Date and Time of the Query: 2019-06-20 T10:28:47 PDT
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Notes for object SN 1999dn

2 note(s) found in NED.

1. 2003PASP..115....1V
Re:SN 1999dn
3.5. SN 1999dn in NGC 7714
SN 1999dn was discovered by Qiu et al. (1999) as part of the BAO
SN Search. It was classified as an SN Ic by Ayani et al. (1999) and
Turatto et al. (1999). Pastorello et al. (1999) describe the strong
resemblance of SN 1999dn to SNe 1997X, 1994I, and 1996aq around maximum
brightness, with He I lines detected; they argue that it should be
considered as an SN Ib/c. Deng et al. (2000) and Matheson et al. (2001a)
further refine the classification to Type Ib; Branch et al. (2002)
consider it the currently best-observed, "fiducial" SN Ib.
Deng et al. (2000) also find strong evidence for both H{alpha} and
C II {lambda}6580. They conclude that the low-mass H skin above the
He layer in SN 1999dn makes this event a possible link between
SNe Ib and IIb, such as SN 1993J (e.g., Filippenko, Matheson, & Ho
1993). From a KAIT image we measure the SN position as
{alpha} = 23h36m14.81, {delta} = +02deg09'08.4, with uncertainty +/-0.5".
SN 1999dn is potentially one of the more interesting objects in
this study, since we can attempt to detect the faint SN in one of our
own HST Snapshot images (GO-8602; see Li et al. 2002, which does not
include SN 1999dn in the analysis) and compare this with the pre-SN
archive image. We obtained a 700 s F814W image (cosmic-ray split pair)
on 2001 January 24 and 700 s splits each in F555W and F814W on
2001 July 10. However, this turned out to be one of the most difficult
sets of HST images for which to establish an astrometric grid, because
of the lack of stars in common between these images and 2MASS
detections (unfortunately, we did not observe the host galaxy at
Palomar). Nonetheless, we can apply a grid, with +/-0.4" uncertainty,
and locate the SN on the PC chip for the first pair of F814W exposures
from 2001 January, with total uncertainty +/-0.6". The SN is most
likely the faint object just east of the error circle center in
Figure 6 (we have applied the routine qzap, written by M. Dickinson,
to the image in the figure to remove residual cosmic-ray hits; the
object to the south is seen at about the same brightness in the
second F814W image pair from 2001 July). The SN had
m_F814W_ = 24.18 +/- 0.18 mag. It is undetected in either band of
the second set of Snapshot images, to V >~ 26.2, V-I <~ 2.0 mag.
(Two 300 s F300W images were also obtained by GO-9124 on
2001 August 3, but the SN had most likely faded well below detection
in these images, so we do not further consider them.)
The site is also in a single 500 s F606W exposure obtained by
GO-5479 on 1996 May 15 and in four F380W images (total exposure time
1800 s) obtained by GO-6672 on 1998 August 29. We show in Figure 7
the SN site in the F606W image (on the PC chip; again, we have applied
qzap to make the image more cosmetically appealing in the figure).
Nothing is detected at the SN site to m_F606W_ >~ 26.0 mag.
Additionally, nothing is detected in the F380W image to
m_F380W_ >~ 24.7 mag. For a distance of about 43 Mpc and Galactic
A_V_ = 0.17 mag (Turatto et al. [1999] indicate no extinction to
the SN), the corrected magnitude and color correspond to
M_V_^0^ >~ -7.3, (U-V)^0^ <~ 2.5 mag for the progenitor.

2. 2001AJ....121.1648M
Re:SN 1999dn
SN 1999dn. - The BAO Supernova Survey found SN 1999dn on 1999 August 20
at magnitude 16 in NGC 7714 (Qiu et al. 1999c). The recession velocity of
SN 1999dn is 2700 km s^-1^, determined from the narrow (H II region)
H{alpha} emission line. The listed velocity of NGC 7714 is 2799 km s^-1^.
There was confusion about the classification of this SN. While Ayani et al.
(1999) and Turatto et al. (1999) described it as a Type Ic SN, Qiu et al.
(1999b) reported it as a Type Ia SN. The helium lines were visible
(Pastorello et al. 1999), so it was also listed as a Type Ib/c SN. Our
spectra (Fig. 25) unambiguously indicate that it is an SN Ib. This was also
the conclusion of Deng et al. (2000), who used a synthetic-spectrum code to
model SN 1999dn. They also suggest that there is evidence for a weak
hydrogen line, implying that SN 1999dn might have had an extremely low mass
hydrogen envelope.

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