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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"
  1. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  2. EP251130a: KAIT optical observations
  3. EP251130A: Optical observation from 1.3m DFOT
  4. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  5. EP251130a: JinShan optical observations
  6. GRB 251201A: MAXI/GSC detection
  7. Fermi GRB 251130B: Global MASTER-Net observations report
  8. GRB 251127A: SVOM/GRM observation
  9. IceCube Alert 251130.75: Global MASTER-Net observations report
  10. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  11. EP251130a: Swift-XRT counterpart detection
  12. GRB 251130B: Fermi GBM Final Localization Correction
  13. EP251130a: Global MASTER-Net observations report
  14. GRB 251130B: Fermi GBM Final Real-time Localization
  15. EP251130a: COLIBRÍ optical counterpart candidate
  16. EP251130a: Einstein Probe detection of an X-ray transient
  17. EP251129a/GRB 251129A: EP-FXT follow-up observations
  18. GRB 251130A: Fermi GBM Final Real-time Localization
  19. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  20. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  21. GRB 251128A: AstroSat CZTI detection
  22. GRB 251129A / EP251129a: SAO RAS optical observations
  23. GRB 251126A: SAO RAS optical observations
  24. GRB 251128A: GECAM-B detection
  25. GRB 251128A: SVOM/GRM observation of a long burst
  26. GRB 251128A: Insight-HXMT/HE detection
  27. SVOM GRB 251129A : MASTER optical counterpart detection
  28. GRB 251129A: Swift-XRT afterglow detection
  29. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  30. Swift trigger 1418333 is not an astrophysical source
  31. GRB 251129A: Swift ToO observations
  32. GRB 251129A / EP251129a: SVOM/VT optical fading
  33. EP251129a: Global MASTER-Net observations report
  34. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  35. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  36. GRB 251129A: Correction to the position of the optical counterpar
  37. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  38. GRB 251128A: Fermi GBM Observation
  39. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  40. GRB 251129A: SVOM detection of a burst
  41. SVOM GRB251129A: Global MASTER-Net observations report
  42. GRB 251129A: SVOM detection of a burst
  43. GRB 251126A: Swift-BAT refined analysis
  44. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  45. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  46. Fermi GRB 251128A: Global MASTER-Net observations report
  47. GRB 251127A: Glowbug gamma-ray detection
  48. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  49. GRB 251126A: further SAO RAS optical observations
  50. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  51. GRB 251126A NUTTelA-TAO Early Measurements
  52. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  53. GRB251126A: MAO/AZT-22 optical observations
  54. GRB 251128A: Fermi GBM Final Real-time Localization
  55. GRB251126A: Continued optical observation from 1.3m DFOT
  56. GRB 251126A: Swift/UVOT Detection
  57. EP251124a: Pan-STARRS ri-band imaging and photometry
  58. GRB 251126A: Mondy and SAO RAS optical observations
  59. GRB 251126A: Swift-XRT refined Analysis
  60. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  61. GRB 251126A: NOT optical observations
  62. GRB 251126A: 1.3m DFOT optical afterglow detection
  63. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  64. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  65. GRB 251125B: GECAM-B detection
  66. Fermi GRB 251127A: Global MASTER-Net observations report
  67. GRB 251127A: Fermi GBM Final Real-time Localization
  68. GRB 251126A: Enhanced Swift-XRT position
  69. GRB 251126A: Kilonova-Catcher optical afterglow detection
  70. GRB 251126A: Asiago i-band detection
  71. GRB 251126A: Nanshan/HMT optical afterglow detection
  72. Swift GRB 251126A: Global MASTER-Net observations report
  73. GRB 251121A: Fermi GBM Observation
  74. GRB 251126A: Prompt enhanced Swift-XRT position
  75. GRB 251126A: GIT discovery of the likely optical afterglow
  76. GRB 251126A: Swift detection of a burst
  77. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  78. EP251124b follow-up observation by EP-FXT
  79. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  80. EP251124b: NOT r- and z-band optical upper limits
  81. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  82. Fermi GRB 251125B: Global MASTER-Net observations report
  83. GRB 251125B: Fermi GBM Final Real-time Localization
  84. EP251124b: Global MASTER-Net observations report
  85. EP251124b: EP-WXT detection of a fast X-ray transient
  86. EP251124a: Xinglong GWAC-F60A optical observation
  87. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  88. Fermi GRB 251125A: Global MASTER-Net observations report
  89. GRB 251125A: Fermi GBM Final Real-time Localization
  90. EP251124a: NOT r- and z-band optical upper limits
  91. EP251124a: Global MASTER-Net observations report
  92. EP251124a: Swift-XRT observations
  93. GRB 251124A: Fermi GBM Localization by automated pipeline
  94. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  95. EP251124a: Optical upper limit with Kinder observations
  96. GRB 251122B: Fermi GBM Final Localization
  97. EP251118A: 6 GHz VLA Detection
  98. Fermi GRB 251124a: Global MASTER-Net observations report
  99. GRB 251124a: Fermi GBM Final Localization
  100. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901

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