Skip to main content
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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"
  1. GRB 251118A: Fermi GBM Observation
  2. GRB 251118A: Swift-XRT afterglow detection
  3. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  4. EP251118a: Optical detection with Kinder observations
  5. GRB 251118A: GECAM-B detection
  6. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  7. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  8. EP251118a / GRB 251118C: SVOM/VT optical observation
  9. The EP-WXT trigger 01709248403 is likely a flaring star
  10. GRB 251118A: NuSTAR detection of bright prompt emission
  11. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  12. GRB 251116C: NOT optical observations
  13. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  14. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  15. GRB 251018A: FRAM-Auger optical detection
  16. GRB 251117A: Swift-XRT observations
  17. EP251118A / GRB 251118C : MASTER optical counterpart observations
  18. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  19. Konus-Wind detection of GRB 251118C (EP251118a)
  20. The EP-WXT trigger 01709248388 is likely a flaring star
  21. EP251118a: FTW optical and NIR observations
  22. GRB 251117A: Insight-HXMT/HE detection
  23. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  24. EP251118a: VLT near-infrared observation
  25. GRB 251116D: SVOM/GRM observation of a long GRB
  26. EP251118a: GOTO optical afterglow detection
  27. GRB 251119A: SVOM detection of a possible burst
  28. EP251118a: NOT spectroscopic redshift of z = 1.216
  29. EP251118a: Global MASTER-Net observations report
  30. EP251118a: preliminary result of EP-FXT follow-up observation
  31. LAT GRB251118.86: Global MASTER-Net observations report
  32. GRB 251118A: Fermi-LAT detection
  33. EP251118a: NOT candidate optical counterpart
  34. GRB 251118A: Swift ToO observations
  35. EP251118a: Einstein Probe detected of a fast X-ray transient
  36. Fermi GRB 251118B: Global MASTER-Net observations report
  37. GRB 251118B: Fermi GBM Final Real-time Localization
  38. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  39. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  40. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  41. GRB 251118A: Fermi GBM Final Real-time Localization
  42. GRB 251116C: SVOM/ECLAIRs refined analysis
  43. GRB 251116B: SVOM/ECLAIRs refined analysis
  44. GRB 251117A: AstroSat CZTI detection
  45. GRB 251114B: Insight-HXMT/HE detection
  46. GRB 251114B: GECAM-B detection of a short burst
  47. GRB 251117A: Fermi GBM observation
  48. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  49. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  50. GRB 251116D: Insight-HXMT/HE detection
  51. GRB 251115A: Swift-XRT observations
  52. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  53. GRB 251117A: SVOM/GRM observation of a short burst
  54. GRB 251117A: Tiled Swift observations
  55. GRB 251117A: Fermi-LAT detection
  56. LAT GRB251117.51: Global MASTER-Net observations report
  57. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  58. GRB 251116C: Swift/BAT arcminute localization of a burst
  59. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  60. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  61. GRB 251116B: SVOM/VT optical upper limit
  62. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  63. GRB 251116C: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  65. GRB 251117A: Fermi GBM Final Localization Correction
  66. GRB 251116D: Glowbug gamma-ray detection
  67. EP251023a: Assy AZT-20 optical observations
  68. EP251023a: UAFO and AbAO optical observations
  69. GRB 251116D: AstroSat CZTI detection
  70. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  71. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  72. GRB 251116C: SVOM/VT optical upper limit
  73. GRB 251025B: further Mondy optical observations
  74. GRB 251111A: Mondy optical upper limit
  75. GRB 251116B: EP-FXT follow-up observation
  76. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  78. GRB 251116B: LCO optical upper limits
  79. GRB 251116C: LCO optical upper limits
  80. SVOM GRB251116C: Global MASTER-Net observations report
  81. GRB 251116C: SVOM detection of a burst
  82. GRB 251116B: SVOM detection of a burst
  83. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  84. GRB 251116A: Fermi GBM Final Real-time Localization
  85. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  86. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  87. GRB 251115A: Tiled Swift observations
  88. GRB 251115A: Fermi-LAT detection
  89. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  90. Fermi GRB 251115A: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  92. GRB 251115A: Fermi GBM Final Real-time Localization
  93. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  94. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  95. GRB 251113A: Glowbug gamma-ray detection
  96. GRB 251113A: AstroSat CZTI detection
  97. GRB 251114B: Fermi GBM Final Real-time Localization
  98. GRB 251112A: Swift-BAT refined analysis
  99. Konus-Wind detection of GRB 251108C
  100. Fermi trigger No 784717756: Global MASTER-Net observations report

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