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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"

44416 results found.

  1. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  2. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  3. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  4. GRB 260310A/AT2026fgk: LBT near-infrared observations
  5. NOEMA Detection of GRB 260310A / AT 2026fgk
  6. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  7. GRB 260318A: SVOM/GRM observation
  8. The EP-WXT trigger 01709258989 is likely a flaring star
  9. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  10. GRB 260318A: GECAM-B observation
  11. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  12. Fermi GRB 260318A: Global MASTER-Net observations report
  13. GRB 260318A: Fermi GBM Final Real-time Localization
  14. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  15. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  16. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  17. GRB 260310A / AT 2026fgk: radio detection with the VLA
  18. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  19. GRB 260310A / AT2026fgk: LCO optical observations
  20. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  21. GRB 260317A: Fermi GBM Final Localization
  22. GRB 260316B: GECAM-B observation
  23. GRB 260316B: SVOM/GRM observation
  24. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  25. EP260316a: COLIBRÍ faint optical counterpart candidate
  26. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  27. GRB 260316B: AstroSat CZTI detection
  28. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  29. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  30. EP260316a: Xinglong optical upper limit
  31. GRB 260316B: Fermi GBM Final Real-time Localization
  32. EP260316a: optical upper limit with Kinder observations
  33. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  34. GRB 260314A: Glowbug gamma-ray detection
  35. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  36. IceCube-260315A: COLIBRÍ optical observations
  37. EP260314a: Xinglong optical upper limit
  38. EP260314a: optical upper limit with Kinder observations
  39. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  40. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  41. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  42. GRB 260310A / AT 2026fgk: iTelescope optical observations
  43. EP260314a: COLIBRÍ optical upper limit
  44. GRID detection of GRB 260312B
  45. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  46. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  47. EP260314a: BOOTES-6/DPR optical upper limits at early times
  48. EP260314a: Global MASTER-Net observations report
  49. EP260314a: SVOM/VT optical candidate
  50. Fermi trigger No 795185313: Global MASTER-Net observations report
  51. IceCube Alert 260315A: Global MASTER-Net observations report
  52. EP260314a: Einstein Probe detection of an X-ray transient
  53. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  54. GRB 260314A: GECAM-B observation of a burst
  55. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  56. GRB 260310A / AT2026fgk: SAO RAS optical observations
  57. GRB 260310A/AT2026fgk: radio detection at 15GHz
  58. GRB 260310A / AT2026fgk: TNG NIR detection
  59. GRB 260310A / AT2026fgk: OASDG optical observations
  60. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  61. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  62. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  63. Fermi GRB 260314A: Global MASTER-Net observations report
  64. Fermi GRB 260313A: Global MASTER-Net observations report
  65. GRB 260314A: Fermi GBM Final Real-time Localization
  66. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  67. GRB 260313A: A Correction to the Fermi GBM Final Localization
  68. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  69. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  70. GRB 260310B: Insight-HXMT/HE detection
  71. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  72. GRB 260310A: NOT optical polarimetry
  73. GRB 260312B: AstroSat CZTI detection
  74. Swift BAT trigger 1500295: A solar flare
  75. GRB 260313A: Fermi GBM Final Real-time Localization
  76. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  77. Swift BAT trigger 1500287: A solar flare
  78. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  79. GRB 260308A: Insight-HXMT/HE detection
  80. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  81. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  82. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  83. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  84. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  85. GRB260310A / AT2026fgk: P200 Spectroscopy
  86. GRB 260312B: Glowbug gamma-ray detection
  87. GRB 260310A: Fermi GBM Observation
  88. GRB 260310A: potential optical counterpart
  89. Fermi GRB 260312B: Global MASTER-Net observations report
  90. Fermi GRB 260311B: Global MASTER-Net observations report
  91. Swift BAT trigger 1500148: A solar flare
  92. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  93. GRB 260312B: Fermi GBM Final Real-time Localization
  94. The EP-WXT trigger 01709258843 is not a real source
  95. GRB 260310B: GECAM-B observation of a burst
  96. Retraction of GCN 43965: GRB is actually solar flare
  97. GRB 260312A: Swift detection of a burst
  98. GRB 260311B: Fermi GBM Final Real-time Localization
  99. GRB 260131A/B: radio detection with the VLA
  100. EP260302a: MeerKAT radio counterpart

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