Skip to main content
New JavaScript client! See news and announcements

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. Swift GRB210211.36: Global MASTER-Net observations report
  2. GRB 210211A: Fermi GBM Final Real-time Localization
  3. GRB 210210A: FRAM-ORM afterglow detection
  4. Fermi trigger No 634659312: Global MASTER-Net observations report
  5. GRB 210210A: Swift-BAT refined analysis
  6. IceCube Alert 210210.50: Global MASTER-Net observations report
  7. Fermi GRB 210210B: Global MASTER-Net observations report
  8. IceCube-210210A: Upper limits from Fermi-GBM Observations
  9. IceCube-210210A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  10. GRB 210210B: Fermi GBM Final Real-time Localization
  11. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  12. GRB 210209A: BOOTES-4/MET optical upper limit
  13. GRB 210210A: LCO Optical Afterglow Detection
  14. Swift GRB 210209A: Global MASTER-Net observations report
  15. GRB 210210A: Swift/UVOT Detection
  16. GRB 210112A: LBT host detection and correction to GCN 29319 (CAHA observations)
  17. GRB 210209A: MITSuME Akeno optical upper limits
  18. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  19. GRB 210209A: Swift/UVOT Upper Limits
  20. GRB 210210A: Swift-XRT refined Analysis
  21. GRB 210208A: GIT optical upper limit
  22. GRB 210210A: Redshift from OSIRIS/GTC
  23. GRB 210209A: Swift-XRT refined Analysis
  24. GRB 210210A: Enhanced Swift-XRT position
  25. GRB 210210A: MASTER afterglow observation
  26. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  27. Swift GRB 210210A: Global MASTER-Net observations report
  28. GRB 210210A: Swift detection of a burst with an optical counterpart
  29. GRB 210209A: Enhanced Swift-XRT position
  30. GRB 210209A: Swift detection of a burst
  31. GRB 210207B: Continued LCO Observations
  32. GRB 210104A: LBT observations
  33. GRB 210208A: BOOTES-2/TELMA optical upper limit
  34. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
  35. GRB 210207B: AstroSat CZTI detection
  36. GRB 210207B: Swift/UVOT Detection
  37. GRB 210207B: Swift-BAT refined analysis
  38. GRB 210207B: Insight-HXMT/HE detection
  39. GRB 210204A: LBT observations and jet break
  40. GRB 210204A: redshift revision of ZTF21aagwbjr/AT2021buv (correction to GCN 29411)
  41. GRB 210207B: LCO Optical Afterglow Detection
  42. GRB 210207B: KAIT Optical Observations
  43. GRB 210208A: A long GRB detected by INTEGRAL
  44. GRB 210207B: AGILE observations
  45. GRB 210207B: Swift-XRT refined Analysis
  46. Konus-Wind detection of GRB 210207B
  47. SGR 1935+2154: MAXI/GSC detection
  48. Konus-Wind detection of GRB 210204A (correction to GCN 29415)
  49. GRB 210207B: AbAO optical upper limit
  50. GRB 210207B: Enhanced Swift-XRT position
  51. GRB 210207B: optical detection with 3.6m Devasthal Optical Telescope
  52. GRB 210207B: Swift detection of a burst with a bright optical counterpart
  53. Fermi GRB 210207A: Global MASTER-Net observations report
  54. GRB 210207A: BALROG localization (Fermi Trigger / GRB 210207603)
  55. GRB 210204A (ZTF21aagwbjr/AT2021buv): Mondy and AbAO optical observations
  56. GRB 210207A: Fermi GBM Final Real-time Localization
  57. Konus-Wind detection of GRB 210204A / ZTF21aagwbjr
  58. GRB 210204A: Optical Observations from HCT
  59. GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
  60. GRB 210204A: Swift ToO observations
  61. VLT/X-shooter redshift of 1.466 for ZTF21aagwbjr/AT2021buv, strengthening its association with GRB 210204A
  62. GRB 210204A: AstroSat CZTI Detection
  63. GRB 210205A: Swift-BAT refined analysis
  64. IPN triangulation of GRB 210204A
  65. GRB 210205A: Swift-XRT refined Analysis
  66. GRB 210205A: MITSuME Ishigaki optical observation
  67. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  68. GRB 210205B: AGILE/MCAL detection of a burst
  69. GRB 210205A: Swift/UVOT Upper Limits
  70. Swift GRB 210205A: Global MASTER-Net observations report
  71. GRB 210205A: Nanshan/NEXT optical upper limit
  72. GRB 210205A: BOOTES-4/MET optical upper limit
  73. GRB 210205A: Enhanced Swift-XRT position
  74. GRB 210205A： GWAC-F60A optical upper limit
  75. GRB 210205A: Swift detection of a burst
  76. Fermi GRB 210204B: Global MASTER-Net observations report
  77. Fermi GRB 210204A: Global MASTER-Net observations report
  78. GRB 210204B: Fermi GBM Final Real-time Localization
  79. GRB 210204: Fermi GBM observation
  80. GRB 210204A: GECAM detection
  81. GRB 210204A: BALROG localization (Fermi Trigger 634112970 / GRB 210204270)
  82. GRB 210204A: Fermi GBM Final Real-time Localization
  83. GRB 210202A: AGILE/MCAL detection
  84. Fermi GBM Observations of a bright burst from SGR J1935+2154
  85. GRB 210202A: Fermi GBM detection
  86. GRB 210202A: Fermi-LAT detection
  87. Fermi GRB 210202A: Global MASTER-Net observations report
  88. Fermi trigger No 633963272: Global MASTER-Net observations report
  89. Recent activity of SGR 1935+2154 as observed by CGBM
  90. GRB 210202A: BALROG localization (Fermi Trigger / GRB 210202841)
  91. INTEGRAL detection of a short burst from SGR 1935+2154
  92. GRB 210202A: Fermi GBM Final Real-time Localization
  93. GRB 210131A: GECAM detection
  94. Fermi trigger No 633879387: Global MASTER-Net observations report
  95. GECAM observations of SGR 1935+2154
  96. GRB 210129A: Insight-HXMT/HE detection
  97. Continued Chandra observations of GW170817 at ~3.3 years since merger
  98. Fermi GBM Observations of SGR J1935+2154
  99. Konus-Wind detection of two bright bursts from SGR 1935+2154
  100. GRB 140330A: Swift-XRT refined Analysis

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov