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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"

12332 results found.

  1. GRB 260104A: COLIBRÍ optical upper limits
  2. Fermi GRB 260104B: Global MASTER-Net observations report
  3. Swift GRB 260104A: Global MASTER-Net observations report
  4. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  5. GRB 260101A: Swift/UVOT Detection
  6. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  7. SVOM GRB260103.08: Global MASTER-Net observations report
  8. SVOM GRB260102A: Global MASTER-Net observations report
  9. GRB 260102A: EP-FXT follow-up observation
  10. EP260101a: Global MASTER-Net observations report
  11. GRB 260102A: LCO optical upper limits
  12. GRB 260102A: Swift-XRT observations
  13. Swift GRB 260101A: Global MASTER-Net observations report
  14. SVOM GRB251231.57: Global MASTER-Net observations report
  15. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  16. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  17. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  18. EP251229a: Optical upper limit with Kinder observations
  19. GRB 251230A: 1.3m DFOT optical upper limit
  20. GRB251230A: 7DT optical upper limits
  21. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  22. EP251229a: BOOTES-2 early optical upper limit
  23. GRB 251230A: GOTO optical upper limit
  24. EP251229a: NOT optical upper limits
  25. Swift GRB 251230A: Global MASTER-Net observations report
  26. EP251229a: Global MASTER-Net observations report
  27. Fermi GRB 251228A: Global MASTER-Net observations report
  28. SVOM GRB251227.07: Global MASTER-Net observations report
  29. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  30. IceCube Alert 251225.84: Global MASTER-Net observations report
  31. EP251222a: Optical upper limit with Kinder observations
  32. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  33. EP251221a: PRIME upper limit
  34. EP251222a: Global MASTER-Net observations report
  35. EP251221a: Liverpool Telescope upper limits
  36. GRB 251222A: Swift-XRT afterglow detection
  37. EP251222a: GOTO optical upper limit
  38. GRB251221A: 7DT optical upper limits
  39. EP251221a: Global MASTER-Net observations report
  40. EP251221a: NOT optical upper limit
  41. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  42. SVOM GRB251222A: Global MASTER-Net observations report
  43. EP251220a: PRIME upper limit
  44. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  45. GRB 251221A: UAFO and Mondy optical upper limit
  46. GRB 251221A: Swift/UVOT Upper Limits
  47. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  48. GRB 251221A: Swift detection of a burst
  49. Swift GRB251221A: Global MASTER-Net observations report
  50. EP251220a: Global MASTER-Net observations report
  51. SVOM GRB251220.98: Global MASTER-Net observations report
  52. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  53. GRB 251220A: MAXI/GSC detection
  54. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  55. IceCube-251218A: COLIBRÍ optical upper limits
  56. SVOM GRB251219.11: Global MASTER-Net observations report
  57. IceCube Alert 251218.85: Global MASTER-Net observations report
  58. GRB 251214B: VIRT Optical Upper Limit
  59. Fermi trigger No 787736968: Global MASTER-Net observations report
  60. Fermi GRB 251217A: Global MASTER-Net observations report
  61. GRB 251215A: Swift/UVOT Upper LImits
  62. Fermi GRB 251216A: Global MASTER-Net observations report
  63. GRB 251202A/EP251202a: Koshka optical upper limit
  64. GRB 251214B: Mondy optical upper limit
  65. GRB 251215A: COLIBRÍ optical upper limit
  66. EP251214b: KAIT optical upper limit
  67. GRB 251215A: Swift-XRT observations
  68. Fermi GRB 251215A: Global MASTER-Net observations report
  69. EP251214a: Optical upper limit with Kinder observations
  70. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  71. GRB 251214B: UAFO optical upper limit
  72. EP251214b: Global MASTER-Net observations report
  73. EP251214a: KAIT optical upper limit
  74. GRB 251214B: Swift/UVOT Detection
  75. EP251214a: EP-FXT non-detection and upper limit
  76. EP251214a: Global MASTER-Net observations report
  77. Fermi trigger No 787396657: Global MASTER-Net observations report
  78. EP251214a: COLIBRÍ optical upper limit
  79. Swift GRB 251214B: Global MASTER-Net observations report
  80. EP251214.305: COLIBRÍ optical upper limit
  81. Fermi GRB 251214A: Global MASTER-Net observations report
  82. EP251212a: Global MASTER-Net observations report
  83. EP251212a: KAIT optical upper limit
  84. EP251212a : COLIBRÍ optical upper limit
  85. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  86. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  87. Fermi GRB 251211B: Global MASTER-Net observations report
  88. IceCube-251210A: DDOTI Optical Upper Limit
  89. SVOM GRB251211.12: Global MASTER-Net observations report
  90. GRB 251205A: 1.3m DFOT optical upper limit
  91. IceCube Alert 251210.46: Global MASTER-Net observations report
  92. EP251124a: Mondy optical upper limit
  93. GRB 251208B: COLIBRÍ optical upper limits
  94. Fermi GRB 251209A: Global MASTER-Net observations report
  95. Fermi GRB 251208C: Global MASTER-Net observations report
  96. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  97. GRB 251208D: LAST optical upper limit
  98. GRB 251208B: GROWTH-India Telescope optical upper limits
  99. GRB 251208D: Swift-XRT observations
  100. GRB 251129A: e-MERLIN C-band observations

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