Skip to main content
JSON Notices via Email, Kafka Cron Jobs, Submitter Profile, GCN is Hiring. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

21912 results found.

  1. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  2. EP250321a: Mondy AZT-33IK Continued Optical Observations
  3. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  4. GRB 250322A: third epoch of NOT optical observations
  5. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  6. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  7. GRB 250322A: further NOT optical observations
  8. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  9. GRB 250322A: Swift/UVOT Upper Limits
  10. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  11. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  12. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  13. GRB 250321B: Swift-XRT observations
  14. EP250321a: TNOT Observation of Optical Counterpart
  15. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  16. SVOM/sb25032302: SVOM detection of a long X-ray transient
  17. GRB 250322A: VLT optical observations
  18. GRB 250322A: VLT near-infrared observations
  19. FRB 250316A: DDOTI Continued Optical Observations
  20. GRB 250322A: NOT optical upper limits
  21. GRB 250322A: Enhanced Swift-XRT position
  22. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  23. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  24. EP250321a: Liverpool Telescope optical follow-up
  25. EP250321a: Mondy AZT-33IK Optical Observations
  26. GRB 250322A: Swift detection of a short burst
  27. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  28. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  29. EP250321A: COLIBRÍ Continuing Optical Observations
  30. EP250321a: WFST optical observations
  31. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  32. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  33. EP250321a: Xinglong 216 decaying optical observations
  34. GRB 250321A: Swift-XRT refined Analysis
  35. EP 250321A: Optical counterpart detection by LCO.
  36. EP250321a: Kinder optical follow-up observations
  37. GRB 250321A: Swift/UVOT Upper Limits
  38. GRB 250320B: SVOM/GRM observation of a long burst
  39. EP250321a: LCO optical counterpart detection
  40. EP250321A: COLIBRÍ Optical Observations
  41. EP250321a: REM optical/NIR afterglow detection
  42. EP250321a: BOOTES-5/JGT optical afterglow detection
  43. EP250321a: TRT optical counterpart detection
  44. EP250321a: Einstein Probe detection of an X-ray transient
  45. GRB 250321A: GOTO optical upper limits
  46. GRB 250314A: Keck/NIRC2 J-band upper limit
  47. EP250226a/GRB 250226A: KAIT optical observations
  48. GRB 250321A: Swift detection of a burst
  49. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  50. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  51. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  52. GRB 250313A: GRBAlpha detection
  53. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  54. GRB 250317B: OHP/T193 continued follow-up
  55. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  56. GRB 250317C: SVOM/GRM observation of a long burst
  57. GRB 250317B: Leavitt Observatory optical upper limit
  58. GRB 250309B/AT2025dws: further ATCA observations
  59. GRB 250317B: Mondy AZT-33IK Optical Observations
  60. GRB 250317C: AstroSat CZTI detection
  61. GRB 250317B: NOT optical observations suggest an optical plateau phase
  62. GRB 250317B: OHP/T193 optical observations
  63. GRB250312A: Swift/UVOT Upper Limits
  64. GRB 250317B: REM optical/NIR observations
  65. GRB 250316A: Swift/UVOT Upper Limits
  66. GRB 250314A: REM optical/NIR upper limits
  67. GRB 250316A: AbAO AS-32 Optical Upper Limit
  68. EP 250317B: Fading optical counterpart detection by LCO
  69. GRB 250316A: Swift-XRT afterglow detection
  70. GRB 250317B: LCO detection of the fading optical afterglow
  71. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  72. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  73. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  74. GRB 250317B: SVOM detection of a burst
  75. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  76. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  77. GRB 250314A: Swift/UVOT Upper Limits
  78. GRB 250312B: GRBAlpha detection
  79. GRB 250314A: Swift XRT Detection
  80. EP250315a: optical counterpart candidate detected by Gemini North
  81. EP250315a: Einstein Probe detection of an X-ray transient
  82. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  83. SVOM/MXT upper limit on GRB 250314A
  84. GRB 250314A: SVOM/VT upper limit
  85. GRB 250314A: NOT near-infrared candidate counterpart
  86. GRB 250313A: Swift-XRT observations
  87. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  88. Konus-Wind detection of GRB 250313A
  89. Konus-Wind detection of GRB 250308A
  90. GRB 250314A: SVOM detection of a burst
  91. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  92. EP250304a: Pan-STARRS r and i-band imaging and photometry
  93. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  94. Fermi GRB 250313A: Global MASTER-Net observations report
  95. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  96. GRB 250312A: Enhanced Swift-XRT position
  97. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  98. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  99. GRB 250312A: Swift detection of a burst
  100. GRB 241213A: VIRT Optical Upper Limit

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