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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"

19089 results found.

  1. GRB 260509A: SVOM detection of a burst
  2. EP260507a: REM optical/NIR observations
  3. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  4. EP260507a: COLIBRÍ optical observations
  5. EP260507a: NOT optical observations
  6. EP260507a: further Liverpool Telescope observations
  7. EP260507a: Liverpool Telescope optical upper limits
  8. EP260507a: TRT optical counterpart detection
  9. EP260507a: Kinder optical counterpart candidate
  10. EP260507a: LCO optical counterpart
  11. EP260507a: Einstein Probe detection of an X-ray transient
  12. GRB 260504B: SVOM/VT optical upper limits
  13. GRB 260421B: radio observation with the VLA
  14. GRB 260504B: SVOM/MXT refined analysis and potential detection
  15. GRB 260502A: SVOM/GRM observation of a short GRB
  16. GRB 260503A: SVOM/GRM observation of a GRB
  17. Konus-Wind detection of GRB 260411C
  18. GRB 260504B: REM optical/NIR observations
  19. GRB 260504B: LCO z-band upper limit
  20. SVOM GRB 260504B: MASTER-OAFA optical observations
  21. GRB 260504B: SVOM detection of a short burst
  22. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  23. EP260502a: Einstein Probe detection of an X-ray transient
  24. GRB 260429A: SVOM/GRM observation of a short burst
  25. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  26. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  27. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  28. EP260429a: LCO optical upper limits
  29. EP260430a: LCO optical upper limits
  30. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  31. EP260430a: Einstein Probe detection of an X-ray transient
  32. EP260429a: EP-WXT detection of a fast X-ray transient
  33. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  34. EP260416a: Mondy and Terskol optical upper limits
  35. GRB 260424B: COLIBRÍ optical upper limit
  36. GRB 260401A: cubesat Avion detection
  37. EP260321a: Upper limits from ATCA radio observations
  38. GRB 260421B: Kilonova-Catcher optical afterglow detection
  39. The EP-WXT trigger 01709258652: Mondy optical observations
  40. EP260416a: Mondy optical observations
  41. GRB 260421B: 3.6m DOT optical observation
  42. EP260416a: ZTSh R band observations
  43. GRB 260421B: SVOM/GRM observation
  44. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  45. GOTO26djh/AT2026jpw: ATCA radio detection
  46. GRB 260421B: J-band upper limit with WINTER
  47. GRB 260421B: LCO optical counterpart detection
  48. GRB 260421A: AstroSat CZTI detection
  49. GRB 260421B: SVOM/VT optical observations
  50. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  51. GRB 260310A: Late-time Chandra X-ray Detection
  52. EP260416a: 1.3m DFOT optical observation
  53. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  54. GRB 260421B: LCO optical afterglow confirmation
  55. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  56. GRB 260421B: TRT optical counterpart detection
  57. GRB 260421B: SVOM detection of a long burst
  58. EP260321a: VLA radio follow-up
  59. GRB 260412A: LCOGT Optical Upper Limits
  60. EP260416a: Optical follow-up observations with Kinder
  61. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  62. GRB 260417A: SVOM/GRM observation
  63. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  64. EP260417a: GROWTH-India Telescope optical upper limit
  65. EP260417b: GROWTH-India Telescope optical upper limit
  66. EP260416a: Ondrejov D50 optical detection
  67. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  68. EP260416a: GMG Optical Observation
  69. EP260416a: LCO observations confirm end of flaring phase
  70. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  71. EP260417a: TRT optical counterpart detection
  72. EP260417a: Einstein Probe detection of an X-ray transient
  73. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  74. EP260417b: Einstein Probe detection of a fast X-ray transient
  75. EP260416a: KAIT optical upper limit
  76. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  77. EP260416a: WFST optical observations and rebrightening
  78. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  79. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  80. EP260416a: COLIBRÍ optical counterpart candidate
  81. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  82. EP260416a: Einstein Probe detection of an X-ray transient
  83. GOTO26djh/AT2026jpw : MASTER OT observation
  84. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  85. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  86. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  87. EP260321a: CMO SAI J,K observations
  88. GRB 260411B: Fermi-LAT detection
  89. GRB 260412A: SVOM detection of a long burst
  90. GRB 260411B: COLIBRÍ optical observations
  91. GRB260411B: 3.6m DOT optical observation
  92. GRB 260411A: SVOM/GRM observation
  93. GRB 260411B: SVOM/GRM observation of a long burst
  94. GRB 260411B: GOTO optical counterpart candidate
  95. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  96. GRB 260410A: COLIBRÍ optical upper limit
  97. EP-WXT01709259790: Optical Upper limits with kinder observations
  98. EP-WXT01709259790: Xinglong optical upper limit
  99. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  100. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification

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