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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 260114A: VLT/MUSE spectroscopic observations
  2. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  3. EP260116a: Global MASTER-Net observations report
  4. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  5. EP260116a: Xinglong optical upper limit
  6. EP260116a: Einstein Probe detection of an X-ray transient
  7. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  8. IceCube Alert 260115.73: Global MASTER-Net observations report
  9. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  10. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  11. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  12. Fermi GRB 260115A: Global MASTER-Net observations report
  13. GRB 260115A: Fermi GBM Final Real-time Localization
  14. GRB260114A: STEP/T80S optical limits
  15. GRB 251222A: radio detection with the VLA
  16. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  17. Konus-Wind detection of GRB 260114A
  18. GRB 260114A: Swift-XRT refined Analysis
  19. GRB 260114A: 6 GHz VLA observations
  20. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  21. GRB 260114A : MITSuME Akeno optical upper limits
  22. GRB 260114A: COLIBRÍ optical upper limits
  23. GRB 260114A: TNG NIR upper limit
  24. GRB 260114A: NOT optical observations
  25. Konus-Wind detection of GRB 251230A / EP251230a
  26. GRB 260114A: SVOM/GRM observation of a short burst
  27. Swift GRB 260114A: Global MASTER-Net observations report
  28. GRB 260114A: GECAM-B observation of a short burst
  29. GRB 260114A: Mondy optical observations
  30. GRB 260114A: Fermi GBM observation
  31. GRB 260112B: GECAM-B observation
  32. GRB 260114A: GMG Optical Observation
  33. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  34. GRB 260114A: Swift detection of a short burst
  35. GRB 260114A: Fermi GBM Final Real-time Localization
  36. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  37. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  38. Swift GRB260113.43: Global MASTER-Net observations report
  39. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  40. EP260110a: TRT optical upper limits
  41. Konus-Wind detection of GRB 260101A
  42. GRB 260111A: Swift-XRT observations
  43. Swift Trigger 1439093: is probably not GRB 260113A
  44. GRB 260111A: COLIBRÍ optical afterglow candidate
  45. GRB 260111A: GECAM-B observation of a burst
  46. GRB 260111A: Fermi GBM Observation
  47. The EP-WXT trigger 01709251266 is likely a flaring star
  48. Swift Trigger 1434591 is not a GRB
  49. GRB 260111A: GOTO optical upper limits
  50. GRB 260112B: Fermi GBM Final Real-time Localization
  51. GRB 260111A: Swift ToO observations
  52. GRB 251230A: Mondy Optical Observations
  53. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  54. GRB 260112A: Fermi GBM Final Real-time Localization
  55. EP260110a: SVOM/VT optical upper limits
  56. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  57. IceCube Alert 260111A: Global MASTER-Net observations report
  58. EP260110a: Global MASTER-Net observations report
  59. Fermi GRB 260111A: Global MASTER-Net observations report
  60. GRB 260111A: Fermi GBM Final Real-time Localization
  61. Swift trigger 1436759 is not an astrophysical event
  62. EP260110a: KAIT optical upper limit
  63. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  64. EP 260110a: COLIBRÍ optical observations
  65. EP260110a: SVOM/C-GFT upper limit
  66. EP260110a: BOOTES-5/JGU optical upper limit
  67. EP260110a: Einstein Probe detection of an X-ray transient
  68. GRB 260109C: LCO optical upper limits
  69. GRB 260109C: Kilonova-Catcher optical upper limit
  70. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  71. Swift Trigger 1434591: possible GRB 260109C
  72. GRB 260109B: Fermi GBM Final Real-time Localization
  73. GRB 260102A: Swift-XRT afterglow detection
  74. GRB 260109A: Fermi GBM Final Real-time Localization
  75. GRB 260104A: Swift-BAT refined analysis
  76. GRB 260101A: Swift-BAT refined analysis
  77. Swift GRB 251230A: Global MASTER-Net OT detection
  78. Fermi GRB 260107A: Global MASTER-Net observations report
  79. GRB 260102A: AbAO optical observations
  80. GRB 260107A: Fermi GBM Final Real-time Localization
  81. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  82. The EP-WXT trigger 01709251112 is likely a flaring star
  83. Fermi GRB 260105A: Global MASTER-Net observations report
  84. GRB 260105B: Fermi GBM Detection
  85. EP260105a: FTW optical observations
  86. EP260104a: FTW optical observations
  87. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  88. GRB 260105A: SVOM/GRM observation
  89. GRB 260105B: SVOM/GRM observation
  90. The EP-WXT trigger 01709251028 is likely a flaring star
  91. FRB 20251229A: COLIBRÍ optical upper limits
  92. Fermi GRB 260105B: Global MASTER-Net observations report
  93. EP260105a: SVOM/VT optical upperlimit
  94. GRB 260105B: Fermi GBM Final Real-time Localization
  95. GRB 260105A: Fermi GBM Final Real-time Localization
  96. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  97. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  98. EP260105a: LCO Optical Upper limit
  99. EP260104a: Global MASTER-Net observations report
  100. EP260104a: Einstein Probe detection of a fast X-ray transient

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