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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 260806A: CALET Gamma-Ray Burst Monitor detection
  2. GRB 260808A: GECAM-B observation
  3. GRB 260807A: SVOM/ECLAIRs refined analysis
  4. EP260806a: MAO/AZT-22 optical observations
  5. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  6. GRB260808B: MAO/AZT-22 optical observations
  7. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  8. GRB 260809A: J-band upper limit with WINTER
  9. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  10. GRB 260806A: Glowbug gamma-ray detection
  11. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  12. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  14. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  15. The EP-WXT trigger 01709278015 is likely a flaring star
  16. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  17. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  18. GRB 260809A: NOT optical observations
  19. GRB260809A: MAO/AZT-22 optical observations
  20. GRB260809A: OHP/T193 optical observations
  21. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 260809A: SVOM/VT optical counterpart
  23. EP260809a: J-band upper limit with WINTER
  24. GRB 260808B: J-band upper limit with WINTER
  25. GRB 260808B: SVOM/ECLAIRs refined analysis
  26. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  27. GRB 260809A: SVOM detection of a faint burst
  28. GRB 260808B: Liverpool Telescope optical observations
  29. GRB 260808B: NOT optical observations
  30. GRB 260808B: LCO optical observations
  31. GRB 260808A: NuSTAR detection of prompt emission
  32. EP260809a: COLIBRÍ optical observations
  33. EP260809a: LCO optical observation
  34. EP260809a: OHP/T193 optical observations
  35. GRB260808B: OHP/T193 optical observations
  36. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  37. EP260809a: Einstein Probe detection of an X-ray transient
  38. GRB 260808B: SVOM/VT optical afterglow confirmation
  39. GRB 260808C: Fermi GBM Final Real-time Localization
  40. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  41. GRB 260808B: SVOM/VT optical candidate from VHF data
  42. GRB 260808B: SVOM detection of a faint burst
  43. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  44. Fermi GRB 260808A: Global MASTER-Net observations report
  45. GRB 260808A: Fermi GBM Final Real-time Localization
  46. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  47. IceCube Alert 260807A: Global MASTER-Net observations report
  48. IceCube-260805A: One candidate from the Zwicky Transient Facility
  49. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. GRB 260807A: SVOM possible detection of a faint burst
  51. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  52. EP260806a: COLIBRÍ optical observations
  53. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  54. EP260806a: SVOM/VT optical observation
  55. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  56. EP260806a: OSIRIS+/GTC redshift z=0.089
  57. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  58. EP260806a: LCO likely optical counterpart
  59. EP260806a: Einstein Probe detection of an X-ray transient
  60. GRB 260715A: cubesat Avion detection
  61. GRB 260709A: cubesat Avion detection
  62. GRB 260708A: cubesat Avion detection
  63. SN 2026stf / GRB 260708A: ATLAS forced photometry
  64. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  65. GRB 260730B: Glowbug gamma-ray detection
  66. GRB 260805C: Glowbug gamma-ray detection
  67. GRB 260805B: Glowbug gamma-ray detection
  68. Fermi GRB 260805A: Global MASTER-Net observations report
  69. GRB 260805B: Fermi GBM Final Localization
  70. GRB 260804A: Glowbug gamma-ray detection
  71. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  72. GRB 260805A: Fermi GBM Final Localization
  73. AT 2026wki: EP/FXT follow-up observations
  74. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  75. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  76. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 260804A: Fermi GBM Final Real-time Localization
  78. GRB 260708A: LCO further optical observations show supernova features
  79. GRB 260803A: Fermi GBM Final Real-time Localization
  80. Fermi GRB 260802B: Global MASTER-Net observations report
  81. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  82. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  83. GRB 260802A: SVOM/VT optical upper limits from VHF data
  84. GRB 260802A: LCO optical upper limits
  85. GRB 260802B: Fermi GBM Final Localization
  86. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. The EP-WXT trigger 01709277420 is likely a flaring star
  88. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  89. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  90. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  91. GRB 260731A: AstroSat CZTI detection of a long burst
  92. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  93. GRB 260730B: AstroSat CZTI detection
  94. EP260731a: COLIBRÍ optical upper limit
  95. EP260731a: NOT optical upper limit
  96. GRB 260730B: NuSTAR detection of prompt emission
  97. EP260731a: Einstein Probe detection of an X-ray transient
  98. GRB 260727A: SVOM/ECLAIRs refined analysis
  99. GRB 260726A: SVOM/ECLAIRs refined analysis
  100. GRB260730A: Fermi GBM Final Localization

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