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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

16029 results found.

  1. GRB 250502A: NOT optical observations
  2. GRB 250502a: Liverpool Telescope optical follow-up
  3. GRB 250502A: AKO Optical Afterglow Detection
  4. GRB 250502A: LCO optical counterpart detection
  5. GRB 250502B: DDOTI Optical Observations
  6. GRB 250502A: Early optical counterpart detection by LCO.
  7. GRB 250430A: Swift/UVOT Detection
  8. GRB 250502A: SVOM/VT optical bump
  9. GRB 250502A: TRT optical afterglow confirmation
  10. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  11. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  12. GRB 250502A: SVOM detection of a burst
  13. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  14. GRB 250430A: SVOM/VT optical observations
  15. GRB 250430A: KAIT optical observations
  16. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  17. GRB 250430A / EP250430a: J-band upper limits with WINTER
  18. GRB 250430A: NUTTelA-TAO Early Measurements
  19. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  20. GRB 250430A: DDOTI Optical Observations
  21. GRB 250430A: Leavitt Observatory optical upper limit
  22. GRB 250430A: Bassano Bresciano Observatory upper limit
  23. GRB 250430A : MITSuME Akeno optical upper limits
  24. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  25. GRB 250430A: AKO Optical Afterglow Detection
  26. GRB 250430A: Kanata optical upper limit
  27. EP 250427A: Optical counterpart detection by LCO.
  28. GRB 250430A: Swift detection of a burst with optical counterpart
  29. EP250428b: FTW optical and NIR observations
  30. EP250427a/GRB250427A: HCT optical follow-up
  31. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  32. SVOM/sb25043004: SVOM detection of a X-ray transient
  33. EP250428b: GROWTH-India telescope optical upper limit
  34. EP250428b: SAO RAS optical upper limit
  35. EP250428b: LAST optical upper limit
  36. GRB 250427A: Swift/UVOT Detection
  37. EP250427a / GRB 250427A: OHP/T193 photometric observations
  38. EP250427a: EP-FXT follow-up observations
  39. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  40. EP250427a: Lesedi optical counterpart detection
  41. EP250427A: COLIBRÍ Continuing Optical Observations
  42. GRB250427A/EP250427a GIT optical afterglow detection:
  43. EP250427a: LT optical counterpart detection
  44. GRB 250427A: Swift-XRT refined Analysis
  45. EP250427a / GRB 250427A: LCO optical counterpart detection
  46. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  47. EP250427A/GRB250427A: Keck/LRIS redshift
  48. EP250427a: REM optical/NIR afterglow detection
  49. GRB 250424A: LCO optical observation
  50. EP250427A: COLIBRÍ Optical Detection
  51. EP250427a: TRT optical counterpart detection
  52. EP 250427a: BOOTES-7 optical afterglow candidate
  53. GRB 250424A: SVOM/GRM observation of a long burst
  54. GRB 250424A: PRIME near-infrared detection
  55. GRB 250424A: WINTER J-band detection
  56. GRB 250424A: SVOM/VT optical observation
  57. GRB 250419A: Mondy Optical Observations
  58. GRB 250424A: Swift/UVOT Detection
  59. Fermi-LAT gamma-ray observations of IceCube-250421A
  60. GRB 250424A: Skynet Optical Observations
  61. GRB 250424A: Kilonova-Catcher optical afterglow detection
  62. GRB 250419a: Continued Liverpool Telescope observations
  63. GRB 250419A: Liverpool Telescope optical upper limit
  64. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  65. GRB 250424A: BlackGEM optical afterglow detection
  66. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  67. GRB 250424A: likely host galaxy
  68. GRB 250424A: DDOTI Afterglow Detection
  69. GRB 250424A: REM optical/NIR afterglow detection
  70. GRB 250424A: Swift detection of a burst with an optical counterpart
  71. Swift GRB 250424A: Global MASTER-Net OT detection
  72. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  73. EP250421a: Nickel optical upper limit
  74. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  75. SVOM/sb25042207: BOOTES-2 early optical upper limit
  76. SVOM/sb25042207: GOTO optical upper limits
  77. GRB250419A: VLA radio detection
  78. GRB 250419A: Mephisto Multi-band Optical Detection
  79. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  80. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  81. EP250421a: NOT optical observations
  82. GRB 250419A: Optical Observations via Virtual Telescope Project
  83. EP250421a: REM optical upper limit
  84. EP250421a: Swift/XRT counterpart detection
  85. EP250421A: COLIBRÍ Optical Upper Limit
  86. GRB 250419A: Mondy Continued Optical Observations
  87. EP250421a: Mephisto optical counterpart confirmation
  88. EP250421a: JinShan likely optical counterpart
  89. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  90. GRB 250419A: Liverpool Telescope observations
  91. GRB 250419A: LCO optical observation
  92. GRB 250419A: JinShan optical observations
  93. GRB 250419A: SVOM/VT optical continuous observations
  94. GRB 250419A: SVOM/C-GFT optical observations
  95. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  96. GRB 250419A: LCO optical afterglow multi-band observations
  97. GRB 250419A: Mondy and AbAO Optical Observations
  98. GRB 250419A: Liverpool Telescope observations
  99. GRB 250419A: AKO Optical Afterglow Detection
  100. GRB 250419A: MASTER optical afterglow observation

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