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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"

28095 results found.

  1. GRB 260303B: NuSTAR detection of prompt emission
  2. EP260302a: Global MASTER-Net observations report
  3. Fermi GRB 260303B: Global MASTER-Net observations report
  4. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  5. EP260302a: analysis of the follow-up EP-FXT observation
  6. EP260302a: LCO observations
  7. EP260302a: BOOTES-7 optical counterpart detection at early times
  8. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  9. GRB 260303A: SVOM detection of a burst
  10. GRB 260228A: EP-FXT follow-up observation
  11. EP260302a: Einstein Probe detection of an X-ray transient
  12. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  13. GRB 251130B: TERI Gamma-ray detection
  14. GRB 260208A: TERI Gamma-ray detection
  15. EP260227a: Mondy optical observations
  16. GRB 260228A: CAHA 2.2m telescope optical upper limit
  17. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. EP260227a: Mephisto optical detection
  19. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  20. EP260227a: SVOM/VT optical observation
  21. GRB 260228A: SVOM/VT optical upper limits
  22. GRB 260225D: SVOM/GRM observation
  23. EP260227A: 3.6m DOT optical afterglow detection
  24. GRB 260225B: SVOM/GRM observation
  25. EP260227a: Liverpool Telescope optical observations
  26. EP260227a: LCOGT Optical Observations
  27. GRB 260226A: Asiago r-band upper limit
  28. EP260227a: Liverpool Telescope observations
  29. EP260227a: COLIBRÍ optical observations
  30. EP260227a: NOT optical observations
  31. EP260227a: Global MASTER-Net observations report
  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. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  41. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  42. GRB 260226A: Glowbug gamma-ray detection
  43. GRB 260226A: NuSTAR detection of bright prompt emission
  44. GRB 260226A : GROWTH-India Telescope optical observations
  45. GRB 260226A: LAST optical upper limit
  46. GRB 260226A: Fermi GBM observation
  47. LAT GRB260226.44: Global MASTER-Net observations report
  48. Fermi GRB 260226A: Global MASTER-Net observations report
  49. GRB 260226A: AstroSat CZTI detection of bright long burst
  50. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  51. EP260224a: LCO optical upper limits
  52. GRB 260225A: EP-FXT follow-up observation
  53. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  54. GRB 260223A: Fermi GBM Observation
  55. GRB 260225A: SVOM/VT optical upper limits
  56. EP260223a: Liverpool Telescope upper limits
  57. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  58. EP260224a: Einstein Probe detection of an X-ray transient
  59. EP 260225.148: COLIBRÍ Confirmation of flaring star
  60. EP260223a: Xinglong optical upper limit
  61. GRB 260223A: Glowbug gamma-ray detection
  62. EP260213a: Mephisto optical upper limits
  63. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  64. sb26021801: SVOM/C-GFT upper limit
  65. EP260223a: COLIBRÍ optical upper limits
  66. EP260223a: Einstein Probe detection of an X-ray transient
  67. GRB 260223A: SVOM/GRM observation
  68. GRB 260223A: COLIBRÍ further optical observations and a brightening
  69. EP260221a: Optical upper limit with Kinder observations
  70. GRB 260223A: COLIBRÍ optical observations
  71. GRB 260223A: DDOTI Optical Candidate
  72. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  73. Fermi GRB 260223A: Global MASTER-Net observations report
  74. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  75. EP260221a: COLIBRÍ optical counterpart candidate
  76. EP260221a: Gemini South z-band upper limit
  77. EP260221a: Global MASTER-Net observations report
  78. EP260221a: EP-FXT follow-up observation
  79. Fermi GRB 260221B: Global MASTER-Net observations report
  80. EP-WXT01709258519: Xinglong optical upper limit
  81. EP260221a: Xinglong optical upper limit
  82. Fermi GRB 260221A: Global MASTER-Net observations report
  83. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  84. EP260221a: GOTO optical upper limit
  85. EP260221a: COLIBRÍ optical upper limit
  86. SVOM alert sb26021801: LCO optical upper limit
  87. EP260221a: Einstein Probe detection of an X-ray transient
  88. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  89. Fermi GRB 260219A: Global MASTER-Net observations report
  90. SVOM alert sb26021801: LAST optical upper limit
  91. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. IceCube Alert 260217A: Global MASTER-Net observations report
  93. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  94. sb26021801: SVOM detection of a long faint X-ray transient
  95. EP-WXT 01709258455: NOT optical upper limits
  96. EP260214b: Mondy optical observations
  97. EP260214b: 1.3m DFOT optical upper limit
  98. EP260210a: Mondy optical upper limits
  99. GRB 260208A: AbAO and Terskol optical upper limits
  100. GRB 260208A: continued Mondy optical observations

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