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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"
  1. GRB 251230A: Enhanced Swift-XRT position
  2. GRB 251230A: Early optical counterpart detection by LCO.
  3. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  4. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  5. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  6. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  7. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  8. Swift GRB 251230A: Global MASTER-Net observations report
  9. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  10. EP251229a: Global MASTER-Net observations report
  11. EP251229a: Einstein Probe detection of an X-ray transient
  12. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  13. GRB 251226A: Glowbug gamma-ray detection
  14. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  15. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  16. Fermi GRB 251228A: Global MASTER-Net observations report
  17. The EP-WXT trigger 01709250662 is likely a flaring star
  18. GRB 251228A: Fermi GBM Final Real-time Localization
  19. GRB 251226A: SVOM/GRM observation
  20. GRB 251226A: GECAM-B detection
  21. SVOM GRB251227.07: Global MASTER-Net observations report
  22. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  23. The EP-WXT trigger 01709250617 is likely a flaring star
  24. IceCube Alert 251225.84: Global MASTER-Net observations report
  25. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  26. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  27. GRB 251222A: NUTTelA-TAO Early Measurements
  28. GRB 251222A/EP251222b: Optical detection with Kinder observations
  29. EP251222a: Optical upper limit with Kinder observations
  30. GRB 251221A: Swift-BAT refined analysis
  31. GRB 251222A/EP251222b: FTW optical and NIR observations
  32. EP251222a: FTW optical and NIR observations
  33. GRB 251205A: Kilonova-Catcher optical afterglow detection
  34. GRB 251222A: AbAO optical observations
  35. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  36. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  37. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  38. GRB 251222A: ZTSH BVRI optical observations
  39. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  40. GRB 251222A: Continued 1.3m DFOT optical observation
  41. EP251220a: 3.6m DOT optical afterglow detection
  42. GRB 251222A: Fermi GBM Observation
  43. EP251220a: CrAO ZTSh optical observations
  44. EP251221a: PRIME upper limit
  45. EP251222a: Global MASTER-Net observations report
  46. GRB 251222A / EP251222b: GECAM-B observation
  47. EP251221a: Liverpool Telescope upper limits
  48. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  49. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  50. Konus-Wind detection of GRB 251222A / EP251222b
  51. GRB 251222A: Swift-XRT afterglow detection
  52. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  53. EP251222a: NTT/ULTRACAM optical observations
  54. EP251222a: GOTO optical upper limit
  55. GRB 251222A / EP251222b: GOTO optical counterpart detection
  56. GRB 251222A / EP251222b: LCO optical observations
  57. GRB 251222A: 1.3m DFOT optical detection
  58. GRB251221A: 7DT optical upper limits
  59. EP251222a: GSP Optical Counterpart Detection
  60. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  61. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  62. EP251222b/GRB 251222A: SVOM/GRM observation
  63. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  64. EP251222a: Einstein Probe detection of an X-ray transient
  65. The EP-WXT trigger 01709250397 is likely a flaring star
  66. EP251221a: Global MASTER-Net observations report
  67. GRB 251222A: PRIME near-infrared detection
  68. EP251221a: NOT optical upper limit
  69. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  70. GRB 251222A: NOT optical observations
  71. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  72. IPN triangulation of GRB 251220B (short)
  73. GRB 251222A: Swift ToO observations
  74. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  75. GRB 251222A: SVOM/VT optical candidate
  76. GRB 251222A: SVOM detection of a long burst
  77. SVOM GRB251222A: Global MASTER-Net observations report
  78. GRB 251222A: Fermi GBM Final Real-time Localization
  79. EP251220a: PRIME upper limit
  80. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  81. GRB 251221A: PRIME near-infrared observation
  82. EP251220a: NOT optical observations
  83. EP251220a: FTW optical and NIR observations
  84. GRB 251221A: UAFO and Mondy optical upper limit
  85. GRB 251221A: Swift-XRT refined Analysis
  86. EP251221a: Einstein Probe detection of a fast X-ray transient
  87. GRB 251221A: Swift/UVOT Upper Limits
  88. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  89. GRB 251221A: Enhanced Swift-XRT position
  90. GRB 251221A: Fermi GBM Observation
  91. GRB 251221B: Fermi GBM Final Real-time Localization
  92. EP251220a: EP-FXT follow-up observation
  93. GRB 251220B: SVOM/GRM observation of a short burst
  94. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  95. EP 251220a: GOTO optical counterpart detection
  96. GRB 251221A: COLIBRÍ detection of the optical counterpart
  97. EP 251220a: COLIBRÍ detection of the optical counterpart
  98. GRB 251221A: Swift detection of a burst
  99. Swift GRB251221A: Global MASTER-Net observations report
  100. GRB 251221A: Fermi GBM Final Real-time Localization

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