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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"

27475 results found.

  1. GRB 260421B: J-band upper limit with WINTER
  2. GRB 260421B: LCO optical counterpart detection
  3. GRB 260421B: Fermi GBM Observation
  4. GOTO26djh/AT2026jpw: radio detection at 15GHz
  5. GRB 260421B: SVOM/VT optical observations
  6. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  7. GRB 260310A: Late-time Chandra X-ray Detection
  8. EP260416a: 1.3m DFOT optical observation
  9. Fermi GRB 260421C: Global MASTER-Net observations report
  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: TRT optical counterpart detection
  15. GRB 260421B: SVOM detection of a long burst
  16. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  17. Fermi GRB 260421A: Global MASTER-Net observations report
  18. EP260321a: VLA radio follow-up
  19. GRB 260412A: LCOGT Optical Upper Limits
  20. EP260416a: Optical follow-up observations with Kinder
  21. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  22. GRB 260417A: SVOM/GRM observation
  23. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  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. EP260417a: Global MASTER-Net observations report
  30. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  31. EP260416a: GMG Optical Observation
  32. Fermi GRB 260417A: Global MASTER-Net observations report
  33. EP260416a: LCO observations confirm end of flaring phase
  34. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  35. EP260417a: TRT optical counterpart detection
  36. EP260417a: Einstein Probe detection of an X-ray transient
  37. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260417b: Einstein Probe detection of a fast X-ray transient
  39. EP260416a: KAIT optical upper limit
  40. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  41. EP260416a: WFST optical observations and rebrightening
  42. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  43. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  44. GRB 260415B: Glowbug gamma-ray detection
  45. GRB 260411B: Glowbug gamma-ray detection
  46. EP260416a: COLIBRÍ optical counterpart candidate
  47. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  48. EP260416a: Global MASTER-Net observations report
  49. EP260416a: Einstein Probe detection of an X-ray transient
  50. GOTO26djh/AT2026jpw : MASTER OT observation
  51. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  52. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  53. GRB 260415B: NuSTAR detection of long prompt emission
  54. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  55. Fermi trigger No 797912738: Global MASTER-Net observations report
  56. GRB 260414A: Glowbug gamma-ray detection
  57. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  58. EP260321a: CMO SAI J,K observations
  59. Fermi GRB 260413A: Global MASTER-Net observations report
  60. GRB 260410A: Glowbug gamma-ray detection of a short burst
  61. Fermi GRB 260412A: Global MASTER-Net observations report
  62. GRB 260412A: Fermi GBM Observation
  63. GRB 260411B: Fermi-LAT detection
  64. GRB 260411B: COLIBRÍ optical observations
  65. GRB 260410B: Fermi GBM Observation
  66. GRB260411B: 3.6m DOT optical observation
  67. GRB 260411A: SVOM/GRM observation
  68. GRB 260411B: SVOM/GRM observation of a long burst
  69. GRB 260409A: Insight-HXMT/HE detection
  70. GRB 260411B: Fermi GBM Detection
  71. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  72. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  73. GRB 260410A: COLIBRÍ optical upper limit
  74. EP-WXT01709259790: Optical Upper limits with kinder observations
  75. GRB 260410A: Fermi GBM Observation
  76. GRB 260410B: SVOM/GRM detection of a short faint burst
  77. EP-WXT01709259790: Xinglong optical upper limit
  78. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  79. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  80. EP260409a: COLIBRÍ optical upper limits
  81. EP260409a: Global MASTER-Net observations report
  82. EP260409a: Einstein Probe detection of an X-ray transient
  83. EP260321a: VLA radio detection
  84. GRB 260407A: Glowbug gamma-ray detection
  85. GRB 260402A: SVOM/ECLAIRs refined analysis
  86. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  87. EP260402a / GRB 260402A: Mephisto optical upper limits
  88. EP-WXT01709259586: Xinglong optical upper limit
  89. EP260403a: Mephisto optical upper limits
  90. EP260402a/GRB 260402A: Xinglong optical upper limit
  91. EP260405a: GMOS-N optical upper limits
  92. EP260405a: Global MASTER-Net observations report
  93. EP260405a: Einstein Probe detection of a fast X-ray transient
  94. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  95. Fermi trigger No 797039833: Global MASTER-Net observations report
  96. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  97. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  98. The EP-WXT trigger 01709259586 is likely a flaring star
  99. GRB 260330B: SVOM/VT further optical observation
  100. EP260403a: LCO optical observations of the counterpart

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