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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').

2445 results found.

  1. GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
  2. GRB 210217A: Mondy optical observations
  3. uGMRT radio detection of GRB 210204A
  4. GRB 210212A: Mondy optical observations
  5. GRB 210210A: CAHA 2nd epoch and jet break confirmation
  6. GRB 210212A: Possible host galaxy counterpart with the NOT
  7. GRB 210212A: BOOTES-4/MET optical upper limit
  8. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  9. GRB 210210A as a BdHN II
  10. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  11. GRB 210209A: BOOTES-4/MET optical upper limit
  12. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  13. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  14. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
  15. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  16. GRB 210205A: BOOTES-4/MET optical upper limit
  17. Short Fermi GRB 210119A or new SGR Swift J1851.2-6148: Possible MASTER Short OT detection
  18. GRB 201227A: continued Chilescope confirmation of variability of possible optical counterpart, redshift estimating
  19. GRB 201216C: TSHAO, Terskol, Mondy optical upper limits
  20. GRB 201227A: Chilescope optical observations, possible optical counterpart
  21. GRB 201229A: SAO RAS optical observations
  22. GRB 201229A: Swift detection of a burst with a possible optical counterpart
  23. Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event
  24. GRB 201221D: Archival PS1 Imaging of the Putative Host Galaxy
  25. IceCube-201222A: IceCube observation of a high-energy neutrino candidate event
  26. Swift Trigger 1014012: possible GRB 201221C
  27. IceCube-201221A: IceCube observation of a high-energy neutrino candidate event
  28. GRB 201214B: Swift BAT location of short burst
  29. GRB 201015A: optical observations and supernova identification
  30. GRB 200826A: GMOS-N detected source magnitude (Correction)
  31. GRB 201015A: 5-GHz radio afterglow detection with the EVN
  32. IceCube-201209A: IceCube observation of a high-energy neutrino candidate event
  33. IceCube-201130A: IceCube observation of a high-energy neutrino candidate event
  34. IceCube-201120A: IceCube observation of a high-energy neutrino candidate event
  35. ZTF20acozryr/AT2020yxz (GRB 201103B): correction to the GCN #28883 CrAO/ZTSh optical observations
  36. IceCube 201114A: Swift followup of Fermi J0703.5+0505
  37. Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
  38. VLASS identifies possible radio counterparts to IceCube-201115A, including a bright BL Lac candidate
  39. IceCube-201115A: IceCube observation of a high-energy neutrino candidate event
  40. IceCube-201114A - IceCube observation of a high-energy neutrino candidate event
  41. ZTF20acozryr/AT2020yxz (GRB 201103B): Flattening of the optical light curve
  42. GRB 201103B: GMG observation (2nd epoch)
  43. GRB 201029A: Swift-XRT refined Analysis
  44. IceCube-201021A: Optical counterpart of WISEA J172314.13+142101.5
  45. Fermi-LAT Gamma-ray Observations of IceCube-201021A and detection of a new gamma-ray source, Fermi J1725.5+1312
  46. IceCube-201021A: IceCube observation of a high-energy neutrino candidate event
  47. GRB 201017A: SAO RAS optical observations
  48. GRB 201017A: Assy and Mondy optical observations, possible afterglow detection
  49. GRB 201015A: Redshift from GTC/OSIRIS
  50. GRB 201013A: TSHAO and AbAO optical observations, afterglow confirmation
  51. IceCube-201014A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 201013A: FRAM-ORM possible afterglow candidate
  53. GRB 201008A: Swift/BAT-GUANO detection and possible arcminute localization
  54. IceCube-201007A - IceCube observation of a high-energy neutrino candidate track-like event
  55. IceCube-200929A: IceCube observation of a high-energy neutrino candidate event
  56. IceCube-200926B: IceCube observation of a high-energy neutrino candidate event
  57. IceCube-200926A: IceCube observation of a high-energy neutrino candidate event
  58. GRB 200922A: Swift detection of a burst with possible optical counterpart
  59. IceCube-200921A: IceCube observation of a high-energy neutrino candidate event
  60. IceCube-200916A - ZTF20acaapwk/SN2020tno classified as SN Ia
  61. IceCube-200916A - IceCube observation of a high-energy neutrino candidate track-like event
  62. IceCube-200911A: IceCube observation of a high-energy neutrino candidate event
  63. GRB 200826A: uGMRT radio upper limit at 1.25 GHz
  64. GRB 200901A: Swift/UVOT Detection
  65. GRB 200826A
  66. GRB 200826A: Lowell Discovery Telescope observations of ZTF20abwysqy
  67. Zwicky Transient Facility discovery of ZTF20abtxwfx/AT2020sev, a fast optical transient and candidate afterglow
  68. GRB 200826A: further analysis of the Konus-Wind data and classification
  69. GRB200826A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 620108997)
  70. Swift Trigger 992444: a possible GRB 200821A
  71. GRB 200806A: Swift/UVOT Possible Detection
  72. IceCube-200806A: IceCube observation of a high-energy neutrino candidate event
  73. GRB 200723A: ATLAS observations of GOTO candidate AT2020qer
  74. GRB 200716C: Kitab optical observations
  75. GRB 200716C: CrAO, Terskol, Assy-Turgen optical observations
  76. Konus-Wind observation of GRB 200716C: correction to GCN 28147
  77. Konus-Wind observation of GRB 200716C
  78. GRB 200716C: possible host galaxy from the SDSS
  79. GRB 200716C: Swift-XRT refined analysis correction
  80. GRB 200623A: Further MMTCam Observations of XRT Source #3
  81. GRB 200623A: LBT optical observations
  82. IceCube-200620A - IceCube observation of a high-energy neutrino candidate track-like event
  83. IceCube-200530A - SN2020lls likely unrelated
  84. Fermi-LAT Gamma-ray Observations of IceCube-200614A and detection of a new gamma-ray source, Fermi J0202.8+3132
  85. IceCube-200615A: IceCube observation of a high-energy neutrino candidate event
  86. IceCube-200614A - IceCube observation of a high-energy neutrino candidate track-like event
  87. GRB 200612A: Swift detection of a burst
  88. IceCube-200530A - SN2020lam classified as SN II without evidence of CSM interaction
  89. IceCube-200530A - IceCube observation of a high-energy neutrino candidate event
  90. Fermi-LAT Gamma-ray Observations of IceCube-190523A
  91. GRB 200522A: Correction to GCN 27792
  92. IceCube-200523A - IceCube observation of a high-energy neutrino candidate event
  93. GRB 200522A: Coincident catalogued galaxy at z~0.4
  94. IceCube-200512A: IceCube observation of a high-energy neutrino candidate event
  95. GRB 200509A: Swift detection of a burst with a possible optical counterpart
  96. SGR 1935+2154: MASTER optical observations
  97. Gagarin-day GRB 200412B: observations with the 3.6m Devasthal Optical Telescope
  98. IceCube-200425A - IceCube observation of a high-energy neutrino candidate event
  99. GRB 200415A correction to GCN 27627 (possible magnetar Giant Flare in Sculptor Galaxy): INTEGRAL observations
  100. GRB 200415A (possible magnetar Giant Flare in Sculptor Galaxy): INTEGRAL observations

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