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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"

15251 results found.

  1. GRB 260131A/B: OHP/T193 optical observations
  2. GRID detection of GRB 260131A/B
  3. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  4. GRB 260130A: Insight-HXMT/HE detection
  5. GRB 260130A: GECAM-B observation of a short burst
  6. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  7. GRB 260127B: Insight-HXMT/HE detection
  8. GRB 260127B: GECAM-B observation of a short burst
  9. GRB 260127A: GECAM-B observation
  10. EP260131a: Liverpool Telescope optical upper limits
  11. EP260131a: COLIBRÍ further observations
  12. Konus-Wind detection of GRB 260128A / EP260128a
  13. GRB 260131A: Insight-HXMT/HE detection
  14. Konus-Wind detection of GRB 260131A/B
  15. EP260131a: COLIBRÍ observations of slow optical fading
  16. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  17. EP260131a: COLIBRÍ optical observations of the counterpart
  18. GRB 260127B: AstroSat CZTI detection
  19. GRB 260130A: Fermi GBM Detection
  20. GRB 260127B: Fermi GBM Detection
  21. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  22. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  23. GRB 260128B: SVOM detection of a burst through offline search
  24. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  25. EP260128a: NOT optical counterpart candidate
  26. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  27. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  28. GRB 260127A: Fermi GBM Observation
  29. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 260127A: COLIBRÍ optical observations
  31. GRB 260127A: NOT optical observations
  32. GRB 260127B: Swift ToO observations
  33. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  34. GRB 260127A: SVOM/C-GFT optical observations
  35. EP260126a: Optical upper limit with Kinder observations
  36. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  37. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  38. Konus-Wind detection of GRB 260120B
  39. GRB 251222A: SVOM/ECLAIRs refined analysis
  40. GRB 260125A: Swift ToO observations
  41. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 260114A: SVOM/VT optical upper limits
  43. GRB 260120A: AstroSat CZTI detection
  44. GRB 260120B: SVOM/GRM observation
  45. GRB 260120A: GECAM-B observation
  46. GRB 260120B: AstroSat CZTI detection
  47. GRB 260114A: Insight-HXMT/HE detection
  48. GRB 260122B: Swift detection of a burst
  49. EP260119a: Mondy and SAO RAS optical upper limits
  50. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  51. EP260116a: COLIBRÍ further observations
  52. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  53. GRB 260120B: Fermi GBM Observation
  54. EP260105a: GTC/HiPERCAM optical observations
  55. GRB 260120B: COLIBRÍ optical upper limits
  56. GRB 260101A: 239Alferov CubeSat detection
  57. EP260119a: Liverpool Telescope optical follow-up observations
  58. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  59. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  60. EP260119a: update of EP-FXT follow-up observation
  61. EP260119a: NOT optical observations
  62. EP260116a: COLIBRÍ detection of a fading optical source
  63. GRB 251208D: SVOM/ECLAIRs refined analysis
  64. GRB 251208D: SVOM/ECLAIRs refined analysis
  65. GRB 260117A: Swift-XRT afterglow detection
  66. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  67. GRB 260115A: AstroSat CZTI detection
  68. GRB 260117A: ZTSh optical upper limit
  69. EP260119a: COLIBRÍ optical counterpart candidate
  70. GRB 260110A: SVOM detection of a burst through offline search
  71. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  72. Swift trigger on the HMXB 1A 1118-61
  73. GRB 260117A: Swift ToO observations
  74. GRB 260117A: SVOM detection of a long faint burst
  75. EP 260116a: COLIBRÍ optical upper limit
  76. GRB 260115A: GECAM-B observation
  77. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  78. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  79. GRB 260114A: VLT/MUSE spectroscopic observations
  80. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  82. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  83. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  84. GRB260114A: STEP/T80S optical limits
  85. Konus-Wind detection of GRB 260114A
  86. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  87. GRB 260114A: COLIBRÍ optical upper limits
  88. GRB 260114A: TNG NIR upper limit
  89. GRB 260114A: NOT optical observations
  90. Konus-Wind detection of GRB 251230A / EP251230a
  91. GRB 260114A: SVOM/GRM observation of a short burst
  92. GRB 260114A: GECAM-B observation of a short burst
  93. GRB 260114A: Fermi GBM observation
  94. GRB 260112B: GECAM-B observation
  95. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  96. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  97. EP260110a: TRT optical upper limits
  98. Konus-Wind detection of GRB 260101A
  99. GRB 260111A: Swift-XRT observations
  100. Swift Trigger 1439093: is probably not GRB 260113A

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