# Finding Rising SN

**URL:** <https://www.rubin.community/t/finding-rising-sn/12227>\
**Category:** Lasair\
**Created:** [July 2, 2026, 3:28am UTC](https://www.rubin.community/t/finding-rising-sn/12227 "2026-07-02T03:28:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![anirbandutta](https://avatars.discourse-cdn.com/v4/letter/a/9fc29f/32.png) [@anirbandutta](https://www.rubin.community/u/anirbandutta)\
**Post date:** [July 2, 2026, 3:28am UTC](https://www.rubin.community/t/finding-rising-sn/12227/1 "2026-07-02T03:28:55Z")

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Hello,

I am trying to find rising SNe/transients, I was wondering if it is possible to find the rise, by doing a subtraction of magnitude between epochs in the **filter itself on lasair** (without getting a hand on the data)?

For example one mag1 - mag2 \< 0 or a spline fit.

Regards,  
Anirban

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**Author:** ![roy](https://sea2.discourse-cdn.com/flex002/user_avatar/www.rubin.community/roy/32/1254_2.png) [@roy](https://www.rubin.community/u/roy)\
**Post date:** [July 9, 2026, 10:58am UTC](https://www.rubin.community/t/finding-rising-sn/12227/2 "2026-07-09T10:58:33Z")

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Hi Anirban  
Certainly you can subtract recent magnitudes, but they are generally in different bands, so you are getting an inseperable combo of colour and brightening.

Look at some [existing Lasair filters](https://lasair.lsst.ac.uk/filters/). For example [BBB KN detector](https://lasair.lsst.ac.uk/filters/1140/) uses the BBB fit (below). Look for filters starting “RISOTTO” – its a research group kindly making their filters public. In each case you can duplicate the filter and edit and see what comes out (you will need a Lasair account first).

Lasair offers significant added value. For your search I might suggest:

- The [Sherlock matching system](https://lasair-lsst.readthedocs.io/en/main/core_functions/sherlock.html) that will find if the alert has a host galaxy.
- The TNS matching on the object page, that tells you if it is already in TNS
- The [BazinBlackBody (BBB) lightcurve fitting](https://github.com/lsst-uk/lasair-examples/blob/main/features/bazinBlackBody/introduction.ipynb).
- Absolute magnitude in filters `objects.absMag` for those objects that have a host galaxy with distance.