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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"

45418 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 260809A
  2. GRB 260810A: Glowbug gamma-ray detection
  3. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  4. GRB 260810A: AstroSat CZTI detection of a long burst
  5. EP260812a: Einstein Probe detection of an X-ray transient
  6. GRB 260809A: SAO RAS optical observations
  7. GRB 260808B: SAO RAS optical observations
  8. GRB 260808B: SVOM/VT optical re-brightening at day 3
  9. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  10. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  11. GRB 260808A: GECAM-B observation
  12. GRB 260807A: SVOM/ECLAIRs refined analysis
  13. EP260806a: MAO/AZT-22 optical observations
  14. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  15. GRB260808B: MAO/AZT-22 optical observations
  16. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  17. GRB 260809A: J-band upper limit with WINTER
  18. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  19. GRB 260806A: Glowbug gamma-ray detection
  20. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  21. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  22. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  23. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  24. The EP-WXT trigger 01709278015 is likely a flaring star
  25. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  26. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  27. GRB 260809A: NOT optical observations
  28. GRB260809A: MAO/AZT-22 optical observations
  29. GRB260809A: OHP/T193 optical observations
  30. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 260809A: SVOM/VT optical counterpart
  32. EP260809a: J-band upper limit with WINTER
  33. GRB 260808B: J-band upper limit with WINTER
  34. GRB 260808B: SVOM/ECLAIRs refined analysis
  35. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  36. GRB 260809A: SVOM detection of a faint burst
  37. GRB 260808B: Liverpool Telescope optical observations
  38. GRB 260808B: NOT optical observations
  39. GRB 260808B: LCO optical observations
  40. GRB 260808A: NuSTAR detection of prompt emission
  41. EP260809a: COLIBRÍ optical observations
  42. EP260809a: LCO optical observation
  43. EP260809a: OHP/T193 optical observations
  44. GRB260808B: OHP/T193 optical observations
  45. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  46. EP260809a: Einstein Probe detection of an X-ray transient
  47. GRB 260808B: SVOM/VT optical afterglow confirmation
  48. GRB 260808C: Fermi GBM Final Real-time Localization
  49. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  50. GRB 260808B: SVOM/VT optical candidate from VHF data
  51. GRB 260808B: SVOM detection of a faint burst
  52. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  53. Fermi GRB 260808A: Global MASTER-Net observations report
  54. GRB 260808A: Fermi GBM Final Real-time Localization
  55. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  56. IceCube Alert 260807A: Global MASTER-Net observations report
  57. IceCube-260805A: One candidate from the Zwicky Transient Facility
  58. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  59. GRB 260807A: SVOM possible detection of a faint burst
  60. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  61. EP260806a: COLIBRÍ optical observations
  62. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  63. EP260806a: SVOM/VT optical observation
  64. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  65. EP260806a: OSIRIS+/GTC redshift z=0.089
  66. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  67. EP260806a: LCO likely optical counterpart
  68. EP260806a: Einstein Probe detection of an X-ray transient
  69. GRB 260715A: cubesat Avion detection
  70. GRB 260709A: cubesat Avion detection
  71. GRB 260708A: cubesat Avion detection
  72. SN 2026stf / GRB 260708A: ATLAS forced photometry
  73. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  74. GRB 260730B: Glowbug gamma-ray detection
  75. GRB 260805C: Glowbug gamma-ray detection
  76. GRB 260805B: Glowbug gamma-ray detection
  77. Fermi GRB 260805A: Global MASTER-Net observations report
  78. GRB 260805B: Fermi GBM Final Localization
  79. GRB 260804A: Glowbug gamma-ray detection
  80. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  81. GRB 260805A: Fermi GBM Final Localization
  82. AT 2026wki: EP/FXT follow-up observations
  83. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  84. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  85. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  86. GRB 260804A: Fermi GBM Final Real-time Localization
  87. GRB 260708A: LCO further optical observations show supernova features
  88. GRB 260803A: Fermi GBM Final Real-time Localization
  89. Fermi GRB 260802B: Global MASTER-Net observations report
  90. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  91. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  92. GRB 260802A: SVOM/VT optical upper limits from VHF data
  93. GRB 260802A: LCO optical upper limits
  94. GRB 260802B: Fermi GBM Final Localization
  95. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. The EP-WXT trigger 01709277420 is likely a flaring star
  97. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  98. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  99. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  100. GRB 260731A: AstroSat CZTI detection of a long burst

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