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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"

45431 results found.

  1. GRB 250916A: further SAO RAS optical observations
  2. GRB 250912A: SVOM/ECLAIRs refined analysis
  3. GRB 250917B: Swift-BAT refined analysis
  4. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  5. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  6. GRB 250918A: Fermi GBM Final Real-time Localization
  7. GRB 250917B: Swift/UVOT Upper Limits
  8. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  9. GRB 250916A: Swift-XRT observations
  10. EP250916a: EP-FXT follow-up observation
  11. GRB 250916A: MAO/AZT-22 optical observations
  12. GRB 250916A: SAO RAS optical observations
  13. GRB 250916A : GIT optical observations
  14. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  15. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  16. GRB 250916A: Glowbug gamma-ray detection
  17. GRB250917B: WFST optical observations
  18. GRB 250916A: Swift ToO observations
  19. GRB 250917B: Fermi GBM Observation
  20. GRB 250917B: Swift-XRT observations
  21. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  22. Fermi GRB 250917B: Global MASTER-Net observations report
  23. GRB 250917B: Swift detection of a short burst
  24. GRB 250916A: GOTO optical counterpart candidate
  25. GRB 250917B: Fermi GBM Final Real-time Localization
  26. GRB 250917A: Fermi GBM Final Real-time Localization
  27. The EP-WXT trigger 01709241037 is likely a flaring star
  28. GRB 250916A: AstroSat CZTI detection of a bright long burst
  29. GRB 250910A: SVOM/ECLAIRs refined analysis
  30. EP250916a: Einstein Probe detection of an X-ray transient
  31. Fermi GRB 250916A: Global MASTER-Net observations report
  32. GRB 250916A: Fermi GBM Final Real-time Localization
  33. EP250827b: VLA Observations
  34. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  35. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  36. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  37. SVOM/sb25091517: SVOM detection of an X-ray transient
  38. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  39. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  40. GRB 250912A: Swift-XRT observations
  41. GRB250912A: VLT/HAWK-I follow-up observations
  42. GRB 250912A: VLT observations
  43. GRB 250912A: Fermi GBM Observation
  44. GRB 250911A: Insight-HXMT detection
  45. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  46. GRB 250912A:SVOM/VT optical upper limit
  47. GRB 250912A: LCO optical upper limit
  48. The EP-WXT trigger 01709240768 is likely a flaring star
  49. Fermi GRB 250912A: Global MASTER-Net observations report
  50. EP250911a: Global MASTER-Net observations report
  51. GRB 250912A: SVOM detection of a burst
  52. GRB 250912A: Fermi GBM Final Real-time Localization
  53. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  54. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  55. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  56. EP250911a: Upper limit from Fermi-GBM Observations
  57. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  58. GRB 250911A: GECAM-B detection
  59. GRB 250911A: Swift-BAT refined analysis
  60. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  61. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  62. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  63. GRB 250910B: SVOM/GRM observation
  64. EP250911a: SVOM/VT optical observation
  65. GRB 250911A: MASTER optical counterpart observations
  66. EP250911a: SAO RAS optical observations
  67. GRB 250911A: Swift-XRT refined Analysis
  68. GRB 250910C: Fermi GBM Final Localization Correction
  69. EP250911a: Swift-XRT observations
  70. EP250911a: Optical detection with Kinder observations
  71. GRB 250911A: Swift/UVOT Detection
  72. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  73. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  74. GRB 250909B: Insight-HXMT detection
  75. GRB 250909B: SVOM/GRM observation
  76. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  77. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  78. EP250911a: COLIBRÍ optical observations
  79. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  80. Fermi GRB 250910B: Global MASTER-Net observations report
  81. EP250911a: LCO optical counterpart discovery
  82. EP250910a: Global MASTER-Net observations report
  83. EP250911a: Einstein Probe detection of an X-ray transient
  84. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  85. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  86. GRB 250903A: SVOM/ECLAIRs refined analysis
  87. GRB 250911A: Enhanced Swift-XRT position
  88. GRB 250911A: Swift-XRT observations
  89. GRB 250911A: COLIBRÍ optical counterpart candidate
  90. GRB 250911A: Swift detection of a burst
  91. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  92. GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
  93. GRB 250910B: Fermi GBM Final Real-time Localization
  94. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  95. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  96. GRB 250909B: AstroSat CZTI detection of a long burst
  97. GRB 250910A: SVOM/VT optical upper limit
  98. EP250908C: GROND observation of the fading optical counterpart
  99. GRB 250910A: LCO optical upper limit
  100. GRB 250909A: AstroSat CZTI detection

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