ZTF Ia Phone-con: 2021-Sep-29

Meeting Agenda:

1. SNe of the week [Joel J]

2. ZTF-DR2 [Mickael R]

3. Calibration [Benjamin R]

4. ZTF21abiuvdk: early spectra [Kate / Luke]

5. AOB / Close

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Participants (13):

• Mickael R, Mat S, Joel J, Benjamin R, Georgios D, Jakob N, Suhail D, Jakob N, Melissa A, Maxime D, Julian B, Dominique F, Ana S-C
• Apologies: Adam M

Notes:

Transients of the Week:

• We found 30 SNIa this week: the full moon slows us down a little
• ZTF21acbpdlz @ z=0.0476: classified very early; going for a spec-at-max
• ZTF21acchwaw: has a host redshift from SEDm: lets get these
• ZTF21acciklh: 91bg-like; beautiful cadence.
• ZTF21acdcxfx @ z=0.026: found despite masking

ZTF-DR2:

• Spectral SEDm re-reductions are underway, but we need help with the typing.
• Email Mickael if you'd like to be involved (Kate, Mat, Joel, Georgios & Jeremy excluded
  • Joel is also collecting all of the non-Ia spectra. It's a huge dataset

Calibration:

• Currently photometry is done by comparing the brightness of stars in PS1: for each quadrant, a ZP and colour correction term are calculated
  • The differences are small for bright stars, but expand at faint magnitudes. Residuals are seen to be correlated (e.g. rings, dust spots, etc).
  • There is scatter at faint magnitudes at approximately the 2% level: aka our photometry is good to the 2% level
• IN2P3, as a team, are redoing every step in the pipeline
  • Current efforts are focussed on characterising the instrument ('starflats','ubercal' and aperture photometry
    • First release in early 2022: Scene Modelling will be introduced in 2022.
  • 'ubercal' is a joint fit of magnitudes, zp variations and extinction: a big computational challenge
    • utilises the overlap / dithering between observations to 'gain' information
    • the resulting matrix is very sparse, but solvable
    • the standard deviation is at the 15 level using just 1% of data. Moving the entire dataset, shortly
  • 'starflats' also utilise dithering: by dithering the stars, so that they appear in all pixels, you can characterise the response on the pixel level
    • This is being led by Estelle R in Lyon.
    • They will now be obtained very month; once in each filter
• The plan is to use this photometry in a ZTF-SNIa-DR3

Kate on ZTF21abiuvdk:

• Very local event; lots of early, early data (inc VLT)
• 86G-like event; subluminuous and transitional
• Luke is modelling it with TARDIS; excellent agreement!
• He's doing abundance modelling at early-times.
• The plan is also to get TRGB information of this object; JWST maybe?
• Let's publish it!

Closing remarks:

• Back next week