Ultraviolet Spectra of a Normal Standard Candle

Target SN-IA: There is no need or capability to test the scheduling of observations of generic targets in Phase I. This warning will go away the next time the proposal is loaded. 0 Assigned ID: 1075 ----- Attempting Submission 1 (Fri Apr 08 23:53:21 GMT 2016) ----- Warning (Visit Planner): Target SN-IA: There is no need or capability to test the scheduling of observations of generic targets in Phase I. This warning will go away the next time the proposal is loaded. acq/peak exposures have been added -1708225681 ----- Attempting Submission 1 (Thu Jul 21 19:01:15 GMT 2016) ----- ----- Attempting Submission 2 (Mon Jun 26 13:16:19 GMT 2017) ----- HST Phase II Proposal 14665 (erptest.apt) successfully submitted. Receipt: # 14665-2 ----- Attempting Submission 3 (Mon Jun 26 18:40:28 GMT 2017) ----- Ultraviolet Spectra of a Normal Standard Candle Type Ia Supernovae (SNe Ia) are important tools in the study of our universe, but are not fully understood at rest-frame ultraviolet (UV) wavelengths. High quality spectra in the mid-UV (<2500 Angstroms) are scarce because of the need for space based observations and the faint flux levels in the UV due to the absorption of iron peak elements. While bad for flux levels, the iron line blanketing makes the UV spectrum very sensitive to differences in the temperature, density, and metallicity--important ingredients for SN modeling. An explosion of ultraviolet observations of type Ia Supernovae (SNe Ia) has revealed a diversity in the UV properties of even optically normal SNe. HST has recently obtained several excellent UV spectra reaching mid-UV wavelengths for examples of SNe that are "UV-blue" or have broad or moderately narrow optical light curves. Yet we are still lacking a good UV spectrum of an UV and optically normal SN Ia. Dozens of UV light curves from Swift/UVOT and dozens of rest-frame UV observations of high redshift SNe observed from the ground and HST will benefit from the physical insight gained from high quality UV spectra. These spectra will be crucial to modelling the varied behavior we observe in the UV. We propose target of opportunity observations with HST to provide mid-UV photometry and spectroscopy of a normal SN Ia this cycle. These will serve as benchmarks against which to compare photometry, other spectroscopy, and theoretical models. This is a target of opportunity program for UV observations of one type Ia supernova to be discovered during cycle 24. We will observe at four epochs spaced by five days for 3,3,3, and 5 orbits each for our nominal target. Swift UV observations will have been performed prior to triggering and will be used to perform the STIS-MAMA safety checks. Some modifications might be required once we trigger based on the brightness of the object. For example, a brighter object might have 6 visits with fewer orbits per visit. Intergalactic Medium and Cosmology 6 false true false false false false SUPPORTED EXT-STAR SUPERNOVA TYPE IA NO J2000 uvw1=15.3 +/- 0.1, uvm2=18.5 +- 0.2 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/CCD Spectroscopic No No G430L 4300 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/CCD Spectroscopic No No G430L 4300 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/CCD Spectroscopic No No G430L 4300 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/CCD Spectroscopic No No G430L 4300 1498501444584 Timing link suitability includes constraints ([06 After 05 by 2.0 to 5.0 days]) The scheduling data was generated by CASM 25.2. 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