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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"

45543 results found.

  1. GRB 260310A / AT 2026fgk: KAIT optical observations
  2. GRB 260320A: NuSTAR detection of prompt emission
  3. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  4. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  5. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  6. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  7. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  8. GRB 260310A/AT2026fgk: LBT near-infrared observations
  9. NOEMA Detection of GRB 260310A / AT 2026fgk
  10. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  11. GRB 260318A: SVOM/GRM observation
  12. The EP-WXT trigger 01709258989 is likely a flaring star
  13. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  14. GRB 260318A: GECAM-B observation
  15. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  16. Fermi GRB 260318A: Global MASTER-Net observations report
  17. GRB 260318A: Fermi GBM Final Real-time Localization
  18. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  19. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  20. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  21. GRB 260310A / AT 2026fgk: radio detection with the VLA
  22. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  23. GRB 260310A / AT2026fgk: LCO optical observations
  24. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  25. GRB 260317A: Fermi GBM Final Localization
  26. GRB 260316B: GECAM-B observation
  27. GRB 260316B: SVOM/GRM observation
  28. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  29. EP260316a: COLIBRÍ faint optical counterpart candidate
  30. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  31. GRB 260316B: AstroSat CZTI detection
  32. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  33. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  34. EP260316a: Xinglong optical upper limit
  35. GRB 260316B: Fermi GBM Final Real-time Localization
  36. EP260316a: optical upper limit with Kinder observations
  37. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  38. GRB 260314A: Glowbug gamma-ray detection
  39. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  40. IceCube-260315A: COLIBRÍ optical observations
  41. EP260314a: Xinglong optical upper limit
  42. EP260314a: optical upper limit with Kinder observations
  43. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  44. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  45. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  46. GRB 260310A / AT 2026fgk: iTelescope optical observations
  47. EP260314a: COLIBRÍ optical upper limit
  48. GRID detection of GRB 260312B
  49. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  50. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  51. EP260314a: BOOTES-6/DPR optical upper limits at early times
  52. EP260314a: Global MASTER-Net observations report
  53. EP260314a: SVOM/VT optical candidate
  54. Fermi trigger No 795185313: Global MASTER-Net observations report
  55. IceCube Alert 260315A: Global MASTER-Net observations report
  56. EP260314a: Einstein Probe detection of an X-ray transient
  57. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  58. GRB 260314A: GECAM-B observation of a burst
  59. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  60. GRB 260310A / AT2026fgk: SAO RAS optical observations
  61. GRB 260310A/AT2026fgk: radio detection at 15GHz
  62. GRB 260310A / AT2026fgk: TNG NIR detection
  63. GRB 260310A / AT2026fgk: OASDG optical observations
  64. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  65. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  66. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  67. Fermi GRB 260314A: Global MASTER-Net observations report
  68. Fermi GRB 260313A: Global MASTER-Net observations report
  69. GRB 260314A: Fermi GBM Final Real-time Localization
  70. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  71. GRB 260313A: A Correction to the Fermi GBM Final Localization
  72. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  73. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  74. GRB 260310B: Insight-HXMT/HE detection
  75. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  76. GRB 260310A: NOT optical polarimetry
  77. GRB 260312B: AstroSat CZTI detection
  78. Swift BAT trigger 1500295: A solar flare
  79. GRB 260313A: Fermi GBM Final Real-time Localization
  80. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  81. Swift BAT trigger 1500287: A solar flare
  82. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  83. GRB 260308A: Insight-HXMT/HE detection
  84. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  85. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  86. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  87. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  88. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  89. GRB260310A / AT2026fgk: P200 Spectroscopy
  90. GRB 260312B: Glowbug gamma-ray detection
  91. GRB 260310A: Fermi GBM Observation
  92. GRB 260310A: potential optical counterpart
  93. Fermi GRB 260312B: Global MASTER-Net observations report
  94. Fermi GRB 260311B: Global MASTER-Net observations report
  95. Swift BAT trigger 1500148: A solar flare
  96. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  97. GRB 260312B: Fermi GBM Final Real-time Localization
  98. The EP-WXT trigger 01709258843 is not a real source
  99. GRB 260310B: GECAM-B observation of a burst
  100. Retraction of GCN 43965: GRB is actually solar flare

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