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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"

26499 results found.

  1. GRB 260601B / EP260601a: AstroSat CZTI detection
  2. GRB 260527A/EP260527a: 6 GHz VLA observations
  3. GRB 260604C: Kilonova-Catcher optical afterglow detection
  4. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  5. The EP-WXT trigger 01709266798 is likely a flaring star
  6. GRB 260604C: Jinshan optical observations
  7. GRB 260604C: Fermi GBM Observation
  8. EP260602d: J-band upper limit with WINTER
  9. EP260602b: J-band upper limit with WINTER
  10. GRB 260604C: LAST detection of optical counterpart candidate
  11. GRB 260604C: SVOM detection of a long burst
  12. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  13. EP260602a: EP-FXT follow-up observation
  14. EP260603a: Einstein Probe detection of a fast X-ray transient
  15. EP260602d: Optical Upper limits with kinder observations
  16. EP260602b: Liverpool Telescope observations
  17. EP260602a: Liverpool Telescope optical upper limits
  18. EP260602b: Liverpool Telescope and LCO observations
  19. EP260602a: GTC and Liverpool Telescope optical observations
  20. GRB 260603A: EP-FXT follow-up observation
  21. EP260601a/GRB 260601B: EP-FXT follow-up observation
  22. GRB 260601B / EP260601a: Mondy optical upper limit
  23. EP260602b: EP-FXT follow-up observation
  24. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  25. GRB 260603A: Kilonova-Catcher optical upper limit
  26. GRB 260603A: SVOM/VT optical observations
  27. EP260602a: NOT NIR J-band observations
  28. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  29. EP260602d: Einstein Probe detection of a fast X-ray transient
  30. GRB 260601A: SVOM/GRM observation of a short burst
  31. EP260602c: Einstein Probe detection of a fast X-ray transient
  32. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  33. EP260602a: COLIBRÍ optical observations
  34. GRB260601B/EP260601a: NOT near-infrared observations
  35. GRB 260603A: SVOM detection of a burst
  36. EP260602b: Einstein Probe detection of a fast X-ray transient
  37. EP260602a: SVOM/VT optical candidate
  38. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  39. GRB 260601B/EP260601a: J-band upper limit with WINTER
  40. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  41. EP260530a/AT 2026nwl: KAIT optical observations
  42. GRB 260602A: Fermi GBM Final Real-time Localization
  43. EP260602a: Optical upper limits with Kinder observations
  44. EP260602a: Einstein Probe detection of a fast X-ray transient
  45. GRB 260601B/EP260601a: SVOM/VT optical observations
  46. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  47. EP260601a: Einstein Probe detection of an X-ray transient
  48. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  49. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  50. GRB 260601A: Glowbug gamma-ray detection of a short burst
  51. GRB 260531B: Glowbug gamma-ray detection
  52. GRB 260601A: Fermi GBM Observation
  53. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  54. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  55. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  56. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  57. The EP-WXT trigger 01709266272 is likely a flaring star
  58. AT2026nik: EP-FXT X-ray counterpart
  59. AT 2026nuz: COLIBRÍ optical observations
  60. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  61. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  62. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  63. EP260526a: SVOM/VT optical upper limits
  64. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  65. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  66. EP260527a/GRB 260527A: EP-FXT follow-up observation
  67. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  68. EP260526a: EP-FXT follow-up observation
  69. EP260527a: SVOM/VT optical observation
  70. EP260527a: COLIBRÍ optical detection
  71. EP260527a: Einstein Probe detection of a fast X-ray transient
  72. The EP-WXT trigger 01709266172 is likely a flaring star
  73. The EP-WXT trigger 01709266147 is likely a flaring star
  74. EP260526a: LCO optical upper limits
  75. EP260526a: Einstein Probe detection of a fast X-ray transient
  76. GRB 260525A: AstroSat CZTI detection
  77. EP260526.405: COLIBRÍ optical upper limits
  78. The EP-WXT trigger 01709266106 is not a real source
  79. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  80. EP-WXT 01709266106: NOT optical upper limits
  81. GRB 260522A: Fermi GBM Observation
  82. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  83. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  84. GRB 260519C: SVOM/GRM observation
  85. GRB 260511A: iTelescope T-75 optical detection
  86. GRB 260520B: SVOM/GRM observation
  87. Konus-Wind detection of GRB 260519C
  88. GRB 260509A: SVOM/ECLAIRs refined analysis
  89. Konus-Wind detection of GRB 260518A
  90. GRB 260518A: AstroSat CZTI detection of a long burst
  91. GRB 260421B: radio detection with the VLA
  92. GRB 260509A: CrAO ZTSh optical upper limit
  93. GRB 260516D: EP-FXT follow-up observation
  94. GRB 260516D: GOTO optical counterpart detection
  95. GRB 260516D: LCO optical observations
  96. GRB 260515A: further Liverpool Telescope observations
  97. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  98. GRB 260516D: GROWTH-India Telescope optical detection
  99. GRB 260516D: SVOM/VT optical bright candidate
  100. GRB 260515A: CrAO ZTSh BVRI optical observations

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