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"

28270 results found.

  1. SVOM/sb25032302: SVOM detection of a long X-ray transient
  2. GRB 250322B: AstroSat CZTI detection of a bright long burst
  3. GRB 250322A: VLT optical observations
  4. GRB 250322A: VLT near-infrared observations
  5. FRB 250316A: DDOTI Continued Optical Observations
  6. GRB 250322A: NOT optical upper limits
  7. GRB 250322A: Enhanced Swift-XRT position
  8. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  9. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  10. EP250321a: Liverpool Telescope optical follow-up
  11. EP250321a: Mondy AZT-33IK Optical Observations
  12. GRB 250322A: Swift detection of a short burst
  13. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  14. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  15. EP250321A: COLIBRÍ Continuing Optical Observations
  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. GRB 250320B: Fermi GBM Observation
  20. EP250321a: Xinglong 216 decaying optical observations
  21. GRB 250321A: Swift-BAT refined analysis
  22. GRB 250321A: Swift-XRT refined Analysis
  23. EP 250321A: Optical counterpart detection by LCO.
  24. EP250321a: Kinder optical follow-up observations
  25. GRB 250321A: Swift/UVOT Upper Limits
  26. GRB 250320B: SVOM/GRM observation of a long burst
  27. EP250321a: LCO optical counterpart detection
  28. EP250321a: Swift-XRT detection of an X-ray source
  29. EP250321A: COLIBRÍ Optical Observations
  30. GRB 250320B: AstroSat CZTI detection
  31. EP250321a: REM optical/NIR afterglow detection
  32. EP250321a: TRT optical counterpart detection
  33. Swift GRB 250321A: Global MASTER-Net observations report
  34. EP250321a: Einstein Probe detection of an X-ray transient
  35. GRB 250321A: GOTO optical upper limits
  36. GRB 250314A: Keck/NIRC2 J-band upper limit
  37. EP250226a/GRB 250226A: KAIT optical observations
  38. GRB 250321A: Fermi GBM Observation
  39. GRB 250321A: Swift detection of a burst
  40. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  41. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  42. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  43. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  44. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  45. GRB 250317D: EIRSAT-1 GMOD Detection
  46. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  47. GRB 250314A: ATCA radio upper limits
  48. GRB 250317B: OHP/T193 continued follow-up
  49. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  50. GRB 250317C: SVOM/GRM observation of a long burst
  51. GRB 250317B: Leavitt Observatory optical upper limit
  52. GRB 250317B: Mondy AZT-33IK Optical Observations
  53. GRB 250317B: NOT optical observations suggest an optical plateau phase
  54. GRB 250317C: GECAM-B detection
  55. GRB 250317B: OHP/T193 optical observations
  56. GRB250312A: Swift/UVOT Upper Limits
  57. GRB 250317B: REM optical/NIR observations
  58. GRB 250317B: Swift-XRT observations
  59. GRB 250316A: Swift/UVOT Upper Limits
  60. GRB 250314A: REM optical/NIR upper limits
  61. GRB 250316A: AbAO AS-32 Optical Upper Limit
  62. EP 250317B: Fading optical counterpart detection by LCO
  63. GRB 250316A: Swift-XRT afterglow detection
  64. GRB 250317B: LCO detection of the fading optical afterglow
  65. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  66. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  67. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  68. GRB 250317B: SVOM detection of a burst
  69. GRB 250316A: Fermi GBM Observation
  70. GRB 250316A: Swift-XRT observations
  71. GRB 250314A: SVOM/GRM analysis
  72. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  73. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  74. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  75. GRB 250314A: EP-FXT afterglow detection
  76. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  77. GRB 250314A: Swift/UVOT Upper Limits
  78. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  79. GRB 250314A: Swift XRT Detection
  80. EP250315a: optical counterpart candidate detected by Gemini North
  81. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  82. EP250315a: Einstein Probe detection of an X-ray transient
  83. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  84. SVOM/MXT upper limit on GRB 250314A
  85. GRB 250314A: SVOM/VT upper limit
  86. GRB 250314A: NOT near-infrared candidate counterpart
  87. GRB 250313A: Fermi GBM Detection
  88. GRB 250312B: Fermi GBM Observation
  89. GRB 250313A: Swift-XRT observations
  90. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  91. GRB 250314A: SVOM detection of a burst
  92. GRB 250313A: AstroSat CZTI detection of a bright long burst
  93. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  94. GRB 250313A: Fermi-LAT detection
  95. EP250304a: Pan-STARRS r and i-band imaging and photometry
  96. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  97. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  98. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  99. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  100. GRB 250312A: Swift-XRT refined Analysis

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