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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"

7301 results found.

  1. GRB 210820A: Swift detection of a burst with an optical counterpart
  2. GRB 210818A: Swift detection of a burst with an optical counterpart
  3. IceCube-210730A: not observable by Fermi-GBM
  4. IceCube-210811A: Upper limits from Fermi-GBM Observations
  5. IceCube-210811A: No Candidate Counterparts from the Zwicky Transient Facility
  6. GRB 210730A: Tautenburg observations
  7. IceCube-210811A - IceCube observation of a high-energy neutrino candidate track-like event
  8. GRB 210802A: Further Swift/XRT observation and afterglow confirmation
  9. GRB 210807C: Swift detection of a burst
  10. GRB 210807A: Swift detection of a burst with an optical counterpart
  11. GRB 210802A: DDOTI Upper Limits
  12. GRB 210802A: Tiled Swift observations
  13. GRB 210731A: MeerLICHT optical afterglow detection
  14. GRB 210731A: Swift detection of a burst
  15. GRB 210730A: Campo Imperatore optical observations
  16. IceCube-210730A - IceCube observation of a high-energy neutrino candidate track-like event
  17. GRB 210724A: Early CAHA 2.2m limit
  18. GRB 210730A: Swift detection of a burst near M82
  19. GRB 210724A: Corrected Swift-XRT enhanced position
  20. GRB 210726A: Deep CAHA 2.2m limit
  21. GRB 210726A: RATIR Optical Upper Limits and Candidate Host Galaxy
  22. GRB 210726A: Swift detection of a burst
  23. GRB 210724A: Zeiss-1000 of Koshka observatory, optical upper limit
  24. GRB 210724A: Afterglow candidate from OSIRIS/GTC
  25. GRB 210725B: Swift detection of a burst
  26. GRB 210725A: KAIT Optical Upper Limit
  27. GRB 210725A: Swift detection of a burst
  28. GRB 210724A: Swift detection of a burst
  29. GRB 210723A: Swift detection of a burst
  30. GRB 210722A: Swift detection of a burst with a bright optical counterpart
  31. IceCube-210717A: IceCube observation of a high-energy neutrino candidate track-like event
  32. GRB 210712A: Swift detection of a burst
  33. GRB 210704A: OSIRIS/GTC Observations and Archival Detection of the Possible Host Galaxy
  34. GRB 210706A: Swift/XRT afterglow confirmation
  35. IceCube-210629A - Spectroscopic observation of AT2021osi
  36. GRB 210706A: optical upper limit of Sintesz-Newton/CrAO and AS-32/AbAO
  37. GRB 210706A: Swift ToO observations
  38. GRB 210704A: CAHA 2.2m Afterglow Detection
  39. GRB 210704A: RATIR optical upper limits
  40. GRB 210704A: TNG detection of the optical afterglow candidate
  41. GRB 210704A: Assy optical afterglow candidate
  42. GRB 210704A: Swift ToO observations
  43. GRB 210702A: Swift detection of a burst with a bright optical counterpart
  44. IceCube-210629A: One Candidate Counterpart from the Zwicky Transient Facility
  45. IceCube-210629A: Upper limits from Fermi-GBM Observations
  46. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  47. GRB 210626A: Swift/XRT afterglow confirmation
  48. GRB 210626A: CAHA 2.2m telescope optical limit
  49. GRB 210626A: Ondrejov D50 optical limit
  50. GRB 210626A: GIT optical upper limit
  51. GRB 210626A: Swift ToO observations
  52. GRB 210622A: Swift ToO observations
  53. Swift Trigger 1057131: detection of a burst from SGR Swift J1555.2-5402
  54. GRB 210619B: Swift detection of a bright burst and optical counterpart
  55. GRB 210618A: Swift-XRT observations
  56. Swift-BAT Trigger 1055000: Swift detection of an outburst from 4U 1543-47
  57. GRB 210610B: Zwicky Transient Facility afterglow detection
  58. GRB 210610B: Swift detection of a burst with bright optical afterglow
  59. GRB 210610A: Swift detection of a burst with an optical counterpart
  60. IceCube-210608A: not observable by Fermi-GBM
  61. IceCube-210608A: IceCube observation of a high-energy neutrino candidate track-like event
  62. GRB 210606A: Swift ToO observations
  63. GRB 210605B: Swift ToO observations
  64. Initial results of a NICER X-ray monitoring of the magnetar, Swift J1555.2-5402
  65. Swift Detection of probable new Swift SGR J1555.2-5402
  66. GRB210529B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 644025222)
  67. GRB 210528B: DDOTI Upper Limits on the Afterglow
  68. Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
  69. GRB210413B: further Swift-XRT observations
  70. GRB 210520A: Tiled Swift observations
  71. GRB 210518.889: DDOTI Upper Limits on the Afterglow
  72. GRB 210517A: Swift detection of a burst
  73. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  74. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  75. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  76. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  77. IceCube-210510A: not observable by Fermi-GBM
  78. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  79. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  80. Swift trigger 1047857 is 4U 1700-377
  81. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 210506A: Swift/BAT-GUANO position retraction
  83. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  84. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  85. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  86. GRB 210506A: Swift ToO observations
  87. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  88. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  89. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  90. GRB 210504A: Swift detection of a burst
  91. Swift Detection of MAXI J1803-298 including an optical counterpart
  92. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  93. GRB 210420B: Correction to AST3-3 YaoAn magnitude
  94. GRB 210421B: Swift ToO observations
  95. GRB 210421A: Swift detection of a burst
  96. GRB 210420B: AST3-3 YaoAn Optical Observation
  97. GRB 210420B: Optical observations
  98. GRB 210419C: Swift detection of a burst
  99. GRB 210419A: Swift detection of a burst
  100. GRB 210413B: Swift ToO observations

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