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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"

27549 results found.

  1. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  2. EP251130a: Swift-XRT counterpart detection
  3. GRB 251130B: Fermi GBM Final Localization Correction
  4. GRB 251130B: Fermi GBM Final Real-time Localization
  5. EP251130a: Einstein Probe detection of an X-ray transient
  6. GRB 251130A: Fermi GBM Final Real-time Localization
  7. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  8. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  9. GRB 251128A: AstroSat CZTI detection
  10. GRB 251129A / EP251129a: SAO RAS optical observations
  11. GRB 251126A: SAO RAS optical observations
  12. GRB 251128A: GECAM-B detection
  13. GRB 251128A: Insight-HXMT/HE detection
  14. SVOM GRB 251129A : MASTER optical counterpart detection
  15. GRB 251129A: Swift-XRT afterglow detection
  16. GRB 251129A: Swift ToO observations
  17. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  18. GRB 251129A: SVOM detection of a burst
  19. GRB 251129A: SVOM detection of a burst
  20. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  21. GRB 251127A: Glowbug gamma-ray detection
  22. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  23. GRB 251126A: further SAO RAS optical observations
  24. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  25. GRB251126A: MAO/AZT-22 optical observations
  26. GRB 251128A: Fermi GBM Final Real-time Localization
  27. GRB251126A: Continued optical observation from 1.3m DFOT
  28. GRB 251126A: Swift/UVOT Detection
  29. EP251124a: Pan-STARRS ri-band imaging and photometry
  30. GRB 251126A: Mondy and SAO RAS optical observations
  31. GRB 251126A: Swift-XRT refined Analysis
  32. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  33. GRB 251126A: NOT optical observations
  34. GRB 251126A: 1.3m DFOT optical afterglow detection
  35. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  36. GRB 251125B: GECAM-B detection
  37. GRB 251127A: Fermi GBM Final Real-time Localization
  38. GRB 251126A: Enhanced Swift-XRT position
  39. GRB 251126A: Kilonova-Catcher optical afterglow detection
  40. GRB 251126A: Asiago i-band detection
  41. GRB 251126A: Nanshan/HMT optical afterglow detection
  42. GRB 251126A: Prompt enhanced Swift-XRT position
  43. GRB 251126A: GIT discovery of the likely optical afterglow
  44. GRB 251126A: Swift detection of a burst
  45. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  46. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  47. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  48. GRB 251125B: Fermi GBM Final Real-time Localization
  49. EP251124b: EP-WXT detection of a fast X-ray transient
  50. EP251124a: Xinglong GWAC-F60A optical observation
  51. GRB 251125A: Fermi GBM Final Real-time Localization
  52. EP251124a: NOT r- and z-band optical upper limits
  53. EP251124a: Swift-XRT observations
  54. GRB 251124A: Fermi GBM Localization by automated pipeline
  55. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  56. GRB 251122B: Fermi GBM Final Localization
  57. EP251118A: 6 GHz VLA Detection
  58. GRB 251124a: Fermi GBM Final Localization
  59. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  60. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  61. EP251124a: Einstein Probe detection of an X-ray transient
  62. GRB 251116C: Swift-XRT confirmation of fading
  63. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  64. EP251118A: 3.6m DOT optical afterglow detection
  65. GRB 251122A / EP251122a: EP-FXT counterpart detection
  66. GRB 251122A / EP251122a: WFST optical observations
  67. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  68. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  69. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  70. GRB 251122A / EP251122a: SVOM detection of a long burst
  71. EP251122a: Einstein Probe detection of an X-ray transient
  72. EP251118a: Continued Optical Detection with Kinder observations
  73. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  74. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  75. EP251118a: Xinglong-2.16m optical observation
  76. GRB 251121A: Fermi GBM Final Real-time Localization
  77. EP251118A: 1.3m DFOT optical afterglow detection
  78. GRB 251118A: Swift/UVOT Detection
  79. GRB 251118A: Glowbug gamma-ray detection
  80. GRB 251118A: Fermi GBM Observation
  81. GRB 251118A: Swift-XRT afterglow detection
  82. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  83. EP251118a: Optical detection with Kinder observations
  84. GRB 251118A: GECAM-B detection
  85. GRB 251118A: NuSTAR detection of bright prompt emission
  86. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  87. GRB 251116C: NOT optical observations
  88. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  89. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  90. GRB 251018A: FRAM-Auger optical detection
  91. GRB 251117A: Swift-XRT observations
  92. Konus-Wind detection of GRB 251118C (EP251118a)
  93. GRB 251117A: Insight-HXMT/HE detection
  94. EP251118a: GOTO optical afterglow detection
  95. GRB 251119A: SVOM detection of a possible burst
  96. EP251118a: NOT spectroscopic redshift of z = 1.216
  97. GRB 251118A: Fermi-LAT detection
  98. EP251118a: NOT candidate optical counterpart
  99. GRB 251118A: Swift ToO observations
  100. EP251118a: Einstein Probe detected of a fast X-ray transient

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