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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"

5025 results found.

  1. EP260502a is likely a flaring star
  2. GRB 260421B: radio observation with the VLA
  3. IPN triangulation of GRB 260429A
  4. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  5. GRB 260429A: SVOM/GRM observation of a short burst
  6. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  7. GRB 260424B: AstroSat CZTI detection
  8. GRB 260429A: Fermi GBM Detection
  9. GRB 260429A: Fermi GBM Final Real-time Localization
  10. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 260424B: Glowbug gamma-ray detection of a short burst
  12. Konus-Wind detection of GRB 260424B
  13. GRB 260424C: Fermi GBM Final Localization
  14. IPN triangulation of GRB 260424B (short)
  15. GRB 260401A: cubesat Avion detection
  16. GRB 260424A: AstroSat CZTI detection of a long burst
  17. GRB 260421B: 3.6m DOT optical observation
  18. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  19. Fermi GRB 260421C: Global MASTER-Net observations report
  20. Fermi GRB 260421B: Global MASTER-Net observations report
  21. EP260416a: Optical follow-up observations with Kinder
  22. Fermi GRB 260417B: Global MASTER-Net observations report
  23. EP260417a: Global MASTER-Net observations report
  24. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  25. Fermi GRB 260417A: Global MASTER-Net observations report
  26. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  27. GRB 260411B: COLIBRÍ optical observations
  28. EP260405a: Global MASTER-Net observations report
  29. The EP-WXT trigger 01709259621 is likely a flaring star
  30. Fermi trigger No 797039833: Global MASTER-Net observations report
  31. GRB 260401A: SVOM/GRM observation
  32. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  33. EP260329b: Mondy and Assy-Turgen optical upper limits
  34. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  35. Fermi trigger No 796485221: Global MASTER-Net observations report
  36. EP260327a: COLIBRÍ optical upper limits
  37. EP260327a: Global MASTER-Net observations report
  38. IPN triangulation of GRB 260316B
  39. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  40. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  41. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  42. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  43. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  44. Fermi GRB 260323A: Global MASTER-Net observations report
  45. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  46. IceCube-260315A: COLIBRÍ optical observations
  47. Fermi trigger No 795185313: Global MASTER-Net observations report
  48. IceCube Alert 260315A: Global MASTER-Net observations report
  49. Fermi GRB 260314A: Global MASTER-Net observations report
  50. Fermi GRB 260313A: Global MASTER-Net observations report
  51. GRB 260310A: potential optical counterpart
  52. Fermi GRB 260311B: Global MASTER-Net observations report
  53. GRB 260311B: Fermi GBM Final Real-time Localization
  54. EP260306a: Mondy optical upper limit
  55. Fermi GRB 260310B: Global MASTER-Net observations report
  56. GRB 260307B: SVOM/ECLAIRs refined analysis
  57. GRB 260208A: radio detection with the VLA
  58. GRB 260207A: TESS Detection and Possible VLA Counterpart
  59. GRB 260303B: AstroSat CZTI detection
  60. GRB 260304A: AstroSat CZTI detection of a long burst
  61. GRB 260303B: NuSTAR detection of prompt emission
  62. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  63. GRB 260303B: Fermi GBM Final Real-time Localization
  64. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  65. EP260227A: 3.6m DOT optical afterglow detection
  66. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  67. LAT GRB260226.44: Global MASTER-Net observations report
  68. EP260214a: VLA 6 GHz detection
  69. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  70. EP260126a: VLA 6 GHz detection
  71. EP260223a: Liverpool Telescope upper limits
  72. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  73. EP260223a: Xinglong optical upper limit
  74. EP260223a: EP-FXT follow-up observation
  75. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  76. EP260223a: COLIBRÍ optical upper limits
  77. GRB 260223A: SVOM/VT optical observation
  78. EP260221a: Optical upper limit with Kinder observations
  79. GRB 260223A: DDOTI Optical Candidate
  80. Fermi GRB 260223A: Global MASTER-Net observations report
  81. IceCube Alert 260217A: Global MASTER-Net observations report
  82. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  83. EP260214b: LCO optical counterpart detection
  84. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  85. GRB 260212A: GECAM-B observation
  86. GRB 260211A - SVOM/ECLAIRs refined analysis
  87. GRB 260210A: SVOM/GRM observation
  88. Fermi GBM Sub-Threshold Detection of GRB 260211A
  89. GRB 260211A: SVOM detection of a burst
  90. Konus-Wind detection of GRB 260209B
  91. Konus-Wind detection of GRB 260127B
  92. EP260210a: Global MASTER-Net observations report
  93. EP260210a: refined analysis of the EP-FXT observation
  94. GRB 260208B: AstroSat CZTI detection of a bright long burst
  95. Fermi GRB 260209A: Global MASTER-Net observations report
  96. Fermi GRB 260208D: Global MASTER-Net observations report
  97. Fermi GRB 260208A: Global MASTER-Net observations report
  98. GRB 260131A/B: Mondy and Terskol optical observations
  99. GRB 260206A: Swift-XRT observations
  100. Fermi trigger No 792135758: Global MASTER-Net observations report

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