Skip to main content
New! BOOM Notices and Schema v7.0.0. 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. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  2. GRB 250312A: Swift detection of a burst
  3. GRB 241213A: VIRT Optical Upper Limit
  4. GRB 241228A: VIRT Optical Upper Limit
  5. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  6. GRB 250223B: Fermi GBM Observation
  7. GRB 250311A: Swift-XRT observations
  8. GRB 250228A: Fermi GBM Observation
  9. GRB 250309B: 1.3m DFOT Optical observations
  10. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  11. EP250311a: Global MASTER-Net observations report
  12. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  13. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  14. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  15. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  16. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  17. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  18. GRB 250309B: PRIME near-infrared detection
  19. EP250304a: Chandra detection
  20. GRB 250225B: Swift-BAT refined analysis
  21. GRB 250311A/EP250311a: TRT optical upper limit
  22. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  23. GRB 250311A: Tiled Swift observations
  24. EP250311a/GRB 250311A: EP-WXT detection
  25. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  26. GRB 250311B: SVOM detection of a burst
  27. GRB 250309B: SVOM/VT optical observation
  28. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  29. The EP-WXT trigger 01709132425 is not a real source
  30. GRB 250309B / AT2025dws: further SAO RAS optical observations
  31. IceCube-250309A: Upper limits from Fermi-GBM Observations
  32. EP250308a: 1.6m Mephisto optical upper limits
  33. Konus-Wind detection of GRB 250309B
  34. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  35. IPN triangulation of GRB 250308A (short)
  36. IPN triangulation of GRB 250309B
  37. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  38. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  39. GRB 250309B: Swift-XRT refined Analysis
  40. GRB 250309B / IceCube-250309A: GECAM-B observations
  41. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  42. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  43. GRB 250309B / AT2025dws: SAO RAS optical observations
  44. GRB 250309B / AT2025dws: Swift-UVOT detection
  45. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  46. GRB 250309B: Fermi GBM Observation
  47. Fermi GRB 250309B: Global MASTER-Net observations report
  48. Fermi GRB 250309A: Global MASTER-Net observations report
  49. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  50. IceCube-250309A: No candidates from the Zwicky Transient Facility
  51. Fermi-LAT gamma-ray observations of IceCube-250309A
  52. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  53. GRB 250309B: Fermi GBM Final Localization
  54. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  55. GRB 230509B: Tiled Swift observations
  56. GRB 250308A: SVOM/GRM observation of a bright short burst
  57. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  58. IceCube Alert 250309.32: Global MASTER-Net observations report
  59. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  60. EP250308a: Global MASTER-Net observations report
  61. EP250308a: GSP optical upper limit
  62. EP250308a: FTW optical and NIR upper limits
  63. EP250308a: Einstein Probe detection of an X-ray transient
  64. EP250308a: NOT optical upper limit
  65. GRB 250309A: Fermi GBM Final Real-time Localization
  66. GRB 250306A: EIRSAT-1 GMOD detection
  67. The EP-WXT trigger 01709132387 is likely a flaring star
  68. Fermi GRB 250307A: Global MASTER-Net observations report
  69. Konus-Wind detection of GRB 250306A
  70. GRB 250307A: Fermi GBM Final Real-time Localization
  71. GRB 250306A: Swift-BAT refined analysis
  72. GRB 250306A: NuSTAR detection of the prompt emission
  73. EP250304a: MeerKAT detection of a possible radio counterpart
  74. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  75. GRB 250305A: AstroSat CZTI detection
  76. EP250302a:Xinglong optical observations
  77. GRB 250306A: AstroSat CZTI detection
  78. Fermi trigger No 762963055: Global MASTER-Net observations report
  79. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  80. Swift GRB 250306A: Global MASTER-Net observations report
  81. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  82. GRB 250306A: Swift detection of a burst
  83. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  84. GRB250101A: Radio upper limits from VLA observations
  85. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  86. GRB 250305A: SVOM/GRM observation of a burst
  87. The EP-WXT trigger 01709132323 is likely a flaring star
  88. EP250304A: Upper limits from Fermi-GBM Observations
  89. Fermi GRB 250305A: Global MASTER-Net observations report
  90. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  91. GRB 250305A: Fermi GBM Final Real-time Localization
  92. EP250302a: Optical Observations at CrAO and SAO RAS
  93. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  94. EP 250304A: Optical counterpart detection by LCO
  95. EP250302A: 1.3m DFOT optical afterglow detection
  96. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  97. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  98. Konus-Wind detection of GRB 250222A
  99. EP250304a: REM NIR upper limits
  100. IPN triangulation of GRB 250222A

Advanced

Download all Circulars as a .tar.gz archive:
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