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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"

26199 results found.

  1. GRB 260412A: SVOM/ECLAIRs refined analysis
  2. GRB 260421B: SVOM/VT optical observations
  3. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  4. GRB 260310A: Late-time Chandra X-ray Detection
  5. EP260416a: 1.3m DFOT optical observation
  6. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  8. Fermi GRB 260421C: Global MASTER-Net observations report
  9. GRB 260421C: Fermi GBM Final Real-time Localization
  10. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  11. Fermi GRB 260421B: Global MASTER-Net observations report
  12. GRB 260421B: LCO optical afterglow confirmation
  13. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  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. GRB 260417B: Fermi GBM Final Real-time Localization
  42. EP260416a: LCO observations confirm end of flaring phase
  43. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  44. EP260417a: TRT optical counterpart detection
  45. EP260417a: Einstein Probe detection of an X-ray transient
  46. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  47. EP260417b: Einstein Probe detection of a fast X-ray transient
  48. EP-WXT trigger 01709259586: KAIT optical observations
  49. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  50. EP260416a: WFST optical observations and rebrightening
  51. GRB 260417A: Fermi GBM Final Real-time Localization
  52. EP260416a: SVOM/VT optical observation
  53. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  54. GRB 260415B: Glowbug gamma-ray detection
  55. EP260416a: COLIBRÍ optical counterpart candidate
  56. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  57. EP260416a: Global MASTER-Net observations report
  58. EP260416a: Einstein Probe detection of an X-ray transient
  59. GRB 260415B: NuSTAR detection of long prompt emission
  60. GRB 260415B: Fermi GBM Final Localization
  61. GRB 260415A: Fermi GBM Final Real-time Localization
  62. Fermi trigger No 797912738: Global MASTER-Net observations report
  63. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  64. GRB 260414A: Fermi GBM Final Real-time Localization
  65. The EP-WXT trigger 01709260122 is likely a flaring star
  66. Fermi GRB 260413A: Global MASTER-Net observations report
  67. GRB 260413A: Fermi GBM Final Real-time Localization
  68. GRB 260411B: GECAM-B observation of a long burst
  69. EP260321a: SVOM/VT optical observations and color changes around peak
  70. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  71. The EP-WXT trigger 01709260010 is likely a flaring star
  72. GRB 260412A: GECAM-B observation of a long burst
  73. Fermi GRB 260412A: Global MASTER-Net observations report
  74. GRB 260412A: Fermi GBM Observation
  75. GRB 260411B: Fermi-LAT detection
  76. GRB 260412A: SVOM detection of a long burst
  77. GRB 260412A: Fermi GBM Final Real-time Localization
  78. GRB 260411B: COLIBRÍ optical observations
  79. GRB 260410B: Fermi GBM Observation
  80. GRB 260411B: Ondrejov D50 optical afterglow detection
  81. GRB260411B: 3.6m DOT optical observation
  82. GRB 260411A: SVOM/GRM observation
  83. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  84. GRB 260411B: SVOM/GRM observation of a long burst
  85. GRB 260411B: Fermi GBM Detection
  86. GRB 260411B: GOTO optical counterpart candidate
  87. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  88. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  89. GRB 260411B: Fermi GBM Final Real-time Localization
  90. GRB 260411A: Fermi GBM Final Real-time Localization
  91. GRB 260410A: COLIBRÍ optical upper limit
  92. EP-WXT01709259790: Optical Upper limits with kinder observations
  93. GRB 260410A: Fermi GBM Observation
  94. GRB 260410B: SVOM/GRM detection of a short faint burst
  95. The EP-WXT trigger 01709259790 is likely a flaring star
  96. GRB 260410B: Fermi GBM Final Real-time Localization
  97. EP-WXT01709259790: Xinglong optical upper limit
  98. GRB 260410A: Fermi-LAT detection
  99. GRB 260410A: Fermi GBM Final Real-time Localization
  100. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations

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