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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"

27392 results found.

  1. GRB 251005C: SVOM/VT optical fading
  2. GRB 251005C: SVOM/GRM observation of a likely short GRB
  3. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  4. GRB 251006B: BALROG localization (Fermi Trigger 781473909 / GRB 251006837)
  5. GRB 251006A (short): Glowbug gamma-ray detection
  6. GRB 251005C: COLIBRÍ optical observations
  7. GRB 251005C: VLT/X-shooter Imaging
  8. GRB 251003A: LAST optical observations
  9. GRB 251002A: LAST optical observations
  10. GRB 251005C: Swift/UVOT Upper Limits
  11. GRB 250902A: MSU cubesats detection
  12. GRB 251005C: Swift-XRT refined Analysis
  13. GRB 251005C: Enhanced Swift-XRT position
  14. GRB 251005C: Swift detection of a burst
  15. GRB 251002A: Mondy/AZT-33IK optical observations
  16. EP251003a: Einstein Probe detection of an X-ray transient
  17. GRB 251003A: J-band detection with WINTER
  18. GRB 251002A: NIR observations with WINTER
  19. Fermi GBM Sub-Threshold Detection of GRB 250910A
  20. GRB 251003A: Swift-BAT refined analysis
  21. GRB 251001B: NIR observations with WINTER
  22. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  23. GRB 251003A: Swift/UVOT Upper Limits
  24. GRB 251002A: Swift/UVOT detection
  25. GRB 251001A: AstroSat CZTI detection
  26. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  27. GRB 251003A: Swift-XRT refined Analysis
  28. GRB 251003A: COLIBRÍ photometric redshift
  29. GRB 251002A: Fermi GBM Observation
  30. GRB 251002A: GOTO detection of optical counterpart
  31. GRB 251001C: SVOM/GRM observation
  32. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  33. GRB 251003A: Enhanced Swift-XRT position
  34. GRB 251002A: AKO Early Optical Afterglow Detection
  35. GRB 251003A: Kilonova-Catcher optical afterglow detection
  36. GRB 251002A: Swift-XRT afterglow detection
  37. GRB 251001B: AbAO optical upper limit
  38. GRB 251002A: Kilonova-Catcher optical afterglow detection
  39. GRB 251002A: AbAO optical observations
  40. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  41. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  42. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  43. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  44. GRB 251002A: EP-FXT counterpart detection
  45. GRB 251003A: LCOGT Optical Detection
  46. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  47. GRB 251003A: Swift detection of a burst
  48. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  49. GRB 251002A: SAO RAS optical observations
  50. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  51. GRB 251002A: LCO optical observation
  52. GRB 251002A: SVOM/VT optical observation
  53. GRB 251002A: SVOM detection of a burst
  54. GRB 251001B: Swift-BAT refined analysis
  55. GRB 251001A: SVOM/GRM observation
  56. GRB 251001B: Swift/UVOT Detection
  57. GRB 251001B: COLIBRÍ optical observations
  58. GRB 251001B: Swift-XRT refined Analysis
  59. GRB 251001B: SVOM/VT optical observation
  60. GRB 251001B: NOT optical observations
  61. GRB 251001C: Glowbug gamma-ray detection
  62. GRB 251001B: Fermi GBM Observation
  63. GRB 251001B: Enhanced Swift-XRT position
  64. GRB 251001B: LCOGT Optical Observations
  65. GRB 250930A: SVOM/GRM observation
  66. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  67. GRB 251001B: Swift detection of a burst
  68. GRB 251001B: Fermi GBM Final Real-time Localization
  69. GRB 251001A: Fermi GBM Detection
  70. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  71. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  72. GRB 251001A: Fermi GBM Final Real-time Localization
  73. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  74. GRB 250925A: MAO/AZT-22 optical observations
  75. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  76. GRB 250925A: Mondy I-band optical observations
  77. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  79. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  80. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  81. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  82. GRB 250924A: SVOM/GRM observation
  83. GRB 250925A: Swift-XRT refined Analysis
  84. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  86. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  88. GRB 250926A: AstroSat CZTI detection
  89. GRB 250925A: Swift-BAT refined analysis
  90. GRB 250925A: Mondy and AbAO optical observations
  91. GRB 250925A: COLIBRÍ photometric redshift
  92. GRB 250925A: SVOM/GWAC-F60A upper limit
  93. GRB 250925A/EP250925a: EP-WXT detection
  94. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  95. GRB 250925A : MITSuME Akeno optical upper limits
  96. GRB 250925A: JinShan optical observations
  97. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  98. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  99. GRB250925A: Liverpool Telescope optical observations
  100. GRB 250925A: NOT optical afterglow candidate

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