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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"

28055 results found.

  1. GRB 250920C: Swift-XRT refined Analysis
  2. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  3. GRB 250920B: Asiago optical observations
  4. GRB 250920B: Kitab-ISON optical upper limit
  5. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  6. GRB 250920C: SVOM/GRM observation
  7. GRB 250917B: KAIT optical upper limit
  8. GRB 250920A: NuSTAR detection of bright prompt emission
  9. GRB 250920C: GROWTH-India Telescope optical observations
  10. GRB 250920C: Swift-BAT refined analysis
  11. GRB 250920B: Swift-BAT refined analysis
  12. GRB 250920C: Enhanced Swift-XRT position
  13. GRB 250920C: Swift/UVOT Detection
  14. GRB 250920B: Fermi GBM Observation
  15. GRB 250920A: Fermi GBM Detection
  16. GRB 250920C: Fermi GBM Observation
  17. GRB 250920B: Swift/UVOT Detection
  18. GRB 250920C: Optical counterpart detection by LCO
  19. GRB 250920A: SVOM/GRM observation
  20. GRB250920C: LCOGT Optical Detection
  21. GRB 250920B: Enhanced Swift-XRT position
  22. GRB 250920B: Swift-XRT refined Analysis
  23. GRB 250920B: SVOM/C-GFT optical observations
  24. GRB 250919A / EP250919a: LCO optical observation
  25. GRB 250920C: Swift detection of a burst
  26. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  27. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  28. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  29. GRB 250919A/EP250919a: SVOM/VT optical observation
  30. GRB 250916A: Mondy R-band optical observations
  31. GRB 250919A: Glowbug gamma-ray detection
  32. GRB 250919A: Fermi GBM Observation
  33. Fermi GRB 250918A: Global MASTER-Net observations report
  34. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  35. GRB 250918A: SVOM/GRM observation
  36. GRB 250919A: Swift-XRT afterglow detection
  37. GRB 250919A: SVOM/GRM observation of a very bright GRB
  38. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  39. EP250919a: Einstein Probe detection of an X-ray transient
  40. GRB 250916A: Fermi GBM Observation
  41. GRB 250916A: KAIT optical observations
  42. GRB 250917B: VLT/HAWK-I near-infrared observations
  43. GRB 250916A: NuSTAR detection of the prompt emission
  44. GRB 250916A: further SAO RAS optical observations
  45. GRB 250917B: Swift-BAT refined analysis
  46. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  47. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  48. GRB 250917B: Swift/UVOT Upper Limits
  49. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  50. GRB 250916A: Swift-XRT observations
  51. GRB 250916A: MAO/AZT-22 optical observations
  52. GRB 250916A: SAO RAS optical observations
  53. GRB 250916A : GIT optical observations
  54. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  55. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  56. GRB 250916A: Glowbug gamma-ray detection
  57. GRB250917B: WFST optical observations
  58. GRB 250917B: Fermi GBM Observation
  59. GRB 250917B: Swift-XRT observations
  60. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  61. GRB 250917B: Swift detection of a short burst
  62. GRB 250916A: AstroSat CZTI detection of a bright long burst
  63. EP250916a: Einstein Probe detection of an X-ray transient
  64. SVOM/sb25091517: SVOM detection of an X-ray transient
  65. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  66. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  67. GRB 250912A: Swift-XRT observations
  68. GRB250912A: VLT/HAWK-I follow-up observations
  69. GRB 250912A: Fermi GBM Observation
  70. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  71. GRB 250912A:SVOM/VT optical upper limit
  72. GRB 250912A: LCO optical upper limit
  73. EP250911a: Global MASTER-Net observations report
  74. GRB 250912A: SVOM detection of a burst
  75. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  76. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  77. EP250911a: Upper limit from Fermi-GBM Observations
  78. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  79. GRB 250911A: GECAM-B detection
  80. GRB 250911A: Swift-BAT refined analysis
  81. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  82. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  83. GRB 250910B: SVOM/GRM observation
  84. EP250911a: SVOM/VT optical observation
  85. GRB 250911A: MASTER optical counterpart observations
  86. EP250911a: SAO RAS optical observations
  87. GRB 250911A: Swift-XRT refined Analysis
  88. EP250911a: Swift-XRT observations
  89. EP250911a: Optical detection with Kinder observations
  90. GRB 250911A: Swift/UVOT Detection
  91. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  92. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  93. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  94. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  95. EP250911a: COLIBRÍ optical observations
  96. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  97. EP250911a: LCO optical counterpart discovery
  98. EP250911a: Einstein Probe detection of an X-ray transient
  99. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  100. GRB 250903A: SVOM/ECLAIRs refined analysis

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