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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').
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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"

17373 results found.

  1. GRB 250507A: SVOM detection of a long burst
  2. GRB 250506A: Mephisto optical upper limits
  3. GRB 250506A: Swift ToO observations
  4. GRB 250502A: Bassano Bresciano Observatory upper limit
  5. GRB 250506A: Xinglong 2.16m optical upper limit
  6. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  7. GRB 250506A: REM optical/NIR upper limits
  8. GRB 250506A: TRT optical observations
  9. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  10. GRB 250506A: SVOM detection of a burst
  11. GRB 250504A: VLT/X-shooter upper limits
  12. GRB 250504A: REM optical/NIR observations
  13. GRB 250502A: REM optical/NIR observations
  14. GRB 250504A: MeerLICHT optical afterglow detection
  15. GRB 250504A: Enhanced Swift-XRT position
  16. GRB 250504A: Swift detection of a burst
  17. GRB 250502A: Swift/UVOT Follow up
  18. GRB 250502A: KAIT optical observations
  19. GRB 250502A: Montarrenti Observatory optical detection
  20. GRB 250502A: Swift-XRT afterglow detection
  21. GRB 250502A: NOT optical observations
  22. GRB 250502A: AKO Optical Afterglow Detection
  23. GRB 250502A: LCO optical counterpart detection
  24. GRB 250502A: Swift ToO observations
  25. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  26. GRB 250502B: DDOTI Optical Observations
  27. GRB 250502A: Early optical counterpart detection by LCO.
  28. GRB 250430A: Swift/UVOT Detection
  29. GRB 250502A: TRT optical afterglow confirmation
  30. GRB 250430A: Enhanced Swift-XRT position
  31. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  32. GRB 250502A: SVOM detection of a burst
  33. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  34. GRB 250430A: KAIT optical observations
  35. GRB 250430A / EP250430a: J-band upper limits with WINTER
  36. GRB 250430A: DDOTI Optical Observations
  37. GRB 250430A: Leavitt Observatory optical upper limit
  38. GRB 250430A: Bassano Bresciano Observatory upper limit
  39. GRB 250430A : MITSuME Akeno optical upper limits
  40. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  41. GRB 250430A: AKO Optical Afterglow Detection
  42. GRB 250430A: Kanata optical upper limit
  43. EP 250427A: Optical counterpart detection by LCO.
  44. GRB 250430A: Swift detection of a burst with optical counterpart
  45. EP250427a/GRB250427A: HCT optical follow-up
  46. SVOM/sb25043004: SVOM detection of a X-ray transient
  47. EP250428b: GROWTH-India telescope optical upper limit
  48. EP250428b: SAO RAS optical upper limit
  49. EP250428b: LAST optical upper limit
  50. GRB 250427A: Swift/UVOT Detection
  51. EP250428b: Einstein Probe detection of a fast X-ray transient
  52. EP250427A: COLIBRÍ Continuing Optical Observations
  53. GRB250427A/EP250427a GIT optical afterglow detection:
  54. EP250427a: LT optical counterpart detection
  55. EP250427a / GRB 250427A: LCO optical counterpart detection
  56. EP250427a: REM optical/NIR afterglow detection
  57. GRB 250424A: LCO optical observation
  58. EP250427A: COLIBRÍ Optical Detection
  59. EP250427a: TRT optical counterpart detection
  60. EP250427a: Global MASTER-Net observations report
  61. EP250427a: Einstein Probe detection of a fast X-ray transient
  62. GRB 250424A: SVOM/GRM observation of a long burst
  63. GRB 250424A: PRIME near-infrared detection
  64. GRB 250424A: WINTER J-band detection
  65. GRB 250419A: Mondy Optical Observations
  66. GRB 250424A: Swift/UVOT Detection
  67. Fermi-LAT gamma-ray observations of IceCube-250421A
  68. GRB 250424A: Skynet Optical Observations
  69. GRB 250424A: Kilonova-Catcher optical afterglow detection
  70. GRB 250419A: SVOM/ECLAIRs refined analysis
  71. GRB 250424A: Enhanced Swift-XRT position
  72. GRB 250424A: AstroSat CZTI detection of a bright long burst
  73. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  74. GRB 250424A: BlackGEM optical afterglow detection
  75. GRB 250424A: DDOTI Afterglow Detection
  76. GRB 250424A: REM optical/NIR afterglow detection
  77. GRB 250424A: Swift detection of a burst with an optical counterpart
  78. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  79. EP250421a: Nickel optical upper limit
  80. SVOM/sb25042207: XRT observations
  81. SVOM/sb25042207: SVOM detection of an X-ray transient
  82. IceCube-250421A: DDOTI Detection of the LAST Candidate
  83. GRB 250419A: Mephisto Multi-band Optical Detection
  84. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  85. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  86. EP250421a: NOT optical observations
  87. GRB 250419A: Optical Observations via Virtual Telescope Project
  88. EP250421a: REM optical upper limit
  89. EP250421A: COLIBRÍ Optical Upper Limit
  90. GRB 250419A: Mondy Continued Optical Observations
  91. GRB 250421B: AstroSat CZTI detection of a bright long burst
  92. EP250421a: Einstein Probe detection of an X-ray transient
  93. EP250421a: Mephisto optical counterpart confirmation
  94. EP250421a: JinShan likely optical counterpart
  95. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  96. GRB 250419A: LCO optical observation
  97. GRB 250419A: JinShan optical observations
  98. GRB 250419A: SVOM/C-GFT optical observations
  99. GRB 250419A: Swift/UVOT Follow up
  100. GRB 250416C / EP250416a: SVOM/GRM observation of a burst

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