Skip to main content
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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 250316A: Swift ToO observations
  2. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  3. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  4. The EP-WXT trigger 01709132801 is likely a flaring star
  5. GRB 250316A: Fermi GBM Final Real-time Localization
  6. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  7. GRB 250314A: EP-FXT afterglow detection
  8. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  9. GRB 250314A: Swift/UVOT Upper Limits
  10. GRB 250312B: GRBAlpha detection
  11. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  12. GRB 250314A: Swift XRT Detection
  13. EP250315a: optical counterpart candidate detected by Gemini North
  14. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  15. EP250315a: Einstein Probe detection of an X-ray transient
  16. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  17. SVOM/MXT upper limit on GRB 250314A
  18. GRB 250314A: SVOM/VT upper limit
  19. GRB 250314A: NOT near-infrared candidate counterpart
  20. GRB 250313A: Fermi GBM Detection
  21. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  22. GRB 250312B: Fermi GBM Observation
  23. GRB 250313A: Swift-XRT observations
  24. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  25. Konus-Wind detection of GRB 250313A
  26. Konus-Wind detection of GRB 250308A
  27. GRB 250314A: SVOM detection of a burst
  28. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  29. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  30. GRB 250313A: SVOM/GRM observation of a bright long burst
  31. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  32. GRB 250313A: AstroSat CZTI detection of a bright long burst
  33. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  34. Fermi trigger No 763581136: Global MASTER-Net observations report
  35. GRB 250313A: Fermi-LAT detection
  36. GRB 250313A: Swift ToO observations
  37. EP250304a: Pan-STARRS r and i-band imaging and photometry
  38. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  39. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  40. Fermi GRB 250313A: Global MASTER-Net observations report
  41. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  42. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  43. GRB 250313A: Fermi GBM Final Real-time Localization
  44. The EP-WXT trigger 01709132551 is not a real source
  45. EP250304a: SVOM/VT optical observation
  46. EP250311a/GRB 250311A: EP-FXT follow-up observation
  47. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  48. EP250302a: Chandra X-ray Detection
  49. GRB 250312A: Swift-XRT refined Analysis
  50. Fermi Gamma-ray Burst Monitor trigger 763509110/250312911 is not a GRB
  51. Fermi trigger No 763509110: Global MASTER-Net observations report
  52. Fermi GRB 250312B: Global MASTER-Net observations report
  53. GRB 250312A: Enhanced Swift-XRT position
  54. GRB 250312B: Fermi GBM Final Localization
  55. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  56. GRB 250226B: Fermi GBM Observation
  57. Swift GRB 250312A: Global MASTER-Net observations report
  58. GRB 250302A: Fermi GBM Observation
  59. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  60. GRB 250312A: Swift detection of a burst
  61. GRB 241213A: VIRT Optical Upper Limit
  62. GRB 241228A: VIRT Optical Upper Limit
  63. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  64. GRB 250223B: Fermi GBM Observation
  65. GRB 250311A: Swift-XRT observations
  66. GRB 250228A: Fermi GBM Observation
  67. GRB 250309B: 1.3m DFOT Optical observations
  68. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  69. EP250311a: Global MASTER-Net observations report
  70. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  71. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  72. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  73. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  74. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  75. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  76. GRB 250309B: PRIME near-infrared detection
  77. EP250304a: Chandra detection
  78. GRB 250225B: Swift-BAT refined analysis
  79. GRB 250311A/EP250311a: TRT optical upper limit
  80. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  81. GRB 250311A: Tiled Swift observations
  82. EP250311a/GRB 250311A: EP-WXT detection
  83. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  84. GRB 250311B: SVOM detection of a burst
  85. GRB 250309B: SVOM/VT optical observation
  86. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  87. The EP-WXT trigger 01709132425 is not a real source
  88. GRB 250309B / AT2025dws: further SAO RAS optical observations
  89. IceCube-250309A: Upper limits from Fermi-GBM Observations
  90. EP250308a: 1.6m Mephisto optical upper limits
  91. Konus-Wind detection of GRB 250309B
  92. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  93. IPN triangulation of GRB 250308A (short)
  94. IPN triangulation of GRB 250309B
  95. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  96. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  97. GRB 250309B: Swift-XRT refined Analysis
  98. GRB 250309B / IceCube-250309A: GECAM-B observations
  99. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  100. Liverpool Telecope observations of AT 2025dws / GRB 250309B

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