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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"

32541 results found.

  1. GRB 260730B: Glowbug gamma-ray detection
  2. GRB 260805B: Glowbug gamma-ray detection
  3. Fermi GRB 260805A: Global MASTER-Net observations report
  4. GRB 260804A: Glowbug gamma-ray detection
  5. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  6. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  7. GRB 260708A: LCO further optical observations show supernova features
  8. Fermi GRB 260802B: Global MASTER-Net observations report
  9. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  10. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  11. GRB 260802A: SVOM/VT optical upper limits from VHF data
  12. GRB 260802A: LCO optical upper limits
  13. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  15. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  16. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  17. GRB 260730B: AstroSat CZTI detection
  18. EP260731a: COLIBRÍ optical upper limit
  19. EP260731a: NOT optical upper limit
  20. GRB 260730B: NuSTAR detection of prompt emission
  21. GRB 260727A: SVOM/ECLAIRs refined analysis
  22. GRB 260726A: SVOM/ECLAIRs refined analysis
  23. EP260728a: COLIBRÍ optical upper limit
  24. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  25. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  26. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  27. EP260727a: SAO RAS optical observations
  28. GRB 260727A: AbAO and SAO RAS optical observations
  29. EP260728a: EP-FXT follow-up observation
  30. GRB 260726A: EP-FXT follow-up observations
  31. GRB 260727A: SVOM/GRM observation
  32. GRB 260726A: Fermi GBM Observation
  33. EP260727a: 1.5m OSN optical counterpart detection
  34. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  35. EP260727a: OHP/T193 optical observations
  36. Konus-Wind detection of GRB 260727A
  37. GRB 260726A: Liverpool Telescope optical observations
  38. GRB 260727A: Liverpool Telescope optical upper limits
  39. EP260727a: Liverpool Telescope confirmation of optical counterpart
  40. EP260727a: NUTTELA-TAO Early Optical Limits
  41. GRB 260727A: EP/FXT follow-up observations
  42. EP260727a: Einstein Probe detection of an X-ray transient
  43. GRB 260727A: Glowbug gamma-ray detection
  44. GRB 260726A: J-band upper limit with WINTER
  45. GRB 260727A: J-band upper limit with WINTER
  46. GRB 260726A: SVOM/VT optical candidate
  47. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  48. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  49. EP260723a: SVOM/ECLAIRs Upper Limit
  50. GRB 260727A: GOTO early optical upper limit
  51. GRB 260727A: AstroSat CZTI detection
  52. GRB 260727A: Kilonova-Catcher optical upper limit
  53. GRB 260727A: LCO optical upper limits
  54. Fermi GRB 260726A: Global MASTER-Net observations report
  55. GRB 260726A: SVOM detection of a burst
  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. GRB 260616A: cubesat Avion detection
  60. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  61. GRB 260602B: cubesat Avion detection
  62. GRB 260601A: cubesat Avion detection
  63. EP260723a: EP-FXT follow-up observation
  64. IPN triangulation of GRB 260706B
  65. GRB 260718A: SVOM/ECLAIRs refined analysis
  66. EP260723a: SVOM/VT optical observation
  67. EP260723a: COLIBRÍ optical observations
  68. EP260723a: NOT optical conterpart confirmation
  69. EP260723a: Liverpool Telescope likely optical counterpart
  70. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  71. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  72. Konus-Wind detection of GRB 260721A
  73. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  74. GRB 260721A: NuSTAR detection of prompt emission
  75. Konus-Wind detection of GRB 260714B
  76. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  77. GRB 260705A: Retraction of optical counterpart
  78. GRB 260714B: Insight-HXMT/HE detection
  79. GRB 260718A: EP-FXT follow-up observation
  80. Fermi GRB 260718A: Global MASTER-Net observations report
  81. GRB 260718A: LCO optical upper limits
  82. GRB 260711A: SVOM/GRM observation
  83. GRB 260710A: SVOM/GRM observation
  84. GRB 260718A: Fermi GBM Observation
  85. GRB 260718A : GRANDMA and KNC upper limits
  86. GRB 260718A: SVOM/VT optical upper limits
  87. GRB 260718A: SVOM/VT optical upper limits from VHF data
  88. GRB 260718A: SVOM detection of a burst
  89. GRB 260714B: SVOM/GRM observation
  90. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  91. GRB 260714B: GECAM-B observation of a burst
  92. GRB 260618B: EP-FXT follow-up observation upper limit
  93. GRB 260714B: COLIBRÍ optical counterpart candidate
  94. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
  95. SVOM sb26071506: Global MASTER-Net observations report
  96. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  97. EP260703a: SVOM/ECLAIRs Upper Limit
  98. GRB 260710A: AstroSat CZTI detection
  99. GRB 260709A: AstroSat CZTI detection
  100. GRB 260714B: AstroSat CZTI detection

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