Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

19549 results found.

  1. GRB 250225B: VLT/Xshooter imaging
  2. GRB 250205A / EP250205A: further radio observations with the VLA
  3. EP250225a: NOT optical candidate counterpart
  4. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  5. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  6. EP250225a: TRT optical upper limits
  7. EP250226a/GRB 250226A: 1.6m Mephisto observations
  8. EP250226a/GRB 250226A: Kinder optical follow-up observations
  9. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  10. GRB 250225B: REM NIR upper limits
  11. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  12. EP250223a: CrAO ZTSH optical observation
  13. GRB 250225B: VLT optical and near-infrared candidate counterpart
  14. GRB 250225B: SVOM/GRM observation of a long burst
  15. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  16. EP250226a / GRB 250226A: TRT optical counterpart observation
  17. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  18. EP250223a: GMG Optical Observation
  19. EP250225a: Einstein Probe detected of a fast X-ray transient
  20. EP250223a: GROWTH-India Telescope optical observations
  21. EP250215A: J band upper limit by SYSU 80cm telescope
  22. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  23. EP250223a: Kinder optical follow-up observations
  24. GRB 250222A: SVOM/GRM observation of a burst
  25. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  26. EP250223a: REM NIR upper limit
  27. EP250223a: TRT optical afterglow observation
  28. EP250223a: refined analysis of the EP-WXT and FXT observations
  29. EP250223a: 1.6m Mephisto and 50cm array observations
  30. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  31. 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
  32. EP250223a: OASDG optical observations
  33. EP250223a: NOT optical afterglow candidate
  34. EP250223a: Einstein Probe detection of an X-ray transient
  35. GRB 250221A: Optical counterpart detection by LCO.
  36. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  37. GRB 250221A: GRANDMA/TAROT Detection
  38. GRB 250221A: 1.6m Mephisto optical detection
  39. GRB 250221A: AKO Optical Upper Limit
  40. GRB 250221A: Swift/UVOT Detection
  41. EP250220a: Liverpool Telescope upper limits
  42. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  43. GRB 250221A: REM optical/NIR afterglow detection
  44. GRB 250221A: Enhanced Swift-XRT position
  45. EP250220a: 1.6m Mephisto observations
  46. EP250220a: Liverpool Telescope optical upper limits
  47. EP250220a: Optical upper limit with Kinder observations
  48. SVOM trigger sb25022102 is not an astrophysical event
  49. SVOM/sb25022102: SVOM detection of an X-ray transient
  50. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  51. GRB 250221A: Swift detection of a burst with an optical counterpart
  52. EP250220a: Xinglong optical upper limit
  53. GRB 250219A: Swift/UVOT Upper Limits
  54. GRB 250219A: OHP/T193 optical upper limit
  55. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  56. GRB 250219A: 1.6m Mephisto optical upper limits
  57. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  58. GRB 250219A: Swift ToO observations
  59. GRB 250219A: SVOM detection of a burst
  60. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  61. GRB 250217C: Swift-XRT observations
  62. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  63. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  64. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  65. GRB 250217C: SVOM/GRM observation
  66. GRB 250217C: Tiled Swift observations
  67. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  68. SVOM/sb25021804: SVOM detection of a long X-ray transient
  69. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  70. GRANDMA/OPD observations of GRB250215A
  71. GRB 250215A / EP250215a: LCO detection of the afterglow
  72. GRB 250215A: Swift/UVOT Upper Limits
  73. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  74. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  75. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  76. GRB 250215A: SVOM/GRM observation
  77. EP250215a / GRB 250215A: AstroSat CZTI detection
  78. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  79. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  80. EP250207b: Xinglong optical upper limit
  81. GRB 250213A: Swift ToO observations
  82. EP250212a: Xinglong optical upper limit
  83. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  84. GRB 250213A: SVOM detection of a burst
  85. GRB 250205A: VIRT Optical Upper Limit
  86. GRB 250205A: Leavitt Observatory optical upper limit
  87. EP250207B: Chandra localization of the X-ray counterpart
  88. EP250212a: Liverpool Telescope optical upper limits
  89. GRB250101A: Radio upper limits from GMRT observations
  90. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  91. EP250207B: GTC z-band Observations
  92. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  93. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  94. EP250207b: NOT optical counterpart candidate
  95. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  96. GRB 250211A: Swift ToO observations
  97. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  98. GRB 250206A: Fermi GBM Observation
  99. GRB 250205A / EP250205A: radio detection with the VLA
  100. EP250207b: Tentative z-band brightening source

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