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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"

7447 results found.

  1. GRB 210618A: Swift-XRT observations
  2. Swift-BAT Trigger 1055000: Swift detection of an outburst from 4U 1543-47
  3. GRB 210610B: Zwicky Transient Facility afterglow detection
  4. GRB 210610B: Swift detection of a burst with bright optical afterglow
  5. GRB 210610A: Swift detection of a burst with an optical counterpart
  6. IceCube-210608A: not observable by Fermi-GBM
  7. IceCube-210608A: IceCube observation of a high-energy neutrino candidate track-like event
  8. GRB 210606A: Swift ToO observations
  9. GRB 210605B: Swift ToO observations
  10. Initial results of a NICER X-ray monitoring of the magnetar, Swift J1555.2-5402
  11. Swift Detection of probable new Swift SGR J1555.2-5402
  12. GRB210529B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 644025222)
  13. GRB 210528B: DDOTI Upper Limits on the Afterglow
  14. Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
  15. GRB210413B: further Swift-XRT observations
  16. GRB 210520A: Tiled Swift observations
  17. GRB 210518.889: DDOTI Upper Limits on the Afterglow
  18. GRB 210517A: Swift detection of a burst
  19. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  20. AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
  21. GRB 210512.786: DDOTI Upper Limits on the Afterglow
  22. GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
  23. IceCube-210510A: not observable by Fermi-GBM
  24. IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
  25. Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
  26. Swift trigger 1047857 is 4U 1700-377
  27. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 210506A: Swift/BAT-GUANO position retraction
  29. HAWC-210507A: No neutrino counterpart candidates in ANTARES search
  30. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  31. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  32. GRB 210506A: Swift ToO observations
  33. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  34. ZTF and LT observations of ZTF21aayokph (AT2021lfa), a fast-fading red transient
  35. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  36. GRB 210504A: Swift detection of a burst
  37. Swift Detection of MAXI J1803-298 including an optical counterpart
  38. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  39. GRB 210420B: Correction to AST3-3 YaoAn magnitude
  40. GRB 210421B: Swift ToO observations
  41. GRB 210421A: Swift detection of a burst
  42. GRB 210420B: AST3-3 YaoAn Optical Observation
  43. GRB 210420B: Optical observations
  44. GRB 210419C: Swift detection of a burst
  45. GRB 210419A: Swift detection of a burst
  46. GRB 210413B: Swift ToO observations
  47. GRB 210411C: LCO Optical Afterglow Candidate
  48. GRB 210406A: 10.4m GTC follow-up observation
  49. GRB 210411C: Swift detection of a burst with an optical counterpart
  50. GRB 210406A: Swift-XRT observations
  51. GRB 210410A: RATIR Optical and NIR Observations
  52. GRB210410A: Candidate optical afterglow by Ondrejov D50
  53. GRB 210406A: Mondy optical afterglow candidate
  54. GRB 210406A: Swift ToO observations
  55. GRB 210406A: Mondy optical upper limit
  56. GRB 210402A: Further NOT optical observations
  57. GRB 210402A: NOT optical afterglow candidate
  58. Konus-Wind detection of GRB 210401A
  59. GRB 210402A: Swift detection of a burst
  60. GRB 210323B: Swift ToO observations
  61. GRB 210323A: Kitab optical upper limit
  62. GRB 210323A: Mondy optical observations, counterpart detection
  63. GRB 210323A: NOT optical afterglow candidate
  64. GRB 210323A: Swift detection of a short burst
  65. GRB210318B: Swift detection of a burst
  66. GRB 210318A: Swift detection of a burst
  67. GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
  68. GRB 210308A: Swift detection of a burst with an optical counterpart
  69. GRB 210307A: Swift detection of a burst
  70. GRB 210306A: Swift detection of a burst with a bright optical counterpart
  71. GRB 210305A: Swift detection of a burst
  72. GRB 210226A: KAIT Optical Upper Limit
  73. GRB 210226A: Swift detection of a burst
  74. GRB 210218A: Swift/UVOT observations
  75. GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
  76. GRB 210222B: Swift detection of a burst with an optical counterpart
  77. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  78. GRB 210217A: Swift detection of a burst with an optical counterpart
  79. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  80. GRB 210208A: 1.3m DFOT Optical upper limit
  81. Swift Trigger 1033144: Detection of SGR 1830-0645
  82. GRB 210212B: Swift ToO observations
  83. GRB 210212A: 1.3m DFOT Optical upper limit
  84. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  85. Swift Trigger 1032350: Detection of SGR 1830-0645
  86. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  87. GRB 210212A: Swift detection of a burst
  88. GRB 210210A as a BdHN II
  89. IceCube-210210A: No neutrino counterpart in ANTARES
  90. GRB 210211A: Swift detection of a burst
  91. IceCube-210210A: Upper limits from Fermi-GBM Observations
  92. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  93. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  94. GRB 210210A: Swift detection of a burst with an optical counterpart
  95. GRB 210209A: Swift detection of a burst
  96. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  97. GRB 210204A: Swift ToO observations
  98. GRB 210205A: Swift detection of a burst
  99. Continued Chandra observations of GW170817 at ~3.3 years since merger
  100. GRB 210120A : 1.3m DFOT optical observations

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