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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"

16161 results found.

  1. GRB 260303A: 1.3m DFOT optical upper limit
  2. EP260214b: ATCA 6 GHz observations
  3. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  4. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  5. GRB 260303A: SVOM/VT optical observations
  6. GRB 260303A: J-band observations with WINTER
  7. EP260227a: Gemini-South optical observations
  8. EP260302a: LCO observations
  9. EP260302a: BOOTES-7 optical counterpart detection at early times
  10. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  11. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  12. EP260227a: Mondy optical observations
  13. GRB 260228A: CAHA 2.2m telescope optical upper limit
  14. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. EP260227a: Mephisto optical detection
  16. EP260227a: further LCO observations
  17. EP260227a: SVOM/VT optical observation
  18. GRB 260228A: SVOM/VT optical upper limits
  19. GRB 260225D: SVOM/GRM observation
  20. EP260227A: 3.6m DOT optical afterglow detection
  21. GRB 260225B: SVOM/GRM observation
  22. GRB 260228A: SVOM detection of a burst
  23. EP260227a: FTW optical and NIR observations
  24. EP260227a: Liverpool Telescope optical observations
  25. EP260227a: LCOGT Optical Observations
  26. EP260227a: Thai National Telescope observations
  27. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  28. EP260227a: Liverpool Telescope observations
  29. EP260227a: COLIBRÍ optical observations
  30. EP260227a: NOT optical observations
  31. GRB 260225A: SVOM/VT optical continued observations and upper limit
  32. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  33. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  34. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  35. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  36. EP260214a: VLT/FORS2 optical observations
  37. GRB 260225A: WINTER J-band upper limit
  38. GRB 260226A: COLIBRÍ optical upper limits
  39. GRB 260226A: LCOGT Optical Upper Limit
  40. GRB 260226A : GROWTH-India Telescope optical observations
  41. GRB 260226A: LAST optical upper limit
  42. EP260224a: LCO optical upper limits
  43. GRB260225A: SVOM/ECLAIRs refined position
  44. GRB 260225A: EP-FXT follow-up observation
  45. GRB 260225A: SVOM/VT optical observation
  46. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  47. GRB 260225A: SVOM/VT optical upper limits
  48. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  49. EP260223a: Xinglong optical upper limit
  50. EP260213a: Mephisto optical upper limits
  51. sb26021801: SVOM/VT optical upper limits
  52. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  53. EP260223a: COLIBRÍ optical upper limits
  54. GRB 260223A: SVOM/VT optical observation
  55. GRB 260223A: SVOM/GRM observation
  56. GRB 260223A: COLIBRÍ further optical observations and a brightening
  57. EP260221a: Optical upper limit with Kinder observations
  58. GRB 260223A: COLIBRÍ optical observations
  59. GRB 260223A: DDOTI Optical Candidate
  60. EP260221a: COLIBRÍ optical counterpart candidate
  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. SVOM alert sb26021801: LAST optical upper limit
  69. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  70. sb26021801: SVOM detection of a long faint X-ray transient
  71. EP-WXT 01709258455: NOT optical upper limits
  72. EP260214b: Mondy optical observations
  73. EP260214b: 1.3m DFOT optical upper limit
  74. EP260210a: Mondy optical upper limits
  75. GRB 260208A: AbAO and Terskol optical upper limits
  76. GRB 260208A: continued Mondy optical observations
  77. EP260214b: Liverpool Telescope optical observations
  78. EP260214b: Optical upper limit with Kinder observations
  79. EP260214a: Optical upper limits with Kinder observations
  80. EP260214b: EP-FXT follow-up observation
  81. EP260214b: DDOTI Optical Detection
  82. EP260214b: GROWTH-India Telescope optical upper limit
  83. EP260214b: SVOM/VT optical observation
  84. EP260214a: NOT optical upper limits
  85. EP260214a: COLIBRÍ optical upper limits
  86. EP260214b: OHP/T120 optical observations
  87. EP260214b: LCO optical counterpart detection
  88. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  89. GRB 260211A: SVOM/VT optical counterpart
  90. EP260214b: COLIBRÍ optical observations
  91. EP260214a: SVOM/VT optical upper limits
  92. EP260214b: NOT optical counterpart detection
  93. EP260213a: Liverpool Telescope optical upper limits
  94. EP260213a: COLIBRÍ optical upper limits
  95. EP260213a: Optical upper limits with Kinder observations
  96. EP260213a: SVOM/VT optical upper limit
  97. EP260213a: Mondy R-band optical upper limit
  98. EP260213a: NUTTelA-TAO Early Optical Limits
  99. EP/WXT 01709258378: NOT optical upper limits
  100. GRB 260212A: SVOM/GRM observation of a long burst

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