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"
  1. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  2. Fermi GRB 250217A: Global MASTER-Net observations report
  3. GRANDMA/OPD observations of GRB250215A
  4. GRB 250217B: Fermi GBM Final Real-time Localization
  5. The EP-WXT trigger 01709131775 is likely a flaring star
  6. GRB 250217A: Fermi GBM Final Real-time Localization
  7. Fermi GRB 250216A: Global MASTER-Net observations report
  8. GRB 250215A / EP250215a: LCO detection of the afterglow
  9. GRB 250216A: Fermi GBM Final Real-time Localization
  10. EP250212a: FTW optical and NIR upper limits
  11. GRB 250215A: Swift/UVOT Upper Limits
  12. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  13. EP250215a / GRB 250215A : GTC redshift z = 4.61
  14. GRB 250215A: Fermi GBM Observation
  15. EP250215a / GRB 250215A : NOT optical observations
  16. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  17. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  18. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  19. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  20. GRB 250215A: Swift-XRT refined Analysis
  21. GRB 250215A: SVOM/GRM observation
  22. EP250215a / GRB 250215A: AstroSat CZTI detection
  23. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  24. EP250215a: Global MASTER-Net observations report
  25. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  26. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  27. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  28. Fermi GRB 250215A: Global MASTER-Net observations report
  29. GRB 250215A: Fermi GBM Final Real-time Localization
  30. Fermi trigger No 761206993: Global MASTER-Net observations report
  31. GRB 250213A：SVOM/VT optical candidate
  32. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  33. EP250207b: Xinglong optical upper limit
  34. Fermi GRB 250214A: Global MASTER-Net observations report
  35. GRB 250213A: Swift ToO observations
  36. GRB 250214A: Fermi GBM Final Real-time Localization
  37. EP250212a: Xinglong optical upper limit
  38. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  39. GRB 250213A: SVOM detection of a burst
  40. EP250212a: Global MASTER-Net observations report
  41. GRB 250205A: VIRT Optical Upper Limit
  42. GRB 250205A: Leavitt Observatory optical upper limit
  43. GRB 250210A: GRBAlpha detection
  44. EP250207B: Chandra localization of the X-ray counterpart
  45. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  46. EP250207b: VLA radio upper limits
  47. EP250212a: Liverpool Telescope optical upper limits
  48. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  49. GRB250101A: Radio upper limits from GMRT observations
  50. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  51. EP250207B: GTC z-band Observations
  52. Fermi GRB 250212A: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  54. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  55. Fermi trigger No 760945500: Global MASTER-Net observations report
  56. EP250207b: NOT optical counterpart candidate
  57. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  58. GRB 250211B: A long GRB detected by INTEGRAL
  59. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  60. GRB 250211A: Swift ToO observations
  61. Integral GRB250211.89: Global MASTER-Net observations report
  62. GRB 250212A: Fermi GBM Final Real-time Localization
  63. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  64. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  65. GRB 250207A: Fermi GBM Observation
  66. GRB 250206A: Fermi GBM Observation
  67. GRB 250205A / EP250205A: radio detection with the VLA
  68. IceCube-250207A: One candidate from the Zwicky Transient Facility
  69. EP250207b: Tentative z-band brightening source
  70. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  71. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  72. Konus-Wind detection of GRB 250207A
  73. Konus-Wind detection of GRB 250206A
  74. GRB 250210A: SVOM/GRM observation of a long burst
  75. EP250207b: Liverpool Telescope possible optical counterpart
  76. EP250207b: Global MASTER-Net observations report
  77. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  78. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  79. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  81. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  82. GRB 250207A: Skynet optical afterglow observations
  83. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  84. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  85. GRB 241128A: VIRT Optical Upper Limit
  86. EP250207b: Gemini GMOS-N z-band observations
  87. EP250207A: Upper limits from Fermi-GBM Observations
  88. GRB 250210A: INTEGRAL SPI-ACS detection
  89. GRB 250210A: AstroSat CZTI detection
  90. EP250207b: a new X-ray transient detected by Einstein Probe
  91. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  92. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  93. Fermi GRB 250210A: Global MASTER-Net observations report
  94. GRB 250210A: Fermi GBM Final Real-time Localization
  95. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  96. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  97. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  99. IceCube Alert 250207.09: Global MASTER-Net observations report
  100. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER

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