# GRB250103A : seen but not measurable

**URL:** <https://forum.astro-colibri.science/t/grb250103a-seen-but-not-measurable/311>\
**Category:** General\
**Tags:** grb\
**Created:** [January 4, 2025, 9:35am UTC](https://forum.astro-colibri.science/t/grb250103a-seen-but-not-measurable/311 "2025-01-04T09:35:13Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![marc.serrau2](https://yyz1.discourse-cdn.com/flex007/user_avatar/forum.astro-colibri.science/marc.serrau2/32/122_2.png) [@marc.serrau2](https://forum.astro-colibri.science/u/marc.serrau2)\
**Post date:** [January 4, 2025, 9:35am UTC](https://forum.astro-colibri.science/t/grb250103a-seen-but-not-measurable/311/1 "2025-01-04T09:35:13Z")

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![image](https://canada1.discourse-cdn.com/flex007/uploads/astro_colibri/original/1X/0202f08b63785b680f6cce776a7f2a11a6d36df6.jpeg)  
Here the GRB counterpart after 1h exposure with G (RAPAS A) filter.  
Or it is the background galaxy… Limiting magnitude is 20 at S/N=5.

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**Author:** ![Fabian.Schussler](https://yyz1.discourse-cdn.com/flex007/user_avatar/forum.astro-colibri.science/fabian.schussler/32/25_2.png) [@Fabian.Schussler](https://forum.astro-colibri.science/u/Fabian.Schussler)\
**Post date:** [January 4, 2025, 11:46am UTC](https://forum.astro-colibri.science/t/grb250103a-seen-but-not-measurable/311/2 "2025-01-04T11:46:44Z")

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Congratulations!  
When did you perform these observations? How do they compare to other reports (e.g. via GCN: [GCN Viewer](https://heasarc.gsfc.nasa.gov/wsgi-scripts/tach/gcn_v2/tach.wsgi/?event=GRB250103A))

The background galaxy is apparently at `i ~ 22.8` (see [GCN - Circulars - 38808 - GRB 250103A: NOT optical observations](https://gcn.nasa.gov/circulars/38808))