submission 5 (Sat Mar 02 00:44:04 GMT 2013) ----- HST Phase I Proposal 1719 (hst_apt.pdf.apt) successfully submitted. ----- Attempting Submission 6 (Sat Mar 02 00:45:58 GMT 2013) ----- HST Phase I Proposal 1719 (hst_apt.pdf.apt) successfully submitted. ----- Attempting Submission 7 (Sat Mar 02 00:50:48 GMT 2013) ----- HST Phase I Proposal 1719 (hst_apt.pdf.apt) successfully submitted. ----- Attempting Submission 8 (Sat Mar 02 00:53:15 GMT 2013) ----- 0 ----- Attempting Submission 1 (Tue Jun 25 09:54:16 GMT 2013) ----- ----- Attempting Submission 2 (Thu Jun 27 20:50:08 GMT 2013) ----- ----- Attempting Submission 3 (Thu Jun 27 21:50:28 GMT 2013) ----- HST Phase II Proposal 13299 (hst_phase2_submit3.apt) successfully submitted. ----- Attempting Submission 4 (Fri Jun 28 00:15:12 GMT 2013) ----- HST Phase II Proposal 13299 (hst_phase2_submit3.apt) successfully submitted. ----- Attempting Submission 5 (Fri Jun 28 00:17:49 GMT 2013) ----- Silver Linings: Using Cloud Maps to Understand the L/T Spectral Transtion Recent observations in the time domain have revealed large amplitude variability for a subset of objects at the transition between cloudy L and clear T spectral types, indicative of patchy cloud coverage. We propose to obtain time-resolved near-infrared spectra of two highly variable L/T transition brown dwarfs and an unusually blue L dwarf in order to make spectrally and spatially resolved maps of their surfaces. By decomposing the spectral time series into principal components we can determine the number of different surface spectra that contribute to the variability and test whether the current paradigm---namely that variability for these objects results due to holes in the cloud layer---is accurate. Our previous Cycle 18 observations (GO12314, PI:Apai) of two early T-dwarfs suggest a simple two-surface scenario where variability across a wide range of atmospheric pressures is correlated, and presumably governed by the horizontal distribution of condensates (Apai, Radigan & Buenzli et al., submitted), while the behavior of a T6.5 dwarf was observed to be significantly more complex (Buenzli et al. 2012). While these data are suggestive, a pattern cannot be inferred from observations of only two objects. The proposed observations will double the sample of variable L/T transition objects mapped with WFC3 grism spectroscopy from 2 to 4, and allow us to establish a pattern; namely, do all L/T transition objects share similar spectral variations, indicative of a common mechanism and number of surface components? We will then investigate whether this pattern extends to unusually blue L-dwarfs, also hypothesized to have patchy clouds. We are monitoring 3 brown dwarfs for variability using WFC3 IR with the G141 grism. The goal is to obtain a precise spectral time series for each target. We stare at each target for N consecutive orbits (where N=3,4 or 5 depending on the rotation period of the target) without dithering. At the beginning of each orbit, a direct image is taken for wavelength calibration. PROGRAM STRUCTURE: Each target is observed in a single visit. Each visit consists of several orbits. One "exposure sequence" has been defined for each orbit. EXPOSURE SEQUENCES: At the beginning of each orbit we take one or more** direct images of the target in the G141 grism FOV for the purpose of wavelength calibration. We then take a series of spectra without dithering, for the remainder of the orbit. We do not offset between the direct image and spectral sequence, nor between individual spectra. The source is placed near the center of the _full array_, which is near the edge of the 256 x 256 sub array. In this position, the 1st order of the spectrum is dispersed along the x-axis of the array, away from the position of the direct image (can the CS please check that this understanding is correct?). **When there was room in the orbit without sacrificing spectral exposures, multiple direct images are taken to protect against cosmic rays. ORIENTATION REQUIREMENTS: We require that the spectral traces of our targets do not overlap with those of other stars in the field. Orientation constraints were calculated as follows: PA=absolute position angle between target and backgound star d= distance between target and background star ORIENT = position angle of HST A_WFC3 = angle of WFC3 wrt HST = 45 deg PA_WFC3 = PA - (A_WFC3 + ORIENT) = position angle between target and background star in WFC3 detector FOV dY = absolute distance between spectral traces, perpedicular to the direction of dispersion We have required that dy > 2 arcseconds, where dY=d * cos(PA_WFC3). In some cases an extra buffer of up to +/- 5 deg was added due to uncertainties in source and background star proper motions. TARGETS Our targets are brown dwarfs (bright in the IR), and do not appear in optical images using the target confirmation tool. They also have significant proper motions, which have been provided. Their positions wrt to the WFC3 FOV have been checked using the Aladin tool. COOL STARS Default false false false false false SUPPORTED STAR BROWN DWARF T This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J=15.3 STAR BROWN DWARF T J2000 J2000 J=15 STAR BROWN DWARF T This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J=14.0 WFC3/IR Spectroscopic No No G141 WFC3/IR Spectroscopic No No G141 WFC3/IR Spectroscopic No No G141 The scheduling data was generated by CASM 21.2. 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CASM was run in Phase II mode. 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