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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 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. SVOM GRB260117.82: Global MASTER-Net observations report
  3. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  4. Swift trigger on the HMXB 1A 1118-61
  5. GRB 260117A: SVOM/VT optical candidate
  6. GRB 260117A: SVOM/C-GFT upper limit
  7. GRB 260117A: Swift-XRT observations
  8. GRB 260117A: Swift ToO observations
  9. GRB 260117A: SVOM detection of a long faint burst
  10. EP 260116a: COLIBRÍ optical upper limit
  11. Swift triggered on the HMXB 1A 1118-61
  12. GRB 260115A: GECAM-B observation
  13. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  14. EP260116a: Liverpool Telescope upper limits
  15. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  16. EP260116A: 1.3m DFOT optical upper limit
  17. GRB 260114A: VLT/MUSE spectroscopic observations
  18. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  19. EP260116a: Global MASTER-Net observations report
  20. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  21. EP260116a: Xinglong optical upper limit
  22. EP260116a: Einstein Probe detection of an X-ray transient
  23. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  24. IceCube Alert 260115.73: Global MASTER-Net observations report
  25. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  26. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  27. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  28. Fermi GRB 260115A: Global MASTER-Net observations report
  29. GRB 260115A: Fermi GBM Final Real-time Localization
  30. GRB260114A: STEP/T80S optical limits
  31. GRB 251222A: radio detection with the VLA
  32. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  33. Konus-Wind detection of GRB 260114A
  34. GRB 260114A: Swift-XRT refined Analysis
  35. GRB 260114A: 6 GHz VLA observations
  36. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  37. GRB 260114A : MITSuME Akeno optical upper limits
  38. GRB 260114A: COLIBRÍ optical upper limits
  39. GRB 260114A: TNG NIR upper limit
  40. GRB 260114A: NOT optical observations
  41. Konus-Wind detection of GRB 251230A / EP251230a
  42. GRB 260114A: SVOM/GRM observation of a short burst
  43. Swift GRB 260114A: Global MASTER-Net observations report
  44. GRB 260114A: GECAM-B observation of a short burst
  45. GRB 260114A: Mondy optical observations
  46. GRB 260114A: Fermi GBM observation
  47. GRB 260112B: GECAM-B observation
  48. GRB 260114A: GMG Optical Observation
  49. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  50. GRB 260114A: Swift detection of a short burst
  51. GRB 260114A: Fermi GBM Final Real-time Localization
  52. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  53. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  54. Swift GRB260113.43: Global MASTER-Net observations report
  55. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  56. EP260110a: TRT optical upper limits
  57. Konus-Wind detection of GRB 260101A
  58. GRB 260111A: Swift-XRT observations
  59. Swift Trigger 1439093: is probably not GRB 260113A
  60. GRB 260111A: COLIBRÍ optical afterglow candidate
  61. GRB 260111A: GECAM-B observation of a burst
  62. GRB 260111A: Fermi GBM Observation
  63. The EP-WXT trigger 01709251266 is likely a flaring star
  64. Swift Trigger 1434591 is not a GRB
  65. GRB 260111A: GOTO optical upper limits
  66. GRB 260112B: Fermi GBM Final Real-time Localization
  67. GRB 260111A: Swift ToO observations
  68. GRB 251230A: Mondy Optical Observations
  69. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  70. GRB 260112A: Fermi GBM Final Real-time Localization
  71. EP260110a: SVOM/VT optical upper limits
  72. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  73. IceCube Alert 260111A: Global MASTER-Net observations report
  74. EP260110a: Global MASTER-Net observations report
  75. Fermi GRB 260111A: Global MASTER-Net observations report
  76. GRB 260111A: Fermi GBM Final Real-time Localization
  77. Swift trigger 1436759 is not an astrophysical event
  78. EP260110a: KAIT optical upper limit
  79. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  80. EP 260110a: COLIBRÍ optical observations
  81. EP260110a: SVOM/C-GFT upper limit
  82. EP260110a: BOOTES-5/JGU optical upper limit
  83. EP260110a: Einstein Probe detection of an X-ray transient
  84. GRB 260109C: LCO optical upper limits
  85. GRB 260109C: Kilonova-Catcher optical upper limit
  86. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  87. Swift Trigger 1434591: possible GRB 260109C
  88. GRB 260109B: Fermi GBM Final Real-time Localization
  89. GRB 260102A: Swift-XRT afterglow detection
  90. GRB 260109A: Fermi GBM Final Real-time Localization
  91. GRB 260104A: Swift-BAT refined analysis
  92. GRB 260101A: Swift-BAT refined analysis
  93. Swift GRB 251230A: Global MASTER-Net OT detection
  94. Fermi GRB 260107A: Global MASTER-Net observations report
  95. GRB 260102A: AbAO optical observations
  96. GRB 260107A: Fermi GBM Final Real-time Localization
  97. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  98. The EP-WXT trigger 01709251112 is likely a flaring star
  99. Fermi GRB 260105A: Global MASTER-Net observations report
  100. GRB 260105B: Fermi GBM Detection

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