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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"

5039 results found.

  1. EP260514a: Global MASTER-Net observations report
  2. GRB 260513A: Fermi GBM Final Real-time Localization
  3. Konus-Wind detection of GRB 260511B
  4. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  5. GRB 260511B: SAO RAS optical observations
  6. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  7. GRB 260510C: AstroSat CZTI detection
  8. Fermi GRB 260511A: Global MASTER-Net observations report
  9. GRB 260511A: LCO optical afterglow detection
  10. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  11. GRB 260510C: MAXI/GSC detection
  12. SVOM GRB 260509A: MASTER-OAFA optical observation
  13. Fermi GRB 260510A: Global MASTER-Net observations report
  14. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  15. EP260502a is likely a flaring star
  16. GRB 260421B: radio observation with the VLA
  17. IPN triangulation of GRB 260429A
  18. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  19. GRB 260429A: SVOM/GRM observation of a short burst
  20. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  21. GRB 260424B: AstroSat CZTI detection
  22. GRB 260429A: Fermi GBM Detection
  23. GRB 260429A: Fermi GBM Final Real-time Localization
  24. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  25. GRB 260424B: Glowbug gamma-ray detection of a short burst
  26. Konus-Wind detection of GRB 260424B
  27. GRB 260424C: Fermi GBM Final Localization
  28. IPN triangulation of GRB 260424B (short)
  29. GRB 260401A: cubesat Avion detection
  30. GRB 260424A: AstroSat CZTI detection of a long burst
  31. GRB 260421B: 3.6m DOT optical observation
  32. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  33. Fermi GRB 260421C: Global MASTER-Net observations report
  34. Fermi GRB 260421B: Global MASTER-Net observations report
  35. EP260416a: Optical follow-up observations with Kinder
  36. Fermi GRB 260417B: Global MASTER-Net observations report
  37. EP260417a: Global MASTER-Net observations report
  38. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  39. Fermi GRB 260417A: Global MASTER-Net observations report
  40. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  41. GRB 260411B: COLIBRÍ optical observations
  42. EP260405a: Global MASTER-Net observations report
  43. The EP-WXT trigger 01709259621 is likely a flaring star
  44. Fermi trigger No 797039833: Global MASTER-Net observations report
  45. GRB 260401A: SVOM/GRM observation
  46. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  47. EP260329b: Mondy and Assy-Turgen optical upper limits
  48. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  49. Fermi trigger No 796485221: Global MASTER-Net observations report
  50. EP260327a: COLIBRÍ optical upper limits
  51. EP260327a: Global MASTER-Net observations report
  52. IPN triangulation of GRB 260316B
  53. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  54. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  55. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  56. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  57. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  58. Fermi GRB 260323A: Global MASTER-Net observations report
  59. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  60. IceCube-260315A: COLIBRÍ optical observations
  61. Fermi trigger No 795185313: Global MASTER-Net observations report
  62. IceCube Alert 260315A: Global MASTER-Net observations report
  63. Fermi GRB 260314A: Global MASTER-Net observations report
  64. Fermi GRB 260313A: Global MASTER-Net observations report
  65. GRB 260310A: potential optical counterpart
  66. Fermi GRB 260311B: Global MASTER-Net observations report
  67. GRB 260311B: Fermi GBM Final Real-time Localization
  68. EP260306a: Mondy optical upper limit
  69. Fermi GRB 260310B: Global MASTER-Net observations report
  70. GRB 260307B: SVOM/ECLAIRs refined analysis
  71. GRB 260208A: radio detection with the VLA
  72. GRB 260207A: TESS Detection and Possible VLA Counterpart
  73. GRB 260303B: AstroSat CZTI detection
  74. GRB 260304A: AstroSat CZTI detection of a long burst
  75. GRB 260303B: NuSTAR detection of prompt emission
  76. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  77. GRB 260303B: Fermi GBM Final Real-time Localization
  78. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  79. EP260227A: 3.6m DOT optical afterglow detection
  80. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  81. LAT GRB260226.44: Global MASTER-Net observations report
  82. EP260214a: VLA 6 GHz detection
  83. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  84. EP260126a: VLA 6 GHz detection
  85. EP260223a: Liverpool Telescope upper limits
  86. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  87. EP260223a: Xinglong optical upper limit
  88. EP260223a: EP-FXT follow-up observation
  89. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  90. EP260223a: COLIBRÍ optical upper limits
  91. GRB 260223A: SVOM/VT optical observation
  92. EP260221a: Optical upper limit with Kinder observations
  93. GRB 260223A: DDOTI Optical Candidate
  94. Fermi GRB 260223A: Global MASTER-Net observations report
  95. IceCube Alert 260217A: Global MASTER-Net observations report
  96. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  97. EP260214b: LCO optical counterpart detection
  98. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  99. GRB 260212A: GECAM-B observation
  100. GRB 260211A - SVOM/ECLAIRs refined analysis

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