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

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