Skip to main content
New SVOM Notices, Planned Retirement of VOEvent Brokers. 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').

18685 results found.

  1. GRB 250221A: 1.6m Mephisto optical detection
  2. GRB 250221A: AKO Optical Upper Limit
  3. GRB 250221A: Swift/UVOT Detection
  4. EP250220a: Liverpool Telescope upper limits
  5. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  6. GRB 250221A: REM optical/NIR afterglow detection
  7. GRB 250221A: Enhanced Swift-XRT position
  8. EP250220a: 1.6m Mephisto observations
  9. EP250220a: Liverpool Telescope optical upper limits
  10. EP250220a: Optical upper limit with Kinder observations
  11. SVOM trigger sb25022102 is not an astrophysical event
  12. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  13. GRB 250221A: Swift detection of a burst with an optical counterpart
  14. Swift GRB250221.15: Global MASTER-Net OT detection
  15. EP250220a: Xinglong optical upper limit
  16. Konus-Wind detection of GRB 250217C (short)
  17. GRB 250219A: Swift/UVOT Upper Limits
  18. GRB 250219A: OHP/T193 optical upper limit
  19. GRB 250219A: NOT optical observations
  20. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  21. GRB 250219A: 1.6m Mephisto optical upper limits
  22. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  23. GRB 250219A: SVOM detection of a burst
  24. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  25. GRB 250217C: Swift-XRT observations
  26. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  27. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  28. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  29. GRB 250217C: SVOM/GRM observation
  30. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  31. SVOM/sb25021804: SVOM detection of a long X-ray transient
  32. GRANDMA/OPD observations of GRB250215A
  33. GRB 250215A / EP250215a: LCO detection of the afterglow
  34. GRB 250215A: Swift/UVOT Upper Limits
  35. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  36. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  37. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  38. GRB 250215A: SVOM/GRM observation
  39. EP250215a / GRB 250215A: AstroSat CZTI detection
  40. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  41. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  42. EP250207b: Xinglong optical upper limit
  43. EP250212a: Xinglong optical upper limit
  44. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  45. GRB 250205A: VIRT Optical Upper Limit
  46. GRB 250205A: Leavitt Observatory optical upper limit
  47. GRB 250210A: GRBAlpha detection
  48. EP250207B: Chandra localization of the X-ray counterpart
  49. EP250212a: Liverpool Telescope optical upper limits
  50. GRB250101A: Radio upper limits from GMRT observations
  51. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  52. EP250207B: GTC z-band Observations
  53. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  54. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  55. EP250207b: NOT optical counterpart candidate
  56. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  57. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  58. GRB 250205A / EP250205A: radio detection with the VLA
  59. EP250207b: Tentative z-band brightening source
  60. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  61. Konus-Wind detection of GRB 250207A
  62. Konus-Wind detection of GRB 250206A
  63. GRB 250210A: SVOM/GRM observation of a long burst
  64. EP250207b: Liverpool Telescope possible optical counterpart
  65. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  67. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  68. GRB 250207A: Skynet optical afterglow observations
  69. GRB 241128A: VIRT Optical Upper Limit
  70. EP250207b: Gemini GMOS-N z-band observations
  71. EP250207b: a new X-ray transient detected by Einstein Probe
  72. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  73. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  74. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  75. GRB 250204B: GRBAlpha detection
  76. GRB 250204A: GRBAlpha detection
  77. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  78. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  79. GRB 250207A: 1.3m DFOT Optical observations
  80. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  81. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  82. GRB 250129A: GRANDMA Continued Afterglow Detection
  83. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  84. GRB 250205A: 1.3m DFOT optical upper limit
  85. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  86. GRB 250206A: Fermi-LAT detection
  87. GRB 250207B: Swift-XRT observations
  88. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  89. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  90. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  92. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  93. GRB 250207A: Enhanced Swift-XRT position
  94. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  95. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  96. GRB 250207A: REM IR afterglow detection
  97. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  98. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  99. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  100. GRB 250207A: REM optical afterglow detection

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