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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"

8476 results found.

  1. GRB 210517A: Swift detection of a burst
  2. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  3. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  4. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  5. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  6. IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
  7. IceCube-210510A: not observable by Fermi-GBM
  8. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  9. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  10. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 210506A: Swift/BAT-GUANO position retraction
  12. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  13. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  14. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  15. GRB 210506A: Swift ToO observations
  16. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  17. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  18. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  19. GRB 210504A: Swift detection of a burst
  20. Swift Detection of MAXI J1803-298 including an optical counterpart
  21. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  22. GRB 210420B: Correction to AST3-3 YaoAn magnitude
  23. GRB 210421B: Swift ToO observations
  24. GRB 210421A: Swift detection of a burst
  25. GRB 210420B: AST3-3 YaoAn Optical Observation
  26. GRB 210420B: Optical observations
  27. GRB 210419C: Swift detection of a burst
  28. GRB 210419A: Swift detection of a burst
  29. GRB 210413B: Swift ToO observations
  30. GRB 210411C: LCO Optical Afterglow Candidate
  31. GRB 210406A: 10.4m GTC follow-up observation
  32. GRB 210411C: Swift detection of a burst with an optical counterpart
  33. GRB 210406A: Swift-XRT observations
  34. GRB 210410A: RATIR Optical and NIR Observations
  35. GRB210410A: Candidate optical afterglow by Ondrejov D50
  36. GRB 210406A: Mondy optical afterglow candidate
  37. GRB 210406A: Swift ToO observations
  38. GRB 210406A: Mondy optical upper limit
  39. GRB 210402A: Further NOT optical observations
  40. GRB 210402A: NOT optical afterglow candidate
  41. Konus-Wind detection of GRB 210401A
  42. GRB 210402A: Swift detection of a burst
  43. GRB 210323B: Swift ToO observations
  44. GRB 210323A: Kitab optical upper limit
  45. GRB 210323A: Mondy optical observations, counterpart detection
  46. GRB 210323A: NOT optical afterglow candidate
  47. GRB 210323A: Swift detection of a short burst
  48. IceCube Astrotrack Bronze 135113_19489408.amon is likely background
  49. GRB210318B: Swift detection of a burst
  50. GRB 210318A: Swift detection of a burst
  51. GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
  52. GRB 210308A: Swift detection of a burst with an optical counterpart
  53. GRB 210307A: Swift detection of a burst
  54. GRB 210306A: Swift detection of a burst with a bright optical counterpart
  55. GRB 210305A: Swift detection of a burst
  56. GRB 210226A: KAIT Optical Upper Limit
  57. GRB 210226A: Swift detection of a burst
  58. GRB 210218A: Swift/UVOT observations
  59. GRB 210222A: CALET Gamma-Ray Burst Monitor detection
  60. GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
  61. GRB 210222B: Swift detection of a burst with an optical counterpart
  62. Fermi GBM Sub-Threshold Detection of GRB 210217A
  63. GRB 210217A: Swift-BAT refined analysis
  64. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  65. GRB 210217A: Swift detection of a burst with an optical counterpart
  66. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  67. GRB 210208A: 1.3m DFOT Optical upper limit
  68. Swift Trigger 1033144: Detection of SGR 1830-0645
  69. GRB 210212B: Swift ToO observations
  70. GRB 210212A: 1.3m DFOT Optical upper limit
  71. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  72. Swift Trigger 1032350: Detection of SGR 1830-0645
  73. IceCube-210210A: Upper limits from a search for additional neutrino events in IceCube
  74. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  75. GRB 210212A: Swift detection of a burst
  76. IceCube-210210A: No neutrino counterpart in ANTARES
  77. GRB 210211A: Swift detection of a burst
  78. IceCube-210210A: Upper limits from Fermi-GBM Observations
  79. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  80. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  81. GRB 210210A: Swift detection of a burst with an optical counterpart
  82. GRB 210209A: Swift detection of a burst
  83. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  84. GRB 210204A: Swift ToO observations
  85. GRB 210205A: Swift detection of a burst
  86. GRB 210120A : 1.3m DFOT optical observations
  87. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  88. GRB 210119A (Swift J1851.2-6148): Swift-BAT refined analysis
  89. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  90. GRB 210112A: 1.3m DFOT Optical upper limit
  91. GRB 210112A: OSN Reddened Afterglow Detection
  92. NuEm-210111A : No neutrino counterpart in ANTARES
  93. GRB 210112A: Kitab a optical upper limit
  94. GRB 210112A: Swift detection of a burst with an optical counterpart
  95. GRB 210102B: Assy optical afterglow identification
  96. GRB 210102B: Tiled Swift observations
  97. GRB 210104B: Swift detection of a burst
  98. GRB 210104A: Swift detection of a burst with a bright optical counterpart
  99. GRB 210102B: Tiled Swift observations
  100. Swift Trigger 1015615 is not a GRB

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