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

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