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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"

20464 results found.

  1. GRB 260307B: possible NOT optical counterpart
  2. GRB 260307B: SVOM/VT upper limit with X band data analysis
  3. Fermi GRB 260307A: Global MASTER-Net observations report
  4. GRB260307B: GROWTH-India Telescope optical upper limit
  5. GRB 260307B: SVOM/C-GFT upper limit
  6. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  7. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  8. GRB 260207A: TESS Detection and Possible VLA Counterpart
  9. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  10. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  11. GRB 260303A: 1.3m DFOT optical upper limit
  12. EP260214b: ATCA 6 GHz observations
  13. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  14. GRB 260303A: SVOM/ECLAIRs refined analysis
  15. Fermi GRB 260305A: Global MASTER-Net observations report
  16. GRB 260303A: SVOM/VT optical observations
  17. GRB 260303A: J-band observations with WINTER
  18. EP260302a: Global MASTER-Net observations report
  19. Fermi GRB 260303B: Global MASTER-Net observations report
  20. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  21. GRB 260228A: SVOM/ECLAIRs refined analysis
  22. GRB 260225A: SVOM/ECLAIRs refined analysis
  23. EP260227a: Gemini-South optical observations
  24. EP260302a: LCO observations
  25. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  26. EP260227a: Mondy optical observations
  27. EP260227a: Mephisto optical detection
  28. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  29. EP260227a: further LCO observations
  30. EP260227A: 3.6m DOT optical afterglow detection
  31. EP260227a: FTW optical and NIR observations
  32. EP260227a: Liverpool Telescope optical observations
  33. EP260227a: LCOGT Optical Observations
  34. GRB 260226A: Asiago r-band upper limit
  35. EP260227a: Thai National Telescope observations
  36. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  37. EP260227a: Liverpool Telescope observations
  38. EP260227a: COLIBRÍ optical observations
  39. EP260227a: NOT optical observations
  40. GRB 260225A: SVOM/VT optical continued observations and upper limit
  41. EP260227a: Global MASTER-Net observations report
  42. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  43. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  44. EP260214a: VLT/FORS2 optical observations
  45. GRB 260225A: WINTER J-band upper limit
  46. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  47. GRB 260226A : GROWTH-India Telescope optical observations
  48. GRB 260226A: LAST optical upper limit
  49. LAT GRB260226.44: Global MASTER-Net observations report
  50. Fermi GRB 260226A: Global MASTER-Net observations report
  51. EP260214a: VLA 6 GHz detection
  52. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  53. EP260126a: VLA 6 GHz detection
  54. GRB 260225A: SVOM detection of a burst
  55. EP260224a: Einstein Probe detection of an X-ray transient
  56. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  57. sb26021801: SVOM/C-GFT upper limit
  58. EP260223a: Einstein Probe detection of an X-ray transient
  59. GRB 260223A: COLIBRÍ further optical observations and a brightening
  60. EP260221a: Optical upper limit with Kinder observations
  61. GRB 260223A: COLIBRÍ optical observations
  62. GRB 260223A: DDOTI Optical Candidate
  63. Fermi GRB 260223A: Global MASTER-Net observations report
  64. EP260221a: Global MASTER-Net observations report
  65. Fermi GRB 260221B: Global MASTER-Net observations report
  66. Fermi GRB 260221A: Global MASTER-Net observations report
  67. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  68. EP260221a: GOTO optical upper limit
  69. Fermi GRB 260219A: Global MASTER-Net observations report
  70. SVOM alert sb26021801: LAST optical upper limit
  71. IceCube Alert 260217A: Global MASTER-Net observations report
  72. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  73. EP-WXT 01709258455: NOT optical upper limits
  74. EP260214b: Mondy optical observations
  75. EP260214b: 1.3m DFOT optical upper limit
  76. EP260210a: Mondy optical upper limits
  77. GRB 260208A: continued Mondy optical observations
  78. EP260214b: Liverpool Telescope optical observations
  79. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  80. EP260214b: Optical upper limit with Kinder observations
  81. EP260214a: Optical upper limits with Kinder observations
  82. EP260214b: DDOTI Optical Detection
  83. EP260214b: GROWTH-India Telescope optical upper limit
  84. EP260214a: VLT near-infrared observation
  85. EP260214a: NOT optical upper limits
  86. EP260214b: OHP/T120 optical observations
  87. EP260214a: refined analysis of the EP-FXT observation
  88. EP260214b: LCO optical counterpart detection
  89. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  90. GRB 260211A: SVOM/VT optical counterpart
  91. EP260214b: COLIBRÍ optical observations
  92. EP260214a: Global MASTER-Net observations report
  93. EP260213a: Global MASTER-Net observations report
  94. EP260213a: Optical upper limits with Kinder observations
  95. EP260213a: NUTTelA-TAO Early Optical Limits
  96. EP260213a: SVOM/C-GFT upper limit
  97. EP260213a: refined analysis of the EP-FXT observation
  98. EP/WXT 01709258378: NOT optical upper limits
  99. GRB 260211A - SVOM/ECLAIRs refined analysis
  100. GRB 260204A: SVOM/ECLAIRs refined analysis

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