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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"

26810 results found.

  1. EP251229a: Einstein Probe detection of an X-ray transient
  2. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  3. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  4. Fermi GRB 251228A: Global MASTER-Net observations report
  5. The EP-WXT trigger 01709250662 is likely a flaring star
  6. GRB 251228A: Fermi GBM Final Real-time Localization
  7. GRB 251226A: SVOM/GRM observation
  8. GRB 251226A: GECAM-B detection
  9. SVOM GRB251227.07: Global MASTER-Net observations report
  10. The EP-WXT trigger 01709250617 is likely a flaring star
  11. IceCube Alert 251225.84: Global MASTER-Net observations report
  12. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  13. GRB 251222A: NUTTelA-TAO Early Measurements
  14. EP251222a: Optical upper limit with Kinder observations
  15. GRB 251221A: Swift-BAT refined analysis
  16. GRB 251222A/EP251222b: FTW optical and NIR observations
  17. EP251222a: FTW optical and NIR observations
  18. GRB 251205A: Kilonova-Catcher optical afterglow detection
  19. GRB 251222A: AbAO optical observations
  20. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  21. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  22. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  23. GRB 251222A: ZTSH BVRI optical observations
  24. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  25. GRB 251222A: Continued 1.3m DFOT optical observation
  26. EP251220a: 3.6m DOT optical afterglow detection
  27. GRB 251222A: Fermi GBM Observation
  28. EP251220a: CrAO ZTSh optical observations
  29. EP251221a: PRIME upper limit
  30. EP251222a: Global MASTER-Net observations report
  31. GRB 251222A / EP251222b: GECAM-B observation
  32. EP251221a: Liverpool Telescope upper limits
  33. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  34. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  35. EP251222a: NTT/ULTRACAM optical observations
  36. EP251222a: GOTO optical upper limit
  37. GRB 251222A / EP251222b: GOTO optical counterpart detection
  38. GRB 251222A / EP251222b: LCO optical observations
  39. GRB 251222A: 1.3m DFOT optical detection
  40. GRB251221A: 7DT optical upper limits
  41. EP251222a: GSP Optical Counterpart Detection
  42. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  43. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  44. EP251222b/GRB 251222A: SVOM/GRM observation
  45. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  46. EP251222a: Einstein Probe detection of an X-ray transient
  47. The EP-WXT trigger 01709250397 is likely a flaring star
  48. EP251221a: Global MASTER-Net observations report
  49. EP251221a: NOT optical upper limit
  50. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  51. GRB 251222A: NOT optical observations
  52. IPN triangulation of GRB 251220B (short)
  53. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  54. GRB 251222A: SVOM/VT optical candidate
  55. GRB 251222A: SVOM detection of a long burst
  56. SVOM GRB251222A: Global MASTER-Net observations report
  57. GRB 251222A: Fermi GBM Final Real-time Localization
  58. EP251220a: PRIME upper limit
  59. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  60. GRB 251221A: PRIME near-infrared observation
  61. EP251220a: NOT optical observations
  62. EP251220a: FTW optical and NIR observations
  63. GRB 251221A: UAFO and Mondy optical upper limit
  64. GRB 251221A: Swift-XRT refined Analysis
  65. EP251221a: Einstein Probe detection of a fast X-ray transient
  66. GRB 251221A: Swift/UVOT Upper Limits
  67. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  68. GRB 251221A: Fermi GBM Observation
  69. GRB 251221B: Fermi GBM Final Real-time Localization
  70. EP251220a: EP-FXT follow-up observation
  71. GRB 251220B: SVOM/GRM observation of a short burst
  72. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  73. EP 251220a: GOTO optical counterpart detection
  74. GRB 251221A: COLIBRÍ detection of the optical counterpart
  75. EP 251220a: COLIBRÍ detection of the optical counterpart
  76. GRB 251221A: Swift detection of a burst
  77. Swift GRB251221A: Global MASTER-Net observations report
  78. GRB 251221A: Fermi GBM Final Real-time Localization
  79. EP251220a: Global MASTER-Net observations report
  80. EP251220a: EP detection of a fast X-ray transient
  81. SVOM GRB251220.98: Global MASTER-Net observations report
  82. GRB 251220B: Fermi GBM Final Real-time Localization
  83. GRB 251219A: SVOM/GRM observation of a short burst
  84. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  85. IceCube-251218A: COLIBRÍ optical upper limits
  86. SVOM GRB251219.11: Global MASTER-Net observations report
  87. IceCube Alert 251218.85: Global MASTER-Net observations report
  88. Fermi trigger No 787736968: Global MASTER-Net observations report
  89. Fermi GRB 251217A: Global MASTER-Net observations report
  90. GRB 251217A: Fermi GBM Final Real-time Localization
  91. GRB 251215A: Swift/UVOT Upper LImits
  92. GRB 251215A: Fermi GBM Observation
  93. Fermi GRB 251216A: Global MASTER-Net observations report
  94. GRB 251215A: COLIBRÍ optical upper limit
  95. GRB 251216A: Fermi GBM Final Real-time Localization
  96. EP251214b: KAIT optical upper limit
  97. Fermi GRB 251215A: Global MASTER-Net observations report
  98. EP251214a: Optical upper limit with Kinder observations
  99. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  100. GRB 251215A: Glowbug gamma-ray detection

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