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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"

2803 results found.

  1. GRB 211130A: MeerLICHT identification of possible afterglow candidate
  2. IceCube-211208A - IceCube observation of a high-energy neutrino candidate track-like event
  3. Swift Trigger 1086826 (possible GRB 211203A) is likely not an astrophysical event
  4. GRB 211106A: HST Observations
  5. IceCube-211125A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  6. IceCube-211125A: IceCube observation of a high-energy neutrino candidate track-like event
  7. IceCube-211123A - IceCube observation of a high-energy neutrino candidate track-like event
  8. GRB 211023A: optical observations and photometric evidence of supernova
  9. IceCube-211117A : IceCube observation of a high-energy neutrino candidate track-like event
  10. IceCube-211116A : IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 211023A: BTA spectroscopic redshift
  12. GRB 211023A: continued 1.3m DFOT Optical Observations and possible jet break
  13. GRB 211024A: Possible afterglow candidate from GIT
  14. Possible Short GRB 211023B: CAHA 2.2m Detection
  15. GRB 211023B: TSHAO optical observation
  16. IceCube-211023A - IceCube observation of a high-energy neutrino candidate track-like event
  17. IceCube-210922A: Hard X-ray flux limit for JCMT/SCUBA2 source from NuSTAR observations
  18. Swift trigger 1078701: MITSuME Akeno optical upper limits
  19. Swift Trigger 1078701: Mondy, CrAO, AbAO observations, possible optical counterpart
  20. GRB 210928A: Swift-XRT analysis (replaces GCN 30914)
  21. IceCube-210922A - IceCube observation of a high-energy neutrino candidate track-like event
  22. GRB 210912A: BOOTES-5/JGT optical afterglow candidate (Correction to GCNC 30823)
  23. IceCube-210811A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 210802A: Further Swift/XRT observation and afterglow confirmation
  25. GRB 210807A: correction to the GCN Circ. #30614 Assy optical observations
  26. GRB 210802A: BOOTES-2/TELMA optical upper limit
  27. IceCube-210730A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 210726A: OSIRIS/GTC observations
  29. GRB 210726A: Deep CAHA 2.2m limit
  30. IceCube-210717A: IceCube observation of a high-energy neutrino candidate track-like event
  31. GRB 210704A: OSIRIS/GTC Observations and Archival Detection of the Possible Host Galaxy
  32. GRB 210704A: Gemini-North Infrared Source Detection
  33. GRB 210708B: Swift-BAT refined analysis
  34. IceCube-210629A - Spectroscopic observation of AT2021osi
  35. GRB 210708B: Swift detection of a possible burst
  36. GRB 210704A: possible local hosts
  37. GRB 210702A: BOOTES-3/YA optical counterpart observations
  38. GRB 210702A: Swift/UVOT redshift
  39. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  40. GRB 210626A: Swift/XRT afterglow confirmation
  41. GRB 210618A: 1.5m OSN optical upper limit
  42. GRB 210619B: Ondrejov D50 detection
  43. GRB 210610A: 1.5m OSN optical observation
  44. GRB 210610B: BOOTES-2/TELMA optical observation
  45. IceCube-210608A: IceCube observation of a high-energy neutrino candidate track-like event
  46. GRB 210607A/MAXI J1733-222: MAXI/GSC detection
  47. GRB210413B: further Swift-XRT observations
  48. GRB 210517A: KCT optical upper limit
  49. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  50. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  51. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  52. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  53. GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
  54. GRB 210411C: A very significant early X-ray afterglow
  55. GRB 210410A: A twin of short GRB 090510 with complementary observations
  56. GRB 210410A: RATIR Optical and NIR Observations
  57. GRB 210207B: Prompt and very late time observations with HCT.
  58. GRB 210323A: Gemini-North Optical Source Detection
  59. GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
  60. GRB 210217A: Mondy optical observations
  61. uGMRT radio detection of GRB 210204A
  62. GRB 210212A: Mondy optical observations
  63. GRB 210210A: CAHA 2nd epoch and jet break confirmation
  64. GRB 210212A: Possible host galaxy counterpart with the NOT
  65. GRB 210212A: BOOTES-4/MET optical upper limit
  66. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  67. GRB 210210A as a BdHN II
  68. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  69. GRB 210209A: BOOTES-4/MET optical upper limit
  70. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  71. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  72. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
  73. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  74. GRB 210205A: BOOTES-4/MET optical upper limit
  75. Short Fermi GRB 210119A or new SGR Swift J1851.2-6148: Possible MASTER Short OT detection
  76. GRB 201227A: continued Chilescope confirmation of variability of possible optical counterpart, redshift estimating
  77. GRB 201216C: TSHAO, Terskol, Mondy optical upper limits
  78. GRB 201227A: Chilescope optical observations, possible optical counterpart
  79. GRB 201229A: SAO RAS optical observations
  80. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  81. Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event
  82. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  83. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  84. Swift Trigger 1014012: possible GRB 201221C
  85. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  86. GRB 201214B: Swift BAT location of short burst
  87. GRB 201015A: optical observations and supernova identification
  88. GRB 200826A: GMOS-N detected source magnitude (Correction)
  89. GRB 201015A: 5-GHz radio afterglow detection with the EVN
  90. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event
  91. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  92. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  93. ZTF20acozryr/AT2020yxz (GRB 201103B): correction to the GCN #28883 CrAO/ZTSh optical observations
  94. IceCube 201114A: Swift followup of Fermi J0703.5+0505
  95. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  96. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  97. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  98. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  99. ZTF20acozryr/AT2020yxz (GRB 201103B): Flattening of the optical light curve
  100. GRB 201103B: GMG observation (2nd epoch)

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