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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

29075 results found.

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

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