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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 260115A: GECAM-B observation
  2. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  3. EP260116a: Liverpool Telescope upper limits
  4. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  5. EP260116A: 1.3m DFOT optical upper limit
  6. GRB 260114A: VLT/MUSE spectroscopic observations
  7. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  8. EP260116a: Global MASTER-Net observations report
  9. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  10. EP260116a: Xinglong optical upper limit
  11. EP260116a: Einstein Probe detection of an X-ray transient
  12. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  13. IceCube Alert 260115.73: Global MASTER-Net observations report
  14. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  15. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  16. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  17. Fermi GRB 260115A: Global MASTER-Net observations report
  18. GRB 260115A: Fermi GBM Final Real-time Localization
  19. GRB260114A: STEP/T80S optical limits
  20. GRB 251222A: radio detection with the VLA
  21. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  22. Konus-Wind detection of GRB 260114A
  23. GRB 260114A: Swift-XRT refined Analysis
  24. GRB 260114A: 6 GHz VLA observations
  25. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  26. GRB 260114A : MITSuME Akeno optical upper limits
  27. GRB 260114A: COLIBRÍ optical upper limits
  28. GRB 260114A: TNG NIR upper limit
  29. GRB 260114A: NOT optical observations
  30. Konus-Wind detection of GRB 251230A / EP251230a
  31. GRB 260114A: SVOM/GRM observation of a short burst
  32. Swift GRB 260114A: Global MASTER-Net observations report
  33. GRB 260114A: GECAM-B observation of a short burst
  34. GRB 260114A: Mondy optical observations
  35. GRB 260114A: Fermi GBM observation
  36. GRB 260112B: GECAM-B observation
  37. GRB 260114A: GMG Optical Observation
  38. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  39. GRB 260114A: Swift detection of a short burst
  40. GRB 260114A: Fermi GBM Final Real-time Localization
  41. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  42. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  43. Swift GRB260113.43: Global MASTER-Net observations report
  44. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  45. EP260110a: TRT optical upper limits
  46. Konus-Wind detection of GRB 260101A
  47. GRB 260111A: Swift-XRT observations
  48. Swift Trigger 1439093: is probably not GRB 260113A
  49. GRB 260111A: COLIBRÍ optical afterglow candidate
  50. GRB 260111A: GECAM-B observation of a burst
  51. GRB 260111A: Fermi GBM Observation
  52. The EP-WXT trigger 01709251266 is likely a flaring star
  53. Swift Trigger 1434591 is not a GRB
  54. GRB 260111A: GOTO optical upper limits
  55. GRB 260112B: Fermi GBM Final Real-time Localization
  56. GRB 260111A: Swift ToO observations
  57. GRB 251230A: Mondy Optical Observations
  58. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  59. GRB 260112A: Fermi GBM Final Real-time Localization
  60. EP260110a: SVOM/VT optical upper limits
  61. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  62. IceCube Alert 260111A: Global MASTER-Net observations report
  63. EP260110a: Global MASTER-Net observations report
  64. Fermi GRB 260111A: Global MASTER-Net observations report
  65. GRB 260111A: Fermi GBM Final Real-time Localization
  66. Swift trigger 1436759 is not an astrophysical event
  67. EP260110a: KAIT optical upper limit
  68. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  69. EP 260110a: COLIBRÍ optical observations
  70. EP260110a: SVOM/C-GFT upper limit
  71. EP260110a: BOOTES-5/JGU optical upper limit
  72. EP260110a: Einstein Probe detection of an X-ray transient
  73. GRB 260109C: LCO optical upper limits
  74. GRB 260109C: Kilonova-Catcher optical upper limit
  75. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  76. Swift Trigger 1434591: possible GRB 260109C
  77. GRB 260109B: Fermi GBM Final Real-time Localization
  78. GRB 260102A: Swift-XRT afterglow detection
  79. GRB 260109A: Fermi GBM Final Real-time Localization
  80. GRB 260104A: Swift-BAT refined analysis
  81. GRB 260101A: Swift-BAT refined analysis
  82. Swift GRB 251230A: Global MASTER-Net OT detection
  83. Fermi GRB 260107A: Global MASTER-Net observations report
  84. GRB 260102A: AbAO optical observations
  85. GRB 260107A: Fermi GBM Final Real-time Localization
  86. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  87. The EP-WXT trigger 01709251112 is likely a flaring star
  88. Fermi GRB 260105A: Global MASTER-Net observations report
  89. GRB 260105B: Fermi GBM Detection
  90. EP260105a: FTW optical observations
  91. EP260104a: FTW optical observations
  92. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  93. GRB 260105A: SVOM/GRM observation
  94. GRB 260105B: SVOM/GRM observation
  95. The EP-WXT trigger 01709251028 is likely a flaring star
  96. FRB 20251229A: COLIBRÍ optical upper limits
  97. Fermi GRB 260105B: Global MASTER-Net observations report
  98. EP260105a: SVOM/VT optical upperlimit
  99. GRB 260105B: Fermi GBM Final Real-time Localization
  100. GRB 260105A: Fermi GBM Final Real-time Localization

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