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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"

26164 results found.

  1. GRB 260503A: GECAM-B observation of a burst
  2. IceCube Alert 260505A: Global MASTER-Net observations report
  3. GRB 260504B: SVOM/VT optical upper limits
  4. GRB 260504B: GECAM-B detection
  5. GRB 260504C: SVOM/GRM observation of short GRB
  6. GRB 260504B: SVOM/GRM spectral analysis
  7. GRB 260504B: SVOM/MXT refined analysis and potential detection
  8. GRB 260504B: EP-FXT upper limit
  9. GRB 260502A: SVOM/GRM observation of a short GRB
  10. GRB 260503A: SVOM/GRM observation of a GRB
  11. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  12. GRB 260504B: REM optical/NIR observations
  13. IPN triangulation of GRB 260429A
  14. GRB 260504B: LCO z-band upper limit
  15. SVOM GRB 260504B: MASTER-OAFA optical observations
  16. GRB 260504B: SVOM detection of a short burst
  17. Fermi GRB 260504A: Global MASTER-Net observations report
  18. GRB 260504A: Fermi GBM Final Real-time Localization
  19. GRB 260503A: Fermi GBM Final Real-time Localization
  20. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  21. GRB 260502A: GECAM-B observation of a short burst
  22. GRB 260502A: Fermi GBM Final Localization
  23. The EP-WXT trigger 01709261576 is likely a flaring star
  24. GRB 260429B / EP260429a: EP-FXT follow-up observation
  25. EP260502a: BOOTES-7: early optical upper limit
  26. EP260502a: Las Cumbres upper limit
  27. EP260502a: Einstein Probe detection of an X-ray transient
  28. GRB 260429A: SVOM/GRM observation of a short burst
  29. EP260429a: Global MASTER-Net observations report
  30. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  31. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  32. EP260429a: LCO optical upper limits
  33. EP260430a: LCO optical upper limits
  34. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  35. GRB 260429A: Fermi GBM Detection
  36. Fermi GRB 260429A: Global MASTER-Net observations report
  37. EP260430a: Global MASTER-Net observations report
  38. EP260430a: Einstein Probe detection of an X-ray transient
  39. EP260429a: EP-WXT detection of a fast X-ray transient
  40. GRB 260429A: Fermi GBM Final Real-time Localization
  41. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  42. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  43. Fermi GRB 260428A: Global MASTER-Net observations report
  44. GRB 260424B: COLIBRÍ optical upper limit
  45. GRB 260428A: Fermi GBM Final Real-time Localization
  46. GRB 260424C: Fermi GBM Final Localization
  47. GRB 260424B: SVOM/GRM detection of a short burst
  48. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  49. IceCube Alert 260425A: Global MASTER-Net observations report
  50. Fermi trigger No 798737427: Global MASTER-Net observations report
  51. GRB 260421B: Kilonova-Catcher optical afterglow detection
  52. The EP-WXT trigger 01709258652: Mondy optical observations
  53. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  54. GRB 260421B: SVOM/ECLAIRs refined analysis
  55. GRB 260421B: 3.6m DOT optical observation
  56. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  57. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  58. GRB 260421B: SVOM/GRM observation
  59. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  60. GRB 260421B: EP-FXT follow-up observation
  61. The EP-WXT trigger 01709260362 is likely a flaring star
  62. GRB 260421B: J-band upper limit with WINTER
  63. GRB 260421B: LCO optical counterpart detection
  64. GRB 260421B: Fermi GBM Observation
  65. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  66. GRB 260412A: SVOM/ECLAIRs refined analysis
  67. GRB 260421B: SVOM/VT optical observations
  68. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  69. GRB 260310A: Late-time Chandra X-ray Detection
  70. EP260416a: 1.3m DFOT optical observation
  71. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  72. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  73. Fermi GRB 260421C: Global MASTER-Net observations report
  74. GRB 260421C: Fermi GBM Final Real-time Localization
  75. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  76. Fermi GRB 260421B: Global MASTER-Net observations report
  77. GRB 260421B: LCO optical afterglow confirmation
  78. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  79. GRB 260421B: SVOM detection of a long burst
  80. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  81. GRB 260421B: Fermi GBM Final Real-time Localization
  82. Fermi GRB 260421A: Global MASTER-Net observations report
  83. GRB 260421A: Fermi GBM Final Real-time Localization
  84. EP260321a: VLA radio follow-up
  85. GRB 260412A: LCOGT Optical Upper Limits
  86. The EP-WXT trigger 01709260314 is likely a flaring star
  87. EP-WXT trigger 01709260303: KAIT optical observations
  88. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  89. The EP-WXT trigger 01709260303 is likely a flaring star
  90. GRB 260417A: SVOM/GRM observation
  91. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  92. GRB 260419B: Fermi GBM Final Real-time Localization
  93. GRB 260419A: Fermi GBM Final Real-time Localization
  94. Fermi trigger No 798275385: Global MASTER-Net observations report
  95. EP260417a: GROWTH-India Telescope optical upper limit
  96. Fermi GRB 260417B: Global MASTER-Net observations report
  97. EP260417b: GROWTH-India Telescope optical upper limit
  98. EP260416a: Ondrejov D50 optical detection
  99. GRB 260418B: Fermi GBM Final Real-time Localization
  100. EP260416a: VLT/FORS2 spectroscopic redshift confirmation

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