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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 260102A: Swift ToO observations
  2. GRB 260101A: Fermi GBM Observation
  3. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  4. GRB 260102A: SVOM detection of a burst
  5. GRB 260101A: GECAM-B detection
  6. GRB 260101A: NOT spectroscopic observations
  7. GRB 260101A: SVOM/GRM observation
  8. GRB 260101A: Swift-XRT refined Analysis
  9. Swift GRB 260101A: Global MASTER-Net observations report
  10. GRB 260101A: Enhanced Swift-XRT position
  11. EP260101a: Einstein Probe detection of an X-ray transient
  12. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  13. GRB 260101A: LCO detection of the optical counterpart
  14. GRB 260101A: Swift detection of a burst with an optical counterpart
  15. GRB 260101A: Fermi GBM Final Real-time Localization
  16. SVOM GRB251231.57: Global MASTER-Net observations report
  17. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  18. GRB 251230A: GRANDMA/TAROT Early Detection
  19. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  20. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  21. EP251229a: Optical upper limit with Kinder observations
  22. GRB 251230A: 1.3m DFOT optical upper limit
  23. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  24. GRB 251230A: Swift-XRT refined Analysis
  25. GRB 251231A: Fermi GBM Final Real-time Localization
  26. GRB 251222A: Mondy Optical Observations
  27. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  28. GRB 251230A: Swift/UVOT detection
  29. GRB251230A: 7DT optical upper limits
  30. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  31. EP251229a: BOOTES-2 early optical upper limit
  32. GRB 251230A: GOTO optical upper limit
  33. EP251229a: NOT optical upper limits
  34. GRB 251230A / EP251230a: SVOM/VT optical observation
  35. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  36. GRB 251230A: Enhanced Swift-XRT position
  37. GRB 251230A: Early optical counterpart detection by LCO.
  38. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  39. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  40. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  41. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  42. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  43. Swift GRB 251230A: Global MASTER-Net observations report
  44. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  45. EP251229a: Global MASTER-Net observations report
  46. EP251229a: Einstein Probe detection of an X-ray transient
  47. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  48. GRB 251226A: Glowbug gamma-ray detection
  49. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  50. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  51. Fermi GRB 251228A: Global MASTER-Net observations report
  52. The EP-WXT trigger 01709250662 is likely a flaring star
  53. GRB 251228A: Fermi GBM Final Real-time Localization
  54. GRB 251226A: SVOM/GRM observation
  55. GRB 251226A: GECAM-B detection
  56. SVOM GRB251227.07: Global MASTER-Net observations report
  57. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  58. The EP-WXT trigger 01709250617 is likely a flaring star
  59. IceCube Alert 251225.84: Global MASTER-Net observations report
  60. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  61. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  62. GRB 251222A: NUTTelA-TAO Early Measurements
  63. GRB 251222A/EP251222b: Optical detection with Kinder observations
  64. EP251222a: Optical upper limit with Kinder observations
  65. GRB 251221A: Swift-BAT refined analysis
  66. GRB 251222A/EP251222b: FTW optical and NIR observations
  67. EP251222a: FTW optical and NIR observations
  68. GRB 251205A: Kilonova-Catcher optical afterglow detection
  69. GRB 251222A: AbAO optical observations
  70. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  71. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  72. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  73. GRB 251222A: ZTSH BVRI optical observations
  74. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  75. GRB 251222A: Continued 1.3m DFOT optical observation
  76. EP251220a: 3.6m DOT optical afterglow detection
  77. GRB 251222A: Fermi GBM Observation
  78. EP251220a: CrAO ZTSh optical observations
  79. EP251221a: PRIME upper limit
  80. EP251222a: Global MASTER-Net observations report
  81. GRB 251222A / EP251222b: GECAM-B observation
  82. EP251221a: Liverpool Telescope upper limits
  83. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  84. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  85. Konus-Wind detection of GRB 251222A / EP251222b
  86. GRB 251222A: Swift-XRT afterglow detection
  87. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  88. EP251222a: NTT/ULTRACAM optical observations
  89. EP251222a: GOTO optical upper limit
  90. GRB 251222A / EP251222b: GOTO optical counterpart detection
  91. GRB 251222A / EP251222b: LCO optical observations
  92. GRB 251222A: 1.3m DFOT optical detection
  93. GRB251221A: 7DT optical upper limits
  94. EP251222a: GSP Optical Counterpart Detection
  95. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  96. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  97. EP251222b/GRB 251222A: SVOM/GRM observation
  98. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  99. EP251222a: Einstein Probe detection of an X-ray transient
  100. The EP-WXT trigger 01709250397 is likely a flaring star

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