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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"

27015 results found.

  1. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  2. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  3. Swift GRB 251230A: Global MASTER-Net observations report
  4. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  5. EP251229a: Global MASTER-Net observations report
  6. EP251229a: Einstein Probe detection of an X-ray transient
  7. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  8. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  9. Fermi GRB 251228A: Global MASTER-Net observations report
  10. The EP-WXT trigger 01709250662 is likely a flaring star
  11. GRB 251228A: Fermi GBM Final Real-time Localization
  12. GRB 251226A: SVOM/GRM observation
  13. GRB 251226A: GECAM-B detection
  14. SVOM GRB251227.07: Global MASTER-Net observations report
  15. The EP-WXT trigger 01709250617 is likely a flaring star
  16. IceCube Alert 251225.84: Global MASTER-Net observations report
  17. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  18. GRB 251222A: NUTTelA-TAO Early Measurements
  19. EP251222a: Optical upper limit with Kinder observations
  20. GRB 251221A: Swift-BAT refined analysis
  21. GRB 251222A/EP251222b: FTW optical and NIR observations
  22. EP251222a: FTW optical and NIR observations
  23. GRB 251205A: Kilonova-Catcher optical afterglow detection
  24. GRB 251222A: AbAO optical observations
  25. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  26. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  27. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  28. GRB 251222A: ZTSH BVRI optical observations
  29. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  30. GRB 251222A: Continued 1.3m DFOT optical observation
  31. EP251220a: 3.6m DOT optical afterglow detection
  32. GRB 251222A: Fermi GBM Observation
  33. EP251220a: CrAO ZTSh optical observations
  34. EP251221a: PRIME upper limit
  35. EP251222a: Global MASTER-Net observations report
  36. GRB 251222A / EP251222b: GECAM-B observation
  37. EP251221a: Liverpool Telescope upper limits
  38. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  39. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  40. EP251222a: NTT/ULTRACAM optical observations
  41. EP251222a: GOTO optical upper limit
  42. GRB 251222A / EP251222b: GOTO optical counterpart detection
  43. GRB 251222A / EP251222b: LCO optical observations
  44. GRB 251222A: 1.3m DFOT optical detection
  45. GRB251221A: 7DT optical upper limits
  46. EP251222a: GSP Optical Counterpart Detection
  47. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  48. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  49. EP251222b/GRB 251222A: SVOM/GRM observation
  50. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  51. EP251222a: Einstein Probe detection of an X-ray transient
  52. The EP-WXT trigger 01709250397 is likely a flaring star
  53. EP251221a: Global MASTER-Net observations report
  54. EP251221a: NOT optical upper limit
  55. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  56. GRB 251222A: NOT optical observations
  57. IPN triangulation of GRB 251220B (short)
  58. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  59. GRB 251222A: SVOM/VT optical candidate
  60. GRB 251222A: SVOM detection of a long burst
  61. SVOM GRB251222A: Global MASTER-Net observations report
  62. GRB 251222A: Fermi GBM Final Real-time Localization
  63. EP251220a: PRIME upper limit
  64. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  65. GRB 251221A: PRIME near-infrared observation
  66. EP251220a: NOT optical observations
  67. EP251220a: FTW optical and NIR observations
  68. GRB 251221A: UAFO and Mondy optical upper limit
  69. GRB 251221A: Swift-XRT refined Analysis
  70. EP251221a: Einstein Probe detection of a fast X-ray transient
  71. GRB 251221A: Swift/UVOT Upper Limits
  72. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  73. GRB 251221A: Fermi GBM Observation
  74. GRB 251221B: Fermi GBM Final Real-time Localization
  75. EP251220a: EP-FXT follow-up observation
  76. GRB 251220B: SVOM/GRM observation of a short burst
  77. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  78. EP 251220a: GOTO optical counterpart detection
  79. GRB 251221A: COLIBRÍ detection of the optical counterpart
  80. EP 251220a: COLIBRÍ detection of the optical counterpart
  81. GRB 251221A: Swift detection of a burst
  82. Swift GRB251221A: Global MASTER-Net observations report
  83. GRB 251221A: Fermi GBM Final Real-time Localization
  84. EP251220a: Global MASTER-Net observations report
  85. EP251220a: EP detection of a fast X-ray transient
  86. SVOM GRB251220.98: Global MASTER-Net observations report
  87. GRB 251220B: Fermi GBM Final Real-time Localization
  88. GRB 251219A: SVOM/GRM observation of a short burst
  89. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  90. IceCube-251218A: COLIBRÍ optical upper limits
  91. SVOM GRB251219.11: Global MASTER-Net observations report
  92. IceCube Alert 251218.85: Global MASTER-Net observations report
  93. Fermi trigger No 787736968: Global MASTER-Net observations report
  94. Fermi GRB 251217A: Global MASTER-Net observations report
  95. GRB 251217A: Fermi GBM Final Real-time Localization
  96. GRB 251215A: Swift/UVOT Upper LImits
  97. GRB 251215A: Fermi GBM Observation
  98. Fermi GRB 251216A: Global MASTER-Net observations report
  99. GRB 251215A: COLIBRÍ optical upper limit
  100. GRB 251216A: Fermi GBM Final Real-time Localization

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