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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"

21787 results found.

  1. EP260329a: NOT optical counterpart candidate
  2. EP260329b: Optical follow-up with Kinder observations
  3. EP 260329b: COLIBRÍ optical observations
  4. EP260329a: Optical upper limit with Kinder observations
  5. EP260329b: LCO optical observations of the counterpart
  6. EP260329b: Einstein Probe detection of an X-ray transient
  7. EP260329a: Einstein Probe detection of an X-ray transient
  8. EP-WXT trigger 01709259209: TRT optical counterpart detection
  9. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  10. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  11. EP260327a: SVOM/VT optical upper limits
  12. EP260327a: WINTER J-band upper limit
  13. EP260327a: COLIBRÍ optical upper limits
  14. GRB 260327A: AstroSat CZTI detection of a long burst
  15. EP260327a: Gemini-North optical upper limits
  16. EP260324a: GROWTH-India Telescope optical observation
  17. EP260327a: Einstein Probe detection of an X-ray transient
  18. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  19. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  20. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  21. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  22. EP260321a: JinShan near-infrared observations
  23. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  24. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  25. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  26. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  27. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  28. EP260321a: COLIBRÍ further optical observations and brightening
  29. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  30. EP260214b: ATCA 6 GHz detection
  31. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  32. EP260321a: GOTO detection of blue variable source
  33. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  34. EP260321a: further Kinder optical observations
  35. GRB 260321A: SVOM/VT optical upper limits
  36. EP260321a: Las Cumbres upper limit
  37. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  39. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  40. EP260321a: SVOM/VT optical upper limit
  41. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  42. EP260321a: Einstein Probe detection of an X-ray transient
  43. GRB 260310A / AT 2026fgk: KAIT optical observations
  44. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  45. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  46. GRB 260318A: SVOM/GRM observation
  47. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  48. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  49. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  50. GRB 260310A / AT 2026fgk: radio detection with the VLA
  51. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  52. GRB 260310A / AT2026fgk: LCO optical observations
  53. GRB 260316B: SVOM/GRM observation
  54. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  55. EP260316a: COLIBRÍ faint optical counterpart candidate
  56. GRB 260316B: AstroSat CZTI detection
  57. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP260316a: Xinglong optical upper limit
  59. EP260316a: optical upper limit with Kinder observations
  60. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  61. IceCube-260315A: COLIBRÍ optical observations
  62. EP260314a: Xinglong optical upper limit
  63. EP260314a: optical upper limit with Kinder observations
  64. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  65. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  66. GRB 260310A / AT 2026fgk: iTelescope optical observations
  67. EP260314a: COLIBRÍ optical upper limit
  68. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  69. EP260314a: SVOM/VT optical candidate
  70. EP260314a: Einstein Probe detection of an X-ray transient
  71. GRB 260310A / AT2026fgk: SAO RAS optical observations
  72. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  73. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  74. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  75. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  76. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  77. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  78. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  79. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  80. GRB 260310A: Fermi GBM Observation
  81. GRB 260310A: potential optical counterpart
  82. GRB 260131A/B: radio detection with the VLA
  83. EP260302a: MeerKAT radio counterpart
  84. GRB 260308A: SVOM/GRM observation of a short GRB
  85. EP260306a: Mondy optical upper limit
  86. GRB 260307B: SVOM/ECLAIRs refined analysis
  87. GRB 260208A: radio detection with the VLA
  88. GRB 260307B: Mephisto optical upper limits
  89. GRB 260307B: possible NOT optical counterpart
  90. GRB 260307B: SVOM/VT upper limit with X band data analysis
  91. GRB260307B: GROWTH-India Telescope optical upper limit
  92. GRB 260307B: SVOM/VT optical candidate
  93. GRB 260307B: SVOM/C-GFT upper limit
  94. GRB 260307B: SVOM detection of a burst
  95. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  96. GRB 260207A: TESS Detection and Possible VLA Counterpart
  97. EP260302a: SVOM/VT optical observation
  98. EP260306a: SVOM/VT optical observation
  99. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  100. EP260306a: Einstein Probe detection of an X-ray transient

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