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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"

21790 results found.

  1. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  2. Swift GRB 251205A : MASTER OT detection with host galaxy
  3. Swift GRB251205A: Global MASTER-Net observations report
  4. GRB 251203C: SVOM/ECLAIRs refined analysis
  5. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  6. GRB 251203C: J-band observations with WINTER
  7. EP251130a: JinShan near-infrared observations
  8. GRB 251203C: SVOM/VT optical counterpart
  9. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  10. GRB 251203B: Swift-XRT observations
  11. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  12. GRB 251203B: LCO optical upper limits
  13. GRB 251203B: SVOM/VT optical observation
  14. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  15. SVOM GRB251203.77: Global MASTER-Net observations report
  16. SVOM GRB251203B: Global MASTER-Net observations report
  17. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  18. EP251130a: MAO/AZT-22 optical observations
  19. GRB 251202A / EP251202a: SVOM/VT optical observation
  20. EP251202a/GRB 251202A: KAIT optical observations
  21. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  22. Fermi GRB 251202B: Global MASTER-Net observations report
  23. GRB251129A/EP251129a: Swift UVOT detection
  24. GRB 251202A: Swift/UVOT Detection
  25. GRB 251201B: Kilonova-Catcher optical afterglow detection
  26. GRB 251201B: Swift/UVOT Detection
  27. EP251130a: continued NOT optical observations indicate steep fading phase
  28. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  29. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  30. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  31. GRB 251202A: GOTO optical afterglow detection
  32. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  33. GRB 251202A: Swift-XRT afterglow detection
  34. Fermi GRB 251202A: Global MASTER-Net observations report
  35. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  36. Swift GRB 251201B: Global MASTER-Net observations report
  37. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  38. EP251130a: Mondy optical observations
  39. EP251130a: Optical detections with Kinder observations
  40. SVOM GRB251201.19: Global MASTER-Net observations report
  41. EP251130a: SAO RAS optical observations
  42. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  43. EP251130a: KAIT optical observations
  44. EP251130A: Optical observation from 1.3m DFOT
  45. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  46. EP251130a: JinShan optical observations
  47. Fermi GRB 251130B: Global MASTER-Net observations report
  48. IceCube Alert 251130.75: Global MASTER-Net observations report
  49. EP251130a: Swift-XRT counterpart detection
  50. EP251130a: Global MASTER-Net observations report
  51. EP251129a/GRB 251129A: EP-FXT follow-up observations
  52. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  53. GRB 251129A / EP251129a: SAO RAS optical observations
  54. GRB 251126A: SAO RAS optical observations
  55. GRB 251129A: Swift-XRT afterglow detection
  56. GRB 251129A: Swift ToO observations
  57. EP251129a: Global MASTER-Net observations report
  58. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  59. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  60. SVOM GRB251129A: Global MASTER-Net observations report
  61. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  62. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  63. Fermi GRB 251128A: Global MASTER-Net observations report
  64. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  65. GRB 251126A: further SAO RAS optical observations
  66. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  67. GRB 251126A NUTTelA-TAO Early Measurements
  68. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  69. GRB251126A: MAO/AZT-22 optical observations
  70. GRB251126A: Continued optical observation from 1.3m DFOT
  71. GRB 251126A: Swift/UVOT Detection
  72. GRB 251126A: Mondy and SAO RAS optical observations
  73. GRB 251126A: NOT optical observations
  74. GRB 251126A: 1.3m DFOT optical afterglow detection
  75. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  76. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  77. Fermi GRB 251127A: Global MASTER-Net observations report
  78. GRB 251126A: Kilonova-Catcher optical afterglow detection
  79. GRB 251126A: Asiago i-band detection
  80. GRB 251126A: Nanshan/HMT optical afterglow detection
  81. Swift GRB 251126A: Global MASTER-Net observations report
  82. GRB 251126A: GIT discovery of the likely optical afterglow
  83. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  84. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  85. EP251124b: NOT r- and z-band optical upper limits
  86. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  87. Fermi GRB 251125B: Global MASTER-Net observations report
  88. EP251124b: Global MASTER-Net observations report
  89. Fermi GRB 251125A: Global MASTER-Net observations report
  90. EP251124a: NOT r- and z-band optical upper limits
  91. EP251124a: Global MASTER-Net observations report
  92. EP251124a: Swift-XRT observations
  93. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  94. EP251124a: Optical upper limit with Kinder observations
  95. EP251118A: 6 GHz VLA Detection
  96. Fermi GRB 251124a: Global MASTER-Net observations report
  97. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  98. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  99. GRB 251116C: Swift-XRT confirmation of fading
  100. GRB 251122A/EP251122a: FTW optical and NIR observations

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