16498( 3) - 15-Mar-2021 17:50:59 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16498 Version: 3 Check-in Time: 15-Mar-2021 17:50:59 STScI Edit Number: 0 Title A STIS look at ASASSN-14ko: a recently discovered periodic nuclear transient with rapid FUV evolution ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Benjamin John Shappee University of Hawaii Y CoI: Anna Payne University of Hawaii N CoI: Dr. Chris S. Kochanek The Ohio State University N CoI: Dr. Katie Auchettl University of California - Santa Cruz N CoI: Dr. Thomas Holoien Carnegie Institution of Washington N CoI: Dr. Krzysztof Z. Stanek The Ohio State University N ------------------------------------------------------------------------------------ Abstract ASASSN-14ko is a recently discovered, periodically flaring, nuclear transient within known AGN ESO 253-G003. The flares have a mean period of ~114 days and a nonzero, negative period derivative. The exact origin of these UV/optical flares is currently unknown. STIS UV observations of the rise, peak, and decline in the UV revealed rapid and dramatic evolution in Dec 2020 showing strong P Cygni profiles in the FUV for C IV and N V that rapidly changed. The UV spectra during all of the epochs substantially differ from any tidal disruption event (TDE) with UV spectroscopic observations and also differ from any AGN/quasar spectrum the proposers are familiar with. The rapid evolution itself is also unprecedented for TDEs which thus far have exhibited static or slowly evolving UV spectra. Most intriguing is that the appearance of the P Cygni profiles appears to correlate with X-ray diminings which are consistent with being due to obscuration. Combining the X-ray and STIS observations for the Dec flare a consistent picture of a rapid outflow, possibly a tidal stream, is emerging. Here we propose for 2 additional early-time STIS spectra covering the earliest phases of ASASSN-14ko's April 2021 outburst. These observations will bring into focus these dramatic spectroscopic and X-rays changes. ------------------------------------------------------------------------------------ Observations Description ------------------------ The impact of reduced-gyro operations on this project are uncertain, but, given that the epochs of these observations are highly constrained it is likely that the effect will be to further constrain or eliminate some of the epochs. ------------------------------------------------------------------------------------ 16498( 3) - 15-Mar-2021 17:50:59 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ASASSN-14KO GALAXY, ACCRETION DISK, RA=05H25M18.1170S +/- 0.10", J2000 Z = V = 14.5 +/- 0.2 at peak: MULTIPLE NUCLEI, DEC=-46D00'20.23" +/- 0.10" 0.042489 W1=15.69(0.04), M2=15.66(0.07), and NUCLEUS, QUASAR W2=15.64(0.04) Reference Frame: ICRS Comments: Note, this is the nucleaus of a galaxy, but, it is a complex galaxy. Please see submission notes. 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 ------------------------------------------------------------------------------------------------------------------------------------ 16498( 3) - 15-Mar-2021 17:50:59 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.3829 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 90.0 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 16498( 3) - 15-Mar-2021 17:50:59 - [ 4] Visit: 01 (Epoch 5) Visit Requirements: BETWEEN 29-MAR-2021:12:00:00 AND 30-MAR-2021:12:00:00 On Hold Comments: Additional Comments: Quiescence before ASASSN-14ko Dec 2020 outburst 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 ASASSN-14KO STIS/CCD ACQ 50CCD MIRROR 1 5 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ASASSN-14KO STIS/FUV ACCUM 52X0.2 G140L 1425 2 500 S PATTERN 2 2 -MAMA see below (4801 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 | ------------------------------------------------------------------------------------------------------------------------------------ ASASSN-14KO 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none 1 none 1 734.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none 2 none 1 734.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none 1 none 1 735.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none 2 none 2 866.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none 1 none 2 866.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none 2 none 2 866.0 S -MAMA 16498( 3) - 15-Mar-2021 17:50:59 - [ 5] Visit: 02 (Epoch 6) Visit Requirements: SCHED 90%; AFTER 01 BY 2.25 D TO 3.25 D On Hold Comments: Additional Comments: Rise of ASASSN-14ko Dec 2020 outburst 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 ASASSN-14KO STIS/CCD ACQ 50CCD MIRROR 1 5 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ASASSN-14KO STIS/FUV ACCUM 52X0.2 G140L 1425 2 500 S PATTERN 2 2 -MAMA see below (4177 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 | ------------------------------------------------------------------------------------------------------------------------------------ ASASSN-14KO 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none 1 none 1 630.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none 2 none 1 630.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none 1 none 1 631.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none 2 none 2 762.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none 1 none 2 762.0 S -MAMA ASASSN-14KO 2 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none 2 none 2 762.0 S -MAMA 16498( 3) - 15-Mar-2021 17:50:59 - [ 6] Summary Form for Proposal 16498 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD, 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 2.25 D TO 3.25 D, BETWEEN 29-MAR-2021:12:00:00 AND 30-MAR-2021:12:00:00, PATTERN 2 2, SCHED 90% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names ASASSN-14KO ------------------------------------------------------------------------------------------------------------------------------------