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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"

24634 results found.

  1. GRB 250129A: Swift-BAT refined analysis
  2. EP 250108A: Upper limits from Fermi-GBM Observations
  3. IPN triangulation of GRB 250204B (short/hard)
  4. IPN triangulation of GRB 250202B
  5. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  6. GRB 250204B: AstroSat CZTI detection of a short burst
  7. GRB 250129A: LCO late afterglow detection
  8. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  9. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  10. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  11. GRB 250202B: NuSTAR detection of the prompt emission
  12. GRB 250202B: Fermi GBM Detection
  13. GRB 250129a: Liverpool Telescope optical follow-up
  14. GRB 240129A: further SAO RAS optical observations
  15. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  16. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  17. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  18. GRB 250129A: SVOM/C-GFT optical observations
  19. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  20. Swift GRB250129A: MASTER 4 days observations report
  21. GRB 250129A: 1.3m DFOT Optical observations
  22. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  23. GRB 250201A: Fermi GBM Final Real-time Localization
  24. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  25. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  26. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  27. GRB 250129A: SAO RAS optical observations
  28. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  29. GRB 250129A: COLIBRÍ Optical Observations
  30. GRB 250129A: iTelescope optical observation
  31. GRB 250129a: Liverpool Telescope optical follow-up
  32. GRB 250129A: TNG NIR afterglow detection
  33. GRB 250129A: AKO Optical Afterglow Detection
  34. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  35. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  36. GRB 250128B: VLA radio upper limit
  37. Ep250125A: 1.3m DFOT optical upper limit
  38. GRB 250129A: Skynet optical observations
  39. GRB 250129A: Swift-XRT refined Analysis
  40. GRB 250128B: Gemini-North optical extended source detection
  41. GRB 250128B: TNG optical upper limit
  42. GRB 250129A: Swift/UVOT Detection
  43. GRB 250128B: VLT/HAWKI near-infrared observations
  44. GRB 250127A: CrAO and Terskol optical upper limits
  45. GRB 250129A: Enhanced Swift-XRT position
  46. GRB 250128B: NOT optical upper limit
  47. GRB 250128B: VLT/FORS2 optical observations
  48. GRB 250129A: REM optical/NIR afterglow detection
  49. GRB 250129A: OHP/T193 optical and spectroscopy observations
  50. GRB 250129A: Early afterglow detection by LCO.
  51. GRB 250128B: OHP/T193 optical upper limit
  52. GRB 250129A: LCO optical observations
  53. GRB 250128B: Enhanced Swift-XRT position
  54. GRB 250129A: Swift detection of a burst with an optical counterpart
  55. Swift GRB 250129A: Global MASTER-Net OT detection
  56. GRB 250128B: Swift-XRT refined Analysis
  57. GRB 250128B: GOTO optical upper limit
  58. EP250125a: Upper limits from Swift/BAT-GUANO
  59. GRB 250128B: LCO optical observations
  60. GRB 250128B: Swift detection of a short burst
  61. GRB 250127A: Swift-XRT observations
  62. GRB 250127B: DDOTI Upper Limit on the Afterglow
  63. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  64. Fermi GRB 250128A: Global MASTER-Net observations report
  65. GRB 250117A: Fermi GBM Observation
  66. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  67. IPN triangulation of GRB 250119C
  68. GRB 250127A: LCO optical upper limit
  69. GRB 241223A: cubesat Avion detection
  70. EP250125A: Non-detection from Fermi-GBM Observations
  71. GRB 250126A: MAXI/GSC detection
  72. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  73. EP250125a: Optical upper limit with Kinder observations
  74. EP250125a: REM optical counterpart detection
  75. GRB 250119C: Fermi GBM Observation
  76. EP250125a: Swift/XRT detection of a fading counterpart
  77. EP250125a: a new X-ray transient detected by Einstein Probe
  78. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  79. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  80. EP250108a: AbAO, CMO and Terskol optical upper limits
  81. GRB 250121A: Fermi GBM Observation
  82. IPN triangulation of GRB 250118B
  83. IPN triangulation of GRB 250119B
  84. GRB 250114A: Swift-BAT refined analysis
  85. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  86. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  87. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  88. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  89. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  90. GRB 250119B: Fermi GBM Observation
  91. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  92. IPN triangulation of GRB 250117A (short)
  93. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  94. EP 250108A: Late-time optical observation by LCO
  95. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  96. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  97. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  98. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  99. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  100. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate

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