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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"

58 results found.

  1. sb25061207: Mephisto optical upper limits
  2. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  3. GRB 250515A: 1.6m Mephisto optical detection
  4. EP250511a: Mephisto optical upper limits
  5. GRB 250506A: Mephisto optical upper limits
  6. GRB 250419A: Mephisto Multi-band Optical Detection
  7. EP250421a: Mephisto optical counterpart confirmation
  8. EP250404a: Mephisto multi-band optical detection
  9. GRB 250403A: 1.6m Mephisto multi-band optical detection
  10. GRB 250327B: Kilonova-Catcher Observations
  11. GRB 250329B: CAHA 2.2m telescope optical limit
  12. GRB 250328A: 1.6m Mephisto optical observations
  13. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  14. GRB 250327B: MASTER detection of OT rebrightening
  15. GRB 250327B: 1.6m Mephisto optical observations
  16. EP250308a: 1.6m Mephisto optical upper limits
  17. GRB 250226A: GRANDMA Optical Observations
  18. GRB 250226A: Fermi GBM Observation
  19. EP250226a/GRB 250226A: 1.6m Mephisto observations
  20. EP250223a: 1.6m Mephisto and 50cm array observations
  21. GRB 250221A: 1.6m Mephisto optical detection
  22. EP250220a: 1.6m Mephisto observations
  23. GRB 250219A: 1.6m Mephisto optical upper limits
  24. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  25. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  26. GRB 250109A / EP250109a: Mephisto optical upper limits
  27. EP250108a: Mephisto detection
  28. GRB 250103A: 1.6m Mephisto optical observations
  29. GRB 241228B: Fermi-LAT detection
  30. GRB 250101A: 1.6m Mephisto multi-band optical followup
  31. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  32. EP241217a: 1.6m Mephisto multi-band optical observations
  33. GRB 241217a/EP241217B: 1.6m Mephisto optical upper limits
  34. EP241201a: 1.6m Mephisto Optical Upper Limits
  35. EP241126a: 1.6m Mephisto Optical Upper Limits
  36. EP trigger ID 01709122294: 1.6m Mephisto multi-band optical observations
  37. GRB 241112B: Mephisto further optical observations
  38. GRB 241115A: Mephisto upper limits
  39. GRB 241113B: Mephisto upper limits
  40. GRB 241113A: 1.6m Mephisto and 50cm array optical upper limits
  41. GRB 241112B: Optical afterglow detection confirmation in revisiting the Mephisto data
  42. GRB 241112B: Mephisto optical upper limits
  43. EP241021a: Optical rebrightening observations with Mephisto
  44. GRB 241030A: Multiband optical detection with Mephisto
  45. GRB 241029A: GOTO optical afterglow detection
  46. GRB 241029A: Mephisto observations
  47. GRB 241018A/sb24101802: Mephisto optical upper limit
  48. GRB 241017A/sb24101702: Mephisto optical upper limit
  49. EP240913a/GRB 240913C: 1.6m Mephisto observations
  50. EP240918a: 1.6m Mephisto multi-band Optical Upper Limit
  51. GRB 240828B: Mephisto optical upper limit
  52. GRB 240825A: MASTER optical counterpart observation
  53. GRB 240825A: 1.6m Mephisto multi-band detection
  54. GRB 240811A: Upper limits with Mephisto
  55. GRB 240805B: Optical detection with 1.6m Mephisto
  56. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  57. GRB231111A: MDM 2.4m Hiltner Telescope Observation
  58. GRB231111A: Optical follow-up observations with Mephisto

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