15855( 4) - 14-Oct-2019 15:06:32 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15855 Version: 4 Check-in Time: 14-Oct-2019 15:06:32 STScI Edit Number: 1 Title A new low-metallicity LBV in M33: Is it a blue straggler? ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Jennifer Andrews University of Arizona Y CoI: Dr. Nathan Smith University of Arizona N ------------------------------------------------------------------------------------ Abstract Luminous blue variables (LBVs) are evolved massive stars that undergo dramatic mass loss and irregular variability. Whether LBVs originate from a single massive progenitor or through binary interaction is still debated. They statistically prefer isolated locations in star forming galaxies, far away from O-type stars, which indicates a likely binary origin. Located in a young stellar cluster, the newly discovered LBV outburst MCA1-B in M33 affords us the rare opportunity to independently age-date an LBV based on the ages of the other cluster members. By determining the cluster turn off mass we can ascertain if the LBV is overluminous compared to the rest of the cluster, and therefore determine decisively if it has been rejuvenated through binary evolution. If it does appear to be younger than the surrounding population, we can determine quantitatively how much mass it has gained or what the likely masses of the merger components were. Only now while the LBV is in a fainter, quiescent phase and only with the UV sensitivity and spatial resolution of WFC3 can we get the UV-to-optical imaging needed to create accurate color-magnitude diagrams of the LBV's host cluster in order to age-date MCA1-B. The LBV eruption of MCA-1B was also unusually hot at peak, which may be linked to its low-metallicity environment in the outskirts of M33; this may provide critical clues about the physical LBV instability. ------------------------------------------------------------------------------------ Observations Description ------------------------ The observations are all set up in one visit of two orbits, but these orbits can be separated as need be. The object(s) of interest are bright enough to likely not need post-flash, but please advise if this should be added. There are no special orients needed, although we would prefer both orbits taken at the same orient if they need to separated into separate visits. We are using full frame instead of sub-array because we need the whole nearby stellar population. ------------------------------------------------------------------------------------ 15855( 4) - 14-Oct-2019 15:06:32 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 MCA1-B STELLAR CLUSTER, OB RA=01H32M37.6800S, J2000 V = 20 ASSOCIATION, OPEN DEC=+30D40'5.60" CLUSTER, YOUNG ASSOCIATION Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15855( 4) - 14-Oct-2019 15:06:32 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15855( 4) - 14-Oct-2019 15:06:32 - [ 4] Visit: 01 Visit Requirements: 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 MCA1-B WFC3/UVI ACCUM UVIS2 F606W 1 216 S (432 PATTERN 1 1-2 S S) ------------------------------------------------------------------------------------------------------------------------------------ 2 MCA1-B WFC3/UVI ACCUM UVIS2 F225W 1 740 S S (1480 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MCA1-B WFC3/UVI ACCUM UVIS2 F438W 1 320 S (320 S S) ------------------------------------------------------------------------------------------------------------------------------------ 4 MCA1-B WFC3/UVI ACCUM UVIS2 F814W 1 271 S (542 PATTERN 1 4-5 S S) ------------------------------------------------------------------------------------------------------------------------------------ 5 MCA1-B WFC3/UVI ACCUM UVIS2 F336W 1 700 S S (1400 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 MCA1-B WFC3/UVI ACCUM UVIS2 F438W 1 320 S (320 POS TARG S S) -3.4088166189286015E-4, -1.425343380764952 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ MCA1-B 1 WFC3/UVI ACCUM UVIS2 F606W 1 none none none 1 N/A S MCA1-B 1 WFC3/UVI ACCUM UVIS2 F606W 2 none none none 1 N/A S MCA1-B 2 WFC3/UVI ACCUM UVIS2 F225W 1 none none none 1 N/A S MCA1-B 2 WFC3/UVI ACCUM UVIS2 F225W 2 none none none 1 N/A S MCA1-B 3 WFC3/UVI ACCUM UVIS2 F438W none none none none 1 N/A S MCA1-B 4 WFC3/UVI ACCUM UVIS2 F814W 1 none none none 2 N/A S MCA1-B 4 WFC3/UVI ACCUM UVIS2 F814W 2 none none none 2 N/A S MCA1-B 5 WFC3/UVI ACCUM UVIS2 F336W 1 none none none 2 N/A S 15855( 4) - 14-Oct-2019 15:06:32 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ MCA1-B 5 WFC3/UVI ACCUM UVIS2 F336W 2 none none none 2 N/A S MCA1-B 6 WFC3/UVI ACCUM UVIS2 F438W none none none none 2 N/A S 15855( 4) - 14-Oct-2019 15:06:32 - [ 6] Summary Form for Proposal 15855 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1-2, PATTERN 1 4-5, POS TARG -3.4088166189286015E-4, -1.425343380764952 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F225W, F336W, F438W, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names MCA1-B ------------------------------------------------------------------------------------------------------------------------------------