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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 260802B: Fermi GBM Final Localization
  2. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. The EP-WXT trigger 01709277420 is likely a flaring star
  4. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  5. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  6. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  7. GRB 260731A: AstroSat CZTI detection of a long burst
  8. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  9. GRB 260730B: AstroSat CZTI detection
  10. EP260731a: COLIBRÍ optical upper limit
  11. EP260731a: NOT optical upper limit
  12. GRB 260730B: NuSTAR detection of prompt emission
  13. EP260731a: Einstein Probe detection of an X-ray transient
  14. GRB 260727A: SVOM/ECLAIRs refined analysis
  15. GRB 260726A: SVOM/ECLAIRs refined analysis
  16. GRB260730A: Fermi GBM Final Localization
  17. EP260728a: COLIBRÍ optical upper limit
  18. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  19. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  20. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  21. EP260729a: Einstein Probe detection of an X-ray transient
  22. EP260727a: SAO RAS optical observations
  23. GRB 260727A: AbAO and SAO RAS optical observations
  24. EP260728a: EP-FXT follow-up observation
  25. GRB 260726A: EP-FXT follow-up observations
  26. EP260728a: Einstein Probe detection of a fast X-ray transient
  27. GRB 260727A: SVOM/GRM observation
  28. GRB 260726A: Fermi GBM Observation
  29. EP260727a: 1.5m OSN optical counterpart detection
  30. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  31. EP260727a: OHP/T193 optical observations
  32. Konus-Wind detection of GRB 260727A
  33. GRB 260726A: Liverpool Telescope optical observations
  34. GRB 260727A: Liverpool Telescope optical upper limits
  35. EP260727a: Liverpool Telescope confirmation of optical counterpart
  36. EP260727a: NUTTELA-TAO Early Optical Limits
  37. GRB 260728A: Fermi GBM Final Localization
  38. GRB 260727A: EP/FXT follow-up observations
  39. EP260727a: Einstein Probe detection of an X-ray transient
  40. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  41. GRB 260727A: Glowbug gamma-ray detection
  42. GRB 260726A: J-band upper limit with WINTER
  43. GRB 260727A: J-band upper limit with WINTER
  44. GRB 260726A: SVOM/VT optical candidate
  45. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  46. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  47. EP260723a: SVOM/ECLAIRs Upper Limit
  48. GRB 260727A: GOTO early optical upper limit
  49. GRB 260727A: AstroSat CZTI detection
  50. GRB 260727A: Kilonova-Catcher optical upper limit
  51. GRB 260727A: LCO optical upper limits
  52. GRB 260727B: Fermi GBM Final Real-time Localization
  53. Fermi GRB 260726A: Global MASTER-Net observations report
  54. GRB 260727A: SVOM detection of a bright long burst
  55. GRB 260726A: SVOM detection of a burst
  56. GRB 260726A: Fermi GBM Final Real-time Localization
  57. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  58. EP260723a: further EP-FXT follow-up observation
  59. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  60. EP260725a: EP-WXT detection of an X-ray transient
  61. GRB 260616A: cubesat Avion detection
  62. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  63. GRB 260602B: cubesat Avion detection
  64. GRB 260601A: cubesat Avion detection
  65. EP260723a: EP-FXT follow-up observation
  66. IPN triangulation of GRB 260706B
  67. GRB 260718A: SVOM/ECLAIRs refined analysis
  68. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  69. EP260723a: SVOM/VT optical observation
  70. EP260723a: COLIBRÍ optical observations
  71. EP260723a: NOT optical conterpart confirmation
  72. EP260723a: Liverpool Telescope likely optical counterpart
  73. EP260723a: EP-WXT detection of a fast X-ray transient
  74. GRB 260723A: Fermi GBM Final Localization
  75. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  76. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  77. IceCube Alert 260722A: Global MASTER-Net observations report
  78. Konus-Wind detection of GRB 260721A
  79. GRB 260722A: Fermi GBM Final Real-time Localization
  80. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  81. Fermi GBM trigger 806384210/260722151 is not a GRB
  82. GRB 260721A: NuSTAR detection of prompt emission
  83. Konus-Wind detection of GRB 260714B
  84. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  85. GRB 260705A: Retraction of optical counterpart
  86. GRB 260714B: Insight-HXMT/HE detection
  87. GRB 260718A: EP-FXT follow-up observation
  88. Fermi trigger No 806104130: Global MASTER-Net observations report
  89. Fermi GRB 260718A: Global MASTER-Net observations report
  90. GRB 260718A: LCO optical upper limits
  91. GRB 260711A: SVOM/GRM observation
  92. GRB 260710A: SVOM/GRM observation
  93. GRB 260718A: Fermi GBM Observation
  94. GRB 260718A : GRANDMA and KNC upper limits
  95. GRB 260718A: SVOM/VT optical upper limits
  96. GRB 260718A: SVOM/VT optical upper limits from VHF data
  97. GRB 260718A: SVOM detection of a burst
  98. GRB 260714B: SVOM/GRM observation
  99. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  100. GRB 260714B: GECAM-B observation of a burst

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