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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 260808B: J-band upper limit with WINTER
  2. GRB 260808B: SVOM/ECLAIRs refined analysis
  3. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  4. GRB 260809A: SVOM detection of a faint burst
  5. GRB 260808B: Liverpool Telescope optical observations
  6. GRB 260808B: NOT optical observations
  7. GRB 260808B: LCO optical observations
  8. GRB 260808A: NuSTAR detection of prompt emission
  9. EP260809a: COLIBRÍ optical observations
  10. EP260809a: LCO optical observation
  11. EP260809a: OHP/T193 optical observations
  12. GRB260808B: OHP/T193 optical observations
  13. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  14. EP260809a: Einstein Probe detection of an X-ray transient
  15. GRB 260808B: SVOM/VT optical afterglow confirmation
  16. GRB 260808C: Fermi GBM Final Real-time Localization
  17. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  18. GRB 260808B: SVOM/VT optical candidate from VHF data
  19. GRB 260808B: SVOM detection of a faint burst
  20. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  21. Fermi GRB 260808A: Global MASTER-Net observations report
  22. GRB 260808A: Fermi GBM Final Real-time Localization
  23. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  24. IceCube Alert 260807A: Global MASTER-Net observations report
  25. IceCube-260805A: One candidate from the Zwicky Transient Facility
  26. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 260807A: SVOM possible detection of a faint burst
  28. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  29. EP260806a: COLIBRÍ optical observations
  30. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  31. EP260806a: SVOM/VT optical observation
  32. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  33. EP260806a: OSIRIS+/GTC redshift z=0.089
  34. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  35. EP260806a: LCO likely optical counterpart
  36. EP260806a: Einstein Probe detection of an X-ray transient
  37. GRB 260715A: cubesat Avion detection
  38. GRB 260709A: cubesat Avion detection
  39. GRB 260708A: cubesat Avion detection
  40. SN 2026stf / GRB 260708A: ATLAS forced photometry
  41. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 260730B: Glowbug gamma-ray detection
  43. GRB 260805C: Glowbug gamma-ray detection
  44. GRB 260805B: Glowbug gamma-ray detection
  45. Fermi GRB 260805A: Global MASTER-Net observations report
  46. GRB 260805B: Fermi GBM Final Localization
  47. GRB 260804A: Glowbug gamma-ray detection
  48. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  49. GRB 260805A: Fermi GBM Final Localization
  50. AT 2026wki: EP/FXT follow-up observations
  51. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  52. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  53. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  54. GRB 260804A: Fermi GBM Final Real-time Localization
  55. GRB 260708A: LCO further optical observations show supernova features
  56. GRB 260803A: Fermi GBM Final Real-time Localization
  57. Fermi GRB 260802B: Global MASTER-Net observations report
  58. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  59. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  60. GRB 260802A: SVOM/VT optical upper limits from VHF data
  61. GRB 260802A: LCO optical upper limits
  62. GRB 260802B: Fermi GBM Final Localization
  63. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. The EP-WXT trigger 01709277420 is likely a flaring star
  65. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  66. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  67. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  68. GRB 260731A: AstroSat CZTI detection of a long burst
  69. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  70. GRB 260730B: AstroSat CZTI detection
  71. EP260731a: COLIBRÍ optical upper limit
  72. EP260731a: NOT optical upper limit
  73. GRB 260730B: NuSTAR detection of prompt emission
  74. EP260731a: Einstein Probe detection of an X-ray transient
  75. GRB 260727A: SVOM/ECLAIRs refined analysis
  76. GRB 260726A: SVOM/ECLAIRs refined analysis
  77. GRB260730A: Fermi GBM Final Localization
  78. EP260728a: COLIBRÍ optical upper limit
  79. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  80. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  81. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  82. EP260729a: Einstein Probe detection of an X-ray transient
  83. EP260727a: SAO RAS optical observations
  84. GRB 260727A: AbAO and SAO RAS optical observations
  85. EP260728a: EP-FXT follow-up observation
  86. GRB 260726A: EP-FXT follow-up observations
  87. EP260728a: Einstein Probe detection of a fast X-ray transient
  88. GRB 260727A: SVOM/GRM observation
  89. GRB 260726A: Fermi GBM Observation
  90. EP260727a: 1.5m OSN optical counterpart detection
  91. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  92. EP260727a: OHP/T193 optical observations
  93. Konus-Wind detection of GRB 260727A
  94. GRB 260726A: Liverpool Telescope optical observations
  95. GRB 260727A: Liverpool Telescope optical upper limits
  96. EP260727a: Liverpool Telescope confirmation of optical counterpart
  97. EP260727a: NUTTELA-TAO Early Optical Limits
  98. GRB 260728A: Fermi GBM Final Localization
  99. GRB 260727A: EP/FXT follow-up observations
  100. EP260727a: Einstein Probe detection of an X-ray transient

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