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

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