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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"

16037 results found.

  1. GRB 250504A: SVOM/VT upper limit
  2. GRB 250504A: REM optical/NIR observations
  3. GRB 250502A: REM optical/NIR observations
  4. GRB 250504A: MeerLICHT optical afterglow detection
  5. GRB 250502A: Mondy and Tien-Shan Optical Observations
  6. GRB 250502A: KAIT optical observations
  7. GRB 250502A: Montarrenti Observatory optical detection
  8. GRB 250502A: Swift-XRT afterglow detection
  9. GRB 250502A: NOT optical observations
  10. GRB 250502a: Liverpool Telescope optical follow-up
  11. GRB 250502A: AKO Optical Afterglow Detection
  12. GRB 250502A: LCO optical counterpart detection
  13. GRB 250502B: DDOTI Optical Observations
  14. GRB 250502A: Early optical counterpart detection by LCO.
  15. GRB 250430A: Swift/UVOT Detection
  16. GRB 250502A: SVOM/VT optical bump
  17. GRB 250502A: TRT optical afterglow confirmation
  18. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  19. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  20. GRB 250502A: SVOM detection of a burst
  21. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  22. GRB 250430A: SVOM/VT optical observations
  23. GRB 250430A: KAIT optical observations
  24. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  25. GRB 250430A / EP250430a: J-band upper limits with WINTER
  26. GRB 250430A: NUTTelA-TAO Early Measurements
  27. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  28. GRB 250430A: DDOTI Optical Observations
  29. GRB 250430A: Leavitt Observatory optical upper limit
  30. GRB 250430A: Bassano Bresciano Observatory upper limit
  31. GRB 250430A : MITSuME Akeno optical upper limits
  32. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  33. GRB 250430A: AKO Optical Afterglow Detection
  34. GRB 250430A: Kanata optical upper limit
  35. EP 250427A: Optical counterpart detection by LCO.
  36. GRB 250430A: Swift detection of a burst with optical counterpart
  37. EP250428b: FTW optical and NIR observations
  38. EP250427a/GRB250427A: HCT optical follow-up
  39. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  40. SVOM/sb25043004: SVOM detection of a X-ray transient
  41. EP250428b: GROWTH-India telescope optical upper limit
  42. EP250428b: SAO RAS optical upper limit
  43. EP250428b: LAST optical upper limit
  44. GRB 250427A: Swift/UVOT Detection
  45. EP250427a / GRB 250427A: OHP/T193 photometric observations
  46. EP250427a: EP-FXT follow-up observations
  47. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  48. EP250427a: Lesedi optical counterpart detection
  49. EP250427A: COLIBRÍ Continuing Optical Observations
  50. GRB250427A/EP250427a GIT optical afterglow detection:
  51. EP250427a: LT optical counterpart detection
  52. GRB 250427A: Swift-XRT refined Analysis
  53. EP250427a / GRB 250427A: LCO optical counterpart detection
  54. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  55. EP250427A/GRB250427A: Keck/LRIS redshift
  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. EP 250427a: BOOTES-7 optical afterglow candidate
  61. GRB 250424A: SVOM/GRM observation of a long burst
  62. GRB 250424A: PRIME near-infrared detection
  63. GRB 250424A: WINTER J-band detection
  64. GRB 250424A: SVOM/VT optical observation
  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: Continued Liverpool Telescope observations
  71. GRB 250419A: Liverpool Telescope optical upper limit
  72. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  73. GRB 250424A: BlackGEM optical afterglow detection
  74. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  75. GRB 250424A: likely host galaxy
  76. GRB 250424A: DDOTI Afterglow Detection
  77. GRB 250424A: REM optical/NIR afterglow detection
  78. GRB 250424A: Swift detection of a burst with an optical counterpart
  79. Swift GRB 250424A: Global MASTER-Net OT detection
  80. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  81. EP250421a: Nickel optical upper limit
  82. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  83. SVOM/sb25042207: BOOTES-2 early optical upper limit
  84. SVOM/sb25042207: GOTO optical upper limits
  85. GRB250419A: VLA radio detection
  86. GRB 250419A: Mephisto Multi-band Optical Detection
  87. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  88. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  89. EP250421a: NOT optical observations
  90. GRB 250419A: Optical Observations via Virtual Telescope Project
  91. EP250421a: REM optical upper limit
  92. EP250421a: Swift/XRT counterpart detection
  93. EP250421A: COLIBRÍ Optical Upper Limit
  94. GRB 250419A: Mondy Continued Optical Observations
  95. EP250421a: Mephisto optical counterpart confirmation
  96. EP250421a: JinShan likely optical counterpart
  97. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  98. GRB 250419A: Liverpool Telescope observations
  99. GRB 250419A: LCO optical observation
  100. GRB 250419A: JinShan optical observations

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