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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"

19543 results found.

  1. Fermi trigger 576241792 / GRB 190406B: MASTER optical observation
  2. GRB 190406B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 576241792)
  3. IPN Triangulation of GRB 190415A
  4. LIGO/Virgo S190412m: Palomar Gattini-IR Wide-field Infrared Follow-up
  5. LIGO/Virgo S190412m: GOTO optical coverage - no notable counterparts
  6. LIGO/Virgo S190412m: Fermi-LAT search for a high-energy gamma-ray counterpart
  7. LIGO/Virgo S190412m: Swift/BAT data search
  8. LIGO/Virgo S190412m: J-GEM optical/NIR follow-up observations
  9. LIGO/Virgo S190412m/G329483: ANTARES neutrino search
  10. LIGO/Virgo S190412m: Hobby-Eberly Telescope VIRUS observations of target galaxies.
  11. LIGO/Virgo S190412m: HAWC follow-up
  12. INTEGRAL prompt observation of S190412m
  13. LIGO-Virgo S190412m: AGILE preliminary analysis
  14. LIGO/Virgo S190408an: GROND Observations of MASTER OT J154209.55-431742.2
  15. IPN triangulation of GRB 190409B (short)
  16. IceCube-190331A: Swift-XRT Follow-up Observations
  17. GRB 190409A: ground analysis reveals a likely spurious event
  18. LIGO/Virgo S190408an: MAXI/GSC Observations
  19. GRB 190404C: MITSuME Akeno and Okayama optical upper limits
  20. LIGO/Virgo S190408an: CALET Observations
  21. LIGO/Virgo S190408an: TMTS Optical Observation
  22. LIGO/Virgo S190408an: DDOTI/OAN Optical Observations
  23. LIGO/Virgo S190408an: HMT optical observations
  24. LIGO/Virgo S190408an: MASTER 3 OT's more detection
  25. LIGO/Virgo ST190408an: Fermi-LAT search for a high-energy gamma-ray counterpart
  26. GRB 190409A: Swift detection of a possible burst
  27. LIGO/Virgo S190408an: SAGUARO follow-up observations
  28. LIGO/Virgo S190408an: MASTER OT detection
  29. LIGO/Virgo S190408an: Swift/BAT data search
  30. LIGO-Virgo S190408an: HAWC follow-up
  31. INTEGRAL observation of S190408an
  32. LIGO-Virgo GW S190408an: J-GEM optical/NIR follow-up observations
  33. LIGO-Virgo S190408an: AGILE MCAL observations
  34. GRB 190404C: Swift-XRT afterglow detection
  35. Fermi TriggNum 576054086 (GRB 1904204.29) / MASTER OT J071404.52+550304.2: CrAO optical observations
  36. GRB190404C: GROWTH-India discovery of optical counterpart
  37. GRB 190404B: Tiled Swift observations
  38. GRB 190330A: MITSuME Akeno and Okayama optical upper limits
  39. Trigger 896552: Swift detection of PSR B1055-52
  40. LIGO/Virgo: Announcing the start of Observing Run 3 (O3) and the beginning of the public gravitational-wave alert era
  41. Konus-Wind observation of GRB 190329A
  42. GRB 190331B: Swift observations of a ground-detected burst
  43. Fermi-LAT Gamma-ray Observations of IceCube-190331A
  44. GRB 190331B: Swift ToO observations
  45. Swift Trigger 895503 is not a GRB
  46. Swift Trigger 895479: Detection of GRO J2058+42
  47. GRB 190326A: Swift-BAT refined analysis - a soft-short GRB or an SGR
  48. Swift Trigger 895257: Detection of GRO J2058+42 in outburst
  49. GRB 190324A: Swift/UVOT Observations
  50. GRB 190324A: Enhanced Swift-XRT position
  51. Further Chandra observations of GW170817 ~581-583 days since merger
  52. GRB 190324A: Swift-XRT observations
  53. Swift detection of LS I +61 303
  54. Correction: Chandra observations of GW170817 ~581 days since merger
  55. Chandra observations of GW170817 ~581 days since merger
  56. Swift Trigger 894268: Detection of GRO J2058+42 in outburst
  57. GRB 190320A: Swift/UVOT Upper Limits
  58. GRB 190320A: Enhanced Swift-XRT position
  59. GRB 190320A: Swift-XRT observations
  60. GRB 190311A: Swift/UVOT Detection
  61. GRB190311A: OAO observations
  62. GRB 190311A: GMG observation
  63. GRB 190311A: Enhanced Swift-XRT position
  64. GRB 190311A: NEXT-0.6m optical afterglow detection
  65. GRB 190311A: Mondy optical observations
  66. GRB 190311A: Swift detection of a burst with optical counterpart
  67. GRB 190305A: Swift-XRT afterglow detection
  68. IPN Triangulation of GRB 190304A (long)
  69. GRB 190306A: Swift-XRT observations
  70. GRB 190306A: Tiled Swift observations
  71. IPN Triangulation of GRB 190305A
  72. GRB 190305A: MAXI/GSC detection
  73. GRB 190305A: Tiled Swift observations
  74. Trigger 890732: Swift detection of MAXI J1631-479
  75. INTEGRAL observation of IceCube-190221A
  76. IceCube-190221A: Swift-XRT Follow-up Observations
  77. IceCube-190221A: Fermi-LAT Gamma-ray observations
  78. GRB 190220B: Fermi GBM observation
  79. GRB 190219A: CrAO and AbAO optical upper limit
  80. GRB 190220B: Kitab Observatory optical upper limit
  81. GRB 190220A: Swift-XRT refined Analysis
  82. GRB 190220A: Enhanced Swift-XRT position
  83. GRB 190219A: NOT optical afterglow candidate
  84. GRB 190219A: NEXT-0.6m optical upper limit
  85. GRB 190220A: Swift detection of a burst with an optical counterpart
  86. GRB 190219A: Enhanced Swift-XRT position
  87. GRB 190219A: Swift detection of a burst
  88. Trigger 889483: Swift detection of Swift J1858.6-0814
  89. GRB190211A: GROWTH-India detection of optical afterglow
  90. GRB 190211A: Tautenburg observations
  91. GRB 190211A: Swift/UVOT Detection
  92. GRB 190211A: NOT optical observations
  93. GRB 180703A: VLT/MUSE host galaxy redshift measurement
  94. GRB190211A: MASTER Global Robotic Net optical observation
  95. GRB 190211A: NEXT-0.6m optical afterglow detection
  96. GRB 190211A: Swift detection of a burst
  97. GRB 190202A: Terskol 2-m optical observations
  98. IPN Triangulation of GRB 190206A (short/extremely bright)
  99. GRB 190203A: Mondy optical observations
  100. GRB190202A: GROWTH-India detection of optical afterglow

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