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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. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  2. GRB 251230A: Swift-XRT refined Analysis
  3. GRB 251231A: Fermi GBM Final Real-time Localization
  4. GRB 251222A: Mondy Optical Observations
  5. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 251230A: Swift/UVOT detection
  7. GRB251230A: 7DT optical upper limits
  8. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  9. EP251229a: BOOTES-2 early optical upper limit
  10. GRB 251230A: GOTO optical upper limit
  11. EP251229a: NOT optical upper limits
  12. GRB 251230A / EP251230a: SVOM/VT optical observation
  13. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  14. GRB 251230A: Enhanced Swift-XRT position
  15. GRB 251230A: Early optical counterpart detection by LCO.
  16. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  17. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  18. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  19. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  20. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  21. Swift GRB 251230A: Global MASTER-Net observations report
  22. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  23. EP251229a: Global MASTER-Net observations report
  24. EP251229a: Einstein Probe detection of an X-ray transient
  25. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  26. GRB 251226A: Glowbug gamma-ray detection
  27. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  28. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  29. Fermi GRB 251228A: Global MASTER-Net observations report
  30. The EP-WXT trigger 01709250662 is likely a flaring star
  31. GRB 251228A: Fermi GBM Final Real-time Localization
  32. GRB 251226A: SVOM/GRM observation
  33. GRB 251226A: GECAM-B detection
  34. SVOM GRB251227.07: Global MASTER-Net observations report
  35. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  36. The EP-WXT trigger 01709250617 is likely a flaring star
  37. IceCube Alert 251225.84: Global MASTER-Net observations report
  38. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  39. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  40. GRB 251222A: NUTTelA-TAO Early Measurements
  41. GRB 251222A/EP251222b: Optical detection with Kinder observations
  42. EP251222a: Optical upper limit with Kinder observations
  43. GRB 251221A: Swift-BAT refined analysis
  44. GRB 251222A/EP251222b: FTW optical and NIR observations
  45. EP251222a: FTW optical and NIR observations
  46. GRB 251205A: Kilonova-Catcher optical afterglow detection
  47. GRB 251222A: AbAO optical observations
  48. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  49. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  50. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  51. GRB 251222A: ZTSH BVRI optical observations
  52. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  53. GRB 251222A: Continued 1.3m DFOT optical observation
  54. EP251220a: 3.6m DOT optical afterglow detection
  55. GRB 251222A: Fermi GBM Observation
  56. EP251220a: CrAO ZTSh optical observations
  57. EP251221a: PRIME upper limit
  58. EP251222a: Global MASTER-Net observations report
  59. GRB 251222A / EP251222b: GECAM-B observation
  60. EP251221a: Liverpool Telescope upper limits
  61. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  62. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  63. Konus-Wind detection of GRB 251222A / EP251222b
  64. GRB 251222A: Swift-XRT afterglow detection
  65. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  66. EP251222a: NTT/ULTRACAM optical observations
  67. EP251222a: GOTO optical upper limit
  68. GRB 251222A / EP251222b: GOTO optical counterpart detection
  69. GRB 251222A / EP251222b: LCO optical observations
  70. GRB 251222A: 1.3m DFOT optical detection
  71. GRB251221A: 7DT optical upper limits
  72. EP251222a: GSP Optical Counterpart Detection
  73. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  74. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  75. EP251222b/GRB 251222A: SVOM/GRM observation
  76. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  77. EP251222a: Einstein Probe detection of an X-ray transient
  78. The EP-WXT trigger 01709250397 is likely a flaring star
  79. EP251221a: Global MASTER-Net observations report
  80. GRB 251222A: PRIME near-infrared detection
  81. EP251221a: NOT optical upper limit
  82. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  83. GRB 251222A: NOT optical observations
  84. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  85. IPN triangulation of GRB 251220B (short)
  86. GRB 251222A: Swift ToO observations
  87. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  88. GRB 251222A: SVOM/VT optical candidate
  89. GRB 251222A: SVOM detection of a long burst
  90. SVOM GRB251222A: Global MASTER-Net observations report
  91. GRB 251222A: Fermi GBM Final Real-time Localization
  92. EP251220a: PRIME upper limit
  93. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  94. GRB 251221A: PRIME near-infrared observation
  95. EP251220a: NOT optical observations
  96. EP251220a: FTW optical and NIR observations
  97. GRB 251221A: UAFO and Mondy optical upper limit
  98. GRB 251221A: Swift-XRT refined Analysis
  99. EP251221a: Einstein Probe detection of a fast X-ray transient
  100. GRB 251221A: Swift/UVOT Upper Limits

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