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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"

20967 results found.

  1. EP260329b: J-band upper limits with WINTER
  2. EP260329a: J-band upper limit with WINTER
  3. GRB 260310A: VLA Multi-frequency Radio Observations
  4. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  5. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  6. EP260329a: EP-FXT follow up observation
  7. EP260329b: Global MASTER-Net observations report
  8. Fermi trigger No 796485221: Global MASTER-Net observations report
  9. EP260329b: Optical follow-up with Kinder observations
  10. EP 260329b: COLIBRÍ optical observations
  11. EP260329a: Optical upper limit with Kinder observations
  12. EP260329b: LCO optical observations of the counterpart
  13. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  14. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  15. EP260327a: SVOM/VT optical upper limits
  16. SMA Detection of GRB 260310A / AT 2026fgk
  17. GRB 260307B: ATCA Radio Upper Limits
  18. EP260327a: WINTER J-band upper limit
  19. EP260327a: COLIBRÍ optical upper limits
  20. EP260327a: Gemini-North optical upper limits
  21. EP260324a: GROWTH-India Telescope optical observation
  22. EP260327a: Global MASTER-Net observations report
  23. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  24. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  25. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  26. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  27. EP260321a: JinShan near-infrared observations
  28. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  29. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  30. EP260321a: Gemini-South confirmation of a supernova
  31. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  32. GRB 260310A: LBT optical observations
  33. EP260321A: Mondy optical observations
  34. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  35. Fermi GRB 260323A: Global MASTER-Net observations report
  36. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  37. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  38. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  39. EP260321a: COLIBRÍ further optical observations and brightening
  40. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  41. EP260214b: ATCA 6 GHz detection
  42. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  43. EP260321a: GOTO detection of blue variable source
  44. EP260321a: further Kinder optical observations
  45. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  46. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  47. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  48. EP260321a: SVOM/VT optical upper limit
  49. GRB 260310A: continued optical observation at Mondy
  50. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  51. EP260321a: Global MASTER-Net observations report
  52. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  53. GRB 260310A / AT 2026fgk: KAIT optical observations
  54. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  55. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  56. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  57. GRB 260310A/AT2026fgk: LBT near-infrared observations
  58. NOEMA Detection of GRB 260310A / AT 2026fgk
  59. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  60. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  61. Fermi GRB 260318A: Global MASTER-Net observations report
  62. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  63. GRB 260310A / AT 2026fgk: radio detection with the VLA
  64. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  65. GRB 260310A / AT2026fgk: LCO optical observations
  66. EP260316a: COLIBRÍ faint optical counterpart candidate
  67. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  68. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  69. EP260316a: optical upper limit with Kinder observations
  70. IceCube-260315A: COLIBRÍ optical observations
  71. EP260314a: optical upper limit with Kinder observations
  72. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  73. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  74. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  75. GRB 260310A / AT 2026fgk: iTelescope optical observations
  76. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  77. EP260314a: Global MASTER-Net observations report
  78. Fermi trigger No 795185313: Global MASTER-Net observations report
  79. IceCube Alert 260315A: Global MASTER-Net observations report
  80. GRB 260310A / AT2026fgk: SAO RAS optical observations
  81. GRB 260310A/AT2026fgk: radio detection at 15GHz
  82. GRB 260310A / AT2026fgk: OASDG optical observations
  83. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  84. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  85. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  86. Fermi GRB 260314A: Global MASTER-Net observations report
  87. Fermi GRB 260313A: Global MASTER-Net observations report
  88. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  89. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  90. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  91. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  92. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  93. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  94. GRB260310A / AT2026fgk: P200 Spectroscopy
  95. GRB 260310A: potential optical counterpart
  96. Fermi GRB 260312B: Global MASTER-Net observations report
  97. Fermi GRB 260311B: Global MASTER-Net observations report
  98. GRB 260131A/B: radio detection with the VLA
  99. EP260302a: MeerKAT radio counterpart
  100. Fermi GRB 260310B: Global MASTER-Net observations report

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