### Question --- What is synchrotron radiation? Draw a typical synchrotron spectrum. From what kind of astrophysical objects is such radiation observed? How can the synchrotron spectrum be used to constrain the age of the source? ### Answer --- ##### What is synchrotron radiation? Draw a typical synchrotron spectrum. ![[Synchrotron Radiation]] ##### From what kind of astrophysical objects is such radiation observed? - Jets in [[Binary Stars#X-Ray Binary|XRBs]]and [[Active Galactic Nuclei|AGN]] (radio emission) - [[Stellar Explosions#Supernova|SNe]] remnants - [[Nebulae#Pulsar Wind Nebula|Pulsar Wind Nebula]] - Galactic [[Interstellar Medium|ISM]] (cosmic rays?) - [[Sun|Sunspots]] - [[Gamma Ray Burst|GRBs]] ##### How can the synchrotron spectrum be used to constrain the age of the source? Using the power law energy distribution for the electron population, we can use the high energy break to infer the amount of time that has passed since the electrons (producing synchrotron radiation) were last accelerated. Since the power emitted by high-energy particles ($\gamma \uparrow$) is larger than the power emitted by lower-energy particles ($\gamma \downarrow$)... $P = \left(\frac{q^{4} B}{6 \pi \epsilon_{0} c^{3}}\right) \frac{\gamma^{4} \beta^{2}}{m_{0}^{2}} \hspace{1cm} \text{or} \hspace{1cm} \frac{\mathrm{d} E}{\mathrm{d} t} \propto \gamma^{2} \propto E^{2}$ ...they lose energy faster, creating a "knee" in the observed synchrotron spectrum. Meaning, older synchrotron sources will break at lower energies. ![[synchrotron_age.png|align:center|600]]