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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"

20456 results found.

  1. EP260329b: LCO optical observations of the counterpart
  2. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  3. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  4. EP260327a: SVOM/VT optical upper limits
  5. SMA Detection of GRB 260310A / AT 2026fgk
  6. GRB 260307B: ATCA Radio Upper Limits
  7. EP260327a: WINTER J-band upper limit
  8. EP260327a: COLIBRÍ optical upper limits
  9. EP260327a: Gemini-North optical upper limits
  10. EP260324a: GROWTH-India Telescope optical observation
  11. EP260327a: Global MASTER-Net observations report
  12. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  13. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  14. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  15. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  16. EP260321a: JinShan near-infrared observations
  17. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  18. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  19. EP260321a: Gemini-South confirmation of a supernova
  20. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  21. GRB 260310A: LBT optical observations
  22. EP260321A: Mondy optical observations
  23. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  24. Fermi GRB 260323A: Global MASTER-Net observations report
  25. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  26. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  27. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  28. EP260321a: COLIBRÍ further optical observations and brightening
  29. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  30. EP260214b: ATCA 6 GHz detection
  31. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  32. EP260321a: GOTO detection of blue variable source
  33. EP260321a: further Kinder optical observations
  34. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  36. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  37. EP260321a: SVOM/VT optical upper limit
  38. GRB 260310A: continued optical observation at Mondy
  39. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  40. EP260321a: Global MASTER-Net observations report
  41. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  42. GRB 260310A / AT 2026fgk: KAIT optical observations
  43. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  44. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  45. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  46. GRB 260310A/AT2026fgk: LBT near-infrared observations
  47. NOEMA Detection of GRB 260310A / AT 2026fgk
  48. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  49. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  50. Fermi GRB 260318A: Global MASTER-Net observations report
  51. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  52. GRB 260310A / AT 2026fgk: radio detection with the VLA
  53. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  54. GRB 260310A / AT2026fgk: LCO optical observations
  55. EP260316a: COLIBRÍ faint optical counterpart candidate
  56. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  57. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP260316a: optical upper limit with Kinder observations
  59. IceCube-260315A: COLIBRÍ optical observations
  60. EP260314a: optical upper limit with Kinder observations
  61. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  62. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  63. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  64. GRB 260310A / AT 2026fgk: iTelescope optical observations
  65. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  66. EP260314a: Global MASTER-Net observations report
  67. Fermi trigger No 795185313: Global MASTER-Net observations report
  68. IceCube Alert 260315A: Global MASTER-Net observations report
  69. GRB 260310A / AT2026fgk: SAO RAS optical observations
  70. GRB 260310A/AT2026fgk: radio detection at 15GHz
  71. GRB 260310A / AT2026fgk: OASDG optical observations
  72. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  73. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  74. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  75. Fermi GRB 260314A: Global MASTER-Net observations report
  76. Fermi GRB 260313A: Global MASTER-Net observations report
  77. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  78. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  79. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  80. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  81. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  82. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  83. GRB260310A / AT2026fgk: P200 Spectroscopy
  84. GRB 260310A: potential optical counterpart
  85. Fermi GRB 260312B: Global MASTER-Net observations report
  86. Fermi GRB 260311B: Global MASTER-Net observations report
  87. GRB 260131A/B: radio detection with the VLA
  88. EP260302a: MeerKAT radio counterpart
  89. Fermi GRB 260310B: Global MASTER-Net observations report
  90. Fermi GRB 260310A: Global MASTER-Net observations report
  91. GRB 260307B: SVOM/ECLAIRs refined analysis
  92. GRB 260208A: radio detection with the VLA
  93. GRB 260307B: possible NOT optical counterpart
  94. GRB 260307B: SVOM/VT upper limit with X band data analysis
  95. Fermi GRB 260307A: Global MASTER-Net observations report
  96. GRB260307B: GROWTH-India Telescope optical upper limit
  97. GRB 260307B: SVOM/C-GFT upper limit
  98. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  99. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  100. GRB 260207A: TESS Detection and Possible VLA Counterpart

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