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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"

19043 results found.

  1. EP260306a: SVOM/VT optical observation
  2. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  3. EP260306a: Einstein Probe detection of an X-ray transient
  4. GRB 260303A: 1.3m DFOT optical upper limit
  5. GRB 260303A: SVOM/VT optical observations
  6. GRB 260303A: J-band observations with WINTER
  7. EP260302a: analysis of the follow-up EP-FXT observation
  8. EP260302a: LCO observations
  9. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  10. GRB 260303A: SVOM detection of a burst
  11. EP260302a: Einstein Probe detection of an X-ray transient
  12. EP260227a: Mondy optical observations
  13. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. EP260227a: Mephisto optical detection
  15. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  16. EP260227a: SVOM/VT optical observation
  17. GRB 260228A: SVOM/VT optical upper limits
  18. GRB 260225D: SVOM/GRM observation
  19. EP260227A: 3.6m DOT optical afterglow detection
  20. GRB 260225B: SVOM/GRM observation
  21. GRB 260228A: SVOM detection of a burst
  22. EP260227a: Liverpool Telescope optical observations
  23. EP260227a: LCOGT Optical Observations
  24. GRB 260226A: Asiago r-band upper limit
  25. EP260227a: Liverpool Telescope observations
  26. EP260227a: COLIBRÍ optical observations
  27. EP260227a: NOT optical observations
  28. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  29. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  30. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  31. EP260214a: VLT/FORS2 optical observations
  32. GRB 260225A: WINTER J-band upper limit
  33. GRB 260226A: COLIBRÍ optical upper limits
  34. GRB 260226A: LCOGT Optical Upper Limit
  35. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  36. GRB 260226A : GROWTH-India Telescope optical observations
  37. GRB 260226A: LAST optical upper limit
  38. GRB 260226A: Fermi GBM observation
  39. EP260224a: LCO optical upper limits
  40. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  41. GRB 260225A: SVOM/VT optical upper limits
  42. EP260223a: Liverpool Telescope upper limits
  43. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  44. GRB 260225A: SVOM detection of a burst
  45. EP260224a: Einstein Probe detection of an X-ray transient
  46. EP 260225.148: COLIBRÍ Confirmation of flaring star
  47. EP260223a: Xinglong optical upper limit
  48. EP260213a: Mephisto optical upper limits
  49. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  50. sb26021801: SVOM/C-GFT upper limit
  51. EP260223a: COLIBRÍ optical upper limits
  52. EP260223a: Einstein Probe detection of an X-ray transient
  53. GRB 260223A: SVOM/GRM observation
  54. GRB 260223A: COLIBRÍ further optical observations and a brightening
  55. EP260221a: Optical upper limit with Kinder observations
  56. GRB 260223A: COLIBRÍ optical observations
  57. GRB 260223A: DDOTI Optical Candidate
  58. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  59. EP260221a: COLIBRÍ optical counterpart candidate
  60. EP260221a: Gemini South z-band upper limit
  61. EP260221a: EP-FXT follow-up observation
  62. EP-WXT01709258519: Xinglong optical upper limit
  63. EP260221a: Xinglong optical upper limit
  64. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  65. EP260221a: GOTO optical upper limit
  66. EP260221a: COLIBRÍ optical upper limit
  67. SVOM alert sb26021801: LCO optical upper limit
  68. EP260221a: Einstein Probe detection of an X-ray transient
  69. SVOM alert sb26021801: LAST optical upper limit
  70. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  72. EP-WXT 01709258455: NOT optical upper limits
  73. EP260214b: Mondy optical observations
  74. EP260214b: 1.3m DFOT optical upper limit
  75. EP260210a: Mondy optical upper limits
  76. Konus-Wind detection of GRB 260212A
  77. GRB 260208A: AbAO and Terskol optical upper limits
  78. GRB 260208A: continued Mondy optical observations
  79. IPN triangulation of GRB 260212A
  80. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  81. EP260214b: Liverpool Telescope optical observations
  82. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  83. EP260214b: Optical upper limit with Kinder observations
  84. EP260214a: Optical upper limits with Kinder observations
  85. EP260214b: EP-FXT follow-up observation
  86. EP260214b: DDOTI Optical Detection
  87. EP260214b: GROWTH-India Telescope optical upper limit
  88. EP260214a: VLT near-infrared observation
  89. EP260214a: NOT optical upper limits
  90. EP260214a: COLIBRÍ optical upper limits
  91. EP260214b: OHP/T120 optical observations
  92. EP260214a: refined analysis of the EP-FXT observation
  93. EP260214b: LCO optical counterpart detection
  94. EP260214b: COLIBRÍ optical observations
  95. EP260214b: NOT optical counterpart detection
  96. EP260214b: Einstein Probe detection of a fast X-ray transient
  97. EP260214a: Einstein Probe detection of an X-ray transient
  98. EP260213a: Liverpool Telescope optical upper limits
  99. EP260213a: COLIBRÍ optical upper limits
  100. EP260213a: Optical upper limits with Kinder observations

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