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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"

21147 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/ECLAIRs refined analysis
  12. EP260502a is likely a flaring star
  13. GRB 260504B: SVOM/VT optical upper limits
  14. GRB 260421B: radio observation with the VLA
  15. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  16. Konus-Wind detection of GRB 260504B (short/hard)
  17. GRB 260504B: SVOM/MXT refined analysis and potential detection
  18. GRB 260504B: EP-FXT upper limit
  19. GRB 260502A: SVOM/GRM observation of a short GRB
  20. GRB 260503A: SVOM/GRM observation of a GRB
  21. Konus-Wind detection of GRB 260411C
  22. GRB 260504B: REM optical/NIR observations
  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. Fermi GRB 260504A: Global MASTER-Net observations report
  27. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  28. EP260502a: Einstein Probe detection of an X-ray transient
  29. GRB 260429A: SVOM/GRM observation of a short burst
  30. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  31. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  32. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  33. EP260429a: LCO optical upper limits
  34. EP260430a: LCO optical upper limits
  35. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  36. EP260430a: Einstein Probe detection of an X-ray transient
  37. EP260429a: EP-WXT detection of a fast X-ray transient
  38. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  39. EP260416a: Mondy and Terskol optical upper limits
  40. GRB 260424B: COLIBRÍ optical upper limit
  41. Konus-Wind detection of GRB 260424B
  42. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  43. GRB 260401A: cubesat Avion detection
  44. EP260321a: Upper limits from ATCA radio observations
  45. GRB 260421B: Kilonova-Catcher optical afterglow detection
  46. EP260416a: Mondy optical observations
  47. GRB 260421B: SVOM/ECLAIRs refined analysis
  48. GRB 260421B: 3.6m DOT optical observation
  49. EP260416a: ZTSh R band observations
  50. GRB 260421B: SVOM/GRM observation
  51. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  52. GOTO26djh/AT2026jpw: ATCA radio detection
  53. GRB 260421B: J-band upper limit with WINTER
  54. GRB 260421B: LCO optical counterpart detection
  55. GOTO26djh/AT2026jpw: radio detection at 15GHz
  56. GRB 260421B: SVOM/VT optical observations
  57. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  58. GRB 260310A: Late-time Chandra X-ray Detection
  59. EP260416a: 1.3m DFOT optical observation
  60. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  61. GRB 260421B: LCO optical afterglow confirmation
  62. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  63. GRB 260421B: TRT optical counterpart detection
  64. GRB 260421B: SVOM detection of a long burst
  65. EP260321a: VLA radio follow-up
  66. GRB 260412A: LCOGT Optical Upper Limits
  67. EP260416a: Optical follow-up observations with Kinder
  68. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  69. GRB 260417A: SVOM/GRM observation
  70. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  71. EP260417a: GROWTH-India Telescope optical upper limit
  72. EP260417b: GROWTH-India Telescope optical upper limit
  73. EP260416a: Ondrejov D50 optical detection
  74. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  75. EP260416a: GMG Optical Observation
  76. Konus-Wind detection of GRB 260411B
  77. EP260416a: LCO observations confirm end of flaring phase
  78. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  79. EP260417a: TRT optical counterpart detection
  80. EP260417a: Einstein Probe detection of an X-ray transient
  81. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  82. EP260417b: Einstein Probe detection of a fast X-ray transient
  83. EP260416a: KAIT optical upper limit
  84. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  85. EP260416a: WFST optical observations and rebrightening
  86. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  87. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  88. EP260416a: COLIBRÍ optical counterpart candidate
  89. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  90. EP260416a: Einstein Probe detection of an X-ray transient
  91. GOTO26djh/AT2026jpw : MASTER OT observation
  92. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  93. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  94. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  95. EP260321a: CMO SAI J,K observations
  96. Konus-Wind detection of GRB 260410A (short/hard)
  97. GRB 260411B: Fermi-LAT detection
  98. GRB 260412A: SVOM detection of a long burst
  99. GRB 260411B: COLIBRÍ optical observations
  100. GRB260411B: 3.6m DOT optical observation

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