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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"
  1. GRB 210213B: Insight-HXMT/HE detection
  2. ZTF21aakruew/AT2021cwd: ZTF and LT discovery of a hostless, red, and rapidly fading optical transient
  3. GRB 210212A: Gemini South optical observations
  4. IceCube alert 134994_1103075 retraction
  5. Fermi GRB 210213A: Global MASTER-Net observations report
  6. IceCube Alert 210213.78: Global MASTER-Net observations report
  7. GRB 210213A: Fermi GBM Final Real-time Localization
  8. GRB 210210A: CAHA 2nd epoch and jet break confirmation
  9. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  10. Swift Trigger 1032350: Detection of SGR 1830-0645
  11. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued CrAO and AbAO optical observations
  12. GRB 210212A: Possible host galaxy counterpart with the NOT
  13. Swift GRB 210212A: Global MASTER-Net observations report
  14. GRB 210212A: MITSuME Akeno optical upper limits
  15. GRB 210212A: Swift-XRT refined Analysis
  16. GRB 210212A: BOOTES-4/MET optical upper limit
  17. IceCube-210210A: Upper limits from a search for additional neutrino events in IceCube
  18. GRB 210212A: Swift/UVOT Upper Limits
  19. GRB 210212A: Swift-BAT refined analysis
  20. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  21. GRB 210212A: Enhanced Swift-XRT position
  22. GRB 210210A : 1.3m DFOT optical observations
  23. GRB 210212A: Swift detection of a burst
  24. GRB 210207B: GECAM detection
  25. GRB 210211A: Swift/UVOT Detection
  26. GRB 210211A: Swift-XRT refined Analysis
  27. GRB 210211A: Swift-BAT refined analysis
  28. GRB 210211A: Fermi GBM observation
  29. GRB 210210A as a BdHN II
  30. Swift-XRT observations of IceCube-210210A
  31. GRB 210209A: Swift-BAT refined analysis
  32. GRB 210211A: Enhanced Swift-XRT position
  33. GRB 210211A: MASTER optical observation of REM OT
  34. GRB 210210A: CAHA detection and likely jet break
  35. IceCube-210210A: No neutrino counterpart in ANTARES
  36. GRB 210211A: REM optical/NIR afterglow detection
  37. Fermi-LAT Gamma-ray Observations of IceCube-210210A
  38. GRB 210211A: Swift detection of a burst
  39. Swift GRB210211.36: Global MASTER-Net observations report
  40. GRB 210211A: Fermi GBM Final Real-time Localization
  41. GRB 210210A: FRAM-ORM afterglow detection
  42. Fermi trigger No 634659312: Global MASTER-Net observations report
  43. GRB 210210A: Swift-BAT refined analysis
  44. IceCube Alert 210210.50: Global MASTER-Net observations report
  45. Fermi GRB 210210B: Global MASTER-Net observations report
  46. IceCube-210210A: Upper limits from Fermi-GBM Observations
  47. IceCube-210210A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  48. GRB 210210B: Fermi GBM Final Real-time Localization
  49. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  50. GRB 210209A: BOOTES-4/MET optical upper limit
  51. GRB 210210A: LCO Optical Afterglow Detection
  52. Swift GRB 210209A: Global MASTER-Net observations report
  53. GRB 210210A: Swift/UVOT Detection
  54. GRB 210112A: LBT host detection and correction to GCN 29319 (CAHA observations)
  55. GRB 210209A: MITSuME Akeno optical upper limits
  56. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  57. GRB 210209A: Swift/UVOT Upper Limits
  58. GRB 210210A: Swift-XRT refined Analysis
  59. GRB 210208A: GIT optical upper limit
  60. GRB 210210A: Redshift from OSIRIS/GTC
  61. GRB 210209A: Swift-XRT refined Analysis
  62. GRB 210210A: Enhanced Swift-XRT position
  63. GRB 210210A: MASTER afterglow observation
  64. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  65. Swift GRB 210210A: Global MASTER-Net observations report
  66. GRB 210210A: Swift detection of a burst with an optical counterpart
  67. GRB 210209A: Enhanced Swift-XRT position
  68. GRB 210209A: Swift detection of a burst
  69. GRB 210207B: Continued LCO Observations
  70. GRB 210104A: LBT observations
  71. GRB 210208A: BOOTES-2/TELMA optical upper limit
  72. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
  73. GRB 210207B: AstroSat CZTI detection
  74. GRB 210207B: Swift/UVOT Detection
  75. GRB 210207B: Swift-BAT refined analysis
  76. GRB 210207B: Insight-HXMT/HE detection
  77. GRB 210204A: LBT observations and jet break
  78. GRB 210204A: redshift revision of ZTF21aagwbjr/AT2021buv (correction to GCN 29411)
  79. GRB 210207B: LCO Optical Afterglow Detection
  80. GRB 210207B: KAIT Optical Observations
  81. GRB 210208A: A long GRB detected by INTEGRAL
  82. GRB 210207B: AGILE observations
  83. GRB 210207B: Swift-XRT refined Analysis
  84. Konus-Wind detection of GRB 210207B
  85. SGR 1935+2154: MAXI/GSC detection
  86. Konus-Wind detection of GRB 210204A (correction to GCN 29415)
  87. GRB 210207B: AbAO optical upper limit
  88. GRB 210207B: Enhanced Swift-XRT position
  89. GRB 210207B: optical detection with 3.6m Devasthal Optical Telescope
  90. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  91. Fermi GRB 210207A: Global MASTER-Net observations report
  92. GRB 210207A: BALROG localization (Fermi Trigger / GRB 210207603)
  93. GRB 210204A (ZTF21aagwbjr/AT2021buv): Mondy and AbAO optical observations
  94. GRB 210207A: Fermi GBM Final Real-time Localization
  95. Konus-Wind detection of GRB 210204A / ZTF21aagwbjr
  96. GRB 210204A: Optical Observations from HCT
  97. GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
  98. GRB 210204A: Swift ToO observations
  99. VLT/X-shooter redshift of 1.466 for ZTF21aagwbjr/AT2021buv, strengthening its association with GRB 210204A
  100. GRB 210204A: AstroSat CZTI Detection

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