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

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