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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"

27323 results found.

  1. GRB 250919A: TERI gamma-ray detection
  2. EP251006a: Global MASTER-Net observations report
  3. GRB 251006A: Fermi GBM Observation
  4. GRB 251003A: Fermi GBM Observation
  5. GRB 251006B: Fermi GBM Observation
  6. GRB 251007B: COLIBRÍ optical upper limit
  7. GRB 251007A: AstroSat CZTI detection
  8. GRB 250917B: iTelescope T-26 upper limit
  9. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  10. GRB 251007A: Swift-XRT refined Analysis
  11. GRB 251007A: Enhanced Swift-XRT position
  12. GRB 251007B: Swift-XRT refined Analysis
  13. GRB 251007B: Enhanced Swift-XRT position
  14. GRB 251007A: AKO Optical Upper Limit
  15. GRB 251007A: SVOM/C-GFT optical observations
  16. GRB 251005C: PRIME J-band upper limit
  17. GRB 251007A: Glowbug gamma-ray detection
  18. GRB 251007B: SVOM/C-GFT upper limit
  19. GRB 251007B: Swift detection of a burst
  20. GRB 251007A: Swift detection of a burst with an optical counterpart
  21. GRB 250702B/EP250702a: JWST/NIRCam Observations
  22. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  23. GRB 251005B: Glowbug gamma-ray detection
  24. EP251003a: LCO and VST fading optical counterpart
  25. GRB 251006B/EP251006a: EP-FXT follow-up observation
  26. GRB 251006B: SVOM/GRM observation
  27. GRB 251006B: COLIBRÍ optical upper limit
  28. GRB 251006B/EP251006a: EP-WXT detection
  29. GRB 251005C: SVOM/VT optical fading
  30. GRB 251005C: SVOM/GRM observation of a likely short GRB
  31. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  32. GRB 251006B: BALROG localization (Fermi Trigger 781473909 / GRB 251006837)
  33. GRB 251006A (short): Glowbug gamma-ray detection
  34. GRB 251005C: COLIBRÍ optical observations
  35. GRB 251005C: VLT/X-shooter Imaging
  36. GRB 251003A: LAST optical observations
  37. GRB 251002A: LAST optical observations
  38. GRB 251005C: Swift/UVOT Upper Limits
  39. GRB 250902A: MSU cubesats detection
  40. GRB 251005C: Swift-XRT refined Analysis
  41. GRB 251005C: Enhanced Swift-XRT position
  42. GRB 251005C: Swift detection of a burst
  43. GRB 251002A: Mondy/AZT-33IK optical observations
  44. EP251003a: Einstein Probe detection of an X-ray transient
  45. GRB 251003A: J-band detection with WINTER
  46. GRB 251002A: NIR observations with WINTER
  47. Fermi GBM Sub-Threshold Detection of GRB 250910A
  48. GRB 251003A: Swift-BAT refined analysis
  49. GRB 251001B: NIR observations with WINTER
  50. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  51. GRB 251003A: Swift/UVOT Upper Limits
  52. GRB 251002A: Swift/UVOT detection
  53. GRB 251001A: AstroSat CZTI detection
  54. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  55. GRB 251003A: Swift-XRT refined Analysis
  56. GRB 251003A: COLIBRÍ photometric redshift
  57. GRB 251002A: Fermi GBM Observation
  58. GRB 251002A: GOTO detection of optical counterpart
  59. GRB 251001C: SVOM/GRM observation
  60. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  61. GRB 251003A: Enhanced Swift-XRT position
  62. GRB 251002A: AKO Early Optical Afterglow Detection
  63. GRB 251003A: Kilonova-Catcher optical afterglow detection
  64. GRB 251002A: Swift-XRT afterglow detection
  65. GRB 251001B: AbAO optical upper limit
  66. GRB 251002A: Kilonova-Catcher optical afterglow detection
  67. GRB 251002A: AbAO optical observations
  68. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  69. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  70. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  71. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  72. GRB 251002A: EP-FXT counterpart detection
  73. GRB 251003A: LCOGT Optical Detection
  74. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  75. GRB 251003A: Swift detection of a burst
  76. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  77. GRB 251002A: SAO RAS optical observations
  78. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  79. GRB 251002A: LCO optical observation
  80. GRB 251002A: SVOM/VT optical observation
  81. GRB 251002A: SVOM detection of a burst
  82. GRB 251001B: Swift-BAT refined analysis
  83. GRB 251001A: SVOM/GRM observation
  84. GRB 251001B: Swift/UVOT Detection
  85. GRB 251001B: COLIBRÍ optical observations
  86. GRB 251001B: Swift-XRT refined Analysis
  87. GRB 251001B: SVOM/VT optical observation
  88. GRB 251001B: NOT optical observations
  89. GRB 251001C: Glowbug gamma-ray detection
  90. GRB 251001B: Fermi GBM Observation
  91. GRB 251001B: Enhanced Swift-XRT position
  92. GRB 251001B: LCOGT Optical Observations
  93. GRB 250930A: SVOM/GRM observation
  94. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  95. GRB 251001B: Swift detection of a burst
  96. GRB 251001B: Fermi GBM Final Real-time Localization
  97. GRB 251001A: Fermi GBM Detection
  98. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  99. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  100. GRB 251001A: Fermi GBM Final Real-time Localization

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