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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

26483 results found.

  1. EP260502a is likely a flaring star
  2. GRB 260503A: GECAM-B observation of a burst
  3. GRB 260430B: Glowbug gamma-ray detection
  4. GRB 260504B: SVOM/VT optical upper limits
  5. GRB 260421B: radio observation with the VLA
  6. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  7. Konus-Wind detection of GRB 260504B (short/hard)
  8. GRB 260504B: GECAM-B detection
  9. GRB 260504C: SVOM/GRM observation of short GRB
  10. GRB 260504B: SVOM/GRM spectral analysis
  11. GRB 260430B: AstroSat CZTI detection of a long burst
  12. GRB 260504B: SVOM/MXT refined analysis and potential detection
  13. GRB 260502A: SVOM/GRM observation of a short GRB
  14. GRB 260503A: SVOM/GRM observation of a GRB
  15. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  16. Konus-Wind detection of GRB 260415C
  17. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  18. Konus-Wind detection of GRB 260411C
  19. GRB 260504B: REM optical/NIR observations
  20. IPN triangulation of GRB 260429A
  21. IPN triangulation of GRB 260428A
  22. GRB 260504B: AST3-2 i-band upper limit
  23. GRB 260504B: LCO z-band upper limit
  24. SVOM GRB 260504B: MASTER-OAFA optical observations
  25. GRB 260504B: SVOM detection of a short burst
  26. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  27. GRB 260502A: GECAM-B observation of a short burst
  28. IPN triangulation of a bright burst from SGR 1E1841-045
  29. GRB 260429B / EP260429a: EP-FXT follow-up observation
  30. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  31. GRB 260429B / EP260429a: AstroSat CZTI detection
  32. EP260502a: BOOTES-7: early optical upper limit
  33. EP260502a: Einstein Probe detection of an X-ray transient
  34. GRB 260429A: SVOM/GRM observation of a short burst
  35. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  36. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  37. GRB 260424B: AstroSat CZTI detection
  38. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  39. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  40. GRB 260429A: Fermi GBM Detection
  41. EP260430a: Einstein Probe detection of an X-ray transient
  42. EP260429a: EP-WXT detection of a fast X-ray transient
  43. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  44. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  45. GRB 260428A: AstroSat CZTI detection
  46. GRB 260424B: Glowbug gamma-ray detection of a short burst
  47. GRB 260424B: COLIBRÍ optical upper limit
  48. Konus-Wind detection of GRB 260424B
  49. IPN triangulation of GRB 260424B (short)
  50. GRB 260424B: SVOM/GRM detection of a short burst
  51. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  53. GRB 260401A: cubesat Avion detection
  54. GRB 260424A: AstroSat CZTI detection of a long burst
  55. EP260321a: Upper limits from ATCA radio observations
  56. GRB 260421B: Kilonova-Catcher optical afterglow detection
  57. GRB 260421B: Insight-HXMT/HE detection
  58. The EP-WXT trigger 01709258652: Mondy optical observations
  59. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  60. GRB 260421B: SVOM/ECLAIRs refined analysis
  61. EP260416a: ZTSh R band observations
  62. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  63. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  64. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  65. GRB 260419A: AstroSat CZTI detection
  66. GRB 260421B: SVOM/GRM observation
  67. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  68. GRB 260421B: EP-FXT follow-up observation
  69. GOTO26djh/AT2026jpw: ATCA radio detection
  70. GRB 260421B: J-band upper limit with WINTER
  71. GRB 260421B: LCO optical counterpart detection
  72. GRB 260421B: Fermi GBM Observation
  73. GRB 260421A: AstroSat CZTI detection
  74. GRB 260412A: SVOM/ECLAIRs refined analysis
  75. GRB 260421B: SVOM/VT optical observations
  76. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  77. GRB 260310A: Late-time Chandra X-ray Detection
  78. GRB 260418A: Insight-HXMT/HE detection
  79. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  80. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  81. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  82. GRB 260421B: BOOTES-7 early optical afterglow detection
  83. GRB 260421B: LCO optical afterglow confirmation
  84. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  85. GRB 260421B: TRT optical counterpart detection
  86. GRB 260421B: SVOM detection of a long burst
  87. GRB 260412A: LCOGT Optical Upper Limits
  88. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  89. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  90. GRB 260417A: SVOM/GRM observation
  91. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  92. EP260417a: GROWTH-India Telescope optical upper limit
  93. EP260417b: GROWTH-India Telescope optical upper limit
  94. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  95. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  96. Konus-Wind detection of GRB 260411B
  97. GRB 260417A: AstroSat CZTI detection
  98. IPN triangulation of GRB 260411B
  99. EP260416a: LCO observations confirm end of flaring phase
  100. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope

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