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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"

25981 results found.

  1. GRB 250924A: Swift-XRT refined Analysis
  2. GRB 250924A: Enhanced Swift-XRT position
  3. GRB 250924A: J-band detection with WINTER
  4. GRB 250924A: GROWTH-India Telescope Upper Limits
  5. GRB 250924A: KAIT optical observations
  6. GRB 250924A: Mondy optical observations, afterglow fading
  7. GRB 250924A: Kilonova-Catcher optical afterglow detection
  8. GRB 250920C: Kilonova-Catcher optical afterglow detection
  9. GRB 250922B: SVOM/GRM observation
  10. GRB 250920C: TRT optical observation
  11. GRB 250924A: COLIBRÍ optical observations
  12. GRB 250919A / EP250919a: further LCO optical observation
  13. GRB 250924A: DDOTI Detection of the Optical Counterpart
  14. GRB 250924A: Swift detection of a burst with an optical counterpart
  15. GRB 250920B: AbAO optical upper limits
  16. GRB 250920C: KAIT optical observations
  17. GRB 250920B: CrAO ZTSH optical observations
  18. GRB 250920C: COLIBRÍ optical observations
  19. GRB 250922C: AstroSat CZTI detection of a short burst
  20. GRB 250920B: SAO RAS optical observations
  21. GRB 250920C: NIR observations with WINTER
  22. GRB 250920B: NIR observations with WINTER
  23. Fermi trigger No 780156732: Global MASTER-Net observations report
  24. GRB 250920C: PRIME near-infrared detection
  25. GRB 250916A: Swift/UVOT Detection
  26. GRB 250920B: Glowbug gamma-ray detection
  27. GRB 250916A: CrAO ZTSh R-band optical observations
  28. GRB 250920C: Swift-XRT refined Analysis
  29. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  30. GRB 250920B: Asiago optical observations
  31. GRB 250920B: Kitab-ISON optical upper limit
  32. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  33. GRB 250920C: SVOM/GRM observation
  34. GRB 250917B: KAIT optical upper limit
  35. GRB 250920A: NuSTAR detection of bright prompt emission
  36. GRB 250920C: GROWTH-India Telescope optical observations
  37. GRB 250920C: Swift-BAT refined analysis
  38. GRB 250920B: Swift-BAT refined analysis
  39. GRB 250920C: Enhanced Swift-XRT position
  40. GRB 250920C: Swift/UVOT Detection
  41. GRB 250920B: Fermi GBM Observation
  42. GRB 250920A: Fermi GBM Detection
  43. GRB 250920C: Fermi GBM Observation
  44. GRB 250920B: Swift/UVOT Detection
  45. GRB 250920C: Optical counterpart detection by LCO
  46. GRB 250920A: SVOM/GRM observation
  47. GRB250920C: LCOGT Optical Detection
  48. GRB 250920B: Enhanced Swift-XRT position
  49. GRB 250920B: Swift-XRT refined Analysis
  50. GRB 250920B: SVOM/C-GFT optical observations
  51. GRB 250919A / EP250919a: LCO optical observation
  52. GRB 250920C: Swift detection of a burst
  53. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  54. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  55. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  56. GRB 250919A/EP250919a: SVOM/VT optical observation
  57. GRB 250916A: Mondy R-band optical observations
  58. GRB 250919A: Glowbug gamma-ray detection
  59. GRB 250919A: Fermi GBM Observation
  60. Fermi GRB 250918A: Global MASTER-Net observations report
  61. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  62. GRB 250918A: SVOM/GRM observation
  63. GRB 250919A: Swift-XRT afterglow detection
  64. GRB 250919A: SVOM/GRM observation of a very bright GRB
  65. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  66. EP250919a: Einstein Probe detection of an X-ray transient
  67. GRB 250916A: Fermi GBM Observation
  68. GRB 250916A: KAIT optical observations
  69. GRB 250917B: VLT/HAWK-I near-infrared observations
  70. GRB 250916A: NuSTAR detection of the prompt emission
  71. GRB 250916A: further SAO RAS optical observations
  72. GRB 250917B: Swift-BAT refined analysis
  73. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  74. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  75. GRB 250917B: Swift/UVOT Upper Limits
  76. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  77. GRB 250916A: Swift-XRT observations
  78. GRB 250916A: MAO/AZT-22 optical observations
  79. GRB 250916A: SAO RAS optical observations
  80. GRB 250916A : GIT optical observations
  81. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  82. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  83. GRB 250916A: Glowbug gamma-ray detection
  84. GRB250917B: WFST optical observations
  85. GRB 250917B: Fermi GBM Observation
  86. GRB 250917B: Swift-XRT observations
  87. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  88. GRB 250917B: Swift detection of a short burst
  89. GRB 250916A: AstroSat CZTI detection of a bright long burst
  90. EP250916a: Einstein Probe detection of an X-ray transient
  91. SVOM/sb25091517: SVOM detection of an X-ray transient
  92. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  93. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  94. GRB 250912A: Swift-XRT observations
  95. GRB250912A: VLT/HAWK-I follow-up observations
  96. GRB 250912A: Fermi GBM Observation
  97. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  98. GRB 250912A:SVOM/VT optical upper limit
  99. GRB 250912A: LCO optical upper limit
  100. EP250911a: Global MASTER-Net observations report

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