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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"

28083 results found.

  1. GRB 260104A: Swift detection of a burst
  2. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  3. GRB 260101A: COLIBRÍ optical observations
  4. SVOM GRB260103.08: Global MASTER-Net observations report
  5. SVOM GRB260102A: Global MASTER-Net observations report
  6. Fermi GBM Sub-Threshold Detection of GRB 260102A
  7. GRB 260102A: EP-FXT follow-up observation
  8. EP260101a: Global MASTER-Net observations report
  9. GRB 260102A: LCO optical upper limits
  10. GRB 260102A: Swift-XRT observations
  11. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  12. GRB 260101A: Fermi GBM Observation
  13. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  14. GRB 260102A: SVOM detection of a burst
  15. GRB 260101A: NOT spectroscopic observations
  16. GRB 260101A: SVOM/GRM observation
  17. GRB 260101A: Swift-XRT refined Analysis
  18. Swift GRB 260101A: Global MASTER-Net observations report
  19. GRB 260101A: Enhanced Swift-XRT position
  20. EP260101a: Einstein Probe detection of an X-ray transient
  21. GRB 260101A: LCO detection of the optical counterpart
  22. GRB 260101A: Swift detection of a burst with an optical counterpart
  23. GRB 260101A: Fermi GBM Final Real-time Localization
  24. SVOM GRB251231.57: Global MASTER-Net observations report
  25. GRB 251230A: GRANDMA/TAROT Early Detection
  26. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  27. EP251229a: Optical upper limit with Kinder observations
  28. GRB 251230A: 1.3m DFOT optical upper limit
  29. GRB 251230A: Swift-XRT refined Analysis
  30. GRB 251222A: Mondy Optical Observations
  31. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  32. GRB 251230A: Swift/UVOT detection
  33. GRB251230A: 7DT optical upper limits
  34. GRB 251230A: GOTO optical upper limit
  35. EP251229a: NOT optical upper limits
  36. GRB 251230A / EP251230a: SVOM/VT optical observation
  37. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  38. GRB 251230A: Enhanced Swift-XRT position
  39. GRB 251230A: Early optical counterpart detection by LCO.
  40. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  41. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  42. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  43. Swift GRB 251230A: Global MASTER-Net observations report
  44. EP251229a: Global MASTER-Net observations report
  45. EP251229a: Einstein Probe detection of an X-ray transient
  46. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  47. GRB 251226A: Glowbug gamma-ray detection
  48. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  49. Fermi GRB 251228A: Global MASTER-Net observations report
  50. GRB 251226A: SVOM/GRM observation
  51. GRB 251226A: GECAM-B detection
  52. SVOM GRB251227.07: Global MASTER-Net observations report
  53. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  54. IceCube Alert 251225.84: Global MASTER-Net observations report
  55. GRB 251222A/EP251222b: Optical detection with Kinder observations
  56. EP251222a: Optical upper limit with Kinder observations
  57. GRB 251221A: Swift-BAT refined analysis
  58. GRB 251205A: Kilonova-Catcher optical afterglow detection
  59. GRB 251222A: AbAO optical observations
  60. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  61. GRB 251222A: ZTSH BVRI optical observations
  62. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  63. GRB 251222A: Continued 1.3m DFOT optical observation
  64. EP251220a: 3.6m DOT optical afterglow detection
  65. GRB 251222A: Fermi GBM Observation
  66. EP251220a: CrAO ZTSh optical observations
  67. EP251221a: PRIME upper limit
  68. EP251222a: Global MASTER-Net observations report
  69. EP251221a: Liverpool Telescope upper limits
  70. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  71. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 251222A: Swift-XRT afterglow detection
  73. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  74. EP251222a: NTT/ULTRACAM optical observations
  75. GRB 251222A / EP251222b: GOTO optical counterpart detection
  76. GRB 251222A / EP251222b: LCO optical observations
  77. GRB 251222A: 1.3m DFOT optical detection
  78. GRB251221A: 7DT optical upper limits
  79. EP251222a: GSP Optical Counterpart Detection
  80. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  81. EP251222a: Einstein Probe detection of an X-ray transient
  82. EP251221a: Global MASTER-Net observations report
  83. GRB 251222A: PRIME near-infrared detection
  84. EP251221a: NOT optical upper limit
  85. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  86. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  87. IPN triangulation of GRB 251220B (short)
  88. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  89. GRB 251222A: SVOM/VT optical candidate
  90. GRB 251222A: SVOM detection of a long burst
  91. SVOM GRB251222A: Global MASTER-Net observations report
  92. EP251220a: PRIME upper limit
  93. GRB 251221A: PRIME near-infrared observation
  94. GRB 251221A: UAFO and Mondy optical upper limit
  95. GRB 251221A: Swift-XRT refined Analysis
  96. EP251221a: Einstein Probe detection of a fast X-ray transient
  97. GRB 251221A: Swift/UVOT Upper Limits
  98. GRB 251221A: Enhanced Swift-XRT position
  99. GRB 251221A: Fermi GBM Observation
  100. GRB 251220B: SVOM/GRM observation of a short burst

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