Summary day 3

Eli Waxman – emission from GW counterparts. Review r-process elements, models of GW merger and ejecta. Summary of observations. Summaryof specific model (several colors of KN, cocoon etc). Propose a simple model. Derive bolometric luminosity, which is well constrained initially because emission is close to black body. Some missing flux in UV early on. After 10 days the spectra are complex so bolometric luminosity is hard to determine. LC is a broken power law from t^-1 to t^-2.8 (break I on day 6 or so). Simple power law behavior suggests simple model. Amount of mass moving at each velocity assumed to be a power law. Energy production rate from isotope mix is approximately epsilon ~1/t (Paczynski). Define the diffusion time, other model parameters, in particular carefully account for electron energy losses. Can naturally explain the observed broken power law. Calculations provide upper limit on opacity (kappa<0.3) and mass (~1% solar mass). Bottom line: single component of ejecta with low opacity (not a lot of Lanthanides, 10^-3 of total). This is too low to account for solar abundance r-process. This is assuming we know Lanthanide opacities, which are uncertain. Going to late times: fits Spitzer data. Without knowing detailed opacities cannot constrain elemental composition.

Doron Kushnir: core collapse SNe. Suggest a model where CC SNe are thermonuclear. Interlude on SNe Ia and the collision model. Results from nebular phase survey of 100 SNe Ia. Back to CC SNe: energy scale for gravitational collapse is 10^53 erg. But observed energy is 10^51, so in the 60’ motivated suggestion these are also thermonuclear. We know the progenitors are massive stars (observationally) and we know for 87A that the neutrino energy is about 10^53 (but kinetic is 10^51). There is an observed correlation between kinetic energy and Ni mass. Two models for how collapse goes to explosion. Popular one is that 1% of neutrino energy is coupled to ejecta. This fails in 1D. People working on multi-D calculations to revive this, all calculations fail to produce more than 10^50 erg if at all. Alternate model: trigger explosions of He-C-O envelope during collapse. Simulations are simple in with some initial conditions sit right in middle of SN distributions. Check the distribution of energies observed vs. models (neutrino or thermonuclear). The fact that more massive progenitors produce stronger (more energetic) explosions, is evidence for thermonuclear. Also means that most remnant compact objects are black holes. Only weak explosions could produce neutron stars.

Eran Ofek – astrometry with ZTF: discussion of sub-mas accuracy astrometry from the ground. Limiting factors are systematics. Poisson noise limits to seeing/sqrt(photon number) which for ZTF is ~1mas. Eran suspects that leading systematic is pixel size variation at level of a few milli-pixel. Discuss astrometry in PTF and ZTF, present results from robust new astrometry code (failure rate less than 1/50000 even in dense fields, vs. Daia DR2). Results from M.Sc project of student Noam Segev, in particular trying to handle variable pixel size.

Noam Segev (WIS) – binary asteroids: detecting binary asteroids using astrometry. Other mthods are limited (high-res imaging from ground, radar), photometry (occultations). Spacecraft a good but for very few objects … New method is based on change in center of light (COL) in binaries, that rotates around the center of mass (COM). Very simple, now running on Gaia, planning for ZTF.

Ofer Springer (WIS) – lensed quasars: review of lensed quasars. Goal is to measure time delays between two images of QSO lensed by a galaxy. Measure (among other things) Ho. Try to find using center of light shifts in. e.g., ZTF (due to flux changes that modify flux ratio between unresolved images).

Assaf Horesh – radio observations for infant SNe: Detect CSM around SNe in high-frequency radio (ALMA, NOEMA, also VLA if possible). Making a catalog of historical detections. Ami is a major facility for rapid reaction, though low resolution. Rapid follow-up of all sort of transients (SNe, TDE, fast transirnts, inclusing 18cow).

Charlotte Ward – search for recoiling BHs. Search for transients with AGN-like variability that are offset from their host center. Done via an AMPEL filter. Light curve models rejects SNe and saves AGN.

Romain Graziani (LPC) – peculiar velocity and cosmology with SNe Ia: next step in cosmology with SNe Ia. Cosntrain sigma8.

Emir Karamehmetoglu – fast SNe Ibn: review of SNe Ibn – narrow He I emission lines. Assumed to be massive WR stars exploding in He-rich CSM. Bright events. A few are rapidly rising and declining, and a few others are slow (both rise and decay). SN2018bcc is an example of fast rising event with good photometry on the rise (rise is 5.6d). Rise shape consistent with t^ law. Also for iPTF15ul which is another similar example. Excellent Keck spectra. Many He I lines with variable profiles, constrain density of material from line ratios. LC is too rapid for radioactive 56Ni, can be produced by CSM. Not much Ni, no evidence for Ni tail. No evidence for ejecta (broad lines). Speculate it may not be a terminal explosion but rather shell-shell interaction. Perhaps PPISNe? There are similarities also to AT2018cow (answer to Q by Brad).

Kishalay De - rare transients in the local universe: results from the CLU experiments. Looking for transients in the CLU catalog of galaxies within 200 Mpc. Spectroscopically complete (no flux limit) – aim for volume limited sample complete to r=-16. Most spectra come from RCF, complemented by P200 (19-20) and Keck (<20). Kishalay will focus on the faint end of SNe down to ILRTs and ILOTs. About 10 objects/week. 50% SNe II, 36% Ia, 22% Ib/c, 6% “rare”. Ca-rich transients. Ib-like spectra with strong Ca in old galaxies. 8 events with good data. Progenitors unknown but must be old – He shells on WDs, WD-NS mergers? The CLU sample of such events is unbiased and complete to 160 Mpc. Also to within 100 kpc from host. 5 events, all hosts are old ellipticals. All Ca-rich in nebular phase. They are 4% of all events within 160 Mpc (15% of SNe Ia!). Have very large offsets from hosts, even compared to SNe Ia. All >20 kpc projected. Discovery rate for Ca-rich events is 1/month.

Ludwig Rauch (Desy) – photo Zs from PS: tool within AMPEL. Want to select only nearby objects for neutrino follow-up (no need for great accuracy). Train ML algorithm on PS1 photometry and SDSS spectroscopy. Use g,r and colors (r-I, i-z). Missing U band, perhaps can include GALEX. Also include in the future galaxy size. Information available on Marshal.

Guy Nir – streak detection: Related to NEO search. Streak detection and also rejection. Detect using matched filter with line+PSF. Method called “Radon transform” which in brute force approach scales as N^3 (N=image size). The newly developed fast radon transform (FRT) takes this down to N^2 (very important). Rejecting streak-like artifacts and impostors (satellites, CRs).

Ofer Yaron – TNS, WISeREP, AstroNotes: report on TNS, WISeREP and new AstroNotes system (a system for writing ATEL-like reports that is handling coordinates and objects in a robust way). Check out the presentation! A discussion on whether to automatically archive ZTF spectra on WISeREP – Jesper suggests to ask approval of data owners and says he approves all NOT spectra.

Maayane Soumagnac – communication coordinators report: presents result of user survey. Want to increase twitter activity but requires input from people. Newsletter updates – new corners, new ideas.

Extra talks:

Eran – the LAST telescope, motivation and concept.

Jakob: AMPEL status.

Shri – ZTF phase II in era of massive spectroscopy.

Take advantage of convergence around 20mag: Gaia, massive spectroscopy, TDA.

ZTF and similar surveys can find ~10^4 SNe per year. Bottleneck is spectroscopy.

-- Thomas Kupfer - 2019-03-17

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