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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"

26301 results found.

  1. GRB 260727A: Glowbug gamma-ray detection
  2. GRB 260726A: J-band upper limit with WINTER
  3. GRB 260727A: J-band upper limit with WINTER
  4. GRB 260726A: SVOM/VT optical candidate
  5. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  6. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  7. EP260723a: SVOM/ECLAIRs Upper Limit
  8. GRB 260727A: GOTO early optical upper limit
  9. GRB 260727A: AstroSat CZTI detection
  10. GRB 260727A: Kilonova-Catcher optical upper limit
  11. GRB 260727A: LCO optical upper limits
  12. GRB 260727A: SVOM detection of a bright long burst
  13. GRB 260726A: SVOM detection of a burst
  14. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  15. EP260723a: further EP-FXT follow-up observation
  16. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  17. EP260725a: EP-WXT detection of an X-ray transient
  18. GRB 260616A: cubesat Avion detection
  19. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  20. GRB 260602B: cubesat Avion detection
  21. GRB 260601A: cubesat Avion detection
  22. EP260723a: EP-FXT follow-up observation
  23. IPN triangulation of GRB 260706B
  24. GRB 260718A: SVOM/ECLAIRs refined analysis
  25. EP260723a: SVOM/VT optical observation
  26. EP260723a: COLIBRÍ optical observations
  27. EP260723a: NOT optical conterpart confirmation
  28. EP260723a: EP-WXT detection of a fast X-ray transient
  29. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  30. Konus-Wind detection of GRB 260721A
  31. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  32. GRB 260721A: NuSTAR detection of prompt emission
  33. Konus-Wind detection of GRB 260714B
  34. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  35. GRB 260705A: Retraction of optical counterpart
  36. GRB 260714B: Insight-HXMT/HE detection
  37. GRB 260718A: EP-FXT follow-up observation
  38. GRB 260718A: LCO optical upper limits
  39. GRB 260711A: SVOM/GRM observation
  40. GRB 260710A: SVOM/GRM observation
  41. GRB 260718A: Fermi GBM Observation
  42. GRB 260718A : GRANDMA and KNC upper limits
  43. GRB 260718A: SVOM/VT optical upper limits
  44. GRB 260718A: SVOM/VT optical upper limits from VHF data
  45. GRB 260718A: SVOM detection of a burst
  46. GRB 260714B: SVOM/GRM observation
  47. GRB 260714B: GECAM-B observation of a burst
  48. GRB 260618B: EP-FXT follow-up observation upper limit
  49. GRB 260714B: COLIBRÍ optical counterpart candidate
  50. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  51. SVOM sb26071506: Global MASTER-Net observations report
  52. sb26071506: SVOM detection of a X-ray transient
  53. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  54. EP260703a: SVOM/ECLAIRs Upper Limit
  55. GRB 260710A: AstroSat CZTI detection
  56. GRB 260709A: AstroSat CZTI detection
  57. GRB 260714B: AstroSat CZTI detection
  58. GRB 260714B: Fermi-LAT detection
  59. GRB 260714B: Fermi GBM Detection
  60. GRB 260706A: ATCA detection of possible radio counterpart
  61. GRB 260705A: ATCA radio observations
  62. EP260713a: Einstein Probe detection of an X-ray transient
  63. GRB 260619A: SVOM/VT continuous optical observations
  64. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  65. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  66. GRB 260708A: GRANDMA Optical Observations
  67. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  68. GRB 260710A: Insight-HXMT/HE detection
  69. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  70. GRB 260708A: LCO optical observations
  71. EP260711a: Einstein Probe detection of an X-ray transient
  72. GRB 260710A: Fermi GBM Detection
  73. GRB 260709A: SVOM/GRM detection
  74. GRB 260709A: GECAM-B observation
  75. IceCube-260708A: Observations with the Vera C. Rubin Observatory
  76. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  77. GRB 260705C: AstroSat CZTI detection
  78. GRB 260708A: Glowbug gamma-ray detection
  79. GRB 260704A: SVOM/ECLAIRs refined analysis
  80. GRB 260706A : GRANDMA Upper limits
  81. GRB 260708A: Kilonova-Catcher optical afterglow detection
  82. GRB 260708A: GECAM-B observation of a burst
  83. IceCube-260708A: One candidate from the Zwicky Transient Facility
  84. GRB 260708A: Fermi-GBM observation
  85. Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
  86. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  87. GRB 260708A: Fermi-LAT detection
  88. GRB 260705B: SVOM/GRM observation
  89. GRB 260706A: Further EP-FXT follow-up observation
  90. GRB 260706A: SVOM/VT optical upper limits
  91. EP260707a (by EP-FXT): NOT optical upper limit
  92. EP260707a is not a real source
  93. EP260707a: TRT optical upper limit
  94. EP260707a: Einstein Probe detection of an X-ray transient
  95. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  96. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  97. GRB 260705C: Glowbug gamma-ray detection of a short burst
  98. GRB 260706A: SVOM/ECLAIRs refined analysis
  99. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  100. GRB 260706A: SVOM/GRM observation

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