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"
  1. EP250227a: Optical upper limits with Kinder observations
  2. EP250227a: NOT optical observations
  3. EP250227a: Einstein Probe detected of a fast X-ray transient
  4. EP250228a: updates on the EP observations
  5. GRB 250226A: Fermi GBM Observation
  6. EP250225a: EP-FXT follow-up observation
  7. EP250223a: J band upper limit by SYSU 80cm telescope
  8. EP250228a: Swift/XRT localisation
  9. EP250228a: Global MASTER-Net observations report
  10. EP250228a: Einstein Probe detection of an X-ray transient
  11. GRB 250226A / EP250226a: LCO detection of the afterglow
  12. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  13. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  14. GRB 250225B: VLT/Xshooter imaging
  15. GRB 250205A / EP250205A: further radio observations with the VLA
  16. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  17. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  18. GRB 250225B: INTEGRAL SPI-ACS detection
  19. EP250225a: NOT optical candidate counterpart
  20. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  21. EP250226a / GRB 250226A: SVOM/VT optical observations
  22. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  23. EP250225a: TRT optical upper limits
  24. EP250226a/GRB 250226A: 1.6m Mephisto observations
  25. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  26. EP250226a/GRB 250226A: Kinder optical follow-up observations
  27. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  28. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  29. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  30. Fermi GRB 250226B: Global MASTER-Net observations report
  31. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  32. GRB 250226B: Fermi GBM Final Real-time Localization
  33. GRB 250225B: Fermi GBM Observation
  34. GRB 250221A: ATCA Detections and Upper Limits
  35. GRB 250225B: REM NIR upper limits
  36. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  37. Konus-Wind detection of GRB 250225B
  38. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  39. EP250223a: CrAO ZTSH optical observation
  40. GRB 250225B: VLT optical and near-infrared candidate counterpart
  41. GRB 250225B: VLT/FORS2 candidate optical afterglow
  42. GRB 250225B: SVOM/GRM observation of a long burst
  43. GRB 250226A: GECAM-B detection
  44. GRB 250221A: EP-FXT detection of the X-ray afterglow
  45. GRB 250214A: SVOM/GRM observation
  46. EP250226a/GRB 250226A: GSP detects optical counterpart
  47. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  48. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  49. EP250226a / GRB 250226A: TRT optical counterpart observation
  50. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  51. EP250226a: Global MASTER-Net observations report
  52. Swift GRB 250225B: Global MASTER-Net observations report
  53. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  54. Fermi GRB 250226A: Global MASTER-Net observations report
  55. Fermi trigger No 762205158: Global MASTER-Net observations report
  56. GRB 250226A: Fermi GBM Final Real-time Localization
  57. EP250225a: Global MASTER-Net observations report
  58. EP250225a: GSP optical upper limit
  59. EP250223a: GMG Optical Observation
  60. EP250225a: Einstein Probe detected of a fast X-ray transient
  61. Fermi GRB 250225A: Global MASTER-Net observations report
  62. GRB 250225B: Swift detection of a burst
  63. EP250223a: GROWTH-India Telescope optical observations
  64. GRB 250221A: Swift-BAT refined analysis
  65. GRB 250223C: SVOM/GRM observation of a long burst
  66. EP250215A: J band upper limit by SYSU 80cm telescope
  67. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  68. GRB 250225A: Fermi GBM Final Real-time Localization
  69. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  70. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  71. EP250223a: Kinder optical follow-up observations
  72. GRB 250207a: ATCA Radio Upper Limits
  73. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  74. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  75. GRB 250119B: VZLUSAT-2 detection
  76. GRB 250223C: Fermi GBM Final Real-time Localization
  77. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  78. GRB 250202B: VZLUSAT-2 detection
  79. GRB 250219A: EP-FXT afterglow detection
  80. EP250223a: GOTO optical afterglow detections
  81. GRB 250222A: SVOM/GRM observation of a burst
  82. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  83. GRB 250210A: VZLUSAT-2 detection
  84. GRB 250206A: VZLUSAT-2 detection
  85. EP250223a: REM NIR upper limit
  86. EP250223a: TRT optical afterglow observation
  87. EP250223a: refined analysis of the EP-WXT and FXT observations
  88. EP250223a: 1.6m Mephisto and 50cm array observations
  89. GRB 250221A: TNOT detection of the optical counterpart
  90. EP250223a: SVOM/VT optical observation
  91. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  92. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  93. The EP-WXT trigger 01709131882 is likely a flaring star
  94. EP250223a: OASDG optical observations
  95. EP250223a: LCO detection of the afterglow
  96. EP250223a: early optical detection by BOOTES-4
  97. EP250223a: NOT redshift z = 2.756
  98. EP250223a: Swift/XRT localization
  99. EP250223a: NOT optical afterglow candidate
  100. GRB 250223B: Fermi GBM Final Localization

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