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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"

19088 results found.

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

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