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

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