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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"

28856 results found.

  1. EP260507a: TRT optical counterpart detection
  2. EP260507a: Kinder optical counterpart candidate
  3. EP260507a: LCO optical counterpart
  4. GRB 260504B: SVOM/ECLAIRs refined analysis
  5. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  6. GRB 260506B: Fermi GBM Final Real-time Localization
  7. EP260502a is likely a flaring star
  8. Fermi GRB 260506A: Global MASTER-Net observations report
  9. GRB 260506A: Fermi GBM Final Real-time Localization
  10. GRB 260503A: GECAM-B observation of a burst
  11. IceCube Alert 260505A: Global MASTER-Net observations report
  12. GRB 260504B: SVOM/VT optical upper limits
  13. GRB 260421B: radio observation with the VLA
  14. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  15. GRB 260504C: SVOM/GRM observation of short GRB
  16. GRB 260504B: SVOM/MXT refined analysis and potential detection
  17. GRB 260502A: SVOM/GRM observation of a short GRB
  18. GRB 260503A: SVOM/GRM observation of a GRB
  19. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  20. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  21. GRB 260504B: REM optical/NIR observations
  22. IPN triangulation of GRB 260429A
  23. IPN triangulation of GRB 260428A
  24. GRB 260504B: LCO z-band upper limit
  25. SVOM GRB 260504B: MASTER-OAFA optical observations
  26. GRB 260504B: SVOM detection of a short burst
  27. Fermi GRB 260504A: Global MASTER-Net observations report
  28. GRB 260504A: Fermi GBM Final Real-time Localization
  29. GRB 260503A: Fermi GBM Final Real-time Localization
  30. GRB 260502A: GECAM-B observation of a short burst
  31. GRB 260502A: Fermi GBM Final Localization
  32. The EP-WXT trigger 01709261576 is likely a flaring star
  33. GRB 260429B / EP260429a: EP-FXT follow-up observation
  34. EP260502a: BOOTES-7: early optical upper limit
  35. EP260502a: Las Cumbres upper limit
  36. GRB 260429A: SVOM/GRM observation of a short burst
  37. EP260429a: Global MASTER-Net observations report
  38. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  39. EP260429a: LCO optical upper limits
  40. EP260430a: LCO optical upper limits
  41. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  42. GRB 260429A: Fermi GBM Detection
  43. Fermi GRB 260429A: Global MASTER-Net observations report
  44. EP260430a: Global MASTER-Net observations report
  45. EP260430a: Einstein Probe detection of an X-ray transient
  46. GRB 260429A: Fermi GBM Final Real-time Localization
  47. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  48. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  49. GRB 260428A: AstroSat CZTI detection
  50. Fermi GRB 260428A: Global MASTER-Net observations report
  51. GRB 260424B: COLIBRÍ optical upper limit
  52. GRB 260428A: Fermi GBM Final Real-time Localization
  53. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  54. GRB 260424C: Fermi GBM Final Localization
  55. GRB 260424B: SVOM/GRM detection of a short burst
  56. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  57. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  58. IceCube Alert 260425A: Global MASTER-Net observations report
  59. Fermi trigger No 798737427: Global MASTER-Net observations report
  60. GRB 260401A: cubesat Avion detection
  61. GRB 260421B: Kilonova-Catcher optical afterglow detection
  62. GRB 260421B: Insight-HXMT/HE detection
  63. The EP-WXT trigger 01709258652: Mondy optical observations
  64. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  65. GRB 260421B: SVOM/ECLAIRs refined analysis
  66. GRB 260421B: 3.6m DOT optical observation
  67. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  68. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  69. GRB 260419A: AstroSat CZTI detection
  70. GRB 260421B: SVOM/GRM observation
  71. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  72. GRB 260421B: EP-FXT follow-up observation
  73. The EP-WXT trigger 01709260362 is likely a flaring star
  74. GRB 260421B: J-band upper limit with WINTER
  75. GRB 260421B: LCO optical counterpart detection
  76. GRB 260421B: Fermi GBM Observation
  77. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  78. GRB 260421A: AstroSat CZTI detection
  79. GRB 260412A: SVOM/ECLAIRs refined analysis
  80. GRB 260421B: SVOM/VT optical observations
  81. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  82. GRB 260310A: Late-time Chandra X-ray Detection
  83. GRB 260418A: Insight-HXMT/HE detection
  84. EP260416a: 1.3m DFOT optical observation
  85. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  86. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  87. Fermi GRB 260421C: Global MASTER-Net observations report
  88. GRB 260421C: Fermi GBM Final Real-time Localization
  89. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  90. Fermi GRB 260421B: Global MASTER-Net observations report
  91. GRB 260421B: BOOTES-7 early optical afterglow detection
  92. GRB 260421B: LCO optical afterglow confirmation
  93. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  94. GRB 260421B: TRT optical counterpart detection
  95. GRB 260421B: SVOM detection of a long burst
  96. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  97. GRB 260421B: Fermi GBM Final Real-time Localization
  98. Fermi GRB 260421A: Global MASTER-Net observations report
  99. GRB 260421A: Fermi GBM Final Real-time Localization
  100. EP260321a: VLA radio follow-up

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