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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"

28884 results found.

  1. The EP-WXT trigger 01709260362 is likely a flaring star
  2. GRB 260421B: J-band upper limit with WINTER
  3. GRB 260421B: LCO optical counterpart detection
  4. GRB 260421B: Fermi GBM Observation
  5. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  6. GRB 260421A: AstroSat CZTI detection
  7. GRB 260412A: SVOM/ECLAIRs refined analysis
  8. GRB 260421B: SVOM/VT optical observations
  9. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  10. GRB 260310A: Late-time Chandra X-ray Detection
  11. GRB 260418A: Insight-HXMT/HE detection
  12. EP260416a: 1.3m DFOT optical observation
  13. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  15. Fermi GRB 260421C: Global MASTER-Net observations report
  16. GRB 260421C: Fermi GBM Final Real-time Localization
  17. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  18. Fermi GRB 260421B: Global MASTER-Net observations report
  19. GRB 260421B: BOOTES-7 early optical afterglow detection
  20. GRB 260421B: LCO optical afterglow confirmation
  21. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  22. GRB 260421B: TRT optical counterpart detection
  23. GRB 260421B: SVOM detection of a long burst
  24. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  25. GRB 260421B: Fermi GBM Final Real-time Localization
  26. Fermi GRB 260421A: Global MASTER-Net observations report
  27. GRB 260421A: Fermi GBM Final Real-time Localization
  28. EP260321a: VLA radio follow-up
  29. GRB 260412A: LCOGT Optical Upper Limits
  30. The EP-WXT trigger 01709260314 is likely a flaring star
  31. EP-WXT trigger 01709260303: KAIT optical observations
  32. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  33. The EP-WXT trigger 01709260303 is likely a flaring star
  34. GRB 260417A: SVOM/GRM observation
  35. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  36. GRB 260419B: Fermi GBM Final Real-time Localization
  37. GRB 260419A: Fermi GBM Final Real-time Localization
  38. Fermi trigger No 798275385: Global MASTER-Net observations report
  39. EP260417a: GROWTH-India Telescope optical upper limit
  40. Fermi GRB 260417B: Global MASTER-Net observations report
  41. EP260417b: GROWTH-India Telescope optical upper limit
  42. EP260416a: Ondrejov D50 optical detection
  43. GRB 260418B: Fermi GBM Final Real-time Localization
  44. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  45. EP260417a: Global MASTER-Net observations report
  46. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  47. GRB 260418A: Fermi GBM Final Real-time Localization
  48. EP260416a: GMG Optical Observation
  49. Fermi GRB 260417A: Global MASTER-Net observations report
  50. Konus-Wind detection of GRB 260411B
  51. GRB 260417B: Fermi GBM Final Real-time Localization
  52. GRB 260417A: AstroSat CZTI detection
  53. IPN triangulation of GRB 260411B
  54. EP260416a: LCO observations confirm end of flaring phase
  55. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  56. EP260417a: TRT optical counterpart detection
  57. EP-WXT trigger 01709259586: KAIT optical observations
  58. GRB 260414A: Insight-HXMT/HE detection
  59. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  60. EP260416a: WFST optical observations and rebrightening
  61. GRB 260417A: Fermi GBM Final Real-time Localization
  62. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  63. GRB 260415B: Glowbug gamma-ray detection
  64. GRB 260411B: Glowbug gamma-ray detection
  65. GRB 260415A: Insight-HXMT/HE detection
  66. EP260416a: COLIBRÍ optical counterpart candidate
  67. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  68. EP260416a: Global MASTER-Net observations report
  69. GRB 260415B: NuSTAR detection of long prompt emission
  70. GRB 260415B: Fermi GBM Final Localization
  71. GRB 260415A: Fermi GBM Final Real-time Localization
  72. Fermi trigger No 797912738: Global MASTER-Net observations report
  73. GRB 260414A: Glowbug gamma-ray detection
  74. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  75. GRB 260412A: Insight-HXMT/HE detection
  76. GRB 260414A: Fermi GBM Final Real-time Localization
  77. The EP-WXT trigger 01709260122 is likely a flaring star
  78. Fermi GRB 260413A: Global MASTER-Net observations report
  79. GRB 260410A: Glowbug gamma-ray detection of a short burst
  80. GRB 260413A: Fermi GBM Final Real-time Localization
  81. GRB 260410B: Insight-HXMT/HE detection
  82. GRB 260410A: Insight-HXMT/HE detection
  83. Konus-Wind detection of GRB 260410A (short/hard)
  84. GRB 260411B: GECAM-B observation of a long burst
  85. EP260321a: SVOM/VT optical observations and color changes around peak
  86. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  87. The EP-WXT trigger 01709260010 is likely a flaring star
  88. GRB 260412A: GECAM-B observation of a long burst
  89. Fermi GRB 260412A: Global MASTER-Net observations report
  90. GRB 260412A: Fermi GBM Observation
  91. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  92. GRB 260411B: Fermi-LAT detection
  93. GRB 260412A: SVOM detection of a long burst
  94. GRB 260412A: Fermi GBM Final Real-time Localization
  95. GRB 260411B: COLIBRÍ optical observations
  96. GRB 260410B: Fermi GBM Observation
  97. GRB 260411B: Ondrejov D50 optical afterglow detection
  98. GRB260411B: 3.6m DOT optical observation
  99. GRB 260411A: SVOM/GRM observation
  100. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst

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