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

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