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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"

26507 results found.

  1. Konus-Wind detection of GRB 250920C
  2. GRB 250920C: KAIT optical observations
  3. GRB 250920B: CrAO ZTSH optical observations
  4. GRB 250920C: COLIBRÍ optical observations
  5. GRB 250920B: SAO RAS optical observations
  6. GRB 250920C: NIR observations with WINTER
  7. GRB 250920B: NIR observations with WINTER
  8. GRB 250920C: PRIME near-infrared detection
  9. GRB 250916A: Swift/UVOT Detection
  10. GRB 250920B: Glowbug gamma-ray detection
  11. GRB 250916A: CrAO ZTSh R-band optical observations
  12. GRB 250920C: Swift-XRT refined Analysis
  13. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  14. GRB 250920B: Asiago optical observations
  15. GRB 250920B: Kitab-ISON optical upper limit
  16. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  17. GRB 250920C: SVOM/GRM observation
  18. GRB 250920C: GROWTH-India Telescope optical observations
  19. GRB 250920C: Enhanced Swift-XRT position
  20. GRB 250920C: Swift/UVOT Detection
  21. GRB 250920B: Fermi GBM Observation
  22. GRB 250920A: Fermi GBM Detection
  23. GRB 250920C: Fermi GBM Observation
  24. GRB 250920B: Swift/UVOT Detection
  25. GRB 250920C: Optical counterpart detection by LCO
  26. GRB 250920A: SVOM/GRM observation
  27. GRB250920C: LCOGT Optical Detection
  28. GRB 250920B: Enhanced Swift-XRT position
  29. GRB 250920B: Swift-XRT refined Analysis
  30. GRB 250920B: SVOM/C-GFT optical observations
  31. GRB 250919A / EP250919a: LCO optical observation
  32. Konus-Wind detection of GRB 250919A
  33. GRB 250920C: Swift detection of a burst
  34. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  35. GRB 250920A: AstroSat CZTI detection
  36. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  37. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  38. GRB 250919A/EP250919a: SVOM/VT optical observation
  39. GRB 250916A: Mondy R-band optical observations
  40. GRB 250919A: Glowbug gamma-ray detection
  41. GRB 250919A: Fermi GBM Observation
  42. GRB 250918A: SVOM/GRM observation
  43. GRB 250919A: Swift-XRT afterglow detection
  44. GRB 250919A: SVOM/GRM observation of a very bright GRB
  45. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  46. EP250919a: Einstein Probe detection of an X-ray transient
  47. GRB 250916A: Fermi GBM Observation
  48. GRB 250916A: KAIT optical observations
  49. GRB 250917B: VLT/HAWK-I near-infrared observations
  50. GRB 250916A: further SAO RAS optical observations
  51. GRB 250912A: SVOM/ECLAIRs refined analysis
  52. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  53. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  54. GRB 250917B: Swift/UVOT Upper Limits
  55. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  56. GRB 250916A: Swift-XRT observations
  57. EP250916a: EP-FXT follow-up observation
  58. GRB 250916A: MAO/AZT-22 optical observations
  59. GRB 250916A: SAO RAS optical observations
  60. GRB 250916A : GIT optical observations
  61. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  62. GRB 250916A: Glowbug gamma-ray detection
  63. GRB250917B: WFST optical observations
  64. GRB 250917B: Fermi GBM Observation
  65. GRB 250917B: Swift-XRT observations
  66. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  67. GRB 250917B: Swift detection of a short burst
  68. The EP-WXT trigger 01709241037 is likely a flaring star
  69. GRB 250916A: AstroSat CZTI detection of a bright long burst
  70. GRB 250910A: SVOM/ECLAIRs refined analysis
  71. EP250916a: Einstein Probe detection of an X-ray transient
  72. SVOM/sb25091517: SVOM detection of an X-ray transient
  73. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  74. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  75. GRB 250912A: Swift-XRT observations
  76. GRB250912A: VLT/HAWK-I follow-up observations
  77. GRB 250912A: Fermi GBM Observation
  78. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  79. GRB 250912A:SVOM/VT optical upper limit
  80. GRB 250912A: LCO optical upper limit
  81. The EP-WXT trigger 01709240768 is likely a flaring star
  82. GRB 250912A: SVOM detection of a burst
  83. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  84. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  85. GRB 250911A: GECAM-B detection
  86. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  87. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  88. GRB 250910B: SVOM/GRM observation
  89. EP250911a: SVOM/VT optical observation
  90. GRB 250911A: MASTER optical counterpart observations
  91. EP250911a: SAO RAS optical observations
  92. GRB 250911A: Swift-XRT refined Analysis
  93. EP250911a: Swift-XRT observations
  94. EP250911a: Optical detection with Kinder observations
  95. GRB 250911A: Swift/UVOT Detection
  96. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  97. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  98. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  99. EP250911a: COLIBRÍ optical observations
  100. EP250911a: Einstein Probe detection of an X-ray transient

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