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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"

26600 results found.

  1. EP260507a: REM optical/NIR observations
  2. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  3. EP260507a: COLIBRÍ optical observations
  4. EP260507a: SVOM/VT optical observations
  5. EP260507a: Liverpool Telescope optical upper limits
  6. GRB 260507A: Fermi GBM Final Real-time Localization
  7. EP260507a: GOTO optical counterpart detection
  8. EP260507a: TRT optical counterpart detection
  9. EP260507a: Kinder optical counterpart candidate
  10. EP260507a: LCO optical counterpart
  11. GRB 260504B: SVOM/ECLAIRs refined analysis
  12. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  13. GRB 260506B: Fermi GBM Final Real-time Localization
  14. EP260502a is likely a flaring star
  15. Fermi GRB 260506A: Global MASTER-Net observations report
  16. GRB 260506A: Fermi GBM Final Real-time Localization
  17. IceCube Alert 260505A: Global MASTER-Net observations report
  18. GRB 260504B: SVOM/VT optical upper limits
  19. GRB 260504C: SVOM/GRM observation of short GRB
  20. GRB 260504B: SVOM/MXT refined analysis and potential detection
  21. GRB 260503A: SVOM/GRM observation of a GRB
  22. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  23. GRB 260504B: REM optical/NIR observations
  24. IPN triangulation of GRB 260429A
  25. GRB 260504B: LCO z-band upper limit
  26. SVOM GRB 260504B: MASTER-OAFA optical observations
  27. GRB 260504B: SVOM detection of a short burst
  28. Fermi GRB 260504A: Global MASTER-Net observations report
  29. GRB 260504A: Fermi GBM Final Real-time Localization
  30. GRB 260503A: Fermi GBM Final Real-time Localization
  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. Fermi GRB 260428A: Global MASTER-Net observations report
  49. GRB 260424B: COLIBRÍ optical upper limit
  50. GRB 260428A: Fermi GBM Final Real-time Localization
  51. GRB 260424C: Fermi GBM Final Localization
  52. GRB 260424B: SVOM/GRM detection of a short burst
  53. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  54. IceCube Alert 260425A: Global MASTER-Net observations report
  55. Fermi trigger No 798737427: Global MASTER-Net observations report
  56. The EP-WXT trigger 01709258652: Mondy optical observations
  57. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  58. GRB 260421B: SVOM/ECLAIRs refined analysis
  59. GRB 260421B: 3.6m DOT optical observation
  60. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  61. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  62. GRB 260421B: SVOM/GRM observation
  63. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  64. GRB 260421B: EP-FXT follow-up observation
  65. The EP-WXT trigger 01709260362 is likely a flaring star
  66. GRB 260421B: J-band upper limit with WINTER
  67. GRB 260421B: LCO optical counterpart detection
  68. GRB 260421B: Fermi GBM Observation
  69. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  70. GRB 260412A: SVOM/ECLAIRs refined analysis
  71. GRB 260421B: SVOM/VT optical observations
  72. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  73. GRB 260310A: Late-time Chandra X-ray Detection
  74. EP260416a: 1.3m DFOT optical observation
  75. Fermi GRB 260421C: Global MASTER-Net observations report
  76. GRB 260421C: Fermi GBM Final Real-time Localization
  77. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  78. Fermi GRB 260421B: Global MASTER-Net observations report
  79. GRB 260421B: LCO optical afterglow confirmation
  80. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  81. GRB 260421B: SVOM detection of a long burst
  82. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  83. GRB 260421B: Fermi GBM Final Real-time Localization
  84. Fermi GRB 260421A: Global MASTER-Net observations report
  85. GRB 260421A: Fermi GBM Final Real-time Localization
  86. EP260321a: VLA radio follow-up
  87. GRB 260412A: LCOGT Optical Upper Limits
  88. The EP-WXT trigger 01709260314 is likely a flaring star
  89. EP-WXT trigger 01709260303: KAIT optical observations
  90. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  91. The EP-WXT trigger 01709260303 is likely a flaring star
  92. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  93. GRB 260419B: Fermi GBM Final Real-time Localization
  94. GRB 260419A: Fermi GBM Final Real-time Localization
  95. Fermi trigger No 798275385: Global MASTER-Net observations report
  96. EP260417a: GROWTH-India Telescope optical upper limit
  97. Fermi GRB 260417B: Global MASTER-Net observations report
  98. EP260417b: GROWTH-India Telescope optical upper limit
  99. EP260416a: Ondrejov D50 optical detection
  100. GRB 260418B: Fermi GBM Final Real-time Localization

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