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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"

28070 results found.

  1. Fermi GRB 260421C: Global MASTER-Net observations report
  2. GRB 260421C: Fermi GBM Final Real-time Localization
  3. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  4. Fermi GRB 260421B: Global MASTER-Net observations report
  5. GRB 260421B: BOOTES-7 early optical afterglow detection
  6. GRB 260421B: LCO optical afterglow confirmation
  7. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  8. GRB 260421B: TRT optical counterpart detection
  9. GRB 260421B: SVOM detection of a long burst
  10. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  11. GRB 260421B: Fermi GBM Final Real-time Localization
  12. Fermi GRB 260421A: Global MASTER-Net observations report
  13. GRB 260421A: Fermi GBM Final Real-time Localization
  14. EP260321a: VLA radio follow-up
  15. GRB 260412A: LCOGT Optical Upper Limits
  16. The EP-WXT trigger 01709260314 is likely a flaring star
  17. EP-WXT trigger 01709260303: KAIT optical observations
  18. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  19. The EP-WXT trigger 01709260303 is likely a flaring star
  20. GRB 260417A: SVOM/GRM observation
  21. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  22. GRB 260419B: Fermi GBM Final Real-time Localization
  23. GRB 260419A: Fermi GBM Final Real-time Localization
  24. Fermi trigger No 798275385: Global MASTER-Net observations report
  25. EP260417a: GROWTH-India Telescope optical upper limit
  26. Fermi GRB 260417B: Global MASTER-Net observations report
  27. EP260417b: GROWTH-India Telescope optical upper limit
  28. EP260416a: Ondrejov D50 optical detection
  29. GRB 260418B: Fermi GBM Final Real-time Localization
  30. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  31. EP260417a: Global MASTER-Net observations report
  32. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  33. GRB 260418A: Fermi GBM Final Real-time Localization
  34. EP260416a: GMG Optical Observation
  35. Fermi GRB 260417A: Global MASTER-Net observations report
  36. Konus-Wind detection of GRB 260411B
  37. GRB 260417B: Fermi GBM Final Real-time Localization
  38. GRB 260417A: AstroSat CZTI detection
  39. IPN triangulation of GRB 260411B
  40. EP260416a: LCO observations confirm end of flaring phase
  41. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  42. EP260417a: TRT optical counterpart detection
  43. EP-WXT trigger 01709259586: KAIT optical observations
  44. GRB 260414A: Insight-HXMT/HE detection
  45. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  46. EP260416a: WFST optical observations and rebrightening
  47. GRB 260417A: Fermi GBM Final Real-time Localization
  48. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  49. GRB 260415B: Glowbug gamma-ray detection
  50. GRB 260411B: Glowbug gamma-ray detection
  51. GRB 260415A: Insight-HXMT/HE detection
  52. EP260416a: COLIBRÍ optical counterpart candidate
  53. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  54. EP260416a: Global MASTER-Net observations report
  55. GRB 260415B: NuSTAR detection of long prompt emission
  56. GRB 260415B: Fermi GBM Final Localization
  57. GRB 260415A: Fermi GBM Final Real-time Localization
  58. Fermi trigger No 797912738: Global MASTER-Net observations report
  59. GRB 260414A: Glowbug gamma-ray detection
  60. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  61. GRB 260412A: Insight-HXMT/HE detection
  62. GRB 260414A: Fermi GBM Final Real-time Localization
  63. The EP-WXT trigger 01709260122 is likely a flaring star
  64. Fermi GRB 260413A: Global MASTER-Net observations report
  65. GRB 260410A: Glowbug gamma-ray detection of a short burst
  66. GRB 260413A: Fermi GBM Final Real-time Localization
  67. GRB 260410B: Insight-HXMT/HE detection
  68. GRB 260410A: Insight-HXMT/HE detection
  69. Konus-Wind detection of GRB 260410A (short/hard)
  70. GRB 260411B: GECAM-B observation of a long burst
  71. EP260321a: SVOM/VT optical observations and color changes around peak
  72. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  73. The EP-WXT trigger 01709260010 is likely a flaring star
  74. GRB 260412A: GECAM-B observation of a long burst
  75. Fermi GRB 260412A: Global MASTER-Net observations report
  76. GRB 260412A: Fermi GBM Observation
  77. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  78. GRB 260411B: Fermi-LAT detection
  79. GRB 260412A: SVOM detection of a long burst
  80. GRB 260412A: Fermi GBM Final Real-time Localization
  81. GRB 260411B: COLIBRÍ optical observations
  82. GRB 260410B: Fermi GBM Observation
  83. GRB 260411B: Ondrejov D50 optical afterglow detection
  84. GRB260411B: 3.6m DOT optical observation
  85. GRB 260411A: SVOM/GRM observation
  86. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  87. GRB 260411B: SVOM/GRM observation of a long burst
  88. GRB 260409A: Insight-HXMT/HE detection
  89. GRB 260411B: Fermi GBM Detection
  90. GRB 260411B: GOTO optical counterpart candidate
  91. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  92. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  93. GRB 260411B: Fermi GBM Final Real-time Localization
  94. GRB 260411A: Fermi GBM Final Real-time Localization
  95. GRB 260410A: COLIBRÍ optical upper limit
  96. EP-WXT01709259790: Optical Upper limits with kinder observations
  97. GRB 260410A: Fermi GBM Observation
  98. GRB 260410B: SVOM/GRM detection of a short faint burst
  99. The EP-WXT trigger 01709259790 is likely a flaring star
  100. GRB 260410B: Fermi GBM Final Real-time Localization

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