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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"

26901 results found.

  1. EP260306a: Gemini-North redshift z = 4.773
  2. EP260306a: SVOM/VT optical observation
  3. EP260302a: Gemini-South redshift z = 1.535
  4. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  5. EP260306a: Einstein Probe detection of an X-ray transient
  6. EP260302a: Optical afterglow rebrightening
  7. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  8. GRB 260303A: 1.3m DFOT optical upper limit
  9. Fermi GRB 260305A: Global MASTER-Net observations report
  10. GRB 260303B: AstroSat CZTI detection
  11. GRB 260303A: SVOM/VT optical observations
  12. GRB 260303A: J-band observations with WINTER
  13. GRB 260303B: NuSTAR detection of prompt emission
  14. EP260302a: Global MASTER-Net observations report
  15. Fermi GRB 260303B: Global MASTER-Net observations report
  16. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  17. EP260302a: analysis of the follow-up EP-FXT observation
  18. EP260302a: LCO observations
  19. EP260302a: BOOTES-7 optical counterpart detection at early times
  20. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  21. GRB 260303A: SVOM detection of a burst
  22. GRB 260228A: EP-FXT follow-up observation
  23. EP260302a: Einstein Probe detection of an X-ray transient
  24. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  25. GRB 251130B: TERI Gamma-ray detection
  26. GRB 260208A: TERI Gamma-ray detection
  27. EP260227a: Mondy optical observations
  28. GRB 260228A: CAHA 2.2m telescope optical upper limit
  29. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. EP260227a: Mephisto optical detection
  31. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  32. EP260227a: SVOM/VT optical observation
  33. GRB 260228A: SVOM/VT optical upper limits
  34. GRB 260225D: SVOM/GRM observation
  35. EP260227A: 3.6m DOT optical afterglow detection
  36. GRB 260225B: SVOM/GRM observation
  37. EP260227a: Liverpool Telescope optical observations
  38. EP260227a: LCOGT Optical Observations
  39. GRB 260226A: Asiago r-band upper limit
  40. EP260227a: Liverpool Telescope observations
  41. EP260227a: COLIBRÍ optical observations
  42. EP260227a: NOT optical observations
  43. EP260227a: Global MASTER-Net observations report
  44. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  45. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  46. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  47. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  48. EP260214a: VLT/FORS2 optical observations
  49. GRB 260225A: WINTER J-band upper limit
  50. GRB 260226A: COLIBRÍ optical upper limits
  51. GRB 260226A: LCOGT Optical Upper Limit
  52. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  53. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  54. GRB 260226A: Glowbug gamma-ray detection
  55. GRB 260226A: NuSTAR detection of bright prompt emission
  56. GRB 260226A : GROWTH-India Telescope optical observations
  57. GRB 260226A: LAST optical upper limit
  58. GRB 260226A: Fermi GBM observation
  59. LAT GRB260226.44: Global MASTER-Net observations report
  60. Fermi GRB 260226A: Global MASTER-Net observations report
  61. GRB 260226A: AstroSat CZTI detection of bright long burst
  62. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  63. EP260224a: LCO optical upper limits
  64. GRB 260225A: EP-FXT follow-up observation
  65. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  66. GRB 260223A: Fermi GBM Observation
  67. GRB 260225A: SVOM/VT optical upper limits
  68. EP260223a: Liverpool Telescope upper limits
  69. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  70. EP260224a: Einstein Probe detection of an X-ray transient
  71. EP 260225.148: COLIBRÍ Confirmation of flaring star
  72. EP260223a: Xinglong optical upper limit
  73. GRB 260223A: Glowbug gamma-ray detection
  74. EP260213a: Mephisto optical upper limits
  75. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  76. sb26021801: SVOM/C-GFT upper limit
  77. EP260223a: COLIBRÍ optical upper limits
  78. EP260223a: Einstein Probe detection of an X-ray transient
  79. GRB 260223A: SVOM/GRM observation
  80. GRB 260223A: COLIBRÍ further optical observations and a brightening
  81. EP260221a: Optical upper limit with Kinder observations
  82. GRB 260223A: COLIBRÍ optical observations
  83. GRB 260223A: DDOTI Optical Candidate
  84. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  85. Fermi GRB 260223A: Global MASTER-Net observations report
  86. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  87. EP260221a: COLIBRÍ optical counterpart candidate
  88. EP260221a: Gemini South z-band upper limit
  89. EP260221a: Global MASTER-Net observations report
  90. EP260221a: EP-FXT follow-up observation
  91. Fermi GRB 260221B: Global MASTER-Net observations report
  92. EP-WXT01709258519: Xinglong optical upper limit
  93. EP260221a: Xinglong optical upper limit
  94. Fermi GRB 260221A: Global MASTER-Net observations report
  95. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  96. EP260221a: GOTO optical upper limit
  97. EP260221a: COLIBRÍ optical upper limit
  98. SVOM alert sb26021801: LCO optical upper limit
  99. EP260221a: Einstein Probe detection of an X-ray transient
  100. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube

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