16026( 4) - 03-Dec-2019 16:20:36 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16026 Version: 4 Check-in Time: 03-Dec-2019 16:20:36 STScI Edit Number: 1 Title Caught in the Act: Closest TDE Discovered Before Peak Light ------------------------------------------------------------------------------------ Type Cycle GO/DD 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Tzu-Yu Hung University of California - Santa Cruz Y CoI: Prof. Ryan Foley University of California - Santa Cruz N CoI: Dr. Stephen Bradley Cenko NASA Goddard Space Flight Center N CoI: Prof. Suvi Gezari University of Maryland N CoI: Dr. Sjoert van Velzen New York University N CoI: Mr. Nathaniel Roth University of Maryland N ------------------------------------------------------------------------------------ Abstract Wide-field optical transient surveys have discovered about a dozen of tidal disruption events (TDEs), which belong to a rare class of transient phenomena that occur when an unlucky star is tidally disrupted by a supermassive black hole (SMBH). In recent years, two emission mechanisms (circularization v.s. reprocessing) have been put forward to explain the excess in the UV and optical emission in TDEs, which is unexpected according to the classical TDE framework. Albeit timely observations have only been made for ~5 TDEs so far, UV spectroscopy is critical to disentangling these scenarios, as most strong atomic features fall in this band. These emission and absorption line diagnostics can shine light on the physical state (velocity, density, composition) of the emitting gas (in analogy with quasars). Being the closest and earliest TDE discovered and classified to date, AT2019qiz (at z=0.0151) is being intensively monitored by observations across the electromagnetic spectrum as it offers the first-ever opportunity to probe the early-time properties of a TDE. Here we propose to obtain 3 epochs of FUV and NUV observations of AT2019qiz at t_peak - 1 month, t_peak, and t_peak + 1 month with HST. These observations will allow us to test whether outflow is ubiquitous amongst TDEs and constrain its early evolution for the first time. ------------------------------------------------------------------------------------ Observations Description ------------------------ We request 3 epochs of UV spectroscopy of the TDE AT2019qiz, over the wavelength range from 1200-3000A. Assuming a typical rise time of 50 days for TDEs, our designed cadence will be sampling AT2019qiz at t = tpeak - 1 month, tpeak, and tpeak + 1 month, respectively. We use the most recent inferred blackbody temperature from the Swift-UVOT pho- 16026( 4) - 03-Dec-2019 16:20:36 - [ 2] tometry (T~22, 000 K) as the input spectrum to estimate the expected SNR in different instrumental congurations. Assuming an orbital visibility of 53 minutes, we find that we can obtain ~35 min of on-source exposure in a single orbit. We can achieve the best SNR in the near-UV (NUV) using STIS with the NUV-MAMA detector. Therefore, we also choose to use STIS with the FUV- MAMA detector for the far-UV (FUV) spectroscopy to avoid switching instruments during the same visit. We request 1 orbit of HST time for each proposed epoch. We estimate the SNR con- servatively by employing the most recent r-band magnitude (~16 mag). We can achieve a SNR per resolution element of >20 for the far UV with the G140L grating (over the range from 1150-1700A and a SNR per resolution element of >30 for the near UV (1650-3150A) for the continuum emission within 1 ks and ~500s exposure time, respectively. Even in the case where the TDE declines rapidly, the 1 ks exposure time will still yield a SNR~5 in the FUV and SNR~8 in the NUV at r = 20 mag. ------------------------------------------------------------------------------------ 16026( 4) - 03-Dec-2019 16:20:36 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 AT2019QIZ GALAXY, ACCRETION DISK, RA=04H46M37.8800S, J2000 V = 16 DISK, NUCLEUS, WIND DEC=-10D13'34.90" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 16026( 4) - 03-Dec-2019 16:20:36 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.55 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 90.0 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 16026( 4) - 03-Dec-2019 16:20:36 - [ 5] Visit: 01 Visit Requirements: BEFORE 22-OCT-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 AT2019QIZ STIS/CCD ACQ F28X50LP MIRROR 1 5 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2019QIZ STIS/FUV ACCUM 52X0.2 G140L 1425 1 335 S PATTERN 1 2 -MAMA (1005 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AT2019QIZ STIS/NUV ACCUM 52X0.2 G230L 2376 1 170 S (510 PATTERN 1 3 -MAMA 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2019QIZ 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 1 N/A -MAMA AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 1 N/A -MAMA AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 1 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 2 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 3 none none none 1 N/A -MAMA 16026( 4) - 03-Dec-2019 16:20:36 - [ 6] Visit: 02 Visit Requirements: AFTER 01 BY 25 D TO 40 D 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 AT2019QIZ STIS/CCD ACQ F28X50LP MIRROR 1 5 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2019QIZ STIS/FUV ACCUM 52X0.2 G140L 1425 1 335 S PATTERN 1 2 -MAMA (1005 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AT2019QIZ STIS/NUV ACCUM 52X0.2 G230L 2376 1 170 S (510 PATTERN 1 3 -MAMA 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2019QIZ 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 1 N/A -MAMA AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 1 N/A -MAMA AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 1 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 2 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 3 none none none 1 N/A -MAMA 16026( 4) - 03-Dec-2019 16:20:36 - [ 7] Visit: 03 Visit Requirements: AFTER 02 BY 25 D TO 40 D 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 AT2019QIZ STIS/CCD ACQ F28X50LP MIRROR 1 5 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2019QIZ STIS/FUV ACCUM 52X0.2 G140L 1425 1 335 S PATTERN 1 2 -MAMA (1005 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AT2019QIZ STIS/NUV ACCUM 52X0.2 G230L 2376 1 170 S (510 PATTERN 1 3 -MAMA 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2019QIZ 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 1 N/A -MAMA AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 1 N/A -MAMA AT2019QIZ 2 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 1 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 2 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/NUV ACCUM 52X0.2 G230L 2376 3 none none none 1 N/A -MAMA 16026( 4) - 03-Dec-2019 16:20:36 - [ 8] Visit: 04 Visit Requirements: AFTER 03 BY 25 D TO 40 D 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 AT2019QIZ STIS/CCD ACQ F28X50LP MIRROR 1 5 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2019QIZ STIS/NUV ACCUM 52X0.2 G230L 2376 1 692 S PATTERN 1 2 -MAMA (2076 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AT2019QIZ STIS/FUV ACCUM 52X0.2 G140L 1425 1 876 S PATTERN 1 3 -MAMA (2628 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2019QIZ 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A AT2019QIZ 2 STIS/NUV ACCUM 52X0.2 G230L 2376 1 none none none 1 N/A -MAMA AT2019QIZ 2 STIS/NUV ACCUM 52X0.2 G230L 2376 2 none none none 1 N/A -MAMA AT2019QIZ 2 STIS/NUV ACCUM 52X0.2 G230L 2376 3 none none none 1 N/A -MAMA AT2019QIZ 3 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 2 N/A -MAMA AT2019QIZ 3 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 2 N/A -MAMA AT2019QIZ 3 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none none none 2 N/A -MAMA 16026( 4) - 03-Dec-2019 16:20:36 - [ 9] Summary Form for Proposal 16026 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 25 D TO 40 D, AFTER 02 BY 25 D TO 40 D, AFTER 03 BY 25 D TO 40 D, BEFORE 22-OCT-2019:00:00:00, PATTERN 1 2, PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names AT2019QIZ ------------------------------------------------------------------------------------------------------------------------------------