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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"

27329 results found.

  1. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  2. GRB 260312B: Glowbug gamma-ray detection
  3. GRB 260310A: Fermi GBM Observation
  4. GRB 260310A: potential optical counterpart
  5. Fermi GRB 260312B: Global MASTER-Net observations report
  6. Fermi GRB 260311B: Global MASTER-Net observations report
  7. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  8. GRB 260131A/B: radio detection with the VLA
  9. EP260302a: MeerKAT radio counterpart
  10. GRB 260308A: SVOM/GRM observation of a short GRB
  11. EP260306a: Mondy optical upper limit
  12. Fermi GRB 260310B: Global MASTER-Net observations report
  13. Fermi GRB 260310A: Global MASTER-Net observations report
  14. GRB 260208A: radio detection with the VLA
  15. GRB 260307A: Glowbug gamma-ray detection
  16. Fermi GBM Sub-Threshold Detection of GRB 260307B
  17. GRB 260307B: Mephisto optical upper limits
  18. GRB 260307B: possible NOT optical counterpart
  19. GRB 260307B: SVOM/VT upper limit with X band data analysis
  20. Fermi GRB 260307A: Global MASTER-Net observations report
  21. GRB260307B: GROWTH-India Telescope optical upper limit
  22. GRB 260307B: SVOM/VT optical candidate
  23. GRB 260307B: SVOM/C-GFT upper limit
  24. GRB 260307B: SVOM detection of a burst
  25. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  26. GRB 260207A: TESS Detection and Possible VLA Counterpart
  27. EP260302a: SVOM/VT optical observation
  28. EP260306a: Gemini-North redshift z = 4.773
  29. EP260306a: SVOM/VT optical observation
  30. EP260302a: Gemini-South redshift z = 1.535
  31. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  32. EP260306a: Einstein Probe detection of an X-ray transient
  33. EP260302a: Optical afterglow rebrightening
  34. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  35. GRB 260303A: 1.3m DFOT optical upper limit
  36. Fermi GRB 260305A: Global MASTER-Net observations report
  37. GRB 260303B: AstroSat CZTI detection
  38. GRB 260303A: SVOM/VT optical observations
  39. GRB 260303A: J-band observations with WINTER
  40. GRB 260303B: NuSTAR detection of prompt emission
  41. EP260302a: Global MASTER-Net observations report
  42. Fermi GRB 260303B: Global MASTER-Net observations report
  43. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  44. EP260302a: analysis of the follow-up EP-FXT observation
  45. EP260302a: LCO observations
  46. EP260302a: BOOTES-7 optical counterpart detection at early times
  47. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  48. GRB 260303A: SVOM detection of a burst
  49. GRB 260228A: EP-FXT follow-up observation
  50. EP260302a: Einstein Probe detection of an X-ray transient
  51. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  52. GRB 251130B: TERI Gamma-ray detection
  53. GRB 260208A: TERI Gamma-ray detection
  54. EP260227a: Mondy optical observations
  55. GRB 260228A: CAHA 2.2m telescope optical upper limit
  56. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  57. EP260227a: Mephisto optical detection
  58. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  59. EP260227a: SVOM/VT optical observation
  60. GRB 260228A: SVOM/VT optical upper limits
  61. GRB 260225D: SVOM/GRM observation
  62. EP260227A: 3.6m DOT optical afterglow detection
  63. GRB 260225B: SVOM/GRM observation
  64. EP260227a: Liverpool Telescope optical observations
  65. EP260227a: LCOGT Optical Observations
  66. GRB 260226A: Asiago r-band upper limit
  67. EP260227a: Liverpool Telescope observations
  68. EP260227a: COLIBRÍ optical observations
  69. EP260227a: NOT optical observations
  70. EP260227a: Global MASTER-Net observations report
  71. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  72. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  73. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  74. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  75. EP260214a: VLT/FORS2 optical observations
  76. GRB 260225A: WINTER J-band upper limit
  77. GRB 260226A: COLIBRÍ optical upper limits
  78. GRB 260226A: LCOGT Optical Upper Limit
  79. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  80. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  81. GRB 260226A: Glowbug gamma-ray detection
  82. GRB 260226A: NuSTAR detection of bright prompt emission
  83. GRB 260226A : GROWTH-India Telescope optical observations
  84. GRB 260226A: LAST optical upper limit
  85. GRB 260226A: Fermi GBM observation
  86. LAT GRB260226.44: Global MASTER-Net observations report
  87. Fermi GRB 260226A: Global MASTER-Net observations report
  88. GRB 260226A: AstroSat CZTI detection of bright long burst
  89. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  90. EP260224a: LCO optical upper limits
  91. GRB 260225A: EP-FXT follow-up observation
  92. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  93. GRB 260223A: Fermi GBM Observation
  94. GRB 260225A: SVOM/VT optical upper limits
  95. EP260223a: Liverpool Telescope upper limits
  96. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  97. EP260224a: Einstein Probe detection of an X-ray transient
  98. EP 260225.148: COLIBRÍ Confirmation of flaring star
  99. EP260223a: Xinglong optical upper limit
  100. GRB 260223A: Glowbug gamma-ray detection

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