Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

4746 results found.

  1. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  2. SVOM/sb25032302: SVOM detection of a long X-ray transient
  3. GRB 250322A: AstroSat CZTI detection of a short burst
  4. GRB 250322B: AstroSat CZTI detection of a bright long burst
  5. GRB 250322A: Gemini-South optical observations
  6. FRB 250316A: DDOTI Continued Optical Observations
  7. GRB 250322A: NOT optical upper limits
  8. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  9. GRB 250322A: MASTER optical observation
  10. EP250321a: Liverpool Telescope optical follow-up
  11. EP250321a: Mondy AZT-33IK Optical Observations
  12. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  13. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP250321A: COLIBRÍ Continuing Optical Observations
  15. GRB 250312A: GECAM-A detection
  16. EP250321a: WFST optical observations
  17. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  18. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  19. EP250321a: Xinglong 216 decaying optical observations
  20. GRB 250321A: Swift-BAT refined analysis
  21. GRB 250321B: SVOM detection of a sub-threshold transient event
  22. EP250321a: SVOM/VT optical observation
  23. EP 250321A: Optical counterpart detection by LCO.
  24. GRB 250320B: SVOM/GRM observation of a long burst
  25. EP250321a: LCO optical counterpart detection
  26. EP250321A: COLIBRÍ Optical Observations
  27. GRB 250320B: AstroSat CZTI detection
  28. Fermi GRB 250320B: Global MASTER-Net observations report
  29. EP250321a: BOOTES-5/JGT optical afterglow detection
  30. EP250321a: Global MASTER-Net observations report
  31. Swift GRB 250321A: Global MASTER-Net observations report
  32. Fermi GRB 250321A: Global MASTER-Net observations report
  33. EP250321a: Einstein Probe detection of an X-ray transient
  34. GRB 250321A: GOTO optical upper limits
  35. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  36. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  37. Fermi GRB 250319B: Global MASTER-Net observations report
  38. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  39. GRB 250313A: GRBAlpha detection
  40. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  41. GRB 250317D: EIRSAT-1 GMOD Detection
  42. EP250302a: VLA observations
  43. GRB 250317B: OHP/T193 continued follow-up
  44. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  45. GRB 250317C: SVOM/GRM observation of a long burst
  46. GRB 250317B: Leavitt Observatory optical upper limit
  47. GRB 250309B/AT2025dws: further ATCA observations
  48. GRB 250317B: Mondy AZT-33IK Optical Observations
  49. GRB 250317C: AstroSat CZTI detection
  50. GRB 250317B: NOT optical observations suggest an optical plateau phase
  51. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  52. GRB 250317C: GECAM-B detection
  53. GRB 250317B: OHP/T193 optical observations
  54. Fermi trigger No 763933627: Global MASTER-Net observations report
  55. GRB 250317B: REM optical/NIR observations
  56. GRB 250316A: AbAO AS-32 Optical Upper Limit
  57. EP 250317B: Fading optical counterpart detection by LCO
  58. GRB 250317B: LCO detection of the fading optical afterglow
  59. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  60. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  61. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  62. GRB 250317B: SVOM detection of a burst
  63. Fermi trigger No 763862734: Global MASTER-Net observations report
  64. Fermi GRB 250316A: Global MASTER-Net observations report
  65. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  66. The EP-WXT trigger 01709132801 is likely a flaring star
  67. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  68. GRB 250314A: EP-FXT afterglow detection
  69. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  70. GRB 250312B: GRBAlpha detection
  71. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  72. EP250315a: Einstein Probe detection of an X-ray transient
  73. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  74. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  75. GRB 250314A: SVOM detection of a burst
  76. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  77. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  78. GRB 250313A: SVOM/GRM observation of a bright long burst
  79. GRB 250313A: AstroSat CZTI detection of a bright long burst
  80. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  81. Fermi trigger No 763581136: Global MASTER-Net observations report
  82. EP250304a: Pan-STARRS r and i-band imaging and photometry
  83. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  84. Fermi GRB 250313A: Global MASTER-Net observations report
  85. The EP-WXT trigger 01709132551 is not a real source
  86. EP250304a: SVOM/VT optical observation
  87. EP250311a/GRB 250311A: EP-FXT follow-up observation
  88. EP250302a: Chandra X-ray Detection
  89. Fermi trigger No 763509110: Global MASTER-Net observations report
  90. Fermi GRB 250312B: Global MASTER-Net observations report
  91. Swift GRB 250312A: Global MASTER-Net observations report
  92. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  93. GRB 241228A: VIRT Optical Upper Limit
  94. GRB 230509B: 1.3m DFOT Optical observations
  95. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  96. EP250311a: Global MASTER-Net observations report
  97. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  98. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  99. EP250304a: Chandra detection
  100. GRB 250311A/EP250311a: TRT optical upper limit

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