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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"

43596 results found.

  1. SVOM GRB260117.82: Global MASTER-Net observations report
  2. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  3. Swift trigger on the HMXB 1A 1118-61
  4. GRB 260117A: SVOM/VT optical candidate
  5. GRB 260117A: SVOM/C-GFT upper limit
  6. GRB 260117A: Swift-XRT observations
  7. GRB 260117A: Swift ToO observations
  8. GRB 260117A: SVOM detection of a long faint burst
  9. EP 260116a: COLIBRÍ optical upper limit
  10. Swift triggered on the HMXB 1A 1118-61
  11. GRB 260115A: GECAM-B observation
  12. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  13. EP260116a: Liverpool Telescope upper limits
  14. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  15. EP260116A: 1.3m DFOT optical upper limit
  16. GRB 260114A: VLT/MUSE spectroscopic observations
  17. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  18. EP260116a: Global MASTER-Net observations report
  19. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  20. EP260116a: Xinglong optical upper limit
  21. EP260116a: Einstein Probe detection of an X-ray transient
  22. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  23. IceCube Alert 260115.73: Global MASTER-Net observations report
  24. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  25. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  26. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  27. Fermi GRB 260115A: Global MASTER-Net observations report
  28. GRB 260115A: Fermi GBM Final Real-time Localization
  29. GRB260114A: STEP/T80S optical limits
  30. GRB 251222A: radio detection with the VLA
  31. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  32. Konus-Wind detection of GRB 260114A
  33. GRB 260114A: Swift-XRT refined Analysis
  34. GRB 260114A: 6 GHz VLA observations
  35. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  36. GRB 260114A : MITSuME Akeno optical upper limits
  37. GRB 260114A: COLIBRÍ optical upper limits
  38. GRB 260114A: TNG NIR upper limit
  39. GRB 260114A: NOT optical observations
  40. Konus-Wind detection of GRB 251230A / EP251230a
  41. GRB 260114A: SVOM/GRM observation of a short burst
  42. Swift GRB 260114A: Global MASTER-Net observations report
  43. GRB 260114A: GECAM-B observation of a short burst
  44. GRB 260114A: Mondy optical observations
  45. GRB 260114A: Fermi GBM observation
  46. GRB 260112B: GECAM-B observation
  47. GRB 260114A: GMG Optical Observation
  48. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  49. GRB 260114A: Swift detection of a short burst
  50. GRB 260114A: Fermi GBM Final Real-time Localization
  51. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  52. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  53. Swift GRB260113.43: Global MASTER-Net observations report
  54. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  55. EP260110a: TRT optical upper limits
  56. Konus-Wind detection of GRB 260101A
  57. GRB 260111A: Swift-XRT observations
  58. Swift Trigger 1439093: is probably not GRB 260113A
  59. GRB 260111A: COLIBRÍ optical afterglow candidate
  60. GRB 260111A: GECAM-B observation of a burst
  61. GRB 260111A: Fermi GBM Observation
  62. The EP-WXT trigger 01709251266 is likely a flaring star
  63. Swift Trigger 1434591 is not a GRB
  64. GRB 260111A: GOTO optical upper limits
  65. GRB 260112B: Fermi GBM Final Real-time Localization
  66. GRB 260111A: Swift ToO observations
  67. GRB 251230A: Mondy Optical Observations
  68. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  69. GRB 260112A: Fermi GBM Final Real-time Localization
  70. EP260110a: SVOM/VT optical upper limits
  71. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  72. IceCube Alert 260111A: Global MASTER-Net observations report
  73. EP260110a: Global MASTER-Net observations report
  74. Fermi GRB 260111A: Global MASTER-Net observations report
  75. GRB 260111A: Fermi GBM Final Real-time Localization
  76. Swift trigger 1436759 is not an astrophysical event
  77. EP260110a: KAIT optical upper limit
  78. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  79. EP 260110a: COLIBRÍ optical observations
  80. EP260110a: SVOM/C-GFT upper limit
  81. EP260110a: BOOTES-5/JGU optical upper limit
  82. EP260110a: Einstein Probe detection of an X-ray transient
  83. GRB 260109C: LCO optical upper limits
  84. GRB 260109C: Kilonova-Catcher optical upper limit
  85. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  86. Swift Trigger 1434591: possible GRB 260109C
  87. GRB 260109B: Fermi GBM Final Real-time Localization
  88. GRB 260102A: Swift-XRT afterglow detection
  89. GRB 260109A: Fermi GBM Final Real-time Localization
  90. GRB 260104A: Swift-BAT refined analysis
  91. GRB 260101A: Swift-BAT refined analysis
  92. Swift GRB 251230A: Global MASTER-Net OT detection
  93. Fermi GRB 260107A: Global MASTER-Net observations report
  94. GRB 260102A: AbAO optical observations
  95. GRB 260107A: Fermi GBM Final Real-time Localization
  96. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  97. The EP-WXT trigger 01709251112 is likely a flaring star
  98. Fermi GRB 260105A: Global MASTER-Net observations report
  99. GRB 260105B: Fermi GBM Detection
  100. EP260105a: FTW optical observations

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