0Assigned ID: 1700
----- Attempting Submission 1 (Thu Apr 08 20:21:39 GMT 2021) -----This is my first time doing a phase 2 - we have used the same setup to programme 15947 for the instruments, ETC and observing strategy.
We have set 2 orients to rotate the detector so that the nearby bright star will not contaminate our target.
Note: 10 Sep 2021. Resubmitted as requested for 6 individual visits of 1 orbit each - however there are no timing/linking constraints in here. Can you please advise?901034360----- Attempting Submission 1 (Fri Jul 16 09:49:01 GMT 2021) -----
----- Attempting Submission 2 (Fri Sep 10 16:18:40 GMT 2021) -----Decoding the clouds on an irradiated inflated brown dwarfWe propose HST time-resolved spectroscopy of a rare, eclipsing white dwarf-brown dwarf binary. The brown dwarf in the binary is a mid-L dwarf and is irradiated by its 10,000 K white dwarf companion. The brown dwarf totally eclipses the white dwarf and the white dwarf parameters are well defined, meaning there is a directly measured radius of the brown dwarf, which is inflated compared to models of field dwarfs at the same age. As such this is the only inflated, irradiated cloudy L dwarf where atmospheric characterisation is possible, leading to insights into the processes occurring in the atmosphere.
We will obtain phase resolved spectra between 1.1 and 1.7 microns using WFC3 with the G141 set up in time-series mode.
We will combine our spectra with global circulation models and atmospheric models to:
1) Determine the effective temperature of the brown dwarf,
2) Study day-night heat redistribution in unprecedented detail
3) Determine if there are significant nightside clouds.
HST can uniquely obtain the high-precision, time-resolved, near-infrared spectroscopy required by our science goals.Observing Mode:
The observations will use the WFC3/IR G141 instrument in time-series mode, similar to the observations performed for the similar systems in HST Program 15947. The instrument's high throughput from 1.1 to 1.7 microns, the remarkable sensitivity in the 1.4~m water absorption band, and the extraordinary photometric stability make WFC3/IR G141 the best and, indeed, the only choice to achieve our goals. Due to the relative faintness of the target, we will to conduct the observations in staring mode. We will use the sub256 array and SPARS25, NSAMP=15 setup, which resulting in a cadence of 313 seconds, and 25s for each non-destructive read. The light curves at this cadence will resolve the spectral modulations at sample rates greater than ten per brown dwarf orbit.
We have specified 2 orient windows as we need to ensure light from a nearby, brighter star( J= 15.026 and H=14.4580) does not contaminate our data. We have specified orients so that the brighter star is well separated in the Y direction.
Exposure Time Calculation and Signal-to-Noise Ratio Estimate:
We estimate the required exposure times and SNR achieved using the WFC3 Exposure Time Calculator. For WD1032+011 we will achieve an SNR=216 in a single G141 exposure in white light. With 10 pixel-wide
spectral bins, typical in exoplanet transmission spectroscopy, the average SNR in each bin will exceed 60. We calculated the SNR requirements on the basis of distinguishing spectral modulations assuming a difference between the day and nightside spectra of 4% and a J-band modulation amplitude of 2%. WD1032+011 has a precise period measurement and ephemeris from radial velocity and lightcurve measurements, allowing us to phase-fold the light curves, further increasing the precision.
Reduced Gyro mode: We do not anticipate reduced gyro mode will affect this programme other than perhaps in reducing schedulability due to our Orient constraints. A smaller field of view is fine.We have built a strong team, collaborating on data from program 15947.
Dr Sarah Casewell is an expert on the observational characteristics of close white dwarf-brown dwarf binaries and irradited brown dwarfs. Dr Casewell has over 12 refereed publications relating to irradiated brown dwarfs, was involved in the discovery of half the known systems, and has published on almost all of them. She is also an expert in white dwarfs, with publications on spectra of white dwarfs both from HST and the ground. She is an expert in optical and infrared spectral analysis and will lead the management of the programme, data interpretation and analysis.
Dr Casewell is an STFC Ernest Rutherford Fellow at the University of Leicester in the UK. As such her independent fellowship will allow her to visit Arizona to work with the co-Is on this programme.
Dr. Daniel Apai is an expert on the observational characterization of extrasolar planet and brown dwarf atmospheres. Dr. Apai has led six HST programs on these topics that resulted in over 20 refereed papers, most of which utilized the same instrument and observing strategy as proposed for in the current proposal. Apai's group has also published numerous observational studies on hot Jupiters, both in transmission and in emission. As US Admin-PI Apai willl be responsible for the administration, and data interpretation. Dr. Apai is an Associate Professor of Astronomy and Planetary Sciences at The University of Arizona.
Dr Yifan Zhou is an expert in HST/WFC3 time-resolved observations of brown dwarfs and planetary-mass objects. Dr Zhou has published five papers based on such data, and hasadditional papers in preparation. Among other results Dr Zhou has provided a new, physically-motivated model for the HST/WFC3 charge trap and delayed release systematics, which has been widely adopted in the community. This correction significantly enhanced the accuracy and efficiency of HST time-resolved observations. He will lend his expertise on HST/WFC3 time-resolved observations to this project. Dr Zhou is a McDonald Fellow at UT Austin, becoming a 51-Peg b fellow in 2021 at UT Austin.
Dr Mark Marley is an expert on the atmospheric modeling of extrasolar planets and brown dwarfs. Dr Marley has led and co-authored over 200 refereed papers on atmospheric characterization. He will support this program through atmospheric modeling utilizing his state-of-the-art models.
Dr Stuart Littlefair is a world-leading expert on high time resolution observations of white dwarf binaries. He is a member of the team that built the high-cadence photometers ULTRACAM and HiPERCAM, and has extensive experience analysing time-series photometry and spectroscopy, including mass determination in white dwarf binaries, and pioneering novel methods for dealing with systematic noise of astrophysical and instrumental origin
Dr Vivien Parmentier is an expert in the atmospheric dynamics and radiative transfer modelling of hot Jupiter atmospheres and will provide models tobe used to interpret the observations. He is co-I on 5 HST proposals using WFC3/UVIS or IR and is PI of one proposal using WFC3/UVIS.
Dr Laura Mayorga (Co-I, JHU/APL) is an expert in one-dimensional theoretical modeling of cloudy and cloudless atmospheres of Jupiter-like planets and observations and modeling of phase curves for terrestrial and giant planets. She will lend her modelling expertise to the programme and her cloud modelling expertise will be essential to the success of the project.
Dr Xianyu Tan is an expert in the atmospheric dynamics of close-in gas giant planets and has produced a global circulation model for the similar system WD0137-349AB. He will generate bespoke GCM models of the system to compare to the HST phase curves.
Mr Ben Lew is an expert in data reduction and analysis of HST/WFC3 time-series spectroscopy. He has been a Co-I on 4 HST proposals and has led 3 papers based on HST/WFC3 data. He will assist with the data reduction.Stellar Physics and Stellar TypesExoplanets and Exoplanet Formation6falsefalsefalsefalsefalsefalsefalsefalseSUPPORTEDSTARBROWN DWARFDANOThis object was generated by the targetselector and retrieved from the SIMBAD database.WD1032J2000J2000z=19.29, Y=18.82, J=18.68, H=18.20WFC3/IRSpectroscopicNoNoG141/private/var/folders/w_/lrgrpxmn21l5cct7f1x383qw0002kw/T/OPVisit3505766834427199228.xmlTiming link suitability includes constraints ([Sequence (01 02 03 04 05 06) within 0.4 days])Hst Same orient constraint links visits (01 02 03 04 05 06)The scheduling data was generated by CASM 29.2.CASM was run in Phase II mode.2(Tic-Visit
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