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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. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  2. GRB 251230A: Swift/UVOT detection
  3. GRB251230A: 7DT optical upper limits
  4. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  5. EP251229a: BOOTES-2 early optical upper limit
  6. GRB 251230A: GOTO optical upper limit
  7. EP251229a: NOT optical upper limits
  8. GRB 251230A / EP251230a: SVOM/VT optical observation
  9. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  10. GRB 251230A: Enhanced Swift-XRT position
  11. GRB 251230A: Early optical counterpart detection by LCO.
  12. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  13. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  14. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  15. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  16. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  17. Swift GRB 251230A: Global MASTER-Net observations report
  18. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  19. EP251229a: Global MASTER-Net observations report
  20. EP251229a: Einstein Probe detection of an X-ray transient
  21. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  22. GRB 251226A: Glowbug gamma-ray detection
  23. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  24. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  25. Fermi GRB 251228A: Global MASTER-Net observations report
  26. The EP-WXT trigger 01709250662 is likely a flaring star
  27. GRB 251228A: Fermi GBM Final Real-time Localization
  28. GRB 251226A: SVOM/GRM observation
  29. GRB 251226A: GECAM-B detection
  30. SVOM GRB251227.07: Global MASTER-Net observations report
  31. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  32. The EP-WXT trigger 01709250617 is likely a flaring star
  33. IceCube Alert 251225.84: Global MASTER-Net observations report
  34. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  35. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  36. GRB 251222A: NUTTelA-TAO Early Measurements
  37. GRB 251222A/EP251222b: Optical detection with Kinder observations
  38. EP251222a: Optical upper limit with Kinder observations
  39. GRB 251221A: Swift-BAT refined analysis
  40. GRB 251222A/EP251222b: FTW optical and NIR observations
  41. EP251222a: FTW optical and NIR observations
  42. GRB 251205A: Kilonova-Catcher optical afterglow detection
  43. GRB 251222A: AbAO optical observations
  44. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  45. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  46. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  47. GRB 251222A: ZTSH BVRI optical observations
  48. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  49. GRB 251222A: Continued 1.3m DFOT optical observation
  50. EP251220a: 3.6m DOT optical afterglow detection
  51. GRB 251222A: Fermi GBM Observation
  52. EP251220a: CrAO ZTSh optical observations
  53. EP251221a: PRIME upper limit
  54. EP251222a: Global MASTER-Net observations report
  55. GRB 251222A / EP251222b: GECAM-B observation
  56. EP251221a: Liverpool Telescope upper limits
  57. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  59. Konus-Wind detection of GRB 251222A / EP251222b
  60. GRB 251222A: Swift-XRT afterglow detection
  61. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  62. EP251222a: NTT/ULTRACAM optical observations
  63. EP251222a: GOTO optical upper limit
  64. GRB 251222A / EP251222b: GOTO optical counterpart detection
  65. GRB 251222A / EP251222b: LCO optical observations
  66. GRB 251222A: 1.3m DFOT optical detection
  67. GRB251221A: 7DT optical upper limits
  68. EP251222a: GSP Optical Counterpart Detection
  69. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  70. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  71. EP251222b/GRB 251222A: SVOM/GRM observation
  72. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  73. EP251222a: Einstein Probe detection of an X-ray transient
  74. The EP-WXT trigger 01709250397 is likely a flaring star
  75. EP251221a: Global MASTER-Net observations report
  76. GRB 251222A: PRIME near-infrared detection
  77. EP251221a: NOT optical upper limit
  78. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  79. GRB 251222A: NOT optical observations
  80. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  81. IPN triangulation of GRB 251220B (short)
  82. GRB 251222A: Swift ToO observations
  83. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  84. GRB 251222A: SVOM/VT optical candidate
  85. GRB 251222A: SVOM detection of a long burst
  86. SVOM GRB251222A: Global MASTER-Net observations report
  87. GRB 251222A: Fermi GBM Final Real-time Localization
  88. EP251220a: PRIME upper limit
  89. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  90. GRB 251221A: PRIME near-infrared observation
  91. EP251220a: NOT optical observations
  92. EP251220a: FTW optical and NIR observations
  93. GRB 251221A: UAFO and Mondy optical upper limit
  94. GRB 251221A: Swift-XRT refined Analysis
  95. EP251221a: Einstein Probe detection of a fast X-ray transient
  96. GRB 251221A: Swift/UVOT Upper Limits
  97. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  98. GRB 251221A: Enhanced Swift-XRT position
  99. GRB 251221A: Fermi GBM Observation
  100. GRB 251221B: Fermi GBM Final Real-time Localization

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