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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"

2750 results found.

  1. GRB 210411C: A very significant early X-ray afterglow
  2. GRB 210410A: A twin of short GRB 090510 with complementary observations
  3. GRB 210410A: RATIR Optical and NIR Observations
  4. GRB 210207B: Prompt and very late time observations with HCT.
  5. GRB 210323A: Gemini-North Optical Source Detection
  6. GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
  7. GRB 210217A: Mondy optical observations
  8. uGMRT radio detection of GRB 210204A
  9. GRB 210212A: Mondy optical observations
  10. GRB 210210A: CAHA 2nd epoch and jet break confirmation
  11. GRB 210212A: Possible host galaxy counterpart with the NOT
  12. GRB 210212A: BOOTES-4/MET optical upper limit
  13. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  14. GRB 210210A as a BdHN II
  15. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  16. GRB 210209A: BOOTES-4/MET optical upper limit
  17. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  18. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  19. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
  20. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  21. GRB 210205A: BOOTES-4/MET optical upper limit
  22. Short Fermi GRB 210119A or new SGR Swift J1851.2-6148: Possible MASTER Short OT detection
  23. GRB 201227A: continued Chilescope confirmation of variability of possible optical counterpart, redshift estimating
  24. GRB 201216C: TSHAO, Terskol, Mondy optical upper limits
  25. GRB 201227A: Chilescope optical observations, possible optical counterpart
  26. GRB 201229A: SAO RAS optical observations
  27. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  28. Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event
  29. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  30. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  31. Swift Trigger 1014012: possible GRB 201221C
  32. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  33. GRB 201214B: Swift BAT location of short burst
  34. GRB 201015A: optical observations and supernova identification
  35. GRB 200826A: GMOS-N detected source magnitude (Correction)
  36. GRB 201015A: 5-GHz radio afterglow detection with the EVN
  37. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event
  38. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  39. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  40. ZTF20acozryr/AT2020yxz (GRB 201103B): correction to the GCN #28883 CrAO/ZTSh optical observations
  41. IceCube 201114A: Swift followup of Fermi J0703.5+0505
  42. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  43. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  44. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  45. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  46. ZTF20acozryr/AT2020yxz (GRB 201103B): Flattening of the optical light curve
  47. GRB 201103B: GMG observation (2nd epoch)
  48. GRB 201029A: Swift-XRT refined Analysis
  49. IceCube-201021A: Optical counterpart of WISEA J172314.13+142101.5
  50. Fermi-LAT Gamma-ray Observations of IceCube-201021A and detection of a new gamma-ray source, Fermi J1725.5+1312
  51. IceCube-201021A: IceCube observation of a high-energy neutrino candidate event
  52. GRB 201017A: SAO RAS optical observations
  53. GRB 201017A: Assy and Mondy optical observations, possible afterglow detection
  54. GRB 201015A: Redshift from GTC/OSIRIS
  55. GRB 201013A: TSHAO and AbAO optical observations, afterglow confirmation
  56. IceCube-201014A - IceCube observation of a high-energy neutrino candidate track-like event
  57. GRB 201013A: FRAM-ORM possible afterglow candidate
  58. GRB 201008A: Swift/BAT-GUANO detection and possible arcminute localization
  59. IceCube-201007A - IceCube observation of a high-energy neutrino candidate track-like event
  60. IceCube-200929A: IceCube observation of a high-energy neutrino candidate event
  61. IceCube-200926B: IceCube observation of a high-energy neutrino candidate event
  62. IceCube-200926A: IceCube observation of a high-energy neutrino candidate event
  63. GRB 200922A: Swift detection of a burst with possible optical counterpart
  64. IceCube-200921A: IceCube observation of a high-energy neutrino candidate event
  65. IceCube-200916A - ZTF20acaapwk/SN2020tno classified as SN Ia
  66. IceCube-200916A - IceCube observation of a high-energy neutrino candidate track-like event
  67. IceCube-200911A: IceCube observation of a high-energy neutrino candidate event
  68. GRB 200826A: uGMRT radio upper limit at 1.25 GHz
  69. GRB 200901A: Swift/UVOT Detection
  70. GRB 200826A
  71. GRB 200826A: Lowell Discovery Telescope observations of ZTF20abwysqy
  72. Zwicky Transient Facility discovery of ZTF20abtxwfx/AT2020sev, a fast optical transient and candidate afterglow
  73. GRB 200826A: further analysis of the Konus-Wind data and classification
  74. GRB200826A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 620108997)
  75. Swift Trigger 992444: a possible GRB 200821A
  76. GRB 200806A: Swift/UVOT Possible Detection
  77. IceCube-200806A: IceCube observation of a high-energy neutrino candidate event
  78. GRB 200723A: ATLAS observations of GOTO candidate AT2020qer
  79. GRB 200716C: Kitab optical observations
  80. GRB 200716C: CrAO, Terskol, Assy-Turgen optical observations
  81. Konus-Wind observation of GRB 200716C: correction to GCN 28147
  82. Konus-Wind observation of GRB 200716C
  83. GRB 200716C: possible host galaxy from the SDSS
  84. GRB 200716C: Swift-XRT refined analysis correction
  85. GRB 200623A: Further MMTCam Observations of XRT Source #3
  86. GRB 200623A: LBT optical observations
  87. IceCube-200620A - IceCube observation of a high-energy neutrino candidate track-like event
  88. IceCube-200530A - SN2020lls likely unrelated
  89. Fermi-LAT Gamma-ray Observations of IceCube-200614A and detection of a new gamma-ray source, Fermi J0202.8+3132
  90. IceCube-200615A: IceCube observation of a high-energy neutrino candidate event
  91. IceCube-200614A - IceCube observation of a high-energy neutrino candidate track-like event
  92. GRB 200612A: Swift detection of a burst
  93. IceCube-200530A - SN2020lam classified as SN II without evidence of CSM interaction
  94. IceCube-200530A - IceCube observation of a high-energy neutrino candidate event
  95. Fermi-LAT Gamma-ray Observations of IceCube-190523A
  96. GRB 200522A: Correction to GCN 27792
  97. IceCube-200523A - IceCube observation of a high-energy neutrino candidate event
  98. GRB 200522A: Coincident catalogued galaxy at z~0.4
  99. IceCube-200512A: IceCube observation of a high-energy neutrino candidate event
  100. GRB 200509A: Swift detection of a burst with a possible optical counterpart

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