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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 260101A: 239Alferov CubeSat detection
  2. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  3. GRB 260120B: Swift detection of a burst
  4. Swift GRB260120B: Global MASTER-Net observations report
  5. GRB 260120B: Fermi GBM Final Real-time Localization
  6. EP260119A: Mondy I-Band Observations
  7. Fermi trigger No 790601190: Global MASTER-Net observations report
  8. Fermi trigger No 790570272: Global MASTER-Net observations report
  9. GRB 260114A: Swift/UVOT Upper Limits
  10. EP260119a: Liverpool Telescope optical follow-up observations
  11. GRB 251202A: further radio observations with the VLA
  12. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  13. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  14. EP260119a: KAIT optical observations
  15. GRB 260120A: Fermi GBM Final Real-time Localization
  16. EP260119a: SVOM/VT optical observation
  17. EP260119a: update of EP-FXT follow-up observation
  18. EP260119a: NOT optical observations
  19. EP260119a: SAO RAS optical observations
  20. SVOM GRB260119.92: Global MASTER-Net observations report
  21. SVOM GRB260119.92: Global MASTER-Net observations report
  22. SVOM GRB260119.90: Global MASTER-Net observations report
  23. EP260116a: COLIBRÍ detection of a fading optical source
  24. GRB 251208D: SVOM/ECLAIRs refined analysis
  25. GRB 251208D: SVOM/ECLAIRs refined analysis
  26. GRB 260117A: Swift-XRT afterglow detection
  27. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  28. EP260119a: Global MASTER-Net observations report
  29. GRB 260115A: AstroSat CZTI detection
  30. EP260119a: LCO optical observations
  31. GRB 260117A: ZTSh optical upper limit
  32. EP260119a: COLIBRÍ optical counterpart candidate
  33. EP260119a: preliminary result from the EP-FXT observation
  34. GRB 260110A: SVOM detection of a burst through offline search
  35. EP260119a: EP-WXT detection of a fast X-ray transient
  36. Swift GRB260118.48: Global MASTER-Net observations report
  37. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  38. SVOM GRB260117.82: Global MASTER-Net observations report
  39. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  40. Swift trigger on the HMXB 1A 1118-61
  41. GRB 260117A: SVOM/VT optical candidate
  42. GRB 260117A: SVOM/C-GFT upper limit
  43. GRB 260117A: Swift-XRT observations
  44. GRB 260117A: Swift ToO observations
  45. GRB 260117A: SVOM detection of a long faint burst
  46. EP 260116a: COLIBRÍ optical upper limit
  47. Swift triggered on the HMXB 1A 1118-61
  48. GRB 260115A: GECAM-B observation
  49. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  50. EP260116a: Liverpool Telescope upper limits
  51. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  52. EP260116A: 1.3m DFOT optical upper limit
  53. GRB 260114A: VLT/MUSE spectroscopic observations
  54. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  55. EP260116a: Global MASTER-Net observations report
  56. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  57. EP260116a: Xinglong optical upper limit
  58. EP260116a: Einstein Probe detection of an X-ray transient
  59. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  60. IceCube Alert 260115.73: Global MASTER-Net observations report
  61. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  62. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  63. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  64. Fermi GRB 260115A: Global MASTER-Net observations report
  65. GRB 260115A: Fermi GBM Final Real-time Localization
  66. GRB260114A: STEP/T80S optical limits
  67. GRB 251222A: radio detection with the VLA
  68. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  69. Konus-Wind detection of GRB 260114A
  70. GRB 260114A: Swift-XRT refined Analysis
  71. GRB 260114A: 6 GHz VLA observations
  72. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  73. GRB 260114A : MITSuME Akeno optical upper limits
  74. GRB 260114A: COLIBRÍ optical upper limits
  75. GRB 260114A: TNG NIR upper limit
  76. GRB 260114A: NOT optical observations
  77. Konus-Wind detection of GRB 251230A / EP251230a
  78. GRB 260114A: SVOM/GRM observation of a short burst
  79. Swift GRB 260114A: Global MASTER-Net observations report
  80. GRB 260114A: GECAM-B observation of a short burst
  81. GRB 260114A: Mondy optical observations
  82. GRB 260114A: Fermi GBM observation
  83. GRB 260112B: GECAM-B observation
  84. GRB 260114A: GMG Optical Observation
  85. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  86. GRB 260114A: Swift detection of a short burst
  87. GRB 260114A: Fermi GBM Final Real-time Localization
  88. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  89. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  90. Swift GRB260113.43: Global MASTER-Net observations report
  91. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  92. EP260110a: TRT optical upper limits
  93. Konus-Wind detection of GRB 260101A
  94. GRB 260111A: Swift-XRT observations
  95. Swift Trigger 1439093: is probably not GRB 260113A
  96. GRB 260111A: COLIBRÍ optical afterglow candidate
  97. GRB 260111A: GECAM-B observation of a burst
  98. GRB 260111A: Fermi GBM Observation
  99. The EP-WXT trigger 01709251266 is likely a flaring star
  100. Swift Trigger 1434591 is not a GRB

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