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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"

21989 results found.

  1. GRB 251006A (short): Glowbug gamma-ray detection
  2. GRB 251005C: COLIBRÍ optical observations
  3. GRB 251005C: VLT/X-shooter Imaging
  4. GRB 251003A: LAST optical observations
  5. GRB 251002A: LAST optical observations
  6. GRB 251005C: AstroSat CZTI detection
  7. GRB 251005​C: Swift/UVOT Upper Limits
  8. GRB 250902A: MSU cubesats detection
  9. GRB 251005C: Enhanced Swift-XRT position
  10. GRB 251005C: GOTO optical upper limits
  11. GRB 251005C: Swift detection of a burst
  12. GRB 251002A: Mondy/AZT-33IK optical observations
  13. EP251003a: Einstein Probe detection of an X-ray transient
  14. GRB 251003A: J-band detection with WINTER
  15. GRB 251002A: NIR observations with WINTER
  16. GRB 251001B: NIR observations with WINTER
  17. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  18. GRB 251003A: Swift/UVOT Upper Limits
  19. GRB 251002A: Swift/UVOT detection
  20. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  21. GRB 251003A: Swift-XRT refined Analysis
  22. GRB 251002A: GOTO detection of optical counterpart
  23. GRB 251001C: SVOM/GRM observation
  24. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  25. GRB 251003A: Enhanced Swift-XRT position
  26. GRB 251002A: AKO Early Optical Afterglow Detection
  27. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  28. GRB 251003A: Kilonova-Catcher optical afterglow detection
  29. GRB 251002A: Swift-XRT afterglow detection
  30. GRB 251001B: AbAO optical upper limit
  31. GRB 251002A: Kilonova-Catcher optical afterglow detection
  32. GRB 251002A: AbAO optical observations
  33. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  34. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  35. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  36. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  37. GRB 251003A: LCOGT Optical Detection
  38. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  39. GRB 251003A: 1.5m OSN afterglow candidate
  40. GRB 251003A: Swift detection of a burst
  41. GRB 251003A: Fermi GBM Final Real-time Localization
  42. GRB 251002A: SAO RAS optical observations
  43. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  44. GRB 251002A: LCO optical observation
  45. GRB 251002A: SVOM/VT optical observation
  46. GRB 251002A: SVOM detection of a burst
  47. GRB 251001A: SVOM/GRM observation
  48. GRB 251001B: Swift/UVOT Detection
  49. GRB 251001B: COLIBRÍ optical observations
  50. GRB 251001B: SVOM/VT optical observation
  51. GRB 251001B: NOT optical observations
  52. GRB 251001C: Glowbug gamma-ray detection
  53. GRB 251001B: Enhanced Swift-XRT position
  54. GRB 251001B: LCOGT Optical Observations
  55. GRB 250930A: SVOM/GRM observation
  56. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  57. GRB 251001B: GOTO optical counterpart detection
  58. GRB 251001B: Swift detection of a burst
  59. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  60. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  61. GRB 250925A: MAO/AZT-22 optical observations
  62. GRB 250925A: Mondy I-band optical observations
  63. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  64. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  65. GRB 250924A: SVOM/GRM observation
  66. GRB 250925A: Swift-XRT refined Analysis
  67. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  69. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  70. GRB 250925A: Swift/UVOT Upper Limits
  71. GRB 250925A: Mondy and AbAO optical observations
  72. GRB 250925A: COLIBRÍ photometric redshift
  73. GRB 250925A: SVOM/GWAC-F60A upper limit
  74. GRB 250925A/EP250925a: EP-WXT detection
  75. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  76. GRB 250925A : MITSuME Akeno optical upper limits
  77. GRB 250925A: JinShan optical observations
  78. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  79. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  80. GRB250925A: Liverpool Telescope optical observations
  81. GRB 250925A: NOT optical afterglow candidate
  82. GRB 250925A: Leavitt Observatory optical upper limit
  83. GRB 250925A: Enhanced Swift-XRT position
  84. GRB 250925A: GROWTH-India Telescope Upper Limits
  85. GRB 250925A: Swift detection of a burst
  86. GRB 250922A: SVOM/GRM observation
  87. GRB 250924A: 1.6m Mephisto optical upper limits
  88. GRB 250924A: SAO RAS optical observations
  89. GRB 250924A: AstroSat CZTI detection
  90. GRB 250914A: AstroSat CZTI detection
  91. GRB 250920B: AstroSat CZTI detection
  92. GRB 250924A: SVOM/VT optical observation
  93. GRB 250924A: Swift/UVOT Detection
  94. GRB 250924A: Swift-XRT refined Analysis
  95. GRB 250924A: Enhanced Swift-XRT position
  96. GRB 250924A: J-band detection with WINTER
  97. GRB 250924A: GROWTH-India Telescope Upper Limits
  98. GRB 250924A: Mondy optical observations, afterglow fading
  99. GRB 250924A: Kilonova-Catcher optical afterglow detection
  100. GRB 250920C: Kilonova-Catcher optical afterglow detection

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