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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"

24365 results found.

  1. GRB 260101A: Swift-BAT refined analysis
  2. Swift GRB 251230A: Global MASTER-Net OT detection
  3. Fermi GRB 260107A: Global MASTER-Net observations report
  4. GRB 260107A: Fermi GBM Final Real-time Localization
  5. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  6. The EP-WXT trigger 01709251112 is likely a flaring star
  7. Fermi GRB 260105A: Global MASTER-Net observations report
  8. GRB 260105B: Fermi GBM Detection
  9. EP260105a: FTW optical observations
  10. EP260104a: FTW optical observations
  11. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  12. GRB 260105A: SVOM/GRM observation
  13. GRB 260105B: SVOM/GRM observation
  14. The EP-WXT trigger 01709251028 is likely a flaring star
  15. Fermi GRB 260105B: Global MASTER-Net observations report
  16. EP260105a: SVOM/VT optical upperlimit
  17. GRB 260105B: Fermi GBM Final Real-time Localization
  18. GRB 260105A: Fermi GBM Final Real-time Localization
  19. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  20. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  21. EP260104a: Global MASTER-Net observations report
  22. EP260105a: Global MASTER-Net observations report
  23. GRB 260104C: Fermi GBM Final Real-time Localization
  24. Fermi GRB 260104B: Global MASTER-Net observations report
  25. Swift GRB 260104A: Global MASTER-Net observations report
  26. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  27. GRB 260104A: Swift-XRT refined Analysis
  28. GRB 260103A: GECAM-B observation of a burst
  29. GRB 260104B: Fermi GBM Final Localization
  30. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  31. SVOM GRB260103.08: Global MASTER-Net observations report
  32. GRB 260102B: Fermi GBM Final Real-time Localization
  33. SVOM GRB260102A: Global MASTER-Net observations report
  34. Fermi GBM Sub-Threshold Detection of GRB 260102A
  35. GRB 260102A: EP-FXT follow-up observation
  36. EP260101a: Global MASTER-Net observations report
  37. GRB 260102A: LCO optical upper limits
  38. GRB 260102A: Swift-XRT observations
  39. GRB 260102A: SVOM/VT optical counterpart
  40. GRB 260101A: Fermi GBM Observation
  41. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 260102A: SVOM detection of a burst
  43. GRB 260101A: NOT spectroscopic observations
  44. GRB 260101A: SVOM/GRM observation
  45. GRB 260101A: Swift-XRT refined Analysis
  46. Swift GRB 260101A: Global MASTER-Net observations report
  47. GRB 260101A: Fermi GBM Final Real-time Localization
  48. SVOM GRB251231.57: Global MASTER-Net observations report
  49. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  50. GRB 251230A: GRANDMA/TAROT Early Detection
  51. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  52. EP251229a: Optical upper limit with Kinder observations
  53. GRB 251230A: 1.3m DFOT optical upper limit
  54. GRB 251231A: Fermi GBM Final Real-time Localization
  55. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB251230A: 7DT optical upper limits
  57. EP251229a: BOOTES-2 early optical upper limit
  58. GRB 251230A / EP251230a: SVOM/VT optical observation
  59. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  60. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  61. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  62. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  63. Swift GRB 251230A: Global MASTER-Net observations report
  64. EP251229a: Global MASTER-Net observations report
  65. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  66. Fermi GRB 251228A: Global MASTER-Net observations report
  67. The EP-WXT trigger 01709250662 is likely a flaring star
  68. GRB 251228A: Fermi GBM Final Real-time Localization
  69. GRB 251226A: SVOM/GRM observation
  70. GRB 251226A: GECAM-B detection
  71. SVOM GRB251227.07: Global MASTER-Net observations report
  72. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  73. The EP-WXT trigger 01709250617 is likely a flaring star
  74. IceCube Alert 251225.84: Global MASTER-Net observations report
  75. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  76. GRB 251222A: NUTTelA-TAO Early Measurements
  77. GRB 251222A/EP251222b: Optical detection with Kinder observations
  78. GRB 251221A: Swift-BAT refined analysis
  79. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  80. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  81. GRB 251222A: Continued 1.3m DFOT optical observation
  82. EP251220a: 3.6m DOT optical afterglow detection
  83. GRB 251222A: Fermi GBM Observation
  84. EP251222a: Global MASTER-Net observations report
  85. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  86. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  87. Konus-Wind detection of GRB 251222A / EP251222b
  88. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  89. EP251222a: GOTO optical upper limit
  90. GRB 251222A / EP251222b: LCO optical observations
  91. GRB 251222A: 1.3m DFOT optical detection
  92. GRB251221A: 7DT optical upper limits
  93. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  94. EP251222b/GRB 251222A: SVOM/GRM observation
  95. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  96. The EP-WXT trigger 01709250397 is likely a flaring star
  97. EP251221a: Global MASTER-Net observations report
  98. EP251221a: NOT optical upper limit
  99. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  100. GRB 251222A: NOT optical observations

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