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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"

42594 results found.

  1. GRB 260105A: SVOM/GRM observation
  2. GRB 260105B: SVOM/GRM observation
  3. The EP-WXT trigger 01709251028 is likely a flaring star
  4. FRB 20251229A: COLIBRÍ optical upper limits
  5. Fermi GRB 260105B: Global MASTER-Net observations report
  6. EP260105a: SVOM/VT optical upperlimit
  7. GRB 260105B: Fermi GBM Final Real-time Localization
  8. GRB 260105A: Fermi GBM Final Real-time Localization
  9. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  10. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  11. EP260105a: LCO Optical Upper limit
  12. EP260104a: Global MASTER-Net observations report
  13. EP260104a: Einstein Probe detection of a fast X-ray transient
  14. GRB 260101A: COLIBRÍ optical upper limits
  15. EP260105a: Global MASTER-Net observations report
  16. EP260105a: Einstein Probe detection of an X-ray transient
  17. GRB 260103A: Insight-HXMT/HE detection
  18. GRB 260104A: COLIBRÍ optical upper limits
  19. GRB 260104C: Fermi GBM Final Real-time Localization
  20. Fermi GRB 260104B: Global MASTER-Net observations report
  21. Swift GRB 260104A: Global MASTER-Net observations report
  22. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  23. GRB 260104A: Swift-XRT refined Analysis
  24. GRB 260104A: Enhanced Swift-XRT position
  25. GRB 260101A: Swift/UVOT Detection
  26. GRB 260103A: GECAM-B observation of a burst
  27. GRB 260104B: Fermi GBM Final Localization
  28. GRB 260104A: Swift detection of a burst
  29. GRB 260103A: SVOM/GRM observation of a possible GRB
  30. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  31. GRB 260101A: COLIBRÍ optical observations
  32. SVOM GRB260103.08: Global MASTER-Net observations report
  33. GRB 260102B: Fermi GBM Final Real-time Localization
  34. SVOM GRB260102A: Global MASTER-Net observations report
  35. Fermi GBM Sub-Threshold Detection of GRB 260102A
  36. GRB 260102A: EP-FXT follow-up observation
  37. EP260101a: Global MASTER-Net observations report
  38. GRB 260102A: LCO optical upper limits
  39. GRB 260102A: Swift-XRT observations
  40. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  41. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  42. GRB 251230A / EP251230a: GECAM-B detection
  43. GRB 260102A: SVOM/VT optical counterpart
  44. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  45. GRB 260102A: Swift ToO observations
  46. GRB 260101A: Fermi GBM Observation
  47. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  48. GRB 260102A: SVOM detection of a burst
  49. GRB 260101A: GECAM-B detection
  50. GRB 260101A: NOT spectroscopic observations
  51. GRB 260101A: SVOM/GRM observation
  52. GRB 260101A: Swift-XRT refined Analysis
  53. Swift GRB 260101A: Global MASTER-Net observations report
  54. GRB 260101A: Enhanced Swift-XRT position
  55. EP260101a: Einstein Probe detection of an X-ray transient
  56. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  57. GRB 260101A: LCO detection of the optical counterpart
  58. GRB 260101A: Swift detection of a burst with an optical counterpart
  59. GRB 260101A: Fermi GBM Final Real-time Localization
  60. SVOM GRB251231.57: Global MASTER-Net observations report
  61. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  62. GRB 251230A: GRANDMA/TAROT Early Detection
  63. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  64. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  65. EP251229a: Optical upper limit with Kinder observations
  66. GRB 251230A: 1.3m DFOT optical upper limit
  67. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  68. GRB 251230A: Swift-XRT refined Analysis
  69. GRB 251231A: Fermi GBM Final Real-time Localization
  70. GRB 251222A: Mondy Optical Observations
  71. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 251230A: Swift/UVOT detection
  73. GRB251230A: 7DT optical upper limits
  74. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  75. EP251229a: BOOTES-2 early optical upper limit
  76. GRB 251230A: GOTO optical upper limit
  77. EP251229a: NOT optical upper limits
  78. GRB 251230A / EP251230a: SVOM/VT optical observation
  79. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  80. GRB 251230A: Enhanced Swift-XRT position
  81. GRB 251230A: Early optical counterpart detection by LCO.
  82. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  83. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  84. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  85. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  86. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  87. Swift GRB 251230A: Global MASTER-Net observations report
  88. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  89. EP251229a: Global MASTER-Net observations report
  90. EP251229a: Einstein Probe detection of an X-ray transient
  91. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  92. GRB 251226A: Glowbug gamma-ray detection
  93. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  94. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  95. Fermi GRB 251228A: Global MASTER-Net observations report
  96. The EP-WXT trigger 01709250662 is likely a flaring star
  97. GRB 251228A: Fermi GBM Final Real-time Localization
  98. GRB 251226A: SVOM/GRM observation
  99. GRB 251226A: GECAM-B detection
  100. SVOM GRB251227.07: Global MASTER-Net observations report

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