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

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