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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"

17850 results found.

  1. EP260509a: Einstein Probe detection of an X-ray transient
  2. GRB 260509A: Liverpool Telescope optical observations
  3. GRB 260510B: SVOM detection of a burst
  4. GRB 260509A: LCO optical observations
  5. GRB 260509A: KAIT optical observations
  6. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  7. GRB 260509A: SVOM/VT optical candidate with VHF data
  8. GRB 260509A: LCO optical counterpart detection
  9. GRB 260509A: SVOM detection of a burst
  10. EP260507a: REM optical/NIR observations
  11. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  12. EP260507a: COLIBRÍ optical observations
  13. EP260507a: NOT optical observations
  14. EP260507a: further Liverpool Telescope observations
  15. EP260507a: Liverpool Telescope optical upper limits
  16. EP260507a: TRT optical counterpart detection
  17. EP260507a: Kinder optical counterpart candidate
  18. EP260507a: LCO optical counterpart
  19. EP260507a: Einstein Probe detection of an X-ray transient
  20. GRB 260504B: AstroSat CZTI detection
  21. EP260502a is likely a flaring star
  22. GRB 260421B: radio observation with the VLA
  23. GRB 260504B: EP-FXT upper limit
  24. GRB 260502A: SVOM/GRM observation of a short GRB
  25. GRB 260503A: SVOM/GRM observation of a GRB
  26. GRB 260504B: REM optical/NIR observations
  27. GRB 260504B: LCO z-band upper limit
  28. GRB 260504B: SVOM detection of a short burst
  29. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  30. The EP-WXT trigger 01709261576 is likely a flaring star
  31. GRB 260429B / EP260429a: EP-FXT follow-up observation
  32. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  33. GRB 260429B / EP260429a: AstroSat CZTI detection
  34. EP260502a: Einstein Probe detection of an X-ray transient
  35. GRB 260429A: SVOM/GRM observation of a short burst
  36. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  37. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  38. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  39. EP260429a: LCO optical upper limits
  40. EP260430a: LCO optical upper limits
  41. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  42. EP260430a: Einstein Probe detection of an X-ray transient
  43. EP260429a: EP-WXT detection of a fast X-ray transient
  44. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  45. EP260416a: Mondy and Terskol optical upper limits
  46. GRB 260424B: COLIBRÍ optical upper limit
  47. EP260321a: Upper limits from ATCA radio observations
  48. GRB 260421B: Kilonova-Catcher optical afterglow detection
  49. EP260416a: Mondy optical observations
  50. GRB 260421B: 3.6m DOT optical observation
  51. EP260416a: ZTSh R band observations
  52. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  53. GRB 260421B: SVOM/GRM observation
  54. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  55. GRB 260421B: EP-FXT follow-up observation
  56. The EP-WXT trigger 01709260362 is likely a flaring star
  57. GOTO26djh/AT2026jpw: ATCA radio detection
  58. GRB 260421B: J-band upper limit with WINTER
  59. GRB 260421B: LCO optical counterpart detection
  60. GRB 260421B: SVOM/VT optical observations
  61. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  62. GRB 260310A: Late-time Chandra X-ray Detection
  63. EP260416a: 1.3m DFOT optical observation
  64. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  65. GRB 260421B: LCO optical afterglow confirmation
  66. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  67. GRB 260421B: TRT optical counterpart detection
  68. GRB 260421B: SVOM detection of a long burst
  69. EP260321a: VLA radio follow-up
  70. GRB 260412A: LCOGT Optical Upper Limits
  71. The EP-WXT trigger 01709260314 is likely a flaring star
  72. EP260416a: Optical follow-up observations with Kinder
  73. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  74. The EP-WXT trigger 01709260303 is likely a flaring star
  75. GRB 260417A: SVOM/GRM observation
  76. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  77. EP260417a: GROWTH-India Telescope optical upper limit
  78. EP260417b: GROWTH-India Telescope optical upper limit
  79. EP260416a: Ondrejov D50 optical detection
  80. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  81. EP260416a: GMG Optical Observation
  82. EP260416a: LCO observations confirm end of flaring phase
  83. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  84. EP260417a: TRT optical counterpart detection
  85. EP260417a: Einstein Probe detection of an X-ray transient
  86. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  87. EP260417b: Einstein Probe detection of a fast X-ray transient
  88. EP260416a: KAIT optical upper limit
  89. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  90. EP260416a: WFST optical observations and rebrightening
  91. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  92. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  93. EP260416a: COLIBRÍ optical counterpart candidate
  94. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  95. EP260416a: Einstein Probe detection of an X-ray transient
  96. GOTO26djh/AT2026jpw : MASTER OT observation
  97. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  98. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  99. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  100. EP260321a: CMO SAI J,K observations

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