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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"

23630 results found.

  1. IPN triangulation of GRB 260428A
  2. GRB 260504B: AST3-2 i-band upper limit
  3. GRB 260504B: LCO z-band upper limit
  4. SVOM GRB 260504B: MASTER-OAFA optical observations
  5. GRB 260504B: SVOM detection of a short burst
  6. Fermi GRB 260504A: Global MASTER-Net observations report
  7. GRB 260504A: Fermi GBM Final Real-time Localization
  8. GRB 260503A: Fermi GBM Final Real-time Localization
  9. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  10. IPN triangulation of a bright burst from SGR 1E1841-045
  11. GRB 260502A: Fermi GBM Final Localization
  12. The EP-WXT trigger 01709261576 is likely a flaring star
  13. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  14. EP260502a: BOOTES-7: early optical upper limit
  15. GRB 260429A: SVOM/GRM observation of a short burst
  16. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  17. EP260429a: Global MASTER-Net observations report
  18. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  19. GRB 260429A: Fermi GBM Detection
  20. Fermi GRB 260429A: Global MASTER-Net observations report
  21. EP260430a: Global MASTER-Net observations report
  22. GRB 260429A: Fermi GBM Final Real-time Localization
  23. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  24. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  25. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  26. Fermi GRB 260428A: Global MASTER-Net observations report
  27. Konus-Wind detection of GRB 260424B
  28. GRB 260428A: Fermi GBM Final Real-time Localization
  29. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  30. GRB 260424C: Fermi GBM Final Localization
  31. IPN triangulation of GRB 260424B (short)
  32. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  33. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  34. IceCube Alert 260425A: Global MASTER-Net observations report
  35. Fermi trigger No 798737427: Global MASTER-Net observations report
  36. GRB 260401A: cubesat Avion detection
  37. GRB 260424A: AstroSat CZTI detection of a long burst
  38. GRB 260421B: SVOM/ECLAIRs refined analysis
  39. GRB 260421B: 3.6m DOT optical observation
  40. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  42. GRB 260421B: SVOM/GRM observation
  43. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  44. GRB 260421B: EP-FXT follow-up observation
  45. The EP-WXT trigger 01709260362 is likely a flaring star
  46. GRB 260421B: Fermi GBM Observation
  47. GRB 260412A: SVOM/ECLAIRs refined analysis
  48. GRB 260421B: SVOM/VT optical observations
  49. GRB 260310A: Late-time Chandra X-ray Detection
  50. EP260416a: 1.3m DFOT optical observation
  51. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  52. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  53. Fermi GRB 260421C: Global MASTER-Net observations report
  54. GRB 260421C: Fermi GBM Final Real-time Localization
  55. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  56. Fermi GRB 260421B: Global MASTER-Net observations report
  57. GRB 260421B: LCO optical afterglow confirmation
  58. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  59. GRB 260421B: TRT optical counterpart detection
  60. GRB 260421B: SVOM detection of a long burst
  61. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  62. GRB 260421B: Fermi GBM Final Real-time Localization
  63. Fermi GRB 260421A: Global MASTER-Net observations report
  64. GRB 260421A: Fermi GBM Final Real-time Localization
  65. GRB 260412A: LCOGT Optical Upper Limits
  66. The EP-WXT trigger 01709260314 is likely a flaring star
  67. The EP-WXT trigger 01709260303 is likely a flaring star
  68. GRB 260417A: SVOM/GRM observation
  69. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  70. GRB 260419B: Fermi GBM Final Real-time Localization
  71. GRB 260419A: Fermi GBM Final Real-time Localization
  72. Fermi trigger No 798275385: Global MASTER-Net observations report
  73. EP260417a: GROWTH-India Telescope optical upper limit
  74. Fermi GRB 260417B: Global MASTER-Net observations report
  75. EP260417b: GROWTH-India Telescope optical upper limit
  76. EP260416a: Ondrejov D50 optical detection
  77. GRB 260418B: Fermi GBM Final Real-time Localization
  78. EP260417a: Global MASTER-Net observations report
  79. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  80. GRB 260418A: Fermi GBM Final Real-time Localization
  81. Fermi GRB 260417A: Global MASTER-Net observations report
  82. Konus-Wind detection of GRB 260411B
  83. GRB 260417B: Fermi GBM Final Real-time Localization
  84. IPN triangulation of GRB 260411B
  85. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  86. EP260417a: TRT optical counterpart detection
  87. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  88. EP260416a: KAIT optical upper limit
  89. GRB 260417A: Fermi GBM Final Real-time Localization
  90. EP260416a: SVOM/VT optical observation
  91. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  92. GRB 260411B: Glowbug gamma-ray detection
  93. EP260416a: Global MASTER-Net observations report
  94. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  95. GRB 260415B: NuSTAR detection of long prompt emission
  96. GRB 260415B: Fermi GBM Final Localization
  97. GRB 260415A: Fermi GBM Final Real-time Localization
  98. Fermi trigger No 797912738: Global MASTER-Net observations report
  99. GRB 260414A: Glowbug gamma-ray detection
  100. GRB 260414A: Fermi GBM Final Real-time Localization

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