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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"

26903 results found.

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

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