Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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 250225B: Swift-BAT refined analysis
  2. GRB 250311A/EP250311a: TRT optical upper limit
  3. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  4. GRB 250311A: Tiled Swift observations
  5. EP250311a/GRB 250311A: EP-WXT detection
  6. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 250311B: SVOM detection of a burst
  8. GRB 250309B: SVOM/VT optical observation
  9. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  10. The EP-WXT trigger 01709132425 is not a real source
  11. GRB 250309B / AT2025dws: further SAO RAS optical observations
  12. IceCube-250309A: Upper limits from Fermi-GBM Observations
  13. EP250308a: 1.6m Mephisto optical upper limits
  14. Konus-Wind detection of GRB 250309B
  15. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  16. IPN triangulation of GRB 250308A (short)
  17. IPN triangulation of GRB 250309B
  18. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  19. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  20. GRB 250309B: Swift-XRT refined Analysis
  21. GRB 250309B / IceCube-250309A: GECAM-B observations
  22. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  23. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  24. GRB 250309B / AT2025dws: SAO RAS optical observations
  25. GRB 250309B / AT2025dws: Swift-UVOT detection
  26. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  27. GRB 250309B: Fermi GBM Observation
  28. Fermi GRB 250309B: Global MASTER-Net observations report
  29. Fermi GRB 250309A: Global MASTER-Net observations report
  30. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  31. IceCube-250309A: No candidates from the Zwicky Transient Facility
  32. Fermi-LAT gamma-ray observations of IceCube-250309A
  33. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  34. GRB 250309B: Fermi GBM Final Localization
  35. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  36. GRB 230509B: Tiled Swift observations
  37. GRB 250308A: SVOM/GRM observation of a bright short burst
  38. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  39. IceCube Alert 250309.32: Global MASTER-Net observations report
  40. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  41. EP250308a: Global MASTER-Net observations report
  42. EP250308a: GSP optical upper limit
  43. EP250308a: FTW optical and NIR upper limits
  44. EP250308a: Einstein Probe detection of an X-ray transient
  45. EP250308a: NOT optical upper limit
  46. GRB 250309A: Fermi GBM Final Real-time Localization
  47. GRB 250306A: EIRSAT-1 GMOD detection
  48. The EP-WXT trigger 01709132387 is likely a flaring star
  49. Fermi GRB 250307A: Global MASTER-Net observations report
  50. Konus-Wind detection of GRB 250306A
  51. GRB 250307A: Fermi GBM Final Real-time Localization
  52. GRB 250306A: Swift-BAT refined analysis
  53. GRB 250306A: NuSTAR detection of the prompt emission
  54. EP250304a: MeerKAT detection of a possible radio counterpart
  55. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  56. GRB 250305A: AstroSat CZTI detection
  57. EP250302a:Xinglong optical observations
  58. GRB 250306A: AstroSat CZTI detection
  59. Fermi trigger No 762963055: Global MASTER-Net observations report
  60. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  61. Swift GRB 250306A: Global MASTER-Net observations report
  62. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  63. GRB 250306A: Swift detection of a burst
  64. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  65. GRB250101A: Radio upper limits from VLA observations
  66. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  67. GRB 250305A: SVOM/GRM observation of a burst
  68. The EP-WXT trigger 01709132323 is likely a flaring star
  69. EP250304A: Upper limits from Fermi-GBM Observations
  70. Fermi GRB 250305A: Global MASTER-Net observations report
  71. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  72. GRB 250305A: Fermi GBM Final Real-time Localization
  73. EP250302a: Optical Observations at CrAO and SAO RAS
  74. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  75. EP 250304A: Optical counterpart detection by LCO
  76. EP250302A: 1.3m DFOT optical afterglow detection
  77. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  78. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  79. Konus-Wind detection of GRB 250222A
  80. EP250304a: REM NIR upper limits
  81. IPN triangulation of GRB 250222A
  82. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  83. EP250302a: Mondy Continued Optical Observations
  84. EP250304a: VLT/X-shooter redshift z = 0.200
  85. EP250304a: Swift-XRT detection of a fading X-ray source
  86. EP250304a: TRT optical counterpart detection
  87. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  88. EP250304a: Global MASTER-Net observations report
  89. EP250304a: Einstein Probe detection of an X-ray transient
  90. The EP-WXT trigger 01709132212 is not a real source
  91. EP250302a: SVOM/VT optical observation
  92. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  93. EP250302a: SAO RAS optical observations
  94. EP250302a : GIT optical follow-up
  95. EP250302a: VLT/X-shooter redshift confirmation
  96. EP250225a: the candidate optical counterpart is an AGN
  97. EP250302a: Kinder optical follow-up observations
  98. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  99. EP250302a: Swift/UVOT detection
  100. EP250302a: NUTTelA-TAO Early Measurments

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