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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"

28089 results found.

  1. IceCube Alert 260425A: Global MASTER-Net observations report
  2. Fermi trigger No 798737427: Global MASTER-Net observations report
  3. GRB 260401A: cubesat Avion detection
  4. EP260321a: Upper limits from ATCA radio observations
  5. GRB 260421B: Kilonova-Catcher optical afterglow detection
  6. The EP-WXT trigger 01709258652: Mondy optical observations
  7. EP260416a: Mondy optical observations
  8. GRB 260421B: 3.6m DOT optical observation
  9. EP260416a: ZTSh R band observations
  10. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 260421B: SVOM/GRM observation
  12. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  13. GRB 260421B: EP-FXT follow-up observation
  14. GOTO26djh/AT2026jpw: ATCA radio detection
  15. GRB 260421B: J-band upper limit with WINTER
  16. GRB 260421B: LCO optical counterpart detection
  17. GRB 260421B: Fermi GBM Observation
  18. GOTO26djh/AT2026jpw: radio detection at 15GHz
  19. GRB 260421B: SVOM/VT optical observations
  20. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  21. GRB 260310A: Late-time Chandra X-ray Detection
  22. EP260416a: 1.3m DFOT optical observation
  23. Fermi GRB 260421C: Global MASTER-Net observations report
  24. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  25. Fermi GRB 260421B: Global MASTER-Net observations report
  26. GRB 260421B: LCO optical afterglow confirmation
  27. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  28. GRB 260421B: TRT optical counterpart detection
  29. GRB 260421B: SVOM detection of a long burst
  30. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  31. Fermi GRB 260421A: Global MASTER-Net observations report
  32. EP260321a: VLA radio follow-up
  33. GRB 260412A: LCOGT Optical Upper Limits
  34. EP260416a: Optical follow-up observations with Kinder
  35. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  36. GRB 260417A: SVOM/GRM observation
  37. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  38. Fermi trigger No 798275385: Global MASTER-Net observations report
  39. EP260417a: GROWTH-India Telescope optical upper limit
  40. Fermi GRB 260417B: Global MASTER-Net observations report
  41. EP260417b: GROWTH-India Telescope optical upper limit
  42. EP260416a: Ondrejov D50 optical detection
  43. EP260417a: Global MASTER-Net observations report
  44. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  45. EP260416a: GMG Optical Observation
  46. Fermi GRB 260417A: Global MASTER-Net observations report
  47. EP260416a: LCO observations confirm end of flaring phase
  48. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  49. EP260417a: TRT optical counterpart detection
  50. EP260417a: Einstein Probe detection of an X-ray transient
  51. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  52. EP260417b: Einstein Probe detection of a fast X-ray transient
  53. EP260416a: KAIT optical upper limit
  54. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  55. EP260416a: WFST optical observations and rebrightening
  56. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  57. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  58. GRB 260415B: Glowbug gamma-ray detection
  59. GRB 260411B: Glowbug gamma-ray detection
  60. EP260416a: COLIBRÍ optical counterpart candidate
  61. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  62. EP260416a: Global MASTER-Net observations report
  63. EP260416a: Einstein Probe detection of an X-ray transient
  64. GOTO26djh/AT2026jpw : MASTER OT observation
  65. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  66. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  67. GRB 260415B: NuSTAR detection of long prompt emission
  68. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  69. Fermi trigger No 797912738: Global MASTER-Net observations report
  70. GRB 260414A: Glowbug gamma-ray detection
  71. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  72. EP260321a: CMO SAI J,K observations
  73. Fermi GRB 260413A: Global MASTER-Net observations report
  74. GRB 260410A: Glowbug gamma-ray detection of a short burst
  75. Fermi GRB 260412A: Global MASTER-Net observations report
  76. GRB 260412A: Fermi GBM Observation
  77. GRB 260411B: Fermi-LAT detection
  78. GRB 260411B: COLIBRÍ optical observations
  79. GRB 260410B: Fermi GBM Observation
  80. GRB260411B: 3.6m DOT optical observation
  81. GRB 260411A: SVOM/GRM observation
  82. GRB 260411B: SVOM/GRM observation of a long burst
  83. GRB 260409A: Insight-HXMT/HE detection
  84. GRB 260411B: Fermi GBM Detection
  85. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  86. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  87. GRB 260410A: COLIBRÍ optical upper limit
  88. EP-WXT01709259790: Optical Upper limits with kinder observations
  89. GRB 260410A: Fermi GBM Observation
  90. GRB 260410B: SVOM/GRM detection of a short faint burst
  91. EP-WXT01709259790: Xinglong optical upper limit
  92. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  93. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  94. EP260409a: COLIBRÍ optical upper limits
  95. EP260409a: Global MASTER-Net observations report
  96. EP260409a: Einstein Probe detection of an X-ray transient
  97. EP260321a: VLA radio detection
  98. GRB 260407A: Glowbug gamma-ray detection
  99. GRB 260402A: SVOM/ECLAIRs refined analysis
  100. GRB 260310A: Continued VLA Multi-frequency Radio Observations

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