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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"
  1. EP260105a: SVOM/VT optical upperlimit
  2. GRB 260105B: Fermi GBM Final Real-time Localization
  3. GRB 260105A: Fermi GBM Final Real-time Localization
  4. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  5. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  6. EP260105a: LCO Optical Upper limit
  7. EP260104a: Global MASTER-Net observations report
  8. EP260104a: Einstein Probe detection of a fast X-ray transient
  9. GRB 260101A: COLIBRÍ optical upper limits
  10. EP260105a: Global MASTER-Net observations report
  11. EP260105a: Einstein Probe detection of an X-ray transient
  12. GRB 260103A: Insight-HXMT/HE detection
  13. GRB 260104A: COLIBRÍ optical upper limits
  14. GRB 260104C: Fermi GBM Final Real-time Localization
  15. Fermi GRB 260104B: Global MASTER-Net observations report
  16. Swift GRB 260104A: Global MASTER-Net observations report
  17. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  18. GRB 260104A: Swift-XRT refined Analysis
  19. GRB 260104A: Enhanced Swift-XRT position
  20. GRB 260101A: Swift/UVOT Detection
  21. GRB 260103A: GECAM-B observation of a burst
  22. GRB 260104B: Fermi GBM Final Localization
  23. GRB 260104A: Swift detection of a burst
  24. GRB 260103A: SVOM/GRM observation of a possible GRB
  25. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  26. GRB 260101A: COLIBRÍ optical observations
  27. SVOM GRB260103.08: Global MASTER-Net observations report
  28. GRB 260102B: Fermi GBM Final Real-time Localization
  29. SVOM GRB260102A: Global MASTER-Net observations report
  30. Fermi GBM Sub-Threshold Detection of GRB 260102A
  31. GRB 260102A: EP-FXT follow-up observation
  32. EP260101a: Global MASTER-Net observations report
  33. GRB 260102A: LCO optical upper limits
  34. GRB 260102A: Swift-XRT observations
  35. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  36. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  37. GRB 251230A / EP251230a: GECAM-B detection
  38. GRB 260102A: SVOM/VT optical counterpart
  39. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  40. GRB 260102A: Swift ToO observations
  41. GRB 260101A: Fermi GBM Observation
  42. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  43. GRB 260102A: SVOM detection of a burst
  44. GRB 260101A: GECAM-B detection
  45. GRB 260101A: NOT spectroscopic observations
  46. GRB 260101A: SVOM/GRM observation
  47. GRB 260101A: Swift-XRT refined Analysis
  48. Swift GRB 260101A: Global MASTER-Net observations report
  49. GRB 260101A: Enhanced Swift-XRT position
  50. EP260101a: Einstein Probe detection of an X-ray transient
  51. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  52. GRB 260101A: LCO detection of the optical counterpart
  53. GRB 260101A: Swift detection of a burst with an optical counterpart
  54. GRB 260101A: Fermi GBM Final Real-time Localization
  55. SVOM GRB251231.57: Global MASTER-Net observations report
  56. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  57. GRB 251230A: GRANDMA/TAROT Early Detection
  58. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  59. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  60. EP251229a: Optical upper limit with Kinder observations
  61. GRB 251230A: 1.3m DFOT optical upper limit
  62. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  63. GRB 251230A: Swift-XRT refined Analysis
  64. GRB 251231A: Fermi GBM Final Real-time Localization
  65. GRB 251222A: Mondy Optical Observations
  66. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 251230A: Swift/UVOT detection
  68. GRB251230A: 7DT optical upper limits
  69. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  70. EP251229a: BOOTES-2 early optical upper limit
  71. GRB 251230A: GOTO optical upper limit
  72. EP251229a: NOT optical upper limits
  73. GRB 251230A / EP251230a: SVOM/VT optical observation
  74. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  75. GRB 251230A: Enhanced Swift-XRT position
  76. GRB 251230A: Early optical counterpart detection by LCO.
  77. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  78. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  79. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  80. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  81. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  82. Swift GRB 251230A: Global MASTER-Net observations report
  83. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  84. EP251229a: Global MASTER-Net observations report
  85. EP251229a: Einstein Probe detection of an X-ray transient
  86. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  87. GRB 251226A: Glowbug gamma-ray detection
  88. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  89. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  90. Fermi GRB 251228A: Global MASTER-Net observations report
  91. The EP-WXT trigger 01709250662 is likely a flaring star
  92. GRB 251228A: Fermi GBM Final Real-time Localization
  93. GRB 251226A: SVOM/GRM observation
  94. GRB 251226A: GECAM-B detection
  95. SVOM GRB251227.07: Global MASTER-Net observations report
  96. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  97. The EP-WXT trigger 01709250617 is likely a flaring star
  98. IceCube Alert 251225.84: Global MASTER-Net observations report
  99. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  100. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB

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