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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 260709A: cubesat Avion detection
  2. GRB 260708A: cubesat Avion detection
  3. SN 2026stf / GRB 260708A: ATLAS forced photometry
  4. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 260730B: Glowbug gamma-ray detection
  6. GRB 260805C: Glowbug gamma-ray detection
  7. GRB 260805B: Glowbug gamma-ray detection
  8. Fermi GRB 260805A: Global MASTER-Net observations report
  9. GRB 260805B: Fermi GBM Final Localization
  10. GRB 260804A: Glowbug gamma-ray detection
  11. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  12. GRB 260805A: Fermi GBM Final Localization
  13. AT 2026wki: EP/FXT follow-up observations
  14. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  15. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  16. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 260804A: Fermi GBM Final Real-time Localization
  18. GRB 260708A: LCO further optical observations show supernova features
  19. GRB 260803A: Fermi GBM Final Real-time Localization
  20. Fermi GRB 260802B: Global MASTER-Net observations report
  21. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  22. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  23. GRB 260802A: SVOM/VT optical upper limits from VHF data
  24. GRB 260802A: LCO optical upper limits
  25. GRB 260802B: Fermi GBM Final Localization
  26. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. The EP-WXT trigger 01709277420 is likely a flaring star
  28. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  29. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  30. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  31. GRB 260731A: AstroSat CZTI detection of a long burst
  32. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  33. GRB 260730B: AstroSat CZTI detection
  34. EP260731a: COLIBRÍ optical upper limit
  35. EP260731a: NOT optical upper limit
  36. GRB 260730B: NuSTAR detection of prompt emission
  37. EP260731a: Einstein Probe detection of an X-ray transient
  38. GRB 260727A: SVOM/ECLAIRs refined analysis
  39. GRB 260726A: SVOM/ECLAIRs refined analysis
  40. GRB260730A: Fermi GBM Final Localization
  41. EP260728a: COLIBRÍ optical upper limit
  42. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  43. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  44. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  45. EP260729a: Einstein Probe detection of an X-ray transient
  46. EP260727a: SAO RAS optical observations
  47. GRB 260727A: AbAO and SAO RAS optical observations
  48. EP260728a: EP-FXT follow-up observation
  49. GRB 260726A: EP-FXT follow-up observations
  50. EP260728a: Einstein Probe detection of a fast X-ray transient
  51. GRB 260727A: SVOM/GRM observation
  52. GRB 260726A: Fermi GBM Observation
  53. EP260727a: 1.5m OSN optical counterpart detection
  54. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  55. EP260727a: OHP/T193 optical observations
  56. Konus-Wind detection of GRB 260727A
  57. GRB 260726A: Liverpool Telescope optical observations
  58. GRB 260727A: Liverpool Telescope optical upper limits
  59. EP260727a: Liverpool Telescope confirmation of optical counterpart
  60. EP260727a: NUTTELA-TAO Early Optical Limits
  61. GRB 260728A: Fermi GBM Final Localization
  62. GRB 260727A: EP/FXT follow-up observations
  63. EP260727a: Einstein Probe detection of an X-ray transient
  64. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  65. GRB 260727A: Glowbug gamma-ray detection
  66. GRB 260726A: J-band upper limit with WINTER
  67. GRB 260727A: J-band upper limit with WINTER
  68. GRB 260726A: SVOM/VT optical candidate
  69. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  70. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  71. EP260723a: SVOM/ECLAIRs Upper Limit
  72. GRB 260727A: GOTO early optical upper limit
  73. GRB 260727A: AstroSat CZTI detection
  74. GRB 260727A: Kilonova-Catcher optical upper limit
  75. GRB 260727A: LCO optical upper limits
  76. GRB 260727B: Fermi GBM Final Real-time Localization
  77. Fermi GRB 260726A: Global MASTER-Net observations report
  78. GRB 260727A: SVOM detection of a bright long burst
  79. GRB 260726A: SVOM detection of a burst
  80. GRB 260726A: Fermi GBM Final Real-time Localization
  81. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  82. EP260723a: further EP-FXT follow-up observation
  83. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  84. EP260725a: EP-WXT detection of an X-ray transient
  85. GRB 260616A: cubesat Avion detection
  86. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  87. GRB 260602B: cubesat Avion detection
  88. GRB 260601A: cubesat Avion detection
  89. EP260723a: EP-FXT follow-up observation
  90. IPN triangulation of GRB 260706B
  91. GRB 260718A: SVOM/ECLAIRs refined analysis
  92. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  93. EP260723a: SVOM/VT optical observation
  94. EP260723a: COLIBRÍ optical observations
  95. EP260723a: NOT optical conterpart confirmation
  96. EP260723a: Liverpool Telescope likely optical counterpart
  97. EP260723a: EP-WXT detection of a fast X-ray transient
  98. GRB 260723A: Fermi GBM Final Localization
  99. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  100. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)

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