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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"

28046 results found.

  1. EP260602d: Optical Upper limits with kinder observations
  2. EP260602b: Liverpool Telescope observations
  3. EP260602a: Liverpool Telescope optical upper limits
  4. EP260602b: Liverpool Telescope and LCO observations
  5. EP260602a: GTC and Liverpool Telescope optical observations
  6. EP260601a/GRB 260601B: EP-FXT follow-up observation
  7. GRB 260601B / EP260601a: Mondy optical upper limit
  8. EP260602b: EP-FXT follow-up observation
  9. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  10. GRB 260603A: Kilonova-Catcher optical upper limit
  11. GRB 260603A: SVOM/VT optical observations
  12. EP260602a: NOT NIR J-band observations
  13. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  14. EP260602d: Einstein Probe detection of a fast X-ray transient
  15. Fermi trigger No 802141998: Global MASTER-Net observations report
  16. GRB 260601A: SVOM/GRM observation of a short burst
  17. EP260602c: Einstein Probe detection of a fast X-ray transient
  18. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  19. EP260602a: COLIBRÍ optical observations
  20. GRB260601B/EP260601a: NOT near-infrared observations
  21. SVOM GRB260603.23: Global MASTER-Net observations report
  22. GRB 260603A: SVOM detection of a burst
  23. EP260602b: Einstein Probe detection of a fast X-ray transient
  24. Fermi GRB 260602B: Global MASTER-Net observations report
  25. Fermi GRB 260602B: Global MASTER-Net observations report
  26. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  27. EP260602a: SVOM/VT optical candidate
  28. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  29. GRB 260601B/EP260601a: J-band upper limit with WINTER
  30. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  31. EP260530a/AT 2026nwl: KAIT optical observations
  32. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  33. EP260602a: Optical upper limits with Kinder observations
  34. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  35. EP260602a: Einstein Probe detection of a fast X-ray transient
  36. GRB 260601B/EP260601a: SVOM/VT optical observations
  37. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  38. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  39. EP260601a: Einstein Probe detection of an X-ray transient
  40. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  41. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  42. GRB 260601A: Glowbug gamma-ray detection of a short burst
  43. GRB 260531B: Glowbug gamma-ray detection
  44. GRB 260601A: Fermi GBM Observation
  45. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  46. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  47. Fermi GRB 260601A: Global MASTER-Net observations report
  48. GRB 260601A: Fermi GBM Final Real-time Localization
  49. The EP-WXT trigger 01709266272 is likely a flaring star
  50. AT2026nik: EP-FXT X-ray counterpart
  51. Fermi trigger No 801900520: Global MASTER-Net observations report
  52. GRB 260531A: MAXI/GSC detection
  53. AT 2026nuz: COLIBRÍ optical observations
  54. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  55. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  56. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  57. Fermi GRB 260529A: Global MASTER-Net observations report
  58. EP260526a: SVOM/VT optical upper limits
  59. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  60. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  61. EP260527a/GRB 260527A: EP-FXT follow-up observation
  62. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  63. EP260527a: SVOM/VT optical observation
  64. EP260527a: COLIBRÍ optical detection
  65. EP260527a: Einstein Probe detection of a fast X-ray transient
  66. Fermi trigger No 801580882: Global MASTER-Net observations report
  67. EP260526a: LCO optical upper limits
  68. EP260526a: Einstein Probe detection of a fast X-ray transient
  69. EP260526.405: COLIBRÍ optical upper limits
  70. The EP-WXT trigger 01709266106 is not a real source
  71. Fermi GRB 260526A: Global MASTER-Net observations report
  72. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  73. EP-WXT 01709266106: NOT optical upper limits
  74. Fermi GRB 260525A: Global MASTER-Net observations report
  75. GRB 260523B: AstroSat CZTI detection
  76. Fermi GRB 260523A: Global MASTER-Net observations report
  77. GRB 260522A: Fermi GBM Observation
  78. GRB 260522B: NuSTAR detection of prompt emission
  79. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  80. Fermi trigger No 801135305: Global MASTER-Net observations report
  81. Fermi GRB 260522A: Global MASTER-Net observations report
  82. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  83. GRB 260511A: iTelescope T-75 optical detection
  84. GRB 260520B: SVOM/GRM observation
  85. GRB 260411B: TERI Gamma-ray detection
  86. GRB 260407A: TERI Gamma-ray detection
  87. GRB 260307A: TERI Gamma-ray detection
  88. GRB 260225D: TERI Gamma-ray detection
  89. GRB 251118A: TERI Gamma-ray detection
  90. GRB 251113A: TERI Gamma-ray detection
  91. GRB 260428A: TERI Gamma-ray detection
  92. GRB 260519C: NuSTAR detection of prompt emission
  93. Konus-Wind detection of GRB 260518A
  94. GRB 260516D: SVOM/ECLAIRs refined analysis
  95. GRB 260421B: radio detection with the VLA
  96. GRB 260509A: CrAO ZTSh optical upper limit
  97. GRB 260516D: GOTO optical counterpart detection
  98. GRB 260516D: LCO optical observations
  99. GRB 260515A: further Liverpool Telescope observations
  100. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations

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