Skip to main content
New! BOOM Notices and Schema v7.0.0. 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"

44271 results found.

  1. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  2. EP250226a/GRB 250226A: Kinder optical follow-up observations
  3. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  4. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  5. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  6. Fermi GRB 250226B: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  8. GRB 250226B: Fermi GBM Final Real-time Localization
  9. GRB 250225B: Fermi GBM Observation
  10. GRB 250221A: ATCA Detections and Upper Limits
  11. GRB 250225B: REM NIR upper limits
  12. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  13. Konus-Wind detection of GRB 250225B
  14. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  15. EP250223a: CrAO ZTSH optical observation
  16. GRB 250225B: VLT optical and near-infrared candidate counterpart
  17. GRB 250225B: VLT/FORS2 candidate optical afterglow
  18. GRB 250225B: SVOM/GRM observation of a long burst
  19. GRB 250226A: GECAM-B detection
  20. GRB 250221A: EP-FXT detection of the X-ray afterglow
  21. GRB 250214A: SVOM/GRM observation
  22. EP250226a/GRB 250226A: GSP detects optical counterpart
  23. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  24. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  25. EP250226a / GRB 250226A: TRT optical counterpart observation
  26. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  27. EP250226a: Global MASTER-Net observations report
  28. Swift GRB 250225B: Global MASTER-Net observations report
  29. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  30. Fermi GRB 250226A: Global MASTER-Net observations report
  31. Fermi trigger No 762205158: Global MASTER-Net observations report
  32. GRB 250226A: Fermi GBM Final Real-time Localization
  33. EP250225a: Global MASTER-Net observations report
  34. EP250225a: GSP optical upper limit
  35. EP250223a: GMG Optical Observation
  36. EP250225a: Einstein Probe detected of a fast X-ray transient
  37. Fermi GRB 250225A: Global MASTER-Net observations report
  38. GRB 250225B: Swift detection of a burst
  39. EP250223a: GROWTH-India Telescope optical observations
  40. GRB 250221A: Swift-BAT refined analysis
  41. GRB 250223C: SVOM/GRM observation of a long burst
  42. EP250215A: J band upper limit by SYSU 80cm telescope
  43. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  44. GRB 250225A: Fermi GBM Final Real-time Localization
  45. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  46. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  47. EP250223a: Kinder optical follow-up observations
  48. GRB 250207a: ATCA Radio Upper Limits
  49. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  50. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  51. GRB 250119B: VZLUSAT-2 detection
  52. GRB 250223C: Fermi GBM Final Real-time Localization
  53. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  54. GRB 250202B: VZLUSAT-2 detection
  55. GRB 250219A: EP-FXT afterglow detection
  56. EP250223a: GOTO optical afterglow detections
  57. GRB 250222A: SVOM/GRM observation of a burst
  58. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  59. GRB 250210A: VZLUSAT-2 detection
  60. GRB 250206A: VZLUSAT-2 detection
  61. EP250223a: REM NIR upper limit
  62. EP250223a: TRT optical afterglow observation
  63. EP250223a: refined analysis of the EP-WXT and FXT observations
  64. EP250223a: 1.6m Mephisto and 50cm array observations
  65. GRB 250221A: TNOT detection of the optical counterpart
  66. EP250223a: SVOM/VT optical observation
  67. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  68. 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
  69. The EP-WXT trigger 01709131882 is likely a flaring star
  70. EP250223a: OASDG optical observations
  71. EP250223a: LCO detection of the afterglow
  72. EP250223a: early optical detection by BOOTES-4
  73. EP250223a: NOT redshift z = 2.756
  74. EP250223a: Swift/XRT localization
  75. EP250223a: NOT optical afterglow candidate
  76. GRB 250223B: Fermi GBM Final Localization
  77. EP250223a: Global MASTER-Net observations report
  78. GRB 250221A: VLA radio detection
  79. Fermi GRB 250223A: Global MASTER-Net observations report
  80. Fermi trigger No 762020305: Global MASTER-Net observations report
  81. GRB 250223A: Fermi GBM Final Real-time Localization
  82. EP250223a: Einstein Probe detection of an X-ray transient
  83. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  84. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  85. GRB 250221A: continued Mondy optical observations, brightening afterglow
  86. GRB 250221A: Optical counterpart detection by LCO.
  87. GRB 250221A: Mondy optical observations
  88. Konus-Wind detection of GRB 250221A
  89. GRB 250221A: Assy optical observations
  90. EP250220a: FTW optical and NIR observations and upper limits
  91. EP250220a: EP-FXT follow-up observations
  92. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  93. GRB 250221A: VLT/X-shooter redshift z = 0.768
  94. GRB 250221A: GRANDMA/TAROT Detection
  95. Fermi trigger No 761805304: Global MASTER-Net observations report
  96. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  97. GRB 250221A: Swift-XRT refined Analysis
  98. GRB 250221A: NOT optical observations
  99. GRB 250221A: 1.6m Mephisto optical detection
  100. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate

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