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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"

22092 results found.

  1. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  2. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  3. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  4. EP260321a: JinShan near-infrared observations
  5. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  6. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  7. EP260321a: Gemini-South confirmation of a supernova
  8. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  9. GRB 260310A: LBT optical observations
  10. EP260321A: Mondy optical observations
  11. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  12. Fermi GRB 260323A: Global MASTER-Net observations report
  13. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  14. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  15. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  16. EP260321a: COLIBRÍ further optical observations and brightening
  17. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  18. EP260214b: ATCA 6 GHz detection
  19. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  20. EP260321a: GOTO detection of blue variable source
  21. EP260321a: further Kinder optical observations
  22. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  23. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  24. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  25. EP260321a: SVOM/VT optical upper limit
  26. GRB 260310A: continued optical observation at Mondy
  27. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  28. EP260321a: Global MASTER-Net observations report
  29. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  30. GRB 260310A / AT 2026fgk: KAIT optical observations
  31. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  32. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  33. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  34. GRB 260310A/AT2026fgk: LBT near-infrared observations
  35. NOEMA Detection of GRB 260310A / AT 2026fgk
  36. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  37. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  38. Fermi GRB 260318A: Global MASTER-Net observations report
  39. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  40. GRB 260310A / AT 2026fgk: radio detection with the VLA
  41. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  42. GRB 260310A / AT2026fgk: LCO optical observations
  43. EP260316a: COLIBRÍ faint optical counterpart candidate
  44. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  45. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  46. EP260316a: optical upper limit with Kinder observations
  47. IceCube-260315A: COLIBRÍ optical observations
  48. EP260314a: optical upper limit with Kinder observations
  49. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  50. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  51. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  52. GRB 260310A / AT 2026fgk: iTelescope optical observations
  53. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  54. EP260314a: Global MASTER-Net observations report
  55. Fermi trigger No 795185313: Global MASTER-Net observations report
  56. IceCube Alert 260315A: Global MASTER-Net observations report
  57. GRB 260310A / AT2026fgk: SAO RAS optical observations
  58. GRB 260310A/AT2026fgk: radio detection at 15GHz
  59. GRB 260310A / AT2026fgk: TNG NIR detection
  60. GRB 260310A / AT2026fgk: OASDG optical observations
  61. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  62. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  63. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  64. Fermi GRB 260314A: Global MASTER-Net observations report
  65. Fermi GRB 260313A: Global MASTER-Net observations report
  66. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  67. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  68. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  69. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  70. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  71. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  72. GRB260310A / AT2026fgk: P200 Spectroscopy
  73. GRB 260310A: potential optical counterpart
  74. Fermi GRB 260312B: Global MASTER-Net observations report
  75. Fermi GRB 260311B: Global MASTER-Net observations report
  76. GRB 260131A/B: radio detection with the VLA
  77. EP260302a: MeerKAT radio counterpart
  78. Fermi GRB 260310B: Global MASTER-Net observations report
  79. Fermi GRB 260310A: Global MASTER-Net observations report
  80. GRB 260307B: SVOM/ECLAIRs refined analysis
  81. GRB 260208A: radio detection with the VLA
  82. GRB 260307B: possible NOT optical counterpart
  83. GRB 260307B: SVOM/VT upper limit with X band data analysis
  84. Fermi GRB 260307A: Global MASTER-Net observations report
  85. GRB260307B: GROWTH-India Telescope optical upper limit
  86. GRB 260307B: SVOM/C-GFT upper limit
  87. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  88. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 260207A: TESS Detection and Possible VLA Counterpart
  90. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  91. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  92. GRB 260303A: 1.3m DFOT optical upper limit
  93. EP260214b: ATCA 6 GHz observations
  94. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  95. GRB 260303A: SVOM/ECLAIRs refined analysis
  96. Fermi GRB 260305A: Global MASTER-Net observations report
  97. GRB 260303A: SVOM/VT optical observations
  98. GRB 260303A: J-band observations with WINTER
  99. EP260302a: Global MASTER-Net observations report
  100. Fermi GRB 260303B: Global MASTER-Net observations report

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