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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 210411C: LCO Optical Afterglow Candidate
  2. GRB 210406A: 10.4m GTC follow-up observation
  3. GRB 210411C: Swift detection of a burst with an optical counterpart
  4. GRB 210406A: Swift-XRT observations
  5. GRB 210410A: RATIR Optical and NIR Observations
  6. GRB210410A: Candidate optical afterglow by Ondrejov D50
  7. GRB 210406A: Mondy optical afterglow candidate
  8. GRB 210406A: Swift ToO observations
  9. GRB 210406A: Mondy optical upper limit
  10. GRB 210402A: Further NOT optical observations
  11. GRB 210402A: NOT optical afterglow candidate
  12. Konus-Wind detection of GRB 210401A
  13. GRB 210402A: Swift detection of a burst
  14. GRB 210323B: Swift ToO observations
  15. GRB 210323A: Kitab optical upper limit
  16. GRB 210323A: Mondy optical observations, counterpart detection
  17. GRB 210323A: NOT optical afterglow candidate
  18. GRB 210323A: Swift detection of a short burst
  19. GRB210318B: Swift detection of a burst
  20. GRB 210318A: Swift detection of a burst
  21. GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
  22. GRB 210308A: Swift detection of a burst with an optical counterpart
  23. GRB 210307A: Swift detection of a burst
  24. GRB 210306A: Swift detection of a burst with a bright optical counterpart
  25. GRB 210305A: Swift detection of a burst
  26. GRB 210226A: KAIT Optical Upper Limit
  27. GRB 210226A: Swift detection of a burst
  28. GRB 210218A: Swift/UVOT observations
  29. GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
  30. GRB 210222B: Swift detection of a burst with an optical counterpart
  31. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  32. GRB 210217A: Swift detection of a burst with an optical counterpart
  33. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  34. GRB 210208A: 1.3m DFOT Optical upper limit
  35. Swift Trigger 1033144: Detection of SGR 1830-0645
  36. GRB 210212B: Swift ToO observations
  37. GRB 210212A: 1.3m DFOT Optical upper limit
  38. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  39. Swift Trigger 1032350: Detection of SGR 1830-0645
  40. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  41. GRB 210212A: Swift detection of a burst
  42. GRB 210210A as a BdHN II
  43. IceCube-210210A: No neutrino counterpart in ANTARES
  44. GRB 210211A: Swift detection of a burst
  45. IceCube-210210A: Upper limits from Fermi-GBM Observations
  46. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  47. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  48. GRB 210210A: Swift detection of a burst with an optical counterpart
  49. GRB 210209A: Swift detection of a burst
  50. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  51. GRB 210204A: Swift ToO observations
  52. GRB 210205A: Swift detection of a burst
  53. Continued Chandra observations of GW170817 at ~3.3 years since merger
  54. GRB 210120A : 1.3m DFOT optical observations
  55. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  56. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  57. GRB 210112A: 1.3m DFOT Optical upper limit
  58. NuEm-210111A : No neutrino counterpart in ANTARES
  59. GRB 210112A: Kitab a optical upper limit
  60. GRB 210112A: Swift detection of a burst with an optical counterpart
  61. GRB 210102B: Assy optical afterglow identification
  62. GW170817: HST observations at 3.4 years from merger
  63. GRB 210102B: Tiled Swift observations
  64. GRB 210104B: Swift detection of a burst
  65. GRB 210104A: Swift detection of a burst with a bright optical counterpart
  66. GRB 210102B: Tiled Swift observations
  67. GRB 201229A: AbAO optical afterglow detection, TSHAO optical upper limit
  68. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  69. GRB 201227A: Tiled Swift observations
  70. GRB 201227A: Swift ToO observations
  71. IceCube-201222A: No Candidate Counterparts from the Zwicky Transient Facility
  72. GRB 201223A: Swift detection of a burst with a bright optical counterpart
  73. GRB 201221D: SMA submm observation
  74. GRB 201221D: LCOGT upper limits
  75. IceCube-201222A: not observable by Fermi-GBM
  76. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  77. GRB 201221D: Lowell Discovery Telescope afterglow observations
  78. GRB 201221D: FRAM-ORM optical limit
  79. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  80. GRB 201221D: candidate optical counterpart from the NOT
  81. GRB 201221D: Swift detection of a bright short burst
  82. Swift Trigger 1014012: possible GRB 201221C
  83. IceCube-201221A: not observable by Fermi-GBM
  84. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  85. GRB 201221A: Swift detection of a burst
  86. GRB 201214A: 1.3m DFOT, optical upper limits
  87. GRB 201216C: VLT afterglow candidate discovery
  88. GRB 201216A: Swift ToO observations
  89. Chandra observations of GW170817 at ~3.3 years since merger (Full report)
  90. VLA observations of GW170817 at ~3.3 years post-merger
  91. GRB 201214B: Swift ToO observations
  92. Potential X-ray KN afterglow from Chandra observations of GW170817 ~3.3 years since merger (3 Epochs of 4)
  93. GRB 201214A: Swift ToO observations
  94. IceCube-201209A: No Candidate Counterparts from the Zwicky Transient Facility
  95. GRB 201203A: 1.3m DFOT, optical upper limits
  96. IceCube-201209A: Upper limits from Fermi-GBM Observations
  97. IceCube-201209A: No neutrino counterpart candidates in ANTARES search
  98. Chandra observations of GW170817 at ~3.3 years since merger (Observation 1 of 4)
  99. GRB 201208A: LCO observations
  100. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event

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