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

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