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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"

18991 results found.

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

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