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"

19386 results found.

  1. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  2. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  3. EP250321A: COLIBRÍ Continuing Optical Observations
  4. EP250321a: WFST optical observations
  5. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  6. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  7. EP250321a: Xinglong 216 decaying optical observations
  8. GRB 250321A: Swift-XRT refined Analysis
  9. EP 250321A: Optical counterpart detection by LCO.
  10. EP250321a: Kinder optical follow-up observations
  11. GRB 250321A: Swift/UVOT Upper Limits
  12. GRB 250320B: SVOM/GRM observation of a long burst
  13. EP250321a: LCO optical counterpart detection
  14. EP250321A: COLIBRÍ Optical Observations
  15. EP250321a: REM optical/NIR afterglow detection
  16. EP250321a: BOOTES-5/JGT optical afterglow detection
  17. EP250321a: TRT optical counterpart detection
  18. EP250321a: Einstein Probe detection of an X-ray transient
  19. GRB 250321A: GOTO optical upper limits
  20. GRB 250314A: Keck/NIRC2 J-band upper limit
  21. EP250226a/GRB 250226A: KAIT optical observations
  22. GRB 250321A: Swift detection of a burst
  23. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  24. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  25. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  26. GRB 250313A: GRBAlpha detection
  27. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  28. GRB 250317B: OHP/T193 continued follow-up
  29. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  30. GRB 250317C: SVOM/GRM observation of a long burst
  31. GRB 250317B: Leavitt Observatory optical upper limit
  32. GRB 250309B/AT2025dws: further ATCA observations
  33. GRB 250317B: Mondy AZT-33IK Optical Observations
  34. GRB 250317C: AstroSat CZTI detection
  35. GRB 250317B: NOT optical observations suggest an optical plateau phase
  36. GRB 250317B: OHP/T193 optical observations
  37. GRB250312A: Swift/UVOT Upper Limits
  38. GRB 250317B: REM optical/NIR observations
  39. GRB 250316A: Swift/UVOT Upper Limits
  40. GRB 250314A: REM optical/NIR upper limits
  41. GRB 250316A: AbAO AS-32 Optical Upper Limit
  42. EP 250317B: Fading optical counterpart detection by LCO
  43. GRB 250316A: Swift-XRT afterglow detection
  44. GRB 250317B: LCO detection of the fading optical afterglow
  45. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  46. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  47. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  48. GRB 250317B: SVOM detection of a burst
  49. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  50. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  51. GRB 250314A: Swift/UVOT Upper Limits
  52. GRB 250312B: GRBAlpha detection
  53. GRB 250314A: Swift XRT Detection
  54. EP250315a: optical counterpart candidate detected by Gemini North
  55. EP250315a: Einstein Probe detection of an X-ray transient
  56. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  57. SVOM/MXT upper limit on GRB 250314A
  58. GRB 250314A: SVOM/VT upper limit
  59. GRB 250314A: NOT near-infrared candidate counterpart
  60. GRB 250313A: Swift-XRT observations
  61. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  62. Konus-Wind detection of GRB 250313A
  63. Konus-Wind detection of GRB 250308A
  64. GRB 250314A: SVOM detection of a burst
  65. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  66. EP250304a: Pan-STARRS r and i-band imaging and photometry
  67. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  68. Fermi GRB 250313A: Global MASTER-Net observations report
  69. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  70. GRB 250312A: Enhanced Swift-XRT position
  71. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  72. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  73. GRB 250312A: Swift detection of a burst
  74. GRB 241213A: VIRT Optical Upper Limit
  75. GRB 241228A: VIRT Optical Upper Limit
  76. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  77. GRB 230509B: 1.3m DFOT Optical observations
  78. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  79. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  80. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  81. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  82. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  83. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  84. GRB 250309B: PRIME near-infrared detection
  85. GRB 250225B: Swift-BAT refined analysis
  86. GRB 250311A/EP250311a: TRT optical upper limit
  87. EP250311a/GRB 250311A: EP-WXT detection
  88. GRB 250309B / AT2025dws: further SAO RAS optical observations
  89. EP250308a: 1.6m Mephisto optical upper limits
  90. IPN triangulation of GRB 250308A (short)
  91. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  92. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  93. GRB 250309B / AT2025dws: SAO RAS optical observations
  94. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  95. GRB 250309B: Fermi GBM Observation
  96. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  97. IceCube-250309A: No candidates from the Zwicky Transient Facility
  98. EP250308a: Einstein Probe detection of an X-ray transient
  99. EP250308a: NOT optical upper limit
  100. Konus-Wind detection of GRB 250306A

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