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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"

8477 results found.

  1. IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube
  2. GRB 210517A: Swift detection of a burst
  3. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  4. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  5. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  6. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  7. IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
  8. IceCube-210510A: not observable by Fermi-GBM
  9. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  10. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  11. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  12. GRB 210506A: Swift/BAT-GUANO position retraction
  13. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  14. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  15. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  16. GRB 210506A: Swift ToO observations
  17. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  18. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  19. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  20. GRB 210504A: Swift detection of a burst
  21. Swift Detection of MAXI J1803-298 including an optical counterpart
  22. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  23. GRB 210420B: Correction to AST3-3 YaoAn magnitude
  24. GRB 210421B: Swift ToO observations
  25. GRB 210421A: Swift detection of a burst
  26. GRB 210420B: AST3-3 YaoAn Optical Observation
  27. GRB 210420B: Optical observations
  28. GRB 210419C: Swift detection of a burst
  29. GRB 210419A: Swift detection of a burst
  30. GRB 210413B: Swift ToO observations
  31. GRB 210411C: LCO Optical Afterglow Candidate
  32. GRB 210406A: 10.4m GTC follow-up observation
  33. GRB 210411C: Swift detection of a burst with an optical counterpart
  34. GRB 210406A: Swift-XRT observations
  35. GRB 210410A: RATIR Optical and NIR Observations
  36. GRB210410A: Candidate optical afterglow by Ondrejov D50
  37. GRB 210406A: Mondy optical afterglow candidate
  38. GRB 210406A: Swift ToO observations
  39. GRB 210406A: Mondy optical upper limit
  40. GRB 210402A: Further NOT optical observations
  41. GRB 210402A: NOT optical afterglow candidate
  42. Konus-Wind detection of GRB 210401A
  43. GRB 210402A: Swift detection of a burst
  44. GRB 210323B: Swift ToO observations
  45. GRB 210323A: Kitab optical upper limit
  46. GRB 210323A: Mondy optical observations, counterpart detection
  47. GRB 210323A: NOT optical afterglow candidate
  48. GRB 210323A: Swift detection of a short burst
  49. IceCube Astrotrack Bronze 135113_19489408.amon is likely background
  50. GRB210318B: Swift detection of a burst
  51. GRB 210318A: Swift detection of a burst
  52. GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
  53. GRB 210308A: Swift detection of a burst with an optical counterpart
  54. GRB 210307A: Swift detection of a burst
  55. GRB 210306A: Swift detection of a burst with a bright optical counterpart
  56. GRB 210305A: Swift detection of a burst
  57. GRB 210226A: KAIT Optical Upper Limit
  58. GRB 210226A: Swift detection of a burst
  59. GRB 210218A: Swift/UVOT observations
  60. GRB 210222A: CALET Gamma-Ray Burst Monitor detection
  61. GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
  62. GRB 210222B: Swift detection of a burst with an optical counterpart
  63. Fermi GBM Sub-Threshold Detection of GRB 210217A
  64. GRB 210217A: Swift-BAT refined analysis
  65. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  66. GRB 210217A: Swift detection of a burst with an optical counterpart
  67. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  68. GRB 210208A: 1.3m DFOT Optical upper limit
  69. Swift Trigger 1033144: Detection of SGR 1830-0645
  70. GRB 210212B: Swift ToO observations
  71. GRB 210212A: 1.3m DFOT Optical upper limit
  72. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  73. Swift Trigger 1032350: Detection of SGR 1830-0645
  74. IceCube-210210A: Upper limits from a search for additional neutrino events in IceCube
  75. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  76. GRB 210212A: Swift detection of a burst
  77. IceCube-210210A: No neutrino counterpart in ANTARES
  78. GRB 210211A: Swift detection of a burst
  79. IceCube-210210A: Upper limits from Fermi-GBM Observations
  80. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  81. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  82. GRB 210210A: Swift detection of a burst with an optical counterpart
  83. GRB 210209A: Swift detection of a burst
  84. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  85. GRB 210204A: Swift ToO observations
  86. GRB 210205A: Swift detection of a burst
  87. GRB 210120A : 1.3m DFOT optical observations
  88. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  89. GRB 210119A (Swift J1851.2-6148): Swift-BAT refined analysis
  90. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  91. GRB 210112A: 1.3m DFOT Optical upper limit
  92. GRB 210112A: OSN Reddened Afterglow Detection
  93. NuEm-210111A : No neutrino counterpart in ANTARES
  94. GRB 210112A: Kitab a optical upper limit
  95. GRB 210112A: Swift detection of a burst with an optical counterpart
  96. GRB 210102B: Assy optical afterglow identification
  97. GRB 210102B: Tiled Swift observations
  98. GRB 210104B: Swift detection of a burst
  99. GRB 210104A: Swift detection of a burst with a bright optical counterpart
  100. GRB 210102B: Tiled Swift observations

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