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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"

31731 results found.

  1. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  2. GRB260310A / AT2026fgk: P200 Spectroscopy
  3. GRB 260312B: Glowbug gamma-ray detection
  4. GRB 260310A: Fermi GBM Observation
  5. GRB 260310A: potential optical counterpart
  6. Fermi GRB 260312B: Global MASTER-Net observations report
  7. Fermi GRB 260311B: Global MASTER-Net observations report
  8. GRB 260310B: GECAM-B observation of a burst
  9. Retraction of GCN 43965: GRB is actually solar flare
  10. GRB 260131A/B: radio detection with the VLA
  11. EP260302a: MeerKAT radio counterpart
  12. GRB260307A: GECAM-B observation of a burst
  13. GRB 260308A: SVOM/GRM observation of a short GRB
  14. EP260306a: Mondy optical upper limit
  15. GRB 260310A: AstroSat CZTI detection of a long burst
  16. Fermi GRB 260310B: Global MASTER-Net observations report
  17. Fermi GRB 260310A: Global MASTER-Net observations report
  18. GRB 260307B: SVOM/ECLAIRs refined analysis
  19. GRB 260208A: radio detection with the VLA
  20. GRB 260307A: Glowbug gamma-ray detection
  21. Fermi GBM Sub-Threshold Detection of GRB 260307B
  22. GRB 260307B: Mephisto optical upper limits
  23. GRB 260307B: possible NOT optical counterpart
  24. GRB 260307B: SVOM/VT upper limit with X band data analysis
  25. Fermi GRB 260307A: Global MASTER-Net observations report
  26. GRB260307B: GROWTH-India Telescope optical upper limit
  27. GRB 260307B: SVOM/VT optical candidate
  28. GRB 260307B: SVOM/C-GFT upper limit
  29. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  30. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  31. GRB 260207A: TESS Detection and Possible VLA Counterpart
  32. EP260302a: SVOM/VT optical observation
  33. EP260306a: Gemini-North redshift z = 4.773
  34. EP260306a: SVOM/VT optical observation
  35. EP260302a: Gemini-South redshift z = 1.535
  36. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  37. EP260306a: Einstein Probe detection of an X-ray transient
  38. EP260302a: Optical afterglow rebrightening
  39. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  40. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  41. GRB 260303A: 1.3m DFOT optical upper limit
  42. EP260214b: ATCA 6 GHz observations
  43. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  44. GRB 260303A: SVOM/ECLAIRs refined analysis
  45. Fermi GRB 260305A: Global MASTER-Net observations report
  46. GRB 260303B: AstroSat CZTI detection
  47. GRB 260303A: SVOM/VT optical observations
  48. GRB 260303A: J-band observations with WINTER
  49. GRB 260303B: NuSTAR detection of prompt emission
  50. EP260302a: Global MASTER-Net observations report
  51. Fermi GRB 260303B: Global MASTER-Net observations report
  52. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  53. GRB 260228A: SVOM/ECLAIRs refined analysis
  54. GRB 260225A: SVOM/ECLAIRs refined analysis
  55. EP260302a: analysis of the follow-up EP-FXT observation
  56. EP260227a: Gemini-South optical observations
  57. EP260302a: LCO observations
  58. EP260302a: BOOTES-7 optical counterpart detection at early times
  59. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  60. GRB 260228A: EP-FXT follow-up observation
  61. GRB 251130B: TERI Gamma-ray detection
  62. GRB 260208A: TERI Gamma-ray detection
  63. EP260227a: Mondy optical observations
  64. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. EP260227a: Mephisto optical detection
  66. GRID detection of GRB 260225D
  67. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  68. EP260227a: further LCO observations
  69. EP260227a: SVOM/VT optical observation
  70. GRB 260228A: SVOM/VT optical upper limits
  71. GRB 260225D: SVOM/GRM observation
  72. EP260227A: 3.6m DOT optical afterglow detection
  73. GRB 260225B: SVOM/GRM observation
  74. EP260227a: FTW optical and NIR observations
  75. EP260227a: Liverpool Telescope optical observations
  76. EP260227a: LCOGT Optical Observations
  77. GRB 260226A: Asiago r-band upper limit
  78. EP260227a: Thai National Telescope observations
  79. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  80. EP260227a: Liverpool Telescope observations
  81. EP260227a: COLIBRÍ optical observations
  82. EP260227a: NOT optical observations
  83. GRB 260225A: SVOM/VT optical continued observations and upper limit
  84. GRID detection of GRB 260223A
  85. EP260227a: Global MASTER-Net observations report
  86. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  87. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  88. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  89. Konus-Wind detection of GRB 260226A
  90. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  91. EP260214a: VLT/FORS2 optical observations
  92. GRB 260225A: WINTER J-band upper limit
  93. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  94. GRB 260226A: COLIBRÍ optical upper limits
  95. GRB 260226A: LCOGT Optical Upper Limit
  96. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  97. GRB 260226A: Glowbug gamma-ray detection
  98. GRB 260226A: NuSTAR detection of bright prompt emission
  99. GRB 260226A : GROWTH-India Telescope optical observations
  100. GRB 260226A: LAST optical upper limit

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