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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 260120B: SVOM/GRM observation
  2. GRB 260120A: GECAM-B observation
  3. GRB 260120B: AstroSat CZTI detection
  4. GRB 260114A: Insight-HXMT/HE detection
  5. GRB 260122B: Swift detection of a burst
  6. Swift GRB260122.97: Global MASTER-Net observations report
  7. EP260119a: Assy AZT-20 optical observations
  8. EP260119a: Mondy and SAO RAS optical upper limits
  9. GRB 260122A: Fermi GBM Final Real-time Localization
  10. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  11. EP260119a: Xinglong optical upper limit
  12. The EP-WXT trigger 01709251871 is likely a flaring star
  13. Fermi GRB 260120C: Global MASTER-Net observations report
  14. GRB 260120B: Swift-BAT refined analysis
  15. GRB 260120B: Swift-XRT refined Analysis
  16. EP260116a: COLIBRÍ further observations
  17. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  18. GRB 260120B: Fermi GBM Observation
  19. EP260105a: GTC/HiPERCAM optical observations
  20. GRB 260120B: Swift/UVOT Detection
  21. GRB 260120B: COLIBRÍ optical upper limits
  22. SVOM GRB260121.06: Global MASTER-Net observations report
  23. GRB 260120B: Enhanced Swift-XRT position
  24. GRB 260120B: SVOM/C-GFT optical counterpart detection
  25. GRB 260120C: Fermi GBM Final Real-time Localization
  26. GRB 260101A: 239Alferov CubeSat detection
  27. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  28. GRB 260120B: Swift detection of a burst
  29. Swift GRB260120B: Global MASTER-Net observations report
  30. GRB 260120B: Fermi GBM Final Real-time Localization
  31. EP260119A: Mondy I-Band Observations
  32. Fermi trigger No 790601190: Global MASTER-Net observations report
  33. Fermi trigger No 790570272: Global MASTER-Net observations report
  34. GRB 260114A: Swift/UVOT Upper Limits
  35. EP260119a: Liverpool Telescope optical follow-up observations
  36. GRB 251202A: further radio observations with the VLA
  37. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  38. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  39. EP260119a: KAIT optical observations
  40. GRB 260120A: Fermi GBM Final Real-time Localization
  41. EP260119a: SVOM/VT optical observation
  42. EP260119a: update of EP-FXT follow-up observation
  43. EP260119a: NOT optical observations
  44. EP260119a: SAO RAS optical observations
  45. SVOM GRB260119.92: Global MASTER-Net observations report
  46. SVOM GRB260119.92: Global MASTER-Net observations report
  47. SVOM GRB260119.90: Global MASTER-Net observations report
  48. EP260116a: COLIBRÍ detection of a fading optical source
  49. GRB 251208D: SVOM/ECLAIRs refined analysis
  50. GRB 251208D: SVOM/ECLAIRs refined analysis
  51. GRB 260117A: Swift-XRT afterglow detection
  52. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  53. EP260119a: Global MASTER-Net observations report
  54. GRB 260115A: AstroSat CZTI detection
  55. EP260119a: LCO optical observations
  56. GRB 260117A: ZTSh optical upper limit
  57. EP260119a: COLIBRÍ optical counterpart candidate
  58. EP260119a: preliminary result from the EP-FXT observation
  59. GRB 260110A: SVOM detection of a burst through offline search
  60. EP260119a: EP-WXT detection of a fast X-ray transient
  61. Swift GRB260118.48: Global MASTER-Net observations report
  62. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  63. SVOM GRB260117.82: Global MASTER-Net observations report
  64. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  65. Swift trigger on the HMXB 1A 1118-61
  66. GRB 260117A: SVOM/VT optical candidate
  67. GRB 260117A: SVOM/C-GFT upper limit
  68. GRB 260117A: Swift-XRT observations
  69. GRB 260117A: Swift ToO observations
  70. GRB 260117A: SVOM detection of a long faint burst
  71. EP 260116a: COLIBRÍ optical upper limit
  72. Swift triggered on the HMXB 1A 1118-61
  73. GRB 260115A: GECAM-B observation
  74. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  75. EP260116a: Liverpool Telescope upper limits
  76. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  77. EP260116A: 1.3m DFOT optical upper limit
  78. GRB 260114A: VLT/MUSE spectroscopic observations
  79. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  80. EP260116a: Global MASTER-Net observations report
  81. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  82. EP260116a: Xinglong optical upper limit
  83. EP260116a: Einstein Probe detection of an X-ray transient
  84. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  85. IceCube Alert 260115.73: Global MASTER-Net observations report
  86. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  87. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  88. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  89. Fermi GRB 260115A: Global MASTER-Net observations report
  90. GRB 260115A: Fermi GBM Final Real-time Localization
  91. GRB260114A: STEP/T80S optical limits
  92. GRB 251222A: radio detection with the VLA
  93. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  94. Konus-Wind detection of GRB 260114A
  95. GRB 260114A: Swift-XRT refined Analysis
  96. GRB 260114A: 6 GHz VLA observations
  97. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  98. GRB 260114A : MITSuME Akeno optical upper limits
  99. GRB 260114A: COLIBRÍ optical upper limits
  100. GRB 260114A: TNG NIR upper limit

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