0Assigned ID: 410
----- Attempting Submission 1 (Fri Apr 08 07:12:36 GMT 2016) -----
HST Phase I Proposal 410 (HST_WD1145.apt) successfully submitted.
Receipt: # 410-1
----- Attempting Submission 2 (Fri Apr 08 18:07:29 GMT 2016) -----
HST Phase I Proposal 410 (HST_WD1145.apt) successfully submitted.
Receipt: # 410-20----- Attempting Submission 1 (Tue Jul 19 09:26:13 GMT 2016) -----
----- Attempting Submission 2 (Wed Jan 18 05:35:32 GMT 2017) -----
----- Attempting Submission 3 (Wed Jan 18 19:21:39 GMT 2017) -----A White Dwarf with an Actively Disintegrating AsteroidWe have recently discovered a white dwarf with an actively disintegrating asteroid. Using data from the Kepler extended mission, transits with periods less than 5 hours have been detected from at least 6 objects. Evidence for circumstellar dust was found by comparing UKIDSS and WISE data. High-resolution optical spectroscopic data from Keck show that the host star is heavily polluted with 11 heavy elements and also displays numerous absorption lines from circumstellar gas. This system has become much more active since its original discovery. We were granted mid-cycle observing time with Hubble and a few other telescopes to perform simultaneous observations. Our preliminary analysis already shows new emerging features. We propose to monitor this system two more times for the next year and study the real time disintegration of an asteroid around a white dwarf.Our goal is threefold: (i) use TIME-TAG data to monitor the potential changes of circumstellar lines; (ii) measure a transit light curve in the ultraviolet; (iii) to detect additional trace elements. To cover all the lines of interest, we will employ the G130M grating with a central wavelength of 1291 Angstrom and a wavelength coverage of 1137-1274 Angstrom and 1292-1432 Angstrom.
We used the COS spectra as an input template and with ETC v24.1, we find that an average S/N of 20 can be reached in most regions for a total exposure time of 17000 sec (6 orbits). For target acquisition, we will only employ ACQ/IMG because the position of our target is well known. Including overheads, a total of 6 orbits is required for each set of observation. In order to cover the full 4.5 period, we separate the 6 orbits into two set of observations, 3 orbits each and separtaed by 10 orbits in between.
We will repeat this set of observations and a total of 12 orbits are required. We prefer the two set of observations to be scheduled at least 30 days apart to understand the long term evolution of the system. We will also combine all the data together to produce a high quality ultraviolet spectrum of the target. The total S/N (including our mid-cycle data) would be over 30 and we will be able to detect or put good upper limit on a set of trace elements.
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