Skip to main content
End of Swift Science Operations, CHIME Notices Unavailable During Upgrade. 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"

28291 results found.

  1. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  2. EP250302a: Mondy Observations and Optical Light Curve
  3. EP250302a: VLT/MUSE optical redshift z = 1.131
  4. EP250302A: VLT near-infrared observations
  5. EP250302A: VLT/X-shooter tentative redshift
  6. EP250302a: OHP/T193 optical and spectroscopic observations
  7. EP250302a: Swift-XRT observations of a fading X-ray source
  8. EP250302a: Einstein Probe detection of an X-ray transient
  9. EP250302a: SVOM/C-GFT optical observations
  10. GRB 250226A: GRANDMA Optical Observations
  11. EP250302a: Montarrenti Observatory optical detection
  12. EP250302a: Nanshan/HMT optical counterpart detection
  13. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  14. GRB 250225B: VLT near-infrared afterglow confirmation
  15. EP250228a: Optical observations with Kinder and Swift/UVOT
  16. Konus-Wind detection of GRB 250226A
  17. GRB 250225B: EIRSAT-1 GMOD Detection
  18. GRB 250226A: KAO Optical Upper Limit
  19. GRB 250226A: AbAO AS-32 Optical Upper Limit
  20. EP250227a: Global MASTER-Net observations report
  21. EP250223A: Upper limits from Fermi-GBM Observations
  22. EP250227a: TRT optical upper limit
  23. GRB 250225B: VLT/HAWKI near-infrared observations
  24. EP250227a: Optical upper limits with Kinder observations
  25. EP250227a: NOT optical observations
  26. EP250227a: Einstein Probe detected of a fast X-ray transient
  27. EP250228a: updates on the EP observations
  28. GRB 250226A: Fermi GBM Observation
  29. EP250223a: J band upper limit by SYSU 80cm telescope
  30. EP250228a: Swift/XRT localisation
  31. EP250228a: Einstein Probe detection of an X-ray transient
  32. GRB 250226A / EP250226a: LCO detection of the afterglow
  33. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  34. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  35. GRB 250225B: VLT/Xshooter imaging
  36. GRB 250205A / EP250205A: further radio observations with the VLA
  37. EP250225a: NOT optical candidate counterpart
  38. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  39. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  40. EP250225a: TRT optical upper limits
  41. EP250226a/GRB 250226A: 1.6m Mephisto observations
  42. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  43. EP250226a/GRB 250226A: Kinder optical follow-up observations
  44. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  45. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  46. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  47. GRB 250225B: Fermi GBM Observation
  48. GRB 250225B: REM NIR upper limits
  49. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  50. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  51. EP250223a: CrAO ZTSH optical observation
  52. GRB 250225B: VLT optical and near-infrared candidate counterpart
  53. GRB 250225B: SVOM/GRM observation of a long burst
  54. EP250226a/GRB 250226A: GSP detects optical counterpart
  55. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  56. EP250226a / GRB 250226A: TRT optical counterpart observation
  57. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  58. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  59. EP250225a: GSP optical upper limit
  60. EP250223a: GMG Optical Observation
  61. EP250225a: Einstein Probe detected of a fast X-ray transient
  62. GRB 250225B: Swift detection of a burst
  63. EP250223a: GROWTH-India Telescope optical observations
  64. GRB 250221A: Swift-BAT refined analysis
  65. EP250215A: J band upper limit by SYSU 80cm telescope
  66. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  67. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  68. EP250223a: Kinder optical follow-up observations
  69. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  70. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  71. GRB 250119B: VZLUSAT-2 detection
  72. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  73. GRB 250202B: VZLUSAT-2 detection
  74. GRB 250222A: SVOM/GRM observation of a burst
  75. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  76. GRB 250206A: VZLUSAT-2 detection
  77. EP250223a: REM NIR upper limit
  78. EP250223a: TRT optical afterglow observation
  79. EP250223a: refined analysis of the EP-WXT and FXT observations
  80. EP250223a: 1.6m Mephisto and 50cm array observations
  81. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  82. 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
  83. EP250223a: OASDG optical observations
  84. EP250223a: LCO detection of the afterglow
  85. EP250223a: Swift/XRT localization
  86. EP250223a: NOT optical afterglow candidate
  87. EP250223a: Einstein Probe detection of an X-ray transient
  88. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  89. GRB 250221A: Optical counterpart detection by LCO.
  90. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  91. GRB 250221A: GRANDMA/TAROT Detection
  92. GRB 250221A: Swift-XRT refined Analysis
  93. GRB 250221A: NOT optical observations
  94. GRB 250221A: 1.6m Mephisto optical detection
  95. GRB 250221A: AKO Optical Upper Limit
  96. GRB 250221A: Swift/UVOT Detection
  97. EP250220a: Liverpool Telescope upper limits
  98. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  99. GRB 250221A: REM optical/NIR afterglow detection
  100. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect

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