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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"
  1. GRB 251007A: AstroSat CZTI detection
  2. GRB 251006B/EP251006a: EP-FXT afterglow detection
  3. GRB 250917B: iTelescope T-26 upper limit
  4. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  5. GRB 251007B: SVOM/VT optical candidate
  6. GRB 251007A: Swift-XRT refined Analysis
  7. GRB 251007A: Enhanced Swift-XRT position
  8. GRB 251007B: Swift-XRT refined Analysis
  9. GRB 251007B: Enhanced Swift-XRT position
  10. GRB 251007A: NOT optical observations
  11. GRB 251007A: AKO Optical Upper Limit
  12. GRB 251007A: CALET Gamma-Ray Burst Monitor detection
  13. GRB 251006B: Insight-HXMT detection
  14. GRB 251007A: SVOM/C-GFT optical observations
  15. GRB 251005C: PRIME J-band upper limit
  16. Swift GRB 251007B: Global MASTER-Net observations report
  17. GRB 251007A: Glowbug gamma-ray detection
  18. GRB 251007B: SVOM/C-GFT upper limit
  19. Swift GRB 251007A: Global MASTER-Net observations report
  20. GRB 251007B: SVOM detection of a faint burst
  21. GRB 251007B: Swift detection of a burst
  22. GRB 251007A: Swift detection of a burst with an optical counterpart
  23. GRB 250702B/EP250702a: JWST/NIRCam Observations
  24. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  25. GRB 251005B: Glowbug gamma-ray detection
  26. EP251003a: LCO and VST fading optical counterpart
  27. GRB 251006B/EP251006a: SVOM/VT optical candidate
  28. GRB 251006B/EP251006a: EP-FXT follow-up observation
  29. GRB 251006B: SVOM/GRM observation
  30. GRB 251006B: COLIBRÍ optical upper limit
  31. GRB 251006B/EP251006a: EP-WXT detection
  32. GRB 251005C: SVOM/VT optical fading
  33. GRB 251005C: SVOM/GRM observation of a likely short GRB
  34. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  35. Fermi GRB 251006B: Global MASTER-Net observations report
  36. GRB 251006B: BALROG localization (Fermi Trigger 781473909 / GRB 251006837)
  37. GRB 251006B: Fermi GBM Final Real-time Localization
  38. GRB 251006A (short): Glowbug gamma-ray detection
  39. GRB 251005C: COLIBRÍ optical observations
  40. Fermi GRB 251006A: Global MASTER-Net observations report
  41. GRB 251005C: VLT/X-shooter Imaging
  42. GRB 251003A: LAST optical observations
  43. GRB 251002A: LAST optical observations
  44. GRB 251006A: Fermi GBM Final Real-time Localization
  45. GRB 251005C: SVOM/VT optical candidate
  46. GRB 251005C: AstroSat CZTI detection
  47. GRB 251005​C: Swift/UVOT Upper Limits
  48. GRB 250902A: MSU cubesats detection
  49. GRB 251005C: Swift-XRT refined Analysis
  50. GRB 251005C: Fermi GBM Observation
  51. Swift GRB 251005A: Global MASTER-Net observations report
  52. GRB 251005C: Enhanced Swift-XRT position
  53. GRB 251005C: GOTO optical upper limits
  54. Fermi trigger No 781367244: Global MASTER-Net observations report
  55. GRB 251005C: Swift detection of a burst
  56. GRB 251005B: Fermi GBM Final Real-time Localization
  57. GRB 251005A: Fermi GBM Final Localization
  58. GRB 251002A: Mondy/AZT-33IK optical observations
  59. GRB 251002A: Insight-HXMT detection
  60. GRB 251002A: Insight-HXMT detection
  61. EP251003a: Einstein Probe detection of an X-ray transient
  62. GRB 251003A: J-band detection with WINTER
  63. GRB 251002A: NIR observations with WINTER
  64. Fermi GBM Sub-Threshold Detection of GRB 250910A
  65. GRB 251003A: Swift-BAT refined analysis
  66. GRB 251001B: NIR observations with WINTER
  67. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  68. GRB 251003A: Swift/UVOT Upper Limits
  69. GRB 251002A: Swift/UVOT detection
  70. GRB 251001A: AstroSat CZTI detection
  71. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  72. GRB 251003A: Swift-XRT refined Analysis
  73. GRB 251003A: COLIBRÍ photometric redshift
  74. GRB 251003A: GOTO detection of the optical counterpart
  75. GRB 251002A: Fermi GBM Observation
  76. LIGO/Virgo/KAGRA S251003at: Retraction of GW compact binary merger candidate
  77. GRB 251002A: GOTO detection of optical counterpart
  78. GRB 251001C: SVOM/GRM observation
  79. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  80. GRB 251003A: Enhanced Swift-XRT position
  81. GRB 251002A: AKO Early Optical Afterglow Detection
  82. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  83. GRB 251003A: Kilonova-Catcher optical afterglow detection
  84. GRB 251002A: Swift-XRT afterglow detection
  85. GRB 251001B: AbAO optical upper limit
  86. GRB 251002A: Kilonova-Catcher optical afterglow detection
  87. GRB 251002A: AbAO optical observations
  88. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  89. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  90. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  91. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  92. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  93. GRB 251002A: EP-FXT counterpart detection
  94. GRB 251003A: LCOGT Optical Detection
  95. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  96. GRB 251003A: 1.5m OSN afterglow candidate
  97. GRB 251003A: Prompt enhanced Swift-XRT position
  98. GRB 251003A: Swift detection of a burst
  99. GRB 251003A: Fermi GBM Final Real-time Localization
  100. Swift GRB251003A: Global MASTER-Net observations report

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