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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"

32531 results found.

  1. GRB 260421B: LCO optical afterglow confirmation
  2. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  3. GRB 260421B: TRT optical counterpart detection
  4. GRB 260421B: SVOM detection of a long burst
  5. Fermi GRB 260421A: Global MASTER-Net observations report
  6. EP260321a: VLA radio follow-up
  7. GRB 260412A: LCOGT Optical Upper Limits
  8. EP260416a: Optical follow-up observations with Kinder
  9. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  10. EP-WXT trigger 01709260303: KAIT optical observations
  11. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  12. GRB 260417A: SVOM/GRM observation
  13. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  14. EP260417a: GROWTH-India Telescope optical upper limit
  15. Fermi GRB 260417B: Global MASTER-Net observations report
  16. EP260417b: GROWTH-India Telescope optical upper limit
  17. EP260416a: Ondrejov D50 optical detection
  18. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  19. EP260417a: Global MASTER-Net observations report
  20. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  21. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  22. EP260416a: GMG Optical Observation
  23. Fermi GRB 260417A: Global MASTER-Net observations report
  24. Konus-Wind detection of GRB 260411B
  25. GRB 260417A: AstroSat CZTI detection
  26. IPN triangulation of GRB 260411B
  27. EP260416a: LCO observations confirm end of flaring phase
  28. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  29. EP260417a: TRT optical counterpart detection
  30. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  31. EP-WXT trigger 01709259586: KAIT optical observations
  32. EP260416a: KAIT optical upper limit
  33. GRB 260414A: Insight-HXMT/HE detection
  34. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  35. EP260416a: WFST optical observations and rebrightening
  36. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  37. EP260416a: SVOM/VT optical observation
  38. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  39. GRB 260415B: Glowbug gamma-ray detection
  40. GRB 260411B: Glowbug gamma-ray detection
  41. GRB 260415A: Insight-HXMT/HE detection
  42. EP260416a: COLIBRÍ optical counterpart candidate
  43. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  44. EP260416a: Global MASTER-Net observations report
  45. GOTO26djh/AT2026jpw : MASTER OT observation
  46. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  47. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  48. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  49. GRB 260415B: NuSTAR detection of long prompt emission
  50. GRB 260414A: Glowbug gamma-ray detection
  51. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  52. EP260321a: CMO SAI J,K observations
  53. GRB 260412A: Insight-HXMT/HE detection
  54. Fermi GRB 260413A: Global MASTER-Net observations report
  55. GRB 260410A: Glowbug gamma-ray detection of a short burst
  56. GRB 260410B: Insight-HXMT/HE detection
  57. GRB 260410A: Insight-HXMT/HE detection
  58. Konus-Wind detection of GRB 260410A (short/hard)
  59. GRB 260411B: GECAM-B observation of a long burst
  60. EP260321a: SVOM/VT optical observations and color changes around peak
  61. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  62. GRB 260412A: GECAM-B observation of a long burst
  63. Fermi GRB 260412A: Global MASTER-Net observations report
  64. GRB 260412A: Fermi GBM Observation
  65. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  66. GRB 260411B: Fermi-LAT detection
  67. GRB 260412A: SVOM detection of a long burst
  68. GRB 260411B: COLIBRÍ optical observations
  69. GRB 260410B: Fermi GBM Observation
  70. GRB 260411B: Ondrejov D50 optical afterglow detection
  71. GRB260411B: 3.6m DOT optical observation
  72. GRB 260411A: SVOM/GRM observation
  73. GRB 260411B: SVOM/GRM observation of a long burst
  74. GRB 260409A: Insight-HXMT/HE detection
  75. GRB 260411B: Fermi GBM Detection
  76. GRB 260411B: GOTO optical counterpart candidate
  77. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  78. GRB 260410A: COLIBRÍ optical upper limit
  79. EP-WXT01709259790: Optical Upper limits with kinder observations
  80. GRB 260410A: Fermi GBM Observation
  81. GRB 260410B: SVOM/GRM detection of a short faint burst
  82. GRB 260410A: Fermi-LAT detection
  83. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  84. EP260321a: Chandra X-ray Non-detection
  85. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  86. GRB 260407A: GECAM-A detection
  87. GRB 260407A: Insight-HXMT/HE detection
  88. EP260409a: SVOM/VT optical upper limits
  89. EP260409a: COLIBRÍ optical upper limits
  90. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  91. EP260409a: Global MASTER-Net observations report
  92. EP260321a: VLA radio detection
  93. GRB 260407A: Glowbug gamma-ray detection
  94. GRB 260402A: SVOM/ECLAIRs refined analysis
  95. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  96. GRB 260310A / AT2026fgk: X-ray rebrightening
  97. EP260402a / GRB 260402A: Mephisto optical upper limits
  98. EP-WXT01709259586: Xinglong optical upper limit
  99. EP260403a: Mephisto optical upper limits
  100. EP260402a/GRB 260402A: Xinglong optical upper limit

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