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

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