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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. GRB260809A: MAO/AZT-22 optical observations
  2. GRB260809A: OHP/T193 optical observations
  3. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  4. GRB 260809A: SVOM/VT optical counterpart
  5. EP260809a: J-band upper limit with WINTER
  6. GRB 260808B: J-band upper limit with WINTER
  7. GRB 260808B: SVOM/ECLAIRs refined analysis
  8. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  9. GRB 260809A: SVOM detection of a faint burst
  10. GRB 260808B: Liverpool Telescope optical observations
  11. GRB 260808B: NOT optical observations
  12. GRB 260808B: LCO optical observations
  13. GRB 260808A: NuSTAR detection of prompt emission
  14. EP260809a: COLIBRÍ optical observations
  15. EP260809a: LCO optical observation
  16. EP260809a: OHP/T193 optical observations
  17. GRB260808B: OHP/T193 optical observations
  18. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  19. EP260809a: Einstein Probe detection of an X-ray transient
  20. GRB 260808B: SVOM/VT optical afterglow confirmation
  21. GRB 260808C: Fermi GBM Final Real-time Localization
  22. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  23. GRB 260808B: SVOM/VT optical candidate from VHF data
  24. GRB 260808B: SVOM detection of a faint burst
  25. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  26. Fermi GRB 260808A: Global MASTER-Net observations report
  27. GRB 260808A: Fermi GBM Final Real-time Localization
  28. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  29. IceCube Alert 260807A: Global MASTER-Net observations report
  30. IceCube-260805A: One candidate from the Zwicky Transient Facility
  31. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. GRB 260807A: SVOM possible detection of a faint burst
  33. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  34. EP260806a: COLIBRÍ optical observations
  35. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260806a: SVOM/VT optical observation
  37. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  38. EP260806a: OSIRIS+/GTC redshift z=0.089
  39. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  40. EP260806a: LCO likely optical counterpart
  41. EP260806a: Einstein Probe detection of an X-ray transient
  42. GRB 260715A: cubesat Avion detection
  43. GRB 260709A: cubesat Avion detection
  44. GRB 260708A: cubesat Avion detection
  45. SN 2026stf / GRB 260708A: ATLAS forced photometry
  46. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  47. GRB 260730B: Glowbug gamma-ray detection
  48. GRB 260805C: Glowbug gamma-ray detection
  49. GRB 260805B: Glowbug gamma-ray detection
  50. Fermi GRB 260805A: Global MASTER-Net observations report
  51. GRB 260805B: Fermi GBM Final Localization
  52. GRB 260804A: Glowbug gamma-ray detection
  53. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  54. GRB 260805A: Fermi GBM Final Localization
  55. AT 2026wki: EP/FXT follow-up observations
  56. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  57. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  58. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  59. GRB 260804A: Fermi GBM Final Real-time Localization
  60. GRB 260708A: LCO further optical observations show supernova features
  61. GRB 260803A: Fermi GBM Final Real-time Localization
  62. Fermi GRB 260802B: Global MASTER-Net observations report
  63. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  64. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  65. GRB 260802A: SVOM/VT optical upper limits from VHF data
  66. GRB 260802A: LCO optical upper limits
  67. GRB 260802B: Fermi GBM Final Localization
  68. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. The EP-WXT trigger 01709277420 is likely a flaring star
  70. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  71. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  72. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  73. GRB 260731A: AstroSat CZTI detection of a long burst
  74. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  75. GRB 260730B: AstroSat CZTI detection
  76. EP260731a: COLIBRÍ optical upper limit
  77. EP260731a: NOT optical upper limit
  78. GRB 260730B: NuSTAR detection of prompt emission
  79. EP260731a: Einstein Probe detection of an X-ray transient
  80. GRB 260727A: SVOM/ECLAIRs refined analysis
  81. GRB 260726A: SVOM/ECLAIRs refined analysis
  82. GRB260730A: Fermi GBM Final Localization
  83. EP260728a: COLIBRÍ optical upper limit
  84. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  85. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  86. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  87. EP260729a: Einstein Probe detection of an X-ray transient
  88. EP260727a: SAO RAS optical observations
  89. GRB 260727A: AbAO and SAO RAS optical observations
  90. EP260728a: EP-FXT follow-up observation
  91. GRB 260726A: EP-FXT follow-up observations
  92. EP260728a: Einstein Probe detection of a fast X-ray transient
  93. GRB 260727A: SVOM/GRM observation
  94. GRB 260726A: Fermi GBM Observation
  95. EP260727a: 1.5m OSN optical counterpart detection
  96. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  97. EP260727a: OHP/T193 optical observations
  98. Konus-Wind detection of GRB 260727A
  99. GRB 260726A: Liverpool Telescope optical observations
  100. GRB 260727A: Liverpool Telescope optical upper limits

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