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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"

28048 results found.

  1. GRB 250920A: NuSTAR detection of bright prompt emission
  2. GRB 250920C: GROWTH-India Telescope optical observations
  3. GRB 250920C: Swift-BAT refined analysis
  4. GRB 250920B: Swift-BAT refined analysis
  5. GRB 250920C: Enhanced Swift-XRT position
  6. GRB 250920C: Swift/UVOT Detection
  7. GRB 250920B: Fermi GBM Observation
  8. GRB 250920A: Fermi GBM Detection
  9. GRB 250920C: Fermi GBM Observation
  10. GRB 250920B: Swift/UVOT Detection
  11. GRB 250920C: Optical counterpart detection by LCO
  12. GRB 250920A: SVOM/GRM observation
  13. GRB250920C: LCOGT Optical Detection
  14. GRB 250920B: Enhanced Swift-XRT position
  15. GRB 250920B: Swift-XRT refined Analysis
  16. GRB 250920B: SVOM/C-GFT optical observations
  17. GRB 250919A / EP250919a: LCO optical observation
  18. GRB 250920C: Swift detection of a burst
  19. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  20. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  21. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  22. GRB 250919A/EP250919a: SVOM/VT optical observation
  23. GRB 250916A: Mondy R-band optical observations
  24. GRB 250919A: Glowbug gamma-ray detection
  25. GRB 250919A: Fermi GBM Observation
  26. Fermi GRB 250918A: Global MASTER-Net observations report
  27. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  28. GRB 250918A: SVOM/GRM observation
  29. GRB 250919A: Swift-XRT afterglow detection
  30. GRB 250919A: SVOM/GRM observation of a very bright GRB
  31. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  32. EP250919a: Einstein Probe detection of an X-ray transient
  33. GRB 250916A: Fermi GBM Observation
  34. GRB 250916A: KAIT optical observations
  35. GRB 250917B: VLT/HAWK-I near-infrared observations
  36. GRB 250916A: NuSTAR detection of the prompt emission
  37. GRB 250916A: further SAO RAS optical observations
  38. GRB 250917B: Swift-BAT refined analysis
  39. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  40. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  41. GRB 250917B: Swift/UVOT Upper Limits
  42. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  43. GRB 250916A: Swift-XRT observations
  44. GRB 250916A: MAO/AZT-22 optical observations
  45. GRB 250916A: SAO RAS optical observations
  46. GRB 250916A : GIT optical observations
  47. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  48. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  49. GRB 250916A: Glowbug gamma-ray detection
  50. GRB250917B: WFST optical observations
  51. GRB 250917B: Fermi GBM Observation
  52. GRB 250917B: Swift-XRT observations
  53. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  54. GRB 250917B: Swift detection of a short burst
  55. GRB 250916A: AstroSat CZTI detection of a bright long burst
  56. EP250916a: Einstein Probe detection of an X-ray transient
  57. SVOM/sb25091517: SVOM detection of an X-ray transient
  58. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  59. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  60. GRB 250912A: Swift-XRT observations
  61. GRB250912A: VLT/HAWK-I follow-up observations
  62. GRB 250912A: Fermi GBM Observation
  63. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  64. GRB 250912A:SVOM/VT optical upper limit
  65. GRB 250912A: LCO optical upper limit
  66. EP250911a: Global MASTER-Net observations report
  67. GRB 250912A: SVOM detection of a burst
  68. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  69. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  70. EP250911a: Upper limit from Fermi-GBM Observations
  71. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  72. GRB 250911A: GECAM-B detection
  73. GRB 250911A: Swift-BAT refined analysis
  74. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  75. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  76. GRB 250910B: SVOM/GRM observation
  77. EP250911a: SVOM/VT optical observation
  78. GRB 250911A: MASTER optical counterpart observations
  79. EP250911a: SAO RAS optical observations
  80. GRB 250911A: Swift-XRT refined Analysis
  81. EP250911a: Swift-XRT observations
  82. EP250911a: Optical detection with Kinder observations
  83. GRB 250911A: Swift/UVOT Detection
  84. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  85. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  86. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  87. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  88. EP250911a: COLIBRÍ optical observations
  89. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  90. EP250911a: LCO optical counterpart discovery
  91. EP250911a: Einstein Probe detection of an X-ray transient
  92. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  93. GRB 250903A: SVOM/ECLAIRs refined analysis
  94. GRB 250911A: Enhanced Swift-XRT position
  95. GRB 250911A: Swift-XRT observations
  96. GRB 250911A: COLIBRÍ optical counterpart candidate
  97. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  98. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  99. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  100. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient

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