The Astrophysical Journal (Jan 2024)
Small-scale Cosmic-Ray Anisotropy Observed by the GRAPES-3 Experiment at TeV Energies
- M. Chakraborty,
- S. Ahmad,
- A. Chandra,
- S. R. Dugad,
- U. D. Goswami,
- S. K. Gupta,
- B. Hariharan,
- Y. Hayashi,
- P. Jagadeesan,
- A. Jain,
- P. Jain,
- S. Kawakami,
- T. Koi,
- H. Kojima,
- S. Mahapatra,
- P. K. Mohanty,
- R. Moharana,
- Y. Muraki,
- T. Nakamura,
- P. K. Nayak,
- T. Nonaka,
- A. Oshima,
- B. P. Pant,
- D. Pattanaik,
- S. Paul,
- G. S. Pradhan,
- M. Rameez,
- K. Ramesh,
- S. Saha,
- R. Sahoo,
- R. Scaria,
- S. Shibata,
- T. Tabata,
- H. Takamaru,
- K. Tanaka,
- F. Varsi,
- K. Yamazaki,
- M. Zuberi
Affiliations
- M. Chakraborty
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- S. Ahmad
- Aligarh Muslim University , Aligarh 202002, India
- A. Chandra
- Aligarh Muslim University , Aligarh 202002, India
- S. R. Dugad
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- U. D. Goswami
- ORCiD
- Dibrugarh University , Dibrugarh 786004, India
- S. K. Gupta
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- B. Hariharan
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- Y. Hayashi
- Graduate School of Science, Osaka Metropolitan University , Sugimoto, Sumiyoshi, Osaka 558-8585, Japan
- P. Jagadeesan
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- A. Jain
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- P. Jain
- Indian Institute of Technology Kanpur , Kanpur 208016, India
- S. Kawakami
- Graduate School of Science, Osaka Metropolitan University , Sugimoto, Sumiyoshi, Osaka 558-8585, Japan
- T. Koi
- College of Engineering, Chubu University , Kasugai, Aichi 487-8501, Japan
- H. Kojima
- Chubu Astronomical Observatory, Chubu University , Kasugai, Aichi 487-8501, Japan
- S. Mahapatra
- Utkal University , Bhubaneswar 751004, India
- P. K. Mohanty
- ORCiD
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- R. Moharana
- Indian Institute of Technology Jodhpur , Jodhpur 342037, India
- Y. Muraki
- ORCiD
- Institute for Space–Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- T. Nakamura
- Faculty of Science and Technology, Kochi University , Kochi 780-8520, Japan
- P. K. Nayak
- ORCiD
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- T. Nonaka
- ORCiD
- Institute for Cosmic Ray Research, Tokyo University , Kashiwa, Chiba 277-8582, Japan
- A. Oshima
- College of Engineering, Chubu University , Kasugai, Aichi 487-8501, Japan
- B. P. Pant
- Indian Institute of Technology Jodhpur , Jodhpur 342037, India
- D. Pattanaik
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]; Utkal University , Bhubaneswar 751004, India
- S. Paul
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- G. S. Pradhan
- Indian Institute of Technology Indore , Indore 453552, India
- M. Rameez
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- K. Ramesh
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- S. Saha
- Indian Institute of Technology Kanpur , Kanpur 208016, India
- R. Sahoo
- Indian Institute of Technology Indore , Indore 453552, India
- R. Scaria
- Indian Institute of Technology Indore , Indore 453552, India
- S. Shibata
- College of Engineering, Chubu University , Kasugai, Aichi 487-8501, Japan
- T. Tabata
- College of Engineering, Chubu University , Kasugai, Aichi 487-8501, Japan
- H. Takamaru
- College of Engineering, Chubu University , Kasugai, Aichi 487-8501, Japan
- K. Tanaka
- Graduate School of Information Sciences, Hiroshima City University , Hiroshima 731-3194, Japan
- F. Varsi
- Indian Institute of Technology Kanpur , Kanpur 208016, India
- K. Yamazaki
- College of Engineering, Chubu University , Kasugai, Aichi 487-8501, Japan
- M. Zuberi
- Tata Institute of Fundamental Research , Homi Bhabha Road, Mumbai 400005, India ; [email protected]
- DOI
- https://doi.org/10.3847/1538-4357/ad132b
- Journal volume & issue
-
Vol. 961,
no. 1
p. 87
Abstract
GRAPES-3 is a mid-altitude (2200 m) and near-equatorial (11.°4N) air shower array, overlapping in its field of view for cosmic-ray observations with experiments that are located in the Northern and Southern Hemispheres. We analyze a sample of 3.7 × 10 ^9 cosmic-ray events collected by the GRAPES-3 experiment between 2013 January 1 and 2016 December 31 with a median energy of ∼16 TeV for study of small-scale (<60°) angular-scale anisotropies. We observed two structures, labeled A and B, that deviate from the expected isotropic distribution of cosmic rays in a statistically significant manner. Structure A spans 50°–80° in R.A. and from −15° to 30° in decl. The relative excess observed in structure A is at the level of (6.5 ± 1.3) × 10 ^−4 with a statistical significance of 6.8 standard deviations. Structure B is observed in the R.A. range 110°–140° and at decl. from −10° to 30°. The relative excess observed in this region is at the level of (4.9 ± 1.4) × 10 ^−4 with a statistical significance of 4.7 standard deviations. These structures are consistent with those reported by Milagro, ARGO-YBJ, and HAWC. These observations could provide a better understanding of the sources of cosmic rays, their propagation, and the magnetic structures in our Galaxy.
Keywords
