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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. EP260119a: COLIBRÍ optical counterpart candidate
  2. EP260119a: preliminary result from the EP-FXT observation
  3. GRB 260110A: SVOM detection of a burst through offline search
  4. EP260119a: EP-WXT detection of a fast X-ray transient
  5. Swift GRB260118.48: Global MASTER-Net observations report
  6. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  7. SVOM GRB260117.82: Global MASTER-Net observations report
  8. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  9. Swift trigger on the HMXB 1A 1118-61
  10. GRB 260117A: SVOM/VT optical candidate
  11. GRB 260117A: SVOM/C-GFT upper limit
  12. GRB 260117A: Swift-XRT observations
  13. GRB 260117A: Swift ToO observations
  14. GRB 260117A: SVOM detection of a long faint burst
  15. EP 260116a: COLIBRÍ optical upper limit
  16. Swift triggered on the HMXB 1A 1118-61
  17. GRB 260115A: GECAM-B observation
  18. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  19. EP260116a: Liverpool Telescope upper limits
  20. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  21. EP260116A: 1.3m DFOT optical upper limit
  22. GRB 260114A: VLT/MUSE spectroscopic observations
  23. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  24. EP260116a: Global MASTER-Net observations report
  25. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  26. EP260116a: Xinglong optical upper limit
  27. EP260116a: Einstein Probe detection of an X-ray transient
  28. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  29. IceCube Alert 260115.73: Global MASTER-Net observations report
  30. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  31. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  32. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  33. Fermi GRB 260115A: Global MASTER-Net observations report
  34. GRB 260115A: Fermi GBM Final Real-time Localization
  35. GRB260114A: STEP/T80S optical limits
  36. GRB 251222A: radio detection with the VLA
  37. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  38. Konus-Wind detection of GRB 260114A
  39. GRB 260114A: Swift-XRT refined Analysis
  40. GRB 260114A: 6 GHz VLA observations
  41. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  42. GRB 260114A : MITSuME Akeno optical upper limits
  43. GRB 260114A: COLIBRÍ optical upper limits
  44. GRB 260114A: TNG NIR upper limit
  45. GRB 260114A: NOT optical observations
  46. Konus-Wind detection of GRB 251230A / EP251230a
  47. GRB 260114A: SVOM/GRM observation of a short burst
  48. Swift GRB 260114A: Global MASTER-Net observations report
  49. GRB 260114A: GECAM-B observation of a short burst
  50. GRB 260114A: Mondy optical observations
  51. GRB 260114A: Fermi GBM observation
  52. GRB 260112B: GECAM-B observation
  53. GRB 260114A: GMG Optical Observation
  54. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  55. GRB 260114A: Swift detection of a short burst
  56. GRB 260114A: Fermi GBM Final Real-time Localization
  57. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  58. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  59. Swift GRB260113.43: Global MASTER-Net observations report
  60. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  61. EP260110a: TRT optical upper limits
  62. Konus-Wind detection of GRB 260101A
  63. GRB 260111A: Swift-XRT observations
  64. Swift Trigger 1439093: is probably not GRB 260113A
  65. GRB 260111A: COLIBRÍ optical afterglow candidate
  66. GRB 260111A: GECAM-B observation of a burst
  67. GRB 260111A: Fermi GBM Observation
  68. The EP-WXT trigger 01709251266 is likely a flaring star
  69. Swift Trigger 1434591 is not a GRB
  70. GRB 260111A: GOTO optical upper limits
  71. GRB 260112B: Fermi GBM Final Real-time Localization
  72. GRB 260111A: Swift ToO observations
  73. GRB 251230A: Mondy Optical Observations
  74. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  75. GRB 260112A: Fermi GBM Final Real-time Localization
  76. EP260110a: SVOM/VT optical upper limits
  77. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  78. IceCube Alert 260111A: Global MASTER-Net observations report
  79. EP260110a: Global MASTER-Net observations report
  80. Fermi GRB 260111A: Global MASTER-Net observations report
  81. GRB 260111A: Fermi GBM Final Real-time Localization
  82. Swift trigger 1436759 is not an astrophysical event
  83. EP260110a: KAIT optical upper limit
  84. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  85. EP 260110a: COLIBRÍ optical observations
  86. EP260110a: SVOM/C-GFT upper limit
  87. EP260110a: BOOTES-5/JGU optical upper limit
  88. EP260110a: Einstein Probe detection of an X-ray transient
  89. GRB 260109C: LCO optical upper limits
  90. GRB 260109C: Kilonova-Catcher optical upper limit
  91. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  92. Swift Trigger 1434591: possible GRB 260109C
  93. GRB 260109B: Fermi GBM Final Real-time Localization
  94. GRB 260102A: Swift-XRT afterglow detection
  95. GRB 260109A: Fermi GBM Final Real-time Localization
  96. GRB 260104A: Swift-BAT refined analysis
  97. GRB 260101A: Swift-BAT refined analysis
  98. Swift GRB 251230A: Global MASTER-Net OT detection
  99. Fermi GRB 260107A: Global MASTER-Net observations report
  100. GRB 260102A: AbAO optical observations

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