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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"

14803 results found.

  1. GRB 260310A / AT2026fgk: TNG NIR detection
  2. GRB 260310A / AT2026fgk: OASDG optical observations
  3. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  4. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  5. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  6. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  7. GRB 260313A: A Correction to the Fermi GBM Final Localization
  8. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  9. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  10. GRB 260310B: Insight-HXMT/HE detection
  11. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  12. GRB 260312B: AstroSat CZTI detection
  13. GRB 260308A: Insight-HXMT/HE detection
  14. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  15. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  16. GRB260310A / AT2026fgk: P200 Spectroscopy
  17. GRB 260310A: Fermi GBM Observation
  18. GRB 260310B: GECAM-B observation of a burst
  19. Retraction of GCN 43965: GRB is actually solar flare
  20. GRB 260312A: Swift detection of a burst
  21. GRB260307A: GECAM-B observation of a burst
  22. GRB 260308A: SVOM/GRM observation of a short GRB
  23. EP260306a: Mondy optical upper limit
  24. GRB 260310A: AstroSat CZTI detection of a long burst
  25. GRB 260307B: SVOM/ECLAIRs refined analysis
  26. GRB 260307B: Mephisto optical upper limits
  27. GRB 260307B: possible NOT optical counterpart
  28. GRB 260307B: SVOM/VT upper limit with X band data analysis
  29. GRB 260307B: SVOM detection of a burst
  30. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  31. GRB 260207A: TESS Detection and Possible VLA Counterpart
  32. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  33. EP260306a: Einstein Probe detection of an X-ray transient
  34. GRB 260303A: 1.3m DFOT optical upper limit
  35. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  36. GRB 260303A: SVOM/ECLAIRs refined analysis
  37. GRB 260303B: AstroSat CZTI detection
  38. GRB 260304A: AstroSat CZTI detection of a long burst
  39. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  40. GRB 260303A: SVOM/VT optical observations
  41. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  42. GRB 260228A: SVOM/ECLAIRs refined analysis
  43. GRB 260225A: SVOM/ECLAIRs refined analysis
  44. EP260302a: LCO observations
  45. EP260302a: BOOTES-7 optical counterpart detection at early times
  46. GRB 260303A: SVOM detection of a burst
  47. GRB 251130B: TERI Gamma-ray detection
  48. GRB 260208A: TERI Gamma-ray detection
  49. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. EP260227a: Mephisto optical detection
  51. GRID detection of GRB 260225D
  52. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  53. GRB 260225D: SVOM/GRM observation
  54. GRB 260225B: SVOM/GRM observation
  55. GRB 260228A: SVOM detection of a burst
  56. EP260227a: Liverpool Telescope optical observations
  57. EP260227a: COLIBRÍ optical observations
  58. EP260227a: NOT optical observations
  59. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  60. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  61. IceCube cascade alert 142200_1517143 retraction
  62. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  63. Konus-Wind detection of GRB 260226A
  64. EP260214a: VLT/FORS2 optical observations
  65. GRB 260225A: WINTER J-band upper limit
  66. GRB 260226A: COLIBRÍ optical upper limits
  67. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  68. GRB 260226A: LAST optical upper limit
  69. GRB 260226A: Fermi-LAT refined analysis
  70. GRB 260226A: AstroSat CZTI detection of bright long burst
  71. GRB 260226A: Fermi-LAT detection of a bright burst
  72. GRB 260225A: EP-FXT follow-up observation
  73. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  74. GRB 260225A: SVOM detection of a burst
  75. EP260213a: Mephisto optical upper limits
  76. sb26021801: SVOM/VT optical upper limits
  77. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  78. GRB 260223A: SVOM/GRM observation
  79. GRB 260223A: COLIBRÍ further optical observations and a brightening
  80. GRB 260223A: COLIBRÍ optical observations
  81. EP260221a: COLIBRÍ optical counterpart candidate
  82. EP260221a: EP-FXT follow-up observation
  83. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  84. GRB 260219A: AstroSat CZTI detection
  85. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  86. GRB 260219A: GECAM-B observation of a long burst
  87. SVOM alert sb26021801: LAST optical upper limit
  88. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  89. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  90. sb26021801: SVOM detection of a long faint X-ray transient
  91. EP260214b: 1.3m DFOT optical upper limit
  92. Konus-Wind detection of GRB 260212A
  93. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  94. GRB 260213A: GECAM-B observation of a short burst
  95. EP260214b: Liverpool Telescope optical observations
  96. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  97. EP260214b: Optical upper limit with Kinder observations
  98. EP260214a: Optical upper limits with Kinder observations
  99. EP260214b: DDOTI Optical Detection
  100. EP260214a: NOT optical upper limits

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