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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"

8295 results found.

  1. GRB 210610B: Zwicky Transient Facility afterglow detection
  2. GRB 210610B: Swift detection of a burst with bright optical afterglow
  3. GRB 210610A: Swift detection of a burst with an optical counterpart
  4. IceCube-210608A: not observable by Fermi-GBM
  5. IceCube-210608A: IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 210606A: Swift ToO observations
  7. GRB 210605B: Swift ToO observations
  8. Initial results of a NICER X-ray monitoring of the magnetar, Swift J1555.2-5402
  9. Fermi GBM Sub-Threshold Detection of new Swift SGR J1555.2-5402
  10. Swift Detection of probable new Swift SGR J1555.2-5402
  11. GRB210529B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 644025222)
  12. GRB 210528B: DDOTI Upper Limits on the Afterglow
  13. Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
  14. GRB210413B: further Swift-XRT observations
  15. GRB 210520A: Tiled Swift observations
  16. Fermi GBM observation of a bright burst from magneta
  17. GRB 210518.889: DDOTI Upper Limits on the Afterglow
  18. IceCube-210516A: No significant detection in HAWC
  19. IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube
  20. GRB 210517A: Swift detection of a burst
  21. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  22. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  23. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  24. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  25. IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
  26. IceCube-210510A: not observable by Fermi-GBM
  27. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  28. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  29. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 210506A: Swift/BAT-GUANO position retraction
  31. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  32. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  33. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  34. GRB 210506A: Swift ToO observations
  35. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  36. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  37. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  38. GRB 210504A: Swift detection of a burst
  39. Swift Detection of MAXI J1803-298 including an optical counterpart
  40. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  41. GRB 210420B: Correction to AST3-3 YaoAn magnitude
  42. GRB 210421B: Swift ToO observations
  43. GRB 210421A: Swift detection of a burst
  44. GRB 210420B: AST3-3 YaoAn Optical Observation
  45. GRB 210420B: Optical observations
  46. GRB 210419C: Swift detection of a burst
  47. GRB 210419A: Swift detection of a burst
  48. GRB 210413B: Swift ToO observations
  49. GRB 210411C: LCO Optical Afterglow Candidate
  50. GRB 210406A: 10.4m GTC follow-up observation
  51. GRB 210411C: Swift detection of a burst with an optical counterpart
  52. GRB 210406A: Swift-XRT observations
  53. GRB 210410A: RATIR Optical and NIR Observations
  54. GRB210410A: Candidate optical afterglow by Ondrejov D50
  55. GRB 210406A: Mondy optical afterglow candidate
  56. GRB 210406A: Swift ToO observations
  57. GRB 210406A: Mondy optical upper limit
  58. GRB 210402A: Further NOT optical observations
  59. GRB 210402A: NOT optical afterglow candidate
  60. Konus-Wind detection of GRB 210401A
  61. GRB 210402A: Swift detection of a burst
  62. GRB 210323B: Swift ToO observations
  63. GRB 210323A: Kitab optical upper limit
  64. GRB 210323A: Mondy optical observations, counterpart detection
  65. GRB 210323A: NOT optical afterglow candidate
  66. GRB 210323A: Swift detection of a short burst
  67. IceCube Astrotrack Bronze 135113_19489408.amon is likely background
  68. GRB210318B: Swift detection of a burst
  69. GRB 210318A: Swift detection of a burst
  70. GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
  71. GRB 210308A: Swift detection of a burst with an optical counterpart
  72. GRB 210307A: Swift detection of a burst
  73. GRB 210306A: Swift detection of a burst with a bright optical counterpart
  74. GRB 210305A: Swift detection of a burst
  75. GRB 210226A: KAIT Optical Upper Limit
  76. GRB 210226A: Swift detection of a burst
  77. GRB 210218A: Swift/UVOT observations
  78. GRB 210222A: CALET Gamma-Ray Burst Monitor detection
  79. GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
  80. GRB 210222B: Swift detection of a burst with an optical counterpart
  81. Fermi GBM Sub-Threshold Detection of GRB 210217A
  82. GRB 210217A: Swift-BAT refined analysis
  83. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  84. GRB 210217A: Swift detection of a burst with an optical counterpart
  85. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  86. GRB 210208A: 1.3m DFOT Optical upper limit
  87. Swift Trigger 1033144: Detection of SGR 1830-0645
  88. GRB 210212B: Swift ToO observations
  89. GRB 210212A: 1.3m DFOT Optical upper limit
  90. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  91. Swift Trigger 1032350: Detection of SGR 1830-0645
  92. IceCube-210210A: Upper limits from a search for additional neutrino events in IceCube
  93. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  94. GRB 210212A: Swift detection of a burst
  95. IceCube-210210A: No neutrino counterpart in ANTARES
  96. GRB 210211A: Swift detection of a burst
  97. IceCube-210210A: Upper limits from Fermi-GBM Observations
  98. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  99. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  100. GRB 210210A: Swift detection of a burst with an optical counterpart

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