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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. SVOM GRB260119.92: Global MASTER-Net observations report
  2. SVOM GRB260119.90: Global MASTER-Net observations report
  3. EP260116a: COLIBRÍ detection of a fading optical source
  4. GRB 251208D: SVOM/ECLAIRs refined analysis
  5. GRB 251208D: SVOM/ECLAIRs refined analysis
  6. GRB 260117A: Swift-XRT afterglow detection
  7. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  8. EP260119a: Global MASTER-Net observations report
  9. GRB 260115A: AstroSat CZTI detection
  10. EP260119a: LCO optical observations
  11. GRB 260117A: ZTSh optical upper limit
  12. EP260119a: COLIBRÍ optical counterpart candidate
  13. EP260119a: preliminary result from the EP-FXT observation
  14. GRB 260110A: SVOM detection of a burst through offline search
  15. EP260119a: EP-WXT detection of a fast X-ray transient
  16. Swift GRB260118.48: Global MASTER-Net observations report
  17. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  18. SVOM GRB260117.82: Global MASTER-Net observations report
  19. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  20. Swift trigger on the HMXB 1A 1118-61
  21. GRB 260117A: SVOM/VT optical candidate
  22. GRB 260117A: SVOM/C-GFT upper limit
  23. GRB 260117A: Swift-XRT observations
  24. GRB 260117A: Swift ToO observations
  25. GRB 260117A: SVOM detection of a long faint burst
  26. EP 260116a: COLIBRÍ optical upper limit
  27. Swift triggered on the HMXB 1A 1118-61
  28. GRB 260115A: GECAM-B observation
  29. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  30. EP260116a: Liverpool Telescope upper limits
  31. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  32. EP260116A: 1.3m DFOT optical upper limit
  33. GRB 260114A: VLT/MUSE spectroscopic observations
  34. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  35. EP260116a: Global MASTER-Net observations report
  36. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  37. EP260116a: Xinglong optical upper limit
  38. EP260116a: Einstein Probe detection of an X-ray transient
  39. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  40. IceCube Alert 260115.73: Global MASTER-Net observations report
  41. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  43. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  44. Fermi GRB 260115A: Global MASTER-Net observations report
  45. GRB 260115A: Fermi GBM Final Real-time Localization
  46. GRB260114A: STEP/T80S optical limits
  47. GRB 251222A: radio detection with the VLA
  48. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  49. Konus-Wind detection of GRB 260114A
  50. GRB 260114A: Swift-XRT refined Analysis
  51. GRB 260114A: 6 GHz VLA observations
  52. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  53. GRB 260114A : MITSuME Akeno optical upper limits
  54. GRB 260114A: COLIBRÍ optical upper limits
  55. GRB 260114A: TNG NIR upper limit
  56. GRB 260114A: NOT optical observations
  57. Konus-Wind detection of GRB 251230A / EP251230a
  58. GRB 260114A: SVOM/GRM observation of a short burst
  59. Swift GRB 260114A: Global MASTER-Net observations report
  60. GRB 260114A: GECAM-B observation of a short burst
  61. GRB 260114A: Mondy optical observations
  62. GRB 260114A: Fermi GBM observation
  63. GRB 260112B: GECAM-B observation
  64. GRB 260114A: GMG Optical Observation
  65. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  66. GRB 260114A: Swift detection of a short burst
  67. GRB 260114A: Fermi GBM Final Real-time Localization
  68. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  69. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  70. Swift GRB260113.43: Global MASTER-Net observations report
  71. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  72. EP260110a: TRT optical upper limits
  73. Konus-Wind detection of GRB 260101A
  74. GRB 260111A: Swift-XRT observations
  75. Swift Trigger 1439093: is probably not GRB 260113A
  76. GRB 260111A: COLIBRÍ optical afterglow candidate
  77. GRB 260111A: GECAM-B observation of a burst
  78. GRB 260111A: Fermi GBM Observation
  79. The EP-WXT trigger 01709251266 is likely a flaring star
  80. Swift Trigger 1434591 is not a GRB
  81. GRB 260111A: GOTO optical upper limits
  82. GRB 260112B: Fermi GBM Final Real-time Localization
  83. GRB 260111A: Swift ToO observations
  84. GRB 251230A: Mondy Optical Observations
  85. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  86. GRB 260112A: Fermi GBM Final Real-time Localization
  87. EP260110a: SVOM/VT optical upper limits
  88. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  89. IceCube Alert 260111A: Global MASTER-Net observations report
  90. EP260110a: Global MASTER-Net observations report
  91. Fermi GRB 260111A: Global MASTER-Net observations report
  92. GRB 260111A: Fermi GBM Final Real-time Localization
  93. Swift trigger 1436759 is not an astrophysical event
  94. EP260110a: KAIT optical upper limit
  95. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  96. EP 260110a: COLIBRÍ optical observations
  97. EP260110a: SVOM/C-GFT upper limit
  98. EP260110a: BOOTES-5/JGU optical upper limit
  99. EP260110a: Einstein Probe detection of an X-ray transient
  100. GRB 260109C: LCO optical upper limits

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