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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"

42185 results found.

  1. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  2. GRB 260429A: Fermi GBM Detection
  3. Fermi GRB 260429A: Global MASTER-Net observations report
  4. EP260430a: Global MASTER-Net observations report
  5. EP260430a: Einstein Probe detection of an X-ray transient
  6. EP260429a: EP-WXT detection of a fast X-ray transient
  7. GRB 260429A: Fermi GBM Final Real-time Localization
  8. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  9. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  10. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 260428A: AstroSat CZTI detection
  12. Fermi GRB 260428A: Global MASTER-Net observations report
  13. EP260416a: Mondy and Terskol optical upper limits
  14. GRB 260424B: Glowbug gamma-ray detection of a short burst
  15. GRB 260424B: COLIBRÍ optical upper limit
  16. Konus-Wind detection of GRB 260424B
  17. GRB 260428A: Fermi GBM Final Real-time Localization
  18. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  19. GRB 260424C: Fermi GBM Final Localization
  20. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  21. GRB 260424B: SVOM/GRM detection of a short burst
  22. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  24. IceCube Alert 260425A: Global MASTER-Net observations report
  25. Fermi trigger No 798737427: Global MASTER-Net observations report
  26. GRB 260401A: cubesat Avion detection
  27. GRB 260424A: AstroSat CZTI detection of a long burst
  28. EP260321a: Upper limits from ATCA radio observations
  29. GRB 260421B: Kilonova-Catcher optical afterglow detection
  30. GRB 260421B: Insight-HXMT/HE detection
  31. The EP-WXT trigger 01709258652: Mondy optical observations
  32. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  33. EP260416a: Mondy optical observations
  34. GRB 260421B: SVOM/ECLAIRs refined analysis
  35. GRB 260421B: 3.6m DOT optical observation
  36. EP260416a: ZTSh R band observations
  37. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  38. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  39. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  40. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  41. GRB 260419A: AstroSat CZTI detection
  42. GRB 260421B: SVOM/GRM observation
  43. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  44. GRB 260421B: EP-FXT follow-up observation
  45. The EP-WXT trigger 01709260362 is likely a flaring star
  46. GOTO26djh/AT2026jpw: ATCA radio detection
  47. GRB 260421B: J-band upper limit with WINTER
  48. GRB 260421B: LCO optical counterpart detection
  49. GRB 260421B: Fermi GBM Observation
  50. GRB 260421A: AstroSat CZTI detection
  51. GOTO26djh/AT2026jpw: radio detection at 15GHz
  52. GRB 260412A: SVOM/ECLAIRs refined analysis
  53. GRB 260421B: SVOM/VT optical observations
  54. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  55. GRB 260310A: Late-time Chandra X-ray Detection
  56. GRB 260418A: Insight-HXMT/HE detection
  57. EP260416a: 1.3m DFOT optical observation
  58. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  59. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  60. Fermi GRB 260421C: Global MASTER-Net observations report
  61. GRB 260421C: Fermi GBM Final Real-time Localization
  62. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  63. Fermi GRB 260421B: Global MASTER-Net observations report
  64. GRB 260421B: BOOTES-7 early optical afterglow detection
  65. GRB 260421B: LCO optical afterglow confirmation
  66. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  67. GRB 260421B: TRT optical counterpart detection
  68. GRB 260421B: SVOM detection of a long burst
  69. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  70. GRB 260421B: Fermi GBM Final Real-time Localization
  71. Fermi GRB 260421A: Global MASTER-Net observations report
  72. GRB 260421A: Fermi GBM Final Real-time Localization
  73. EP260321a: VLA radio follow-up
  74. GRB 260412A: LCOGT Optical Upper Limits
  75. The EP-WXT trigger 01709260314 is likely a flaring star
  76. EP260416a: Optical follow-up observations with Kinder
  77. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  78. EP-WXT trigger 01709260303: KAIT optical observations
  79. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  80. The EP-WXT trigger 01709260303 is likely a flaring star
  81. GRB 260417A: SVOM/GRM observation
  82. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  83. GRB 260419B: Fermi GBM Final Real-time Localization
  84. GRB 260419A: Fermi GBM Final Real-time Localization
  85. Fermi trigger No 798275385: Global MASTER-Net observations report
  86. EP260417a: GROWTH-India Telescope optical upper limit
  87. Fermi GRB 260417B: Global MASTER-Net observations report
  88. EP260417b: GROWTH-India Telescope optical upper limit
  89. EP260416a: Ondrejov D50 optical detection
  90. GRB 260418B: Fermi GBM Final Real-time Localization
  91. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  92. EP260417a: Global MASTER-Net observations report
  93. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  94. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  95. GRB 260418A: Fermi GBM Final Real-time Localization
  96. EP260416a: GMG Optical Observation
  97. Fermi GRB 260417A: Global MASTER-Net observations report
  98. Konus-Wind detection of GRB 260411B
  99. GRB 260417B: Fermi GBM Final Real-time Localization
  100. GRB 260417A: AstroSat CZTI detection

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