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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"

41921 results found.

  1. GRB 260421B: Fermi GBM Observation
  2. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  3. GRB 260421A: AstroSat CZTI detection
  4. GOTO26djh/AT2026jpw: radio detection at 15GHz
  5. GRB 260412A: SVOM/ECLAIRs refined analysis
  6. GRB 260421B: SVOM/VT optical observations
  7. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  8. GRB 260310A: Late-time Chandra X-ray Detection
  9. GRB 260418A: Insight-HXMT/HE detection
  10. EP260416a: 1.3m DFOT optical observation
  11. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  12. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  13. Fermi GRB 260421C: Global MASTER-Net observations report
  14. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  15. Fermi GRB 260421B: Global MASTER-Net observations report
  16. GRB 260421B: BOOTES-7 early optical afterglow detection
  17. GRB 260421B: LCO optical afterglow confirmation
  18. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  19. GRB 260421B: TRT optical counterpart detection
  20. GRB 260421B: SVOM detection of a long burst
  21. Fermi GRB 260421A: Global MASTER-Net observations report
  22. EP260321a: VLA radio follow-up
  23. GRB 260412A: LCOGT Optical Upper Limits
  24. The EP-WXT trigger 01709260314 is likely a flaring star
  25. EP260416a: Optical follow-up observations with Kinder
  26. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  27. EP-WXT trigger 01709260303: KAIT optical observations
  28. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  29. The EP-WXT trigger 01709260303 is likely a flaring star
  30. GRB 260417A: SVOM/GRM observation
  31. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  32. Fermi trigger No 798275385: Global MASTER-Net observations report
  33. EP260417a: GROWTH-India Telescope optical upper limit
  34. Fermi GRB 260417B: Global MASTER-Net observations report
  35. EP260417b: GROWTH-India Telescope optical upper limit
  36. EP260416a: Ondrejov D50 optical detection
  37. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  38. EP260417a: Global MASTER-Net observations report
  39. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  40. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  41. EP260416a: GMG Optical Observation
  42. Fermi GRB 260417A: Global MASTER-Net observations report
  43. Konus-Wind detection of GRB 260411B
  44. GRB 260417A: AstroSat CZTI detection
  45. IPN triangulation of GRB 260411B
  46. EP260416a: LCO observations confirm end of flaring phase
  47. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  48. EP260417a: TRT optical counterpart detection
  49. EP260417a: Einstein Probe detection of an X-ray transient
  50. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  51. EP260417b: Einstein Probe detection of a fast X-ray transient
  52. EP-WXT trigger 01709259586: KAIT optical observations
  53. EP260416a: KAIT optical upper limit
  54. GRB 260414A: Insight-HXMT/HE detection
  55. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  56. EP260416a: WFST optical observations and rebrightening
  57. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  58. EP260416a: SVOM/VT optical observation
  59. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  60. GRB 260415B: Glowbug gamma-ray detection
  61. GRB 260411B: Glowbug gamma-ray detection
  62. GRB 260415A: Insight-HXMT/HE detection
  63. EP260416a: COLIBRÍ optical counterpart candidate
  64. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  65. EP260416a: Global MASTER-Net observations report
  66. EP260416a: Einstein Probe detection of an X-ray transient
  67. GOTO26djh/AT2026jpw : MASTER OT observation
  68. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  69. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  70. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  71. GRB 260415B: NuSTAR detection of long prompt emission
  72. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  73. Fermi trigger No 797912738: Global MASTER-Net observations report
  74. GRB 260414A: Glowbug gamma-ray detection
  75. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  76. EP260321a: CMO SAI J,K observations
  77. GRB 260412A: Insight-HXMT/HE detection
  78. The EP-WXT trigger 01709260122 is likely a flaring star
  79. Fermi GRB 260413A: Global MASTER-Net observations report
  80. GRB 260410A: Glowbug gamma-ray detection of a short burst
  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 260411B: COLIBRÍ optical observations
  95. GRB 260410B: Fermi GBM Observation
  96. GRB 260411B: Ondrejov D50 optical afterglow detection
  97. GRB260411B: 3.6m DOT optical observation
  98. GRB 260411A: SVOM/GRM observation
  99. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  100. GRB 260411B: SVOM/GRM observation of a long burst

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