# Search for Very High Energy Gamma Rays from the Northern $\textit{Fermi}$ Bubble Region with HAWC

## TL;DR

This study used HAWC data to search for very high energy gamma rays from the Northern Fermi Bubble but found no significant emission, setting upper limits that constrain certain cosmic-ray models.

## Contribution

First search for very high energy gamma rays from the Northern Fermi Bubble using HAWC data, providing upper limits that challenge some hadronic emission models.

## Key findings

- No significant gamma-ray excess detected.
- Upper limits constrain proton spectra beyond 100 TeV.
- Results disfavor hadronic models based on neutrino data.

## Abstract

We present a search of very high energy gamma-ray emission from the Northern $\textit{Fermi}$ Bubble region using data collected with the High Altitude Water Cherenkov (HAWC) gamma-ray observatory. The size of the data set is 290 days. No significant excess is observed in the Northern $\textit{Fermi}$ Bubble region, hence upper limits above $1\,\text{TeV}$ are calculated. The upper limits are between $3\times 10^{-7}\,\text{GeV}\, \text{cm}^{-2}\, \text{s}^{-1}\,\text{sr}^{-1}$ and $4\times 10^{-8}\,\text{GeV}\,\text{cm}^{-2}\,\text{s}^{-1}\,\text{sr}^{-1}$. The upper limits disfavor a proton injection spectrum that extends beyond $100\,\text{TeV}$ without being suppressed. They also disfavor a hadronic injection spectrum derived from neutrino measurements.