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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"

42205 results found.

  1. EP260329b: Einstein Probe detection of an X-ray transient
  2. EP260329a: Einstein Probe detection of an X-ray transient
  3. EP-WXT trigger 01709259209: TRT optical counterpart detection
  4. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  5. GRID detection of GRB 260326A
  6. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  7. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  8. EP260327a: SVOM/VT optical upper limits
  9. SMA Detection of GRB 260310A / AT 2026fgk
  10. GRB 260307B: ATCA Radio Upper Limits
  11. EP260327a: WINTER J-band upper limit
  12. EP260327a: COLIBRÍ optical upper limits
  13. GRB 260327A: AstroSat CZTI detection of a long burst
  14. EP260327a: Gemini-North optical upper limits
  15. EP260324a: GROWTH-India Telescope optical observation
  16. EP260327a: Global MASTER-Net observations report
  17. EP260327a: Einstein Probe detection of an X-ray transient
  18. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  19. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  20. The EP-WXT trigger 01709259173 is likely a flaring star
  21. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  22. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  23. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  24. GRB 260326A: Fermi GBM Detection
  25. EP260321a: JinShan near-infrared observations
  26. GRB 260325A: Fermi GBM Final Localization
  27. GRB 260326A: Fermi GBM Final Real-time Localization
  28. EP260321a: Upper limits from a neutrino search with IceCube
  29. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  30. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  31. GRID detection of GRB 260320A
  32. EP260321a: Gemini-South confirmation of a supernova
  33. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  34. GRB 260310A: LBT optical observations
  35. EP260321A: Mondy optical observations
  36. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  37. The EP-WXT trigger 01709259112 is likely a flaring star
  38. Fermi GRB 260323A: Global MASTER-Net observations report
  39. GRB 260323A: Fermi GBM Final Real-time Localization
  40. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  41. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  42. GRB 260322A: Fermi GBM Final Localization
  43. GRB 260320A: Glowbug gamma-ray detection
  44. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  45. EP260321a: COLIBRÍ further optical observations and brightening
  46. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  47. EP260214b: ATCA 6 GHz detection
  48. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  49. GRB 260321A: EP-FXT follow-up observation
  50. The EP-WXT trigger 01709259045 is likely a flaring star
  51. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  52. EP260321a: GOTO detection of blue variable source
  53. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  54. EP260321a: further Kinder optical observations
  55. GRB 260321A: SVOM/VT optical upper limits
  56. EP260321a: Las Cumbres upper limit
  57. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  58. GRB 260320A: Insight-HXMT/HE detection
  59. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  60. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  61. EP260321a: SVOM/VT optical upper limit
  62. GRB 260310A: continued optical observation at Mondy
  63. Fermi GBM Sub-Threshold Detection of GRB 260321A
  64. GRB 260321A: SVOM detection of a burst
  65. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  66. EP260321a: Global MASTER-Net observations report
  67. EP260321a: Einstein Probe detection of an X-ray transient
  68. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  69. GRB 260318A: Glowbug gamma-ray detection
  70. GRB 260310A / AT 2026fgk: KAIT optical observations
  71. GRB 260320A: NuSTAR detection of prompt emission
  72. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  73. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  74. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  75. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  76. GRB 260310A/AT2026fgk: LBT near-infrared observations
  77. NOEMA Detection of GRB 260310A / AT 2026fgk
  78. GRB 260318A: SVOM/GRM observation
  79. The EP-WXT trigger 01709258989 is likely a flaring star
  80. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  81. GRB 260318A: GECAM-B observation
  82. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  83. Fermi GRB 260318A: Global MASTER-Net observations report
  84. GRB 260318A: Fermi GBM Final Real-time Localization
  85. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  86. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  87. GRB 260310A / AT 2026fgk: radio detection with the VLA
  88. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  89. GRB 260310A / AT2026fgk: LCO optical observations
  90. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  91. GRB 260317A: Fermi GBM Final Localization
  92. GRB 260316B: GECAM-B observation
  93. GRB 260316B: SVOM/GRM observation
  94. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  95. EP260316a: COLIBRÍ faint optical counterpart candidate
  96. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  97. GRB 260316B: AstroSat CZTI detection
  98. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  99. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  100. EP260316a: Xinglong optical upper limit

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