Are Photons With Monstrous Energies Coming From the Galaxy’s Largest Accelerator?

Source of 200 TeV Photons

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Photons with an energy of 200 teraelectronvolts are probably discharged by protons hitting interstellar gas. The main source of protons is pulsar HAWC J1825-134 (in the orange circle), the function of the real accelerator is played by the star cluster [BDS2003] 8 (dark blue). Credit: HAWC

For years, in the vastness of our galaxy, astrophysicists have actually been locating pevatrons – natural accelerators of particles with monstrous energies. Thanks to the HAWC Observatory for Cosmic Radiation, another likely trace of their presence has actually simply been discovered: photons with a few of the greatest energies. However, what is especially crucial is that this time the high-energy photons have actually not just been tape-recorded, however likewise their likely location of origin has actually been identified.

We understand they exist, we simply don’t understand where precisely they are or what they appear like. Pevatrons – since this is what we are speaking about here – are the biggest natural particle accelerators in our galaxy, efficient in speeding up protons and electrons to energies even numerous billions of times higher than the energy of photons of noticeable light. The issue with identifying pevatrons originates from the truth that the particles they speed up bring an electrical charge and are for that reason deflected by electromagnetic fields in the galaxy. The discovery which has actually simply been made thanks to information gathered by the High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory brings us considerably more detailed to discovering the very first cosmic pevatron and comprehending its nature.

The HAWC Observatory lies on the slope of the Sierra Negra volcano in Mexico, at an elevation of 4,100 m. It includes 300 water tanks, each surrounded by delicate photomultipliers. When a particle of secondary cosmic radiation taking a trip at a speed much faster than the speed of light in water gets in a tank, there is an electro-magnetic “boom” – a weak flash of radiation (Cherenkov), spotted and enhanced by the photomultipliers. A cautious analysis of flashes observed at the exact same time in private tanks makes it possible to draw out details about the type, energy and instructions of the particle of the main cosmic radiation which started the tape-recorded waterfall of secondary particles.

“Based on data collected by the HAWC, we were able to determine the source of photons with energies of about 200 teraelectronvolts. For photons, this is an extreme value, one hundred trillion times greater than the energy typical of photons perceived by our eyes,” states Dr. Sabrina Casanova from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow. Together with Dr. Francisco Sales Greus (IFJ PAN & IFIC) and PhD trainee Dezhi Huang from the Michigan Technological University in Houghton (U.S.A.), she is among the primary authors of the analysis released in the outstanding huge journal The Astrophysical Journal Letters.

Compared to protons and electrons, photons have an enjoyable function: they disregard electromagnetic fields and go to their target along the quickest course that space-time permits. So, when the instructions from which the photons are coming is determined within a galaxy, it is generally possible to identify their source. This is not a simple job, however in this case it succeeded. The source of the 200 TeV photons ended up being an area of the just recently found pulsar eHWC J1825-134, noticeable in the southern hemisphere in the background of the Vela constellation, and lying at a range of about 13 thousand light years from Earth.

Observations of such high-energy photons are uncommon, and it is even rarer to determine the source. The record presently comes from photons with energies of 450 TeV, spotted with the Sino-Japanese ASgamma detector in Tibet. In that case, the photons originated from the area of a pulsar in the well-known Crab nebula in the background of the Taurus constellation.

“We now know of two mechanisms that can explain the existence of photons with energies of 200 TeV and above,” describes Dr. Salesa Greus, prior to elaborating: “According to the first, the source of such energetic photons could be electrons with slightly higher energies, emitted by supernova remnants or pulsars and then interacting with the microwave background radiation filling the Universe. This case seems to fit the Crab nebula. The second variant of the course of events assumes that photons are born due to the interaction of protons emitted by a pulsar with matter in interstellar space. What is particularly interesting in this scenario is that the energies of the protons must be at least an order of magnitude greater than the energies of the observed photons!”.

The area of the eHWC J1825-134 pulsar is a complicated huge structure with numerous sources of high-energy gamma rays within it. HAWC scientists have actually identified that the origin of the 200 TeV photons was not the pulsar itself, however a formerly unidentified source: a neighboring cloud of interstellar product. It surrounds a young cluster of stars, about one million years of ages, designated as [BDS2003] 8. The observed photons might therefore have actually been discharged by protons from the eHWC J1825-134 pulsar which, within the [BDS2003] 8 star cluster, had sufficient time to speed up in the regional electromagnetic field to energies of a couple of petaelectronvolts and produce energetic photons in the interaction with the cloud. If this variation of the course of occasions is validated in subsequent observations, we would be handling the very first pevatron determined in our galaxy.

“For the time being, we have too little data to unambiguously decide on the nature of the cosmic accelerator responsible for the generation of 200 TeV photons in the region of eHWC J1825-134. If, however, there is a galactic pevatron hiding somewhere, we have managed to find a really excellent candidate,” notes Dr. Casanova.

Reference: “Evidence of 200 TeV Photons from HAWC J1825-134” by A. Albert, R. Alfaro, C. Alvarez, J. R. Angeles Camacho, J. C. Arteaga-Velázquez, K. P. Arunbabu, D. Avila Rojas, H. A. Ayala Solares, V. Baghmanyan, E. Belmont-Moreno, S. Y. BenZvi, C. Brisbois, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, E. De la Fuente, R. Diaz Hernandez, B. L. Dingus, M. A. DuVernois, M. Durocher, J. C. Díaz-Vélez, K. Engel, C. Espinoza, K. Fang, H. Fleischhack, N. Fraija, A. Galván-Gámez, D. Garcia, J. A. García-González, F. Garfias, G. Giacinti, M. M. González, J. A. Goodman, J. P. Harding, B. Hona, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, A. Jardin-Blicq, V. Joshi, G. J. Kunde, A. Lara, W. H. Lee, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, J. Lundeen, K. Malone, V. Marandon, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, N. Omodei, A. Peisker, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, H. Salazar, F. Salesa Greus, A. Sandoval, M. Schneider, F. Serna, R. W. Springer, K. Tollefson, I. Torres, R. Torres-Escobedo, F. Ureña-Mena, L. Villaseñor, E. Willox, H. Zhou and C. de León, 28 January 2021, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/abd77b

The research study of researchers from the IFJ PAN was moneyed by a grant from the Polish National Sci – ence Centre.