15686( 2) - 07-Feb-2019 19:49:32 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15686 Version: 2 Check-in Time: 07-Feb-2019 19:49:32 STScI Edit Number: 0 Title A near-IR spectrum of the old Type Ia SN 2017erp ------------------------------------------------------------------------------------ Type Cycle GO/DD 26 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Or Graur Harvard University Y ------------------------------------------------------------------------------------ Abstract We ask for 1 orbit of WFC3/IR+G141 to acquire a spectrum of a Type Ia supernova (SN Ia) >500 days after maximum light. The SN in question, SN 2017erp, is one that we have been following along with several other SNe Ia with HST in F160W and F350LP. These observations have revealed a plateau in the F160W (H) band, after which the light curve once again begins to decline. Several works have published near-IR spectra of SNe Ia taken during this plateau, but no near-IR spectrum of a SN Ia exists at >500 days, during the second decline phase. The spectrum we will acquire through this proposal will be the first such spectrum for a SN Ia; reveal why SNe Ia transition from the plateau to the decline phase; and complete our analysis. ------------------------------------------------------------------------------------ Observations Description ------------------------ The goal of this program is to obtain a G141 spectrum of a faint supernova (F160W=22 mag, Vega). It is located in an outer spiral arm of a nearby, face-on galaxy, so there is fear of contamination. I ask that the observations be carried out as soon as possible, to maximize the signal-to-noise ratio of the resultant spectrum. The available visibility windows, coupled with the above constraint, afford only a limited range of orients. To minimize contamination, I ask that the orient be limited to +305 to +307 degrees. I couple the grism observation with a direct image in F160W. Although usually F140W would be used, I have been observing this supernova in F160W, so another photometry point in this filter would be valuable. ------------------------------------------------------------------------------------ 15686( 2) - 07-Feb-2019 19:49:32 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN-2017ERP EXT-STAR, SUPERNOVA RA=15H09M14.8100S, J2000 F160W = 21.5 (Vega) TYPE IA DEC=-11D20'3.20" Reference Frame: Other: SIMBAD Extended: NO Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.5 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 15686( 2) - 07-Feb-2019 19:49:32 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.636 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 41.788 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15686( 2) - 07-Feb-2019 19:49:32 - [ 4] Visit: 01 (grism sequence) Visit Requirements: ORIENT 305D TO 307 D; BEFORE 10-MAR-2019:00:00:00 On Hold Comments: Additional Comments: 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 SN-2017ERP WFC3/IR MULTIAC GRISM1024 G141 SAMP-SEQ=SPARS100, NSAMP=12 1 DEF PATTERN 3 1-2 CUM (2205.872 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2017ERP WFC3/IR MULTIAC GRISM1024 F160W NSAMP=10, SAMP-SEQ=SPARS25 1 DEF CUM (455.874 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN-2017ERP 1 WFC3/IR MULTIAC GRISM102 G141 1 none none none 1 N/A CUM 4 SN-2017ERP 1 WFC3/IR MULTIAC GRISM102 G141 2 none none none 1 N/A CUM 4 SN-2017ERP 2 WFC3/IR MULTIAC GRISM102 F160W 1 none none none 1 N/A CUM 4 SN-2017ERP 2 WFC3/IR MULTIAC GRISM102 F160W 2 none none none 1 N/A CUM 4 15686( 2) - 07-Feb-2019 19:49:32 - [ 5] Summary Form for Proposal 15686 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures GRISM1024 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=10, NSAMP=12, SAMP-SEQ=SPARS100, SAMP-SEQ=SPARS25 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 10-MAR-2019:00:00:00, ORIENT 305D TO 307 D, PATTERN 3 1-2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F160W, G141 ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN-2017ERP ------------------------------------------------------------------------------------------------------------------------------------