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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"

2623 results found.

  1. Tev Blazar as possible optical counterpart of the high-energy neutrino IceCube-220303A
  2. IceCube-220303A - IceCube observation of a high-energy neutrino candidate track-like event
  3. IceCube-220225A - IceCube observation of a high-energy neutrino candidate track-like event
  4. IceCube Alert 220220.60:NuEm-220220A: MASTER optical possible counterpart
  5. ZTF22aabjpxh/AT2022cva: ZTF Discovery of a Rapidly Fading Transient with a Likely Long-GRB Counterpart
  6. IceCube-220221A - IceCube observation of a high-energy neutrino candidate track-like event
  7. ZTF22aaajecp/AT2022cmc: Keck DEIMOS Redshift
  8. GRB 220211A: redshift lower limit estimating
  9. GRB 210919A: SPI-ACS/INTEGRAL observation and evaluation of Ep
  10. IceCube-220205B - IceCube observation of a high-energy neutrino candidate track-like event
  11. IceCube-220205A - IceCube observation of a high-energy neutrino candidate track-like event
  12. IceCube-220202A: IceCube observation of a high-energy neutrino candidate track-like event
  13. Swift currently in safe hold with science slews disabled
  14. IceCube-220115A - IceCube observation of a high-energy neutrino candidate track-like event
  15. Konus-Wind detection of GRB 220101A (correction to GCN 31433)
  16. GRB 211227A: A possible short GRB with extended emission at z = 0.228?
  17. IceCube-211216B - IceCube observation of a high-energy neutrino candidate track-like event
  18. IceCube-211216A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 211211A - Gemini K-band detection
  20. GRB 211211A: redshift estimation and SPI-ACS/INTEGRAL detection
  21. GRB 211130A: MeerLICHT identification of possible afterglow candidate
  22. IceCube-211208A - IceCube observation of a high-energy neutrino candidate track-like event
  23. Swift Trigger 1086826 (possible GRB 211203A) is likely not an astrophysical event
  24. GRB 211106A: HST Observations
  25. IceCube-211125A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  26. IceCube-211125A: IceCube observation of a high-energy neutrino candidate track-like event
  27. IceCube-211123A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 211023A: optical observations and photometric evidence of supernova
  29. IceCube-211117A : IceCube observation of a high-energy neutrino candidate track-like event
  30. IceCube-211116A : IceCube observation of a high-energy neutrino candidate track-like event
  31. GRB 211023A: BTA spectroscopic redshift
  32. GRB 211023A: continued 1.3m DFOT Optical Observations and possible jet break
  33. GRB 211024A: Possible afterglow candidate from GIT
  34. Possible Short GRB 211023B: CAHA 2.2m Detection
  35. GRB 211023B: TSHAO optical observation
  36. IceCube-211023A - IceCube observation of a high-energy neutrino candidate track-like event
  37. IceCube-210922A: Hard X-ray flux limit for JCMT/SCUBA2 source from NuSTAR observations
  38. Swift trigger 1078701: MITSuME Akeno optical upper limits
  39. Swift Trigger 1078701: Mondy, CrAO, AbAO observations, possible optical counterpart
  40. GRB 210928A: Swift-XRT analysis (replaces GCN 30914)
  41. IceCube-210922A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 210912A: BOOTES-5/JGT optical afterglow candidate (Correction to GCNC 30823)
  43. IceCube-210811A - IceCube observation of a high-energy neutrino candidate track-like event
  44. GRB 210802A: Further Swift/XRT observation and afterglow confirmation
  45. GRB 210807A: correction to the GCN Circ. #30614 Assy optical observations
  46. GRB 210802A: BOOTES-2/TELMA optical upper limit
  47. IceCube-210730A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 210726A: OSIRIS/GTC observations
  49. GRB 210726A: Deep CAHA 2.2m limit
  50. IceCube-210717A: IceCube observation of a high-energy neutrino candidate track-like event
  51. GRB 210704A: OSIRIS/GTC Observations and Archival Detection of the Possible Host Galaxy
  52. GRB 210704A: Gemini-North Infrared Source Detection
  53. GRB 210708B: Swift-BAT refined analysis
  54. IceCube-210629A - Spectroscopic observation of AT2021osi
  55. GRB 210708B: Swift detection of a possible burst
  56. GRB 210704A: possible local hosts
  57. GRB 210702A: BOOTES-3/YA optical counterpart observations
  58. GRB 210702A: Swift/UVOT redshift
  59. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  60. GRB 210626A: Swift/XRT afterglow confirmation
  61. GRB 210618A: 1.5m OSN optical upper limit
  62. GRB 210619B: Ondrejov D50 detection
  63. GRB 210610A: 1.5m OSN optical observation
  64. GRB 210610B: BOOTES-2/TELMA optical observation
  65. IceCube-210608A: IceCube observation of a high-energy neutrino candidate track-like event
  66. GRB 210607A/MAXI J1733-222: MAXI/GSC detection
  67. GRB210413B: further Swift-XRT observations
  68. GRB 210517A: KCT optical upper limit
  69. IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
  70. IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
  71. Fermi-LAT Gamma-ray Observations of IceCube-210503A and detection of a new gamma-ray source, Fermi J0931.9+3633
  72. IceCube-210503A: IceCube observation of a high-energy neutrino candidate event
  73. GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
  74. GRB 210411C: A very significant early X-ray afterglow
  75. GRB 210410A: A twin of short GRB 090510 with complementary observations
  76. GRB 210410A: RATIR Optical and NIR Observations
  77. GRB 210207B: Prompt and very late time observations with HCT.
  78. GRB 210323A: Gemini-North Optical Source Detection
  79. GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
  80. GRB 210217A: Mondy optical observations
  81. uGMRT radio detection of GRB 210204A
  82. GRB 210212A: Mondy optical observations
  83. GRB 210210A: CAHA 2nd epoch and jet break confirmation
  84. GRB 210212A: Possible host galaxy counterpart with the NOT
  85. GRB 210212A: BOOTES-4/MET optical upper limit
  86. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  87. GRB 210210A as a BdHN II
  88. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  89. GRB 210209A: BOOTES-4/MET optical upper limit
  90. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  91. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  92. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
  93. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  94. GRB 210205A: BOOTES-4/MET optical upper limit
  95. Short Fermi GRB 210119A or new SGR Swift J1851.2-6148: Possible MASTER Short OT detection
  96. GRB 201227A: continued Chilescope confirmation of variability of possible optical counterpart, redshift estimating
  97. GRB 201216C: TSHAO, Terskol, Mondy optical upper limits
  98. GRB 201227A: Chilescope optical observations, possible optical counterpart
  99. GRB 201229A: SAO RAS optical observations
  100. GRB 201229A: Swift detection of a burst with a possible optical counterpart

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