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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

38114 results found.

  1. GRB 260322A: Fermi GBM Final Localization
  2. GRB 260320A: Glowbug gamma-ray detection
  3. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  4. GRB 260321A: EP-FXT follow-up observation
  5. GRB 260321A: SVOM/VT optical upper limits
  6. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  7. GRB 260320A: Insight-HXMT/HE detection
  8. GRB 260310A: continued optical observation at Mondy
  9. Fermi GBM Sub-Threshold Detection of GRB 260321A
  10. GRB 260321A: SVOM detection of a burst
  11. EP260321a: Global MASTER-Net observations report
  12. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  13. GRB 260318A: Glowbug gamma-ray detection
  14. GRB 260310A / AT 2026fgk: KAIT optical observations
  15. GRB 260320A: NuSTAR detection of prompt emission
  16. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  17. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  18. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  19. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  20. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  21. GRB 260310A/AT2026fgk: LBT near-infrared observations
  22. NOEMA Detection of GRB 260310A / AT 2026fgk
  23. GRB 260318A: SVOM/GRM observation
  24. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  25. GRB 260318A: GECAM-B observation
  26. Fermi GRB 260318A: Global MASTER-Net observations report
  27. GRB 260318A: Fermi GBM Final Real-time Localization
  28. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  29. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  30. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  31. GRB 260310A / AT 2026fgk: radio detection with the VLA
  32. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  33. GRB 260310A / AT2026fgk: LCO optical observations
  34. GRB 260317A: Fermi GBM Final Localization
  35. GRB 260316B: GECAM-B observation
  36. GRB 260316B: SVOM/GRM observation
  37. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  38. GRB 260316B: AstroSat CZTI detection
  39. GRB 260316B: Fermi GBM Final Real-time Localization
  40. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  41. GRB 260314A: Glowbug gamma-ray detection
  42. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  43. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  44. GRB 260310A / AT 2026fgk: iTelescope optical observations
  45. GRID detection of GRB 260312B
  46. EP260314a: Global MASTER-Net observations report
  47. Fermi trigger No 795185313: Global MASTER-Net observations report
  48. IceCube Alert 260315A: Global MASTER-Net observations report
  49. GRB 260314A: GECAM-B observation of a burst
  50. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  51. GRB 260310A / AT2026fgk: SAO RAS optical observations
  52. GRB 260310A/AT2026fgk: radio detection at 15GHz
  53. GRB 260310A / AT2026fgk: TNG NIR detection
  54. GRB 260310A / AT2026fgk: OASDG optical observations
  55. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  56. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  57. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  58. Fermi GRB 260314A: Global MASTER-Net observations report
  59. Fermi GRB 260313A: Global MASTER-Net observations report
  60. GRB 260314A: Fermi GBM Final Real-time Localization
  61. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  62. GRB 260313A: A Correction to the Fermi GBM Final Localization
  63. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  64. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  65. GRB 260310B: Insight-HXMT/HE detection
  66. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  67. GRB 260310A: NOT optical polarimetry
  68. GRB 260312B: AstroSat CZTI detection
  69. Swift BAT trigger 1500295: A solar flare
  70. GRB 260313A: Fermi GBM Final Real-time Localization
  71. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  72. Swift BAT trigger 1500287: A solar flare
  73. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  74. GRB 260308A: Insight-HXMT/HE detection
  75. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  76. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  77. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  78. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  79. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  80. GRB260310A / AT2026fgk: P200 Spectroscopy
  81. GRB 260312B: Glowbug gamma-ray detection
  82. GRB 260310A: Fermi GBM Observation
  83. GRB 260310A: potential optical counterpart
  84. Fermi GRB 260312B: Global MASTER-Net observations report
  85. Fermi GRB 260311B: Global MASTER-Net observations report
  86. Swift BAT trigger 1500148: A solar flare
  87. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  88. GRB 260312B: Fermi GBM Final Real-time Localization
  89. GRB 260310B: GECAM-B observation of a burst
  90. Retraction of GCN 43965: GRB is actually solar flare
  91. GRB 260312A: Swift detection of a burst
  92. GRB 260311B: Fermi GBM Final Real-time Localization
  93. GRB 260131A/B: radio detection with the VLA
  94. GRB260307A: GECAM-B observation of a burst
  95. GRB 260308A: SVOM/GRM observation of a short GRB
  96. EP260306a: Mondy optical upper limit
  97. GRB 260310A: AstroSat CZTI detection of a long burst
  98. GRB 260311A: Fermi GBM Final Real-time Localization
  99. Fermi GRB 260310B: Global MASTER-Net observations report
  100. GRB 260310B: Fermi GBM Final Real-time Localization

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