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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"

25713 results found.

  1. GRB 251003A: Fermi GBM Observation
  2. GRB 251006B: Fermi GBM Observation
  3. GRB 251007B: COLIBRÍ optical upper limit
  4. GRB 251007A: AstroSat CZTI detection
  5. GRB 250917B: iTelescope T-26 upper limit
  6. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  7. GRB 251007A: Swift-XRT refined Analysis
  8. GRB 251007A: Enhanced Swift-XRT position
  9. GRB 251007B: Swift-XRT refined Analysis
  10. GRB 251007B: Enhanced Swift-XRT position
  11. GRB 251007A: AKO Optical Upper Limit
  12. GRB 251007A: SVOM/C-GFT optical observations
  13. GRB 251005C: PRIME J-band upper limit
  14. GRB 251007A: Glowbug gamma-ray detection
  15. GRB 251007B: SVOM/C-GFT upper limit
  16. GRB 251007B: Swift detection of a burst
  17. GRB 251007A: Swift detection of a burst with an optical counterpart
  18. GRB 250702B/EP250702a: JWST/NIRCam Observations
  19. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  20. GRB 251005B: Glowbug gamma-ray detection
  21. EP251003a: LCO and VST fading optical counterpart
  22. GRB 251006B/EP251006a: EP-FXT follow-up observation
  23. GRB 251006B: SVOM/GRM observation
  24. GRB 251006B: COLIBRÍ optical upper limit
  25. GRB 251006B/EP251006a: EP-WXT detection
  26. GRB 251005C: SVOM/VT optical fading
  27. GRB 251005C: SVOM/GRM observation of a likely short GRB
  28. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  29. GRB 251006B: BALROG localization (Fermi Trigger 781473909 / GRB 251006837)
  30. GRB 251006A (short): Glowbug gamma-ray detection
  31. GRB 251005C: COLIBRÍ optical observations
  32. GRB 251005C: VLT/X-shooter Imaging
  33. GRB 251003A: LAST optical observations
  34. GRB 251002A: LAST optical observations
  35. GRB 251005​C: Swift/UVOT Upper Limits
  36. GRB 250902A: MSU cubesats detection
  37. GRB 251005C: Swift-XRT refined Analysis
  38. GRB 251005C: Enhanced Swift-XRT position
  39. GRB 251005C: Swift detection of a burst
  40. GRB 251002A: Mondy/AZT-33IK optical observations
  41. EP251003a: Einstein Probe detection of an X-ray transient
  42. GRB 251002A: NIR observations with WINTER
  43. GRB 251003A: Swift/UVOT Upper Limits
  44. GRB 251002A: Swift/UVOT detection
  45. GRB 251001A: AstroSat CZTI detection
  46. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  47. GRB 251003A: Swift-XRT refined Analysis
  48. GRB 251003A: COLIBRÍ photometric redshift
  49. GRB 251002A: Fermi GBM Observation
  50. GRB 251002A: GOTO detection of optical counterpart
  51. GRB 251001C: SVOM/GRM observation
  52. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  53. GRB 251003A: Enhanced Swift-XRT position
  54. GRB 251002A: AKO Early Optical Afterglow Detection
  55. GRB 251003A: Kilonova-Catcher optical afterglow detection
  56. GRB 251002A: Swift-XRT afterglow detection
  57. GRB 251001B: AbAO optical upper limit
  58. GRB 251002A: Kilonova-Catcher optical afterglow detection
  59. GRB 251002A: AbAO optical observations
  60. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  61. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  62. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  63. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  64. GRB 251002A: EP-FXT counterpart detection
  65. GRB 251003A: LCOGT Optical Detection
  66. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  67. GRB 251003A: Swift detection of a burst
  68. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  69. GRB 251002A: SAO RAS optical observations
  70. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  71. GRB 251002A: LCO optical observation
  72. GRB 251002A: SVOM/VT optical observation
  73. GRB 251002A: SVOM detection of a burst
  74. GRB 251001B: Swift-BAT refined analysis
  75. GRB 251001A: SVOM/GRM observation
  76. GRB 251001B: Swift/UVOT Detection
  77. GRB 251001B: COLIBRÍ optical observations
  78. GRB 251001B: Swift-XRT refined Analysis
  79. GRB 251001B: SVOM/VT optical observation
  80. GRB 251001B: NOT optical observations
  81. GRB 251001C: Glowbug gamma-ray detection
  82. GRB 251001B: Fermi GBM Observation
  83. GRB 251001B: Enhanced Swift-XRT position
  84. GRB 251001B: LCOGT Optical Observations
  85. GRB 250930A: SVOM/GRM observation
  86. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  87. GRB 251001B: Swift detection of a burst
  88. GRB 251001B: Fermi GBM Final Real-time Localization
  89. GRB 251001A: Fermi GBM Detection
  90. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  91. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  92. GRB 251001A: Fermi GBM Final Real-time Localization
  93. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  94. GRB 250925A: MAO/AZT-22 optical observations
  95. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  96. GRB 250925A: Mondy I-band optical observations
  97. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  99. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  100. Fermi-LAT Gamma-ray Observations of IceCube-250926A

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