Summary day 2

Neill (SEDM overview): review SEDM enhancements to increase reliability. Basically rebuilt the instrument from mechanical point of view, airtight enclosure etc. Replaced pickup prism, plumbing, cabling. Seems to show 20% improvement in efficiency! Planning to replace mirrors (pickoff and fold) in order to enhance throughput in blue and red sides. This is drop-in replacement, no nighttime lost. Pushing the limit now below g=19.5 and toward g=20. Can remove airmass limits. Waiting for clear weather for final throughput analysis.

Additional SEDM talks: Nadia, Rigault (pipeline). Please cite their papers!

Many thanks to the technical staff, engineers and mountain staff!

Nadia Blagorodnova (SEDM stats and performance): Showing how to access assignments via pharos to know what is going on and improve/modify assignment. Contact Nadia for an account. With remove airmass bound more targets should be accessible. Scheduler preview available. Looks at automated extractions, finding charts. Nadia shows usage statistics per program. Most use is BCS/RCF. 65% of specra produce classifications! Almost full use for science, mostly spectroscopy (no longer any shortage). Shows examples of interesting transients: ILRTs, LBVs, SN Ia-CSM, TDEs. Spectra are dominated by SNe Ia (>50%), but also many other types. Second most productive classifier after pessto, and catching up. Over 50% of request are completed.

Rachel Bruch – first year infant SN results: So far 350 CC SNe, 80% are SNe II. 184 spectroscopically classified SNe II for which we have access, of which 78 with non-detections <2.5d prior to first detection. Using ZTFquery tool by Rigault to get statistics and make sure no objects missed. Defining “Infant SNe” by 2.5d from non detection with rise of at least 0.5mag. This leaves 29 events. Most of these are regular SNe II (not IIb or IIn). Most objects are found in summer (mostly July). Most infants are within 2d of limit and about 50% within 1d. First spectra obtained within 2d of non detection for 11 objects (14 within 5d). Review of nature of “flash spectroscopy” features. Main marker is He II 4686. Shows how this is detected even by P60. 64% of events with spectra within 2d show flash features – these are common, and thus CSM is common. ZTF is really robust in finding infant SNe, we need more spectroscopy follow-up, applied for.

Maayane Soumagnac – Survey of SNe IIn: Trying to answer the question: how many SNe IIn show evidence for non-spherical CSM. Review of SNe IIn. Connection with LBVs as possible progenitors motivates studies testing CSM asphericity. Reports on PTF12glz from GALEX+PTF campaign. Analyzed using a simple slab diffusion model. Apparently growing radius during the optically thick phase of SNe IIn is a signature of non-spherical CSM. Started survey with Swift (UV photometry) + ZTF g,r to measure r(t). Indication from 6 events that aspherical CSM may be common.

Steve Schulze – PTF CC sample: update on the big project on PTF CC host sample analysis. Motivation: use galaxy properties to constrain progenitor metallicity and maybe mass. Review of collection of host data from other survey from UV to IR. Have to properly account for survey properties (PSF, pixel scale) that vary a lot between WISE, GALEX, SDSS, PS etc. Account for contamination by, e.g., AGN. Have to remove foreground stars. Then measure SED and fit for galaxy parameters like mass, SFR. Use emission lines in SN spectra to study host. Tracers of metallicity and SFR. Need to correct for dust, absolute flux calibration. Effect of absorption (especially Balmer) from underlying stars. Line ratios help solve problems so you can more easily do metallicity but not SFR (requires absolute scale). Applications: a host galaxy color-color diagram to select SLSNe early – r-i<0.18 or so is a good cut. Result on host properties: compare with general star forming galaxies as a function of SN type. Most CC SNe just trace star forming galaxies. Indications for transient production efficiency that is metallicity dependent for SLSNe, GRB-SN, and also Ic-BL and SLSN-II. On the BPT diagram, CC SNe follow star forming region, but a population of luminous transients (SLSNe, GRB, also ZTF18abukavn) seem to require very massive progenitors with high ionization flux. ZTF18abukavn is extreme also compared to SNe Ic-BL – at end of distribution.

Yi Yang – spectropolarimetry of ZTF SNe: review of polarimetry and specpol. Tracer of source geometry (level of asphericity). Specpol of early SN provide: for Type Ia – test explosion models. Also test companion interaction. For CC – another method to study CSM geometry. Shows result of infant SN Ia 2019np. A series of specpol data from VLT starting -15 before before peak. Constrains both merger models and sub-chandra He models. New data for SN Ia-CSM (18evt). Now: waiting for a young nearby CC SN!

Eran Ofek: the fast transient ZTF18abfzgpl: gone before you know it! Single night ZTF detections with a single spectrum, P60 strong upper limits 2 days later, radio limit (nearby unrelated source) and weak X-ray probably also unrelated. From fast LC: V~0.3c, ejecta mass ~10-2 Msun, if shock breakout requires a huge star. Too bright to be similar to KN 170817. Could be an AIC? Peter suggest other radioactive elements from He burning (Cr, Ti).

After-lunch session – missed – apologies to Ludwig, Danny, Matteo and Ashish.

-- Thomas Kupfer - 2019-03-17

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