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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. EP260809a: Einstein Probe detection of an X-ray transient
  2. GRB 260808B: SVOM/VT optical afterglow confirmation
  3. GRB 260808C: Fermi GBM Final Real-time Localization
  4. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  5. GRB 260808B: SVOM/VT optical candidate from VHF data
  6. GRB 260808B: SVOM detection of a faint burst
  7. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  8. Fermi GRB 260808A: Global MASTER-Net observations report
  9. GRB 260808A: Fermi GBM Final Real-time Localization
  10. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  11. IceCube Alert 260807A: Global MASTER-Net observations report
  12. IceCube-260805A: One candidate from the Zwicky Transient Facility
  13. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 260807A: SVOM possible detection of a faint burst
  15. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  16. EP260806a: COLIBRÍ optical observations
  17. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP260806a: SVOM/VT optical observation
  19. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  20. EP260806a: OSIRIS+/GTC redshift z=0.089
  21. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  22. EP260806a: LCO likely optical counterpart
  23. EP260806a: Einstein Probe detection of an X-ray transient
  24. GRB 260715A: cubesat Avion detection
  25. GRB 260709A: cubesat Avion detection
  26. GRB 260708A: cubesat Avion detection
  27. SN 2026stf / GRB 260708A: ATLAS forced photometry
  28. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  29. GRB 260730B: Glowbug gamma-ray detection
  30. GRB 260805C: Glowbug gamma-ray detection
  31. GRB 260805B: Glowbug gamma-ray detection
  32. Fermi GRB 260805A: Global MASTER-Net observations report
  33. GRB 260805B: Fermi GBM Final Localization
  34. GRB 260804A: Glowbug gamma-ray detection
  35. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  36. GRB 260805A: Fermi GBM Final Localization
  37. AT 2026wki: EP/FXT follow-up observations
  38. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  39. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  40. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 260804A: Fermi GBM Final Real-time Localization
  42. GRB 260708A: LCO further optical observations show supernova features
  43. GRB 260803A: Fermi GBM Final Real-time Localization
  44. Fermi GRB 260802B: Global MASTER-Net observations report
  45. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  46. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  47. GRB 260802A: SVOM/VT optical upper limits from VHF data
  48. GRB 260802A: LCO optical upper limits
  49. GRB 260802B: Fermi GBM Final Localization
  50. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. The EP-WXT trigger 01709277420 is likely a flaring star
  52. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  53. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  54. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  55. GRB 260731A: AstroSat CZTI detection of a long burst
  56. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  57. GRB 260730B: AstroSat CZTI detection
  58. EP260731a: COLIBRÍ optical upper limit
  59. EP260731a: NOT optical upper limit
  60. GRB 260730B: NuSTAR detection of prompt emission
  61. EP260731a: Einstein Probe detection of an X-ray transient
  62. GRB 260727A: SVOM/ECLAIRs refined analysis
  63. GRB 260726A: SVOM/ECLAIRs refined analysis
  64. GRB260730A: Fermi GBM Final Localization
  65. EP260728a: COLIBRÍ optical upper limit
  66. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  67. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  68. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  69. EP260729a: Einstein Probe detection of an X-ray transient
  70. EP260727a: SAO RAS optical observations
  71. GRB 260727A: AbAO and SAO RAS optical observations
  72. EP260728a: EP-FXT follow-up observation
  73. GRB 260726A: EP-FXT follow-up observations
  74. EP260728a: Einstein Probe detection of a fast X-ray transient
  75. GRB 260727A: SVOM/GRM observation
  76. GRB 260726A: Fermi GBM Observation
  77. EP260727a: 1.5m OSN optical counterpart detection
  78. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  79. EP260727a: OHP/T193 optical observations
  80. Konus-Wind detection of GRB 260727A
  81. GRB 260726A: Liverpool Telescope optical observations
  82. GRB 260727A: Liverpool Telescope optical upper limits
  83. EP260727a: Liverpool Telescope confirmation of optical counterpart
  84. EP260727a: NUTTELA-TAO Early Optical Limits
  85. GRB 260728A: Fermi GBM Final Localization
  86. GRB 260727A: EP/FXT follow-up observations
  87. EP260727a: Einstein Probe detection of an X-ray transient
  88. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  89. GRB 260727A: Glowbug gamma-ray detection
  90. GRB 260726A: J-band upper limit with WINTER
  91. GRB 260727A: J-band upper limit with WINTER
  92. GRB 260726A: SVOM/VT optical candidate
  93. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  94. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  95. EP260723a: SVOM/ECLAIRs Upper Limit
  96. GRB 260727A: GOTO early optical upper limit
  97. GRB 260727A: AstroSat CZTI detection
  98. GRB 260727A: Kilonova-Catcher optical upper limit
  99. GRB 260727A: LCO optical upper limits
  100. GRB 260727B: Fermi GBM Final Real-time Localization

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