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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"

3106 results found.

  1. GRB 260430B: AstroSat CZTI detection of a long burst
  2. SVOM GRB 260504B: MASTER-OAFA optical observations
  3. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  4. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  5. GRB 260429A: Fermi GBM Detection
  6. Fermi GRB 260429A: Global MASTER-Net observations report
  7. EP260430a: Einstein Probe detection of an X-ray transient
  8. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  9. IPN triangulation of GRB 260424B (short)
  10. IceCube Alert 260425A: Global MASTER-Net observations report
  11. GRB 260419A: AstroSat CZTI detection
  12. GRB 260310A: Late-time Chandra X-ray Detection
  13. Fermi GRB 260421B: Global MASTER-Net observations report
  14. Fermi GRB 260421A: Global MASTER-Net observations report
  15. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  16. GRB 260419B: Fermi GBM Final Real-time Localization
  17. Fermi GRB 260417A: Global MASTER-Net observations report
  18. EP260416a: WFST optical observations and rebrightening
  19. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  20. EP260416a: Global MASTER-Net observations report
  21. EP260321a: CMO SAI J,K observations
  22. GRB 260414A: Fermi GBM Final Real-time Localization
  23. Fermi GRB 260412A: Global MASTER-Net observations report
  24. GRB 260410B: Fermi GBM Observation
  25. GRB 260411B: Fermi GBM Final Real-time Localization
  26. GRB 260410A: COLIBRÍ optical upper limit
  27. EP260329a: COLIBRÍ optical upper limit
  28. EP260329a: EP-FXT follow up observation
  29. EP-WXT trigger 01709259209: TRT optical counterpart detection
  30. EP260327a: SVOM/VT optical upper limits
  31. EP260327a: Global MASTER-Net observations report
  32. The EP-WXT trigger 01709259045 is likely a flaring star
  33. GRB 260318A: Fermi GBM Final Real-time Localization
  34. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  35. Fermi trigger No 795185313: Global MASTER-Net observations report
  36. Fermi GRB 260313A: Global MASTER-Net observations report
  37. Fermi GRB 260310A: Global MASTER-Net observations report
  38. GRB 260307B: SVOM/C-GFT upper limit
  39. GRB 260303A: SVOM/ECLAIRs refined analysis
  40. Fermi GRB 260305A: Global MASTER-Net observations report
  41. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  42. GRB 260303A: SVOM detection of a burst
  43. GRB 260302A: Fermi GBM Final Real-time Localization
  44. EP260227a: Mephisto optical detection
  45. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  46. Fermi GRB 260226A: Global MASTER-Net observations report
  47. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  48. Fermi GRB 260221B: Global MASTER-Net observations report
  49. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  50. Fermi GRB 260219A: Global MASTER-Net observations report
  51. IPN triangulation of GRB 260212A
  52. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  53. GRB 260204A: SVOM/ECLAIRs refined analysis
  54. Fermi GRB 260209A: Global MASTER-Net observations report
  55. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  56. LAT GRB 260208B: Global MASTER-Net observations report
  57. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  58. GRB 260206A: Swift-XRT observations
  59. Fermi trigger No 792135758: Global MASTER-Net observations report
  60. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  61. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  62. EP260131a: SVOM/VT optical observation
  63. GRB 260130A: Fermi GBM Detection
  64. GRB 260127B: Fermi GBM Detection
  65. Fermi GRB 260129A: Global MASTER-Net observations report
  66. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  67. Fermi GRB 260127B: Global MASTER-Net observations report
  68. Swift GRB 260127A: Global MASTER-Net observations report
  69. GRB 260114A: SVOM/VT optical upper limits
  70. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  71. EP260116a: COLIBRÍ further observations
  72. SVOM GRB260121.06: Global MASTER-Net observations report
  73. SVOM GRB260119.90: Global MASTER-Net observations report
  74. EP260119a: Global MASTER-Net observations report
  75. SVOM GRB260117.82: Global MASTER-Net observations report
  76. GRB 260117A: SVOM/C-GFT upper limit
  77. GRB 251222A: radio detection with the VLA
  78. Konus-Wind detection of GRB 251230A / EP251230a
  79. GRB 260112A: Fermi GBM Final Real-time Localization
  80. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  81. Swift Trigger 1434591: possible GRB 260109C
  82. Fermi GRB 260107A: Global MASTER-Net observations report
  83. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  84. The EP-WXT trigger 01709251112 is likely a flaring star
  85. GRB 260105B: Fermi GBM Detection
  86. GRB 260105A: SVOM/GRM observation
  87. The EP-WXT trigger 01709251028 is likely a flaring star
  88. GRB 260105A: Fermi GBM Final Real-time Localization
  89. EP260104a: Global MASTER-Net observations report
  90. EP260105a: Global MASTER-Net observations report
  91. Fermi GRB 260104B: Global MASTER-Net observations report
  92. GRB 260101A: COLIBRÍ optical observations
  93. SVOM GRB260103.08: Global MASTER-Net observations report
  94. GRB 260102B: Fermi GBM Final Real-time Localization
  95. GRB 260102A: EP-FXT follow-up observation
  96. GRB 260101A: NOT spectroscopic observations
  97. Fermi GRB 251228A: Global MASTER-Net observations report
  98. GRB 251228A: Fermi GBM Final Real-time Localization
  99. SVOM GRB251227.07: Global MASTER-Net observations report
  100. GRB 251222A / EP251222b: GOTO optical counterpart detection

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