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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"

36154 results found.

  1. GRB 251201B: SVOM/VT optical fading
  2. Swift GRB 251201B : MASTER optical counterpart detection
  3. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  4. Swift GRB 251201B: Global MASTER-Net observations report
  5. GRB 251201B: Enhanced Swift-XRT position
  6. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  7. GRB 251130B: AstroSat CZTI detection
  8. GRB 251201B: Swift detection of a burst with an optical counterpart
  9. GRB 251201B: Fermi GBM Final Real-time Localization
  10. EP251130a: Mondy optical observations
  11. EP251130a: SAO RAS optical observations
  12. EP251130a: KAIT optical observations
  13. GRB 251201A: MAXI/GSC detection
  14. Fermi GRB 251130B: Global MASTER-Net observations report
  15. GRB 251127A: SVOM/GRM observation
  16. GRB 251130B: Fermi GBM Final Localization Correction
  17. GRB 251130B: Fermi GBM Final Real-time Localization
  18. EP251129a/GRB 251129A: EP-FXT follow-up observations
  19. GRB 251130A: Fermi GBM Final Real-time Localization
  20. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  21. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  22. GRB 251128A: AstroSat CZTI detection
  23. GRB 251129A / EP251129a: SAO RAS optical observations
  24. GRB 251126A: SAO RAS optical observations
  25. GRB 251128A: GECAM-B detection
  26. GRB 251128A: SVOM/GRM observation of a long burst
  27. GRB 251128A: Insight-HXMT/HE detection
  28. SVOM GRB 251129A : MASTER optical counterpart detection
  29. GRB 251129A: Swift-XRT afterglow detection
  30. GRB 251129A: Swift ToO observations
  31. GRB 251129A / EP251129a: SVOM/VT optical fading
  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. GRB 251129A: SVOM detection of a burst
  40. GRB 251126A: Swift-BAT refined analysis
  41. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  42. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  43. Fermi GRB 251128A: Global MASTER-Net observations report
  44. GRB 251127A: Glowbug gamma-ray detection
  45. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  46. GRB 251126A: further SAO RAS optical observations
  47. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  48. GRB 251126A NUTTelA-TAO Early Measurements
  49. GRB251126A: MAO/AZT-22 optical observations
  50. GRB 251128A: Fermi GBM Final Real-time Localization
  51. GRB251126A: Continued optical observation from 1.3m DFOT
  52. GRB 251126A: Swift/UVOT Detection
  53. GRB 251126A: Mondy and SAO RAS optical observations
  54. GRB 251126A: Swift-XRT refined Analysis
  55. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  56. GRB 251126A: NOT optical observations
  57. GRB 251126A: 1.3m DFOT optical afterglow detection
  58. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  59. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  60. GRB 251125B: GECAM-B detection
  61. Fermi GRB 251127A: Global MASTER-Net observations report
  62. GRB 251127A: Fermi GBM Final Real-time Localization
  63. GRB 251126A: Enhanced Swift-XRT position
  64. GRB 251126A: Kilonova-Catcher optical afterglow detection
  65. GRB 251126A: Asiago i-band detection
  66. GRB 251126A: Nanshan/HMT optical afterglow detection
  67. Swift GRB 251126A: Global MASTER-Net observations report
  68. GRB 251121A: Fermi GBM Observation
  69. GRB 251126A: Prompt enhanced Swift-XRT position
  70. GRB 251126A: GIT discovery of the likely optical afterglow
  71. GRB 251126A: Swift detection of a burst
  72. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  73. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  74. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  75. Fermi GRB 251125B: Global MASTER-Net observations report
  76. GRB 251125B: Fermi GBM Final Real-time Localization
  77. Fermi GRB 251125A: Global MASTER-Net observations report
  78. GRB 251125A: Fermi GBM Final Real-time Localization
  79. GRB 251124A: Fermi GBM Localization by automated pipeline
  80. GRB 251122B: Fermi GBM Final Localization
  81. Fermi GRB 251124a: Global MASTER-Net observations report
  82. GRB 251124a: Fermi GBM Final Localization
  83. GRB 251116C: Swift-XRT confirmation of fading
  84. GRB 251122A/EP251122a: FTW optical and NIR observations
  85. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  86. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  87. GRB 251122A / EP251122a: EP-FXT counterpart detection
  88. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 251122A / EP251122a: WFST optical observations
  90. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  91. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  92. GRB 251122A / EP251122a: LCO optical upper limits
  93. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  94. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  95. GRB 251122A / EP251122a: SVOM detection of a long burst
  96. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  97. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  98. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  99. EP251118a: Xinglong-2.16m optical observation
  100. GRB 251115A: Fermi GBM Observation

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