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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"

45423 results found.

  1. GRB 260104A: Swift-BAT refined analysis
  2. GRB 260101A: Swift-BAT refined analysis
  3. Swift GRB 251230A: Global MASTER-Net OT detection
  4. Fermi GRB 260107A: Global MASTER-Net observations report
  5. GRB 260102A: AbAO optical observations
  6. GRB 260107A: Fermi GBM Final Real-time Localization
  7. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  8. The EP-WXT trigger 01709251112 is likely a flaring star
  9. Fermi GRB 260105A: Global MASTER-Net observations report
  10. GRB 260105B: Fermi GBM Detection
  11. EP260105a: FTW optical observations
  12. EP260104a: FTW optical observations
  13. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  14. GRB 260105A: SVOM/GRM observation
  15. GRB 260105B: SVOM/GRM observation
  16. The EP-WXT trigger 01709251028 is likely a flaring star
  17. FRB 20251229A: COLIBRÍ optical upper limits
  18. Fermi GRB 260105B: Global MASTER-Net observations report
  19. EP260105a: SVOM/VT optical upperlimit
  20. GRB 260105B: Fermi GBM Final Real-time Localization
  21. GRB 260105A: Fermi GBM Final Real-time Localization
  22. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  23. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  24. EP260105a: LCO Optical Upper limit
  25. EP260104a: Global MASTER-Net observations report
  26. EP260104a: Einstein Probe detection of a fast X-ray transient
  27. GRB 260101A: COLIBRÍ optical upper limits
  28. EP260105a: Global MASTER-Net observations report
  29. EP260105a: Einstein Probe detection of an X-ray transient
  30. GRB 260103A: Insight-HXMT/HE detection
  31. GRB 260104A: COLIBRÍ optical upper limits
  32. GRB 260104C: Fermi GBM Final Real-time Localization
  33. Fermi GRB 260104B: Global MASTER-Net observations report
  34. Swift GRB 260104A: Global MASTER-Net observations report
  35. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  36. GRB 260104A: Swift-XRT refined Analysis
  37. GRB 260104A: Enhanced Swift-XRT position
  38. GRB 260101A: Swift/UVOT Detection
  39. GRB 260103A: GECAM-B observation of a burst
  40. GRB 260104B: Fermi GBM Final Localization
  41. GRB 260104A: Swift detection of a burst
  42. GRB 260103A: SVOM/GRM observation of a possible GRB
  43. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  44. GRB 260101A: COLIBRÍ optical observations
  45. SVOM GRB260103.08: Global MASTER-Net observations report
  46. GRB 260102B: Fermi GBM Final Real-time Localization
  47. SVOM GRB260102A: Global MASTER-Net observations report
  48. Fermi GBM Sub-Threshold Detection of GRB 260102A
  49. GRB 260102A: EP-FXT follow-up observation
  50. EP260101a: Global MASTER-Net observations report
  51. GRB 260102A: LCO optical upper limits
  52. GRB 260102A: Swift-XRT observations
  53. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  54. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  55. GRB 251230A / EP251230a: GECAM-B detection
  56. GRB 260102A: SVOM/VT optical counterpart
  57. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  58. GRB 260102A: Swift ToO observations
  59. GRB 260101A: Fermi GBM Observation
  60. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  61. GRB 260102A: SVOM detection of a burst
  62. GRB 260101A: GECAM-B detection
  63. GRB 260101A: NOT spectroscopic observations
  64. GRB 260101A: SVOM/GRM observation
  65. GRB 260101A: Swift-XRT refined Analysis
  66. Swift GRB 260101A: Global MASTER-Net observations report
  67. GRB 260101A: Enhanced Swift-XRT position
  68. EP260101a: Einstein Probe detection of an X-ray transient
  69. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  70. GRB 260101A: LCO detection of the optical counterpart
  71. GRB 260101A: Swift detection of a burst with an optical counterpart
  72. GRB 260101A: Fermi GBM Final Real-time Localization
  73. SVOM GRB251231.57: Global MASTER-Net observations report
  74. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  75. GRB 251230A: GRANDMA/TAROT Early Detection
  76. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  77. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  78. EP251229a: Optical upper limit with Kinder observations
  79. GRB 251230A: 1.3m DFOT optical upper limit
  80. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  81. GRB 251230A: Swift-XRT refined Analysis
  82. GRB 251231A: Fermi GBM Final Real-time Localization
  83. GRB 251222A: Mondy Optical Observations
  84. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  85. GRB 251230A: Swift/UVOT detection
  86. GRB251230A: 7DT optical upper limits
  87. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  88. EP251229a: BOOTES-2 early optical upper limit
  89. GRB 251230A: GOTO optical upper limit
  90. EP251229a: NOT optical upper limits
  91. GRB 251230A / EP251230a: SVOM/VT optical observation
  92. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  93. GRB 251230A: Enhanced Swift-XRT position
  94. GRB 251230A: Early optical counterpart detection by LCO.
  95. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  96. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  97. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  98. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  99. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  100. Swift GRB 251230A: Global MASTER-Net observations report

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