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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

5809 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 260809A
  2. GRB 260810A: Glowbug gamma-ray detection
  3. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  4. GRB 260810A: AstroSat CZTI detection of a long burst
  5. GRB 260809A: SAO RAS optical observations
  6. GRB 260808B: SAO RAS optical observations
  7. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  8. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  9. GRB260809A: MAO/AZT-22 optical observations
  10. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 260808B: Liverpool Telescope optical observations
  12. EP260809a: COLIBRÍ optical observations
  13. Fermi GRB 260808A: Global MASTER-Net observations report
  14. GRB 260709A: cubesat Avion detection
  15. Fermi GRB 260805A: Global MASTER-Net observations report
  16. GRB 260805A: Fermi GBM Final Localization
  17. GRB 260804A: Fermi GBM Final Real-time Localization
  18. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  19. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  20. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  21. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  22. GRB 260705A: Retraction of optical counterpart
  23. GRB 260718A: EP-FXT follow-up observation
  24. Fermi trigger No 806104130: Global MASTER-Net observations report
  25. Fermi GRB 260718A: Global MASTER-Net observations report
  26. GRB 260709A: AstroSat CZTI detection
  27. GRB 260706A: ATCA detection of possible radio counterpart
  28. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  29. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  30. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  31. IceCube-260708A: One candidate from the Zwicky Transient Facility
  32. IceCube Alert 260709A: Global MASTER-Net observations report
  33. EP260707a (by EP-FXT): NOT optical upper limit
  34. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  35. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  36. GRB 260707A: Fermi GBM Final Real-time Localization
  37. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  38. Fermi trigger No 804738310: Global MASTER-Net observations report
  39. Fermi GRB 260703A: Global MASTER-Net observations report
  40. Fermi trigger No 804552016: Global MASTER-Net observations report
  41. EP260626a: COLIBRÍ optical upper limit
  42. MASS-Cube (GRID 2.0) detection of GRB 260616B
  43. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  44. EP260618a: EP-FXT follow-up observation
  45. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB260616C: MAXI/GSC detection
  47. EP260610b: MAO/AZT-22 optical observations
  48. EP260610a: COLIBRÍ optical upper limits
  49. EP260610a: Einstein Probe detection of a fast X-ray transient
  50. GRB 260609A: Fermi GBM Final Localization
  51. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  52. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  53. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  54. EP260603a: COLIBRÍ optical upper limit
  55. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  56. Fermi GRB 260604C: Global MASTER-Net observations report
  57. Fermi GRB 260604C: Global MASTER-Net observations report
  58. Fermi trigger No 802141998: Global MASTER-Net observations report
  59. SVOM GRB260603.23: Global MASTER-Net observations report
  60. Fermi GRB 260602B: Global MASTER-Net observations report
  61. Fermi GRB 260602B: Global MASTER-Net observations report
  62. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  63. Fermi GRB 260601A: Global MASTER-Net observations report
  64. Fermi trigger No 801900520: Global MASTER-Net observations report
  65. GRB 260531A: MAXI/GSC detection
  66. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  67. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  68. GRB 260522B: Fermi GBM Final Real-time Localization
  69. Fermi trigger No 801135305: Global MASTER-Net observations report
  70. Fermi GRB 260522A: Global MASTER-Net observations report
  71. GRB 260520B: Fermi GBM Final Localization
  72. GRB 260509A: SVOM/ECLAIRs refined analysis
  73. GRB 260509A: CrAO ZTSh optical upper limit
  74. GRB 260515A: CrAO ZTSh BVRI optical observations
  75. Fermi GRB 260516C: Global MASTER-Net observations report
  76. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  77. GRID detection of GRB 260507A
  78. SVOM GRB 260515A: Global MASTER-Net observations report
  79. EP260507a: Xinglong Schmidt optical counterpart detection
  80. Fermi GRB 260512A: Global MASTER-Net observations report
  81. EP260512a: COLIBRÍ optical upper limits
  82. MASS-Cube (GRID 2.0) detection of GRB 260507A
  83. GRB 260511B: SAO RAS optical observations
  84. GRB 260511B: GOTO optical counterpart detection
  85. GRB 260511B: SVOM/VT optical observations
  86. Fermi GRB 260511A: Global MASTER-Net observations report
  87. GRB 260509A: Liverpool Telescope optical observations
  88. GRB 260509A: SVOM/VT optical candidate with VHF data
  89. GRB 260509A: LCO optical counterpart detection
  90. GRB 260509A: GOTO optical counterpart candidate
  91. GRB 260509A: SVOM detection of a burst
  92. EP260507a: Liverpool Telescope optical upper limits
  93. GRB 260504B: AstroSat CZTI detection
  94. IceCube Alert 260505A: Global MASTER-Net observations report
  95. Konus-Wind detection of GRB 260504B (short/hard)
  96. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  97. GRB 260504B: REM optical/NIR observations
  98. IPN triangulation of GRB 260429A
  99. GRB 260504B: AST3-2 i-band upper limit
  100. GRB 260504B: LCO z-band upper limit

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