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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"

23659 results found.

  1. GRB 250920B: Swift-BAT refined analysis
  2. GRB 250920B: Fermi GBM Observation
  3. GRB 250920A: Fermi GBM Detection
  4. GRB 250920C: Fermi GBM Observation
  5. Swift GRB 250920C: Global MASTER-Net observations report
  6. GRB 250920A: SVOM/GRM observation
  7. GRB250920C: LCOGT Optical Detection
  8. GRB 250920B: Swift-XRT refined Analysis
  9. GRB 250920B: SVOM/C-GFT optical observations
  10. GRB 250920C: GOTO optical counterpart candidate
  11. GRB 250919A / EP250919a: LCO optical observation
  12. Konus-Wind detection of GRB 250919A
  13. GRB 250920C: Swift detection of a burst
  14. GRB 250920C: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  16. Swift GRB 250920B: Global MASTER-Net observations report
  17. GRB 250920B: Fermi GBM Final Real-time Localization
  18. GRB 250920A: BALROG localization (Fermi Trigger 780029651 / GRB 250920121)
  19. GRB 250920A: Fermi GBM Final Localization
  20. GRB 250919A/EP250919a: SVOM/VT optical observation
  21. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  22. GRB 250919A: Fermi GBM Observation
  23. Fermi GRB 250918A: Global MASTER-Net observations report
  24. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  25. GRB 250918A: SVOM/GRM observation
  26. GRB 250919A: Swift-XRT afterglow detection
  27. GRB 250919A: Fermi-LAT detection
  28. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  29. GRB 250919A: SVOM/GRM observation of a very bright GRB
  30. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  31. EP250919a: Global MASTER-Net observations report
  32. GRB 250916A: Fermi GBM Observation
  33. Fermi GRB 250919A: Global MASTER-Net observations report
  34. GRB 250919A: Fermi GBM Final Real-time Localization
  35. GRB 250916A: KAIT optical observations
  36. GRB 250916A: NuSTAR detection of the prompt emission
  37. GRB 250912A: SVOM/ECLAIRs refined analysis
  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 250918A: Fermi GBM Final Real-time Localization
  42. EP250916a: EP-FXT follow-up observation
  43. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  44. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  45. GRB 250916A: Glowbug gamma-ray detection
  46. GRB 250917B: Fermi GBM Observation
  47. GRB 250917B: Swift-XRT observations
  48. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  49. Fermi GRB 250917B: Global MASTER-Net observations report
  50. GRB 250916A: GOTO optical counterpart candidate
  51. GRB 250917B: Fermi GBM Final Real-time Localization
  52. GRB 250917A: Fermi GBM Final Real-time Localization
  53. The EP-WXT trigger 01709241037 is likely a flaring star
  54. GRB 250916A: AstroSat CZTI detection of a bright long burst
  55. GRB 250910A: SVOM/ECLAIRs refined analysis
  56. Fermi GRB 250916A: Global MASTER-Net observations report
  57. GRB 250916A: Fermi GBM Final Real-time Localization
  58. EP250827b: VLA Observations
  59. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  60. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  61. SVOM/sb25091517: SVOM detection of an X-ray transient
  62. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  63. GRB250912A: VLT/HAWK-I follow-up observations
  64. GRB 250912A: VLT observations
  65. GRB 250912A: Fermi GBM Observation
  66. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  67. GRB 250912A:SVOM/VT optical upper limit
  68. The EP-WXT trigger 01709240768 is likely a flaring star
  69. Fermi GRB 250912A: Global MASTER-Net observations report
  70. EP250911a: Global MASTER-Net observations report
  71. GRB 250912A: SVOM detection of a burst
  72. GRB 250912A: Fermi GBM Final Real-time Localization
  73. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  74. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  75. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  76. EP250911a: Upper limit from Fermi-GBM Observations
  77. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  78. GRB 250911A: GECAM-B detection
  79. GRB 250911A: Swift-BAT refined analysis
  80. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  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 250910C: Fermi GBM Final Localization Correction
  86. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  87. GRB 250909B: SVOM/GRM observation
  88. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  89. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  90. Fermi GRB 250910B: Global MASTER-Net observations report
  91. EP250911a: LCO optical counterpart discovery
  92. EP250910a: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  94. GRB 250903A: SVOM/ECLAIRs refined analysis
  95. GRB 250911A: Swift detection of a burst
  96. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  97. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  98. GRB 250910B: Fermi GBM Final Real-time Localization
  99. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  100. GRB 250910A: SVOM/VT optical upper limit

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