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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: Swift-XRT afterglow detection
  2. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  3. EP260119a: Global MASTER-Net observations report
  4. GRB 260115A: AstroSat CZTI detection
  5. EP260119a: LCO optical observations
  6. GRB 260117A: ZTSh optical upper limit
  7. EP260119a: COLIBRÍ optical counterpart candidate
  8. EP260119a: preliminary result from the EP-FXT observation
  9. GRB 260110A: SVOM detection of a burst through offline search
  10. EP260119a: EP-WXT detection of a fast X-ray transient
  11. Swift GRB260118.48: Global MASTER-Net observations report
  12. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  13. SVOM GRB260117.82: Global MASTER-Net observations report
  14. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  15. Swift trigger on the HMXB 1A 1118-61
  16. GRB 260117A: SVOM/VT optical candidate
  17. GRB 260117A: SVOM/C-GFT upper limit
  18. GRB 260117A: Swift-XRT observations
  19. GRB 260117A: Swift ToO observations
  20. GRB 260117A: SVOM detection of a long faint burst
  21. EP 260116a: COLIBRÍ optical upper limit
  22. Swift triggered on the HMXB 1A 1118-61
  23. GRB 260115A: GECAM-B observation
  24. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  25. EP260116a: Liverpool Telescope upper limits
  26. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  27. EP260116A: 1.3m DFOT optical upper limit
  28. GRB 260114A: VLT/MUSE spectroscopic observations
  29. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  30. EP260116a: Global MASTER-Net observations report
  31. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  32. EP260116a: Xinglong optical upper limit
  33. EP260116a: Einstein Probe detection of an X-ray transient
  34. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  35. IceCube Alert 260115.73: Global MASTER-Net observations report
  36. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  38. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  39. Fermi GRB 260115A: Global MASTER-Net observations report
  40. GRB 260115A: Fermi GBM Final Real-time Localization
  41. GRB260114A: STEP/T80S optical limits
  42. GRB 251222A: radio detection with the VLA
  43. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  44. Konus-Wind detection of GRB 260114A
  45. GRB 260114A: Swift-XRT refined Analysis
  46. GRB 260114A: 6 GHz VLA observations
  47. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  48. GRB 260114A : MITSuME Akeno optical upper limits
  49. GRB 260114A: COLIBRÍ optical upper limits
  50. GRB 260114A: TNG NIR upper limit
  51. GRB 260114A: NOT optical observations
  52. Konus-Wind detection of GRB 251230A / EP251230a
  53. GRB 260114A: SVOM/GRM observation of a short burst
  54. Swift GRB 260114A: Global MASTER-Net observations report
  55. GRB 260114A: GECAM-B observation of a short burst
  56. GRB 260114A: Mondy optical observations
  57. GRB 260114A: Fermi GBM observation
  58. GRB 260112B: GECAM-B observation
  59. GRB 260114A: GMG Optical Observation
  60. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  61. GRB 260114A: Swift detection of a short burst
  62. GRB 260114A: Fermi GBM Final Real-time Localization
  63. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  64. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  65. Swift GRB260113.43: Global MASTER-Net observations report
  66. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  67. EP260110a: TRT optical upper limits
  68. Konus-Wind detection of GRB 260101A
  69. GRB 260111A: Swift-XRT observations
  70. Swift Trigger 1439093: is probably not GRB 260113A
  71. GRB 260111A: COLIBRÍ optical afterglow candidate
  72. GRB 260111A: GECAM-B observation of a burst
  73. GRB 260111A: Fermi GBM Observation
  74. The EP-WXT trigger 01709251266 is likely a flaring star
  75. Swift Trigger 1434591 is not a GRB
  76. GRB 260111A: GOTO optical upper limits
  77. GRB 260112B: Fermi GBM Final Real-time Localization
  78. GRB 260111A: Swift ToO observations
  79. GRB 251230A: Mondy Optical Observations
  80. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  81. GRB 260112A: Fermi GBM Final Real-time Localization
  82. EP260110a: SVOM/VT optical upper limits
  83. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  84. IceCube Alert 260111A: Global MASTER-Net observations report
  85. EP260110a: Global MASTER-Net observations report
  86. Fermi GRB 260111A: Global MASTER-Net observations report
  87. GRB 260111A: Fermi GBM Final Real-time Localization
  88. Swift trigger 1436759 is not an astrophysical event
  89. EP260110a: KAIT optical upper limit
  90. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP 260110a: COLIBRÍ optical observations
  92. EP260110a: SVOM/C-GFT upper limit
  93. EP260110a: BOOTES-5/JGU optical upper limit
  94. EP260110a: Einstein Probe detection of an X-ray transient
  95. GRB 260109C: LCO optical upper limits
  96. GRB 260109C: Kilonova-Catcher optical upper limit
  97. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  98. Swift Trigger 1434591: possible GRB 260109C
  99. GRB 260109B: Fermi GBM Final Real-time Localization
  100. GRB 260102A: Swift-XRT afterglow detection

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