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

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