20 research outputs found
Concerning the Verity of the MMRD Relation for Novae
It has long been claimed that novae reaching the highest luminosity at the
peak of their eruptions appear to fade the fastest from maximum light. The
relationship between peak brightness and fade rate is known as the
Maximum-Magnitude, Rate-of-Decline (MMRD) relation. Lightcurve parameters for
the most recent sample of M31 recurrent novae are presented and used to
buttress the case that the observed MMRD relation can be explained as a
consequence of observational selection effects coupled with expectations from
standard nova models.Comment: 5 pages; 1 figure; 1 table (figure data); abbreviated version
accepted for publication in Research Notes of the AA
Do the Outburst Properties of M31N 2008-12a Depend on the Time Since the Previous Eruption?
Photometric observations spanning the UV to the near IR during the nine most
recent eruptions (2014-2022) of the extragalactic nova M31N 2008-12a are
presented and analyzed in order to explore whether the lightcurve properties
for a given eruption, specifically the peak magnitudes and fade rates, are
correlated with the time interval since the previous eruption. No significant
correlation between the pre-eruption interval and the rate of decline was
found, however it appears that the brightness at the peak of an outburst may be
positively correlated with the time interval since the previous eruption.Comment: 5 pages, 1 figure, 1 table (data behind the figure); accepted for
publication in Research Notes of the AA
(3200) Phaethon: Bulk density from Yarkovsky drift detection
The recent close approach of the NEA (3200) Phaethon offered a rare
opportunity to obtain high-quality observational data. We used the newly
obtained optical light curves to improve the spin and shape model of Phaethon
and to determine its surface physical properties derived by thermophysical
modeling. We also used the available astrometric observations of Phaethon,
including those obtained by the Arecibo radar and the Gaia spacecraft, to
constrain the secular drift of the orbital semimajor axis. This constraint
allowed us to estimate the bulk density by assuming that the drift is dominated
by the Yarkovsky effect. We used the convex inversion model to derive the 3D
shape model of Phaethon, and a detailed numerical approach for an accurate
analysis of the Yarkovsky effect. We obtained a unique solution for Phaethon's
pole orientation at ecliptic longitude and latitude
(uncertainty of ), and confirm the previously reported
thermophysical properties ( km, SI). Phaethon
has a top-like shape with possible north-south asymmetry. The characteristic
size of the regolith grains is 1-2 cm. The orbit analysis reveals a secular
drift of the semimajor axis of au Myr. With
the derived volume-equivalent size of 5.1~km, the bulk density is
g cm. If the size is slightly larger km, as
suggested by radar data, would decrease to g cm. We
further investigated the suggestion that Phaethon may be in a cluster with
asteroids (155140) 2005 UD and (225416) 1999 YC that was formed by rotational
fission of a critically spinning parent body. Phaethon's is consistent
with typical values for large ( km) C-complex asteroids and supports its
association with asteroid (2) Pallas. These findings render a cometary origin
unlikely for Phaethon.Comment: Accepted for publication in A&
M31N 2013-10c: A Newly Identified Recurrent Nova in M31
The nova M31N 2023-11f (2023yoa) has been recently identified as the second
eruption of a previously recognized nova, M31N 2013-10c, establishing the
latter object as the 21st recurrent nova system thus far identified in M31.
Here we present well sampled -band lightcurves of both the 2013 and 2023
eruptions of this system. The photometric evolution of each eruption was quite
similar as expected for the same progenitor system. The 2013 and 2023 eruptions
each reached peak magnitudes just brighter than , with fits to the
declining branches of the eruptions yielding times to decline by two magnitudes
of and days, respectively. M31N 2013-10c
has an absolute magnitude at peak, , making it the most
luminous known recurrent nova in M31.Comment: 4 pages, 1 figure, 1 table; Accepted for publication in RNAA
The January 2015 outburst of a red nova in M31
M31N 2015-01a (or M31LRN 2015) is a red nova that erupted in January 2015 --
the first event of this kind observed in M31 since 1988. Very few similar
events have been confirmed as of 2015. Most of them are considered to be
products of stellar mergers. Results of an extensive optical monitoring of the
transient in the period January-March 2015 are presented. Eight optical
telescopes were used for imaging. Spectra were obtained on BTA, GTC and the
Rozhen 2m telescope. We present a highly accurate 70 d lightcurve and
astrometry with a 0.05" uncertainty. The color indices reached a minimum 2-3 d
before peak brightness and rapidly increased afterwards. The spectral type
changed from F5I to F0I in 6 d before the maximum and then to K3I in the next
30 d. The luminosity of the transient was estimated to
during the optical maximum. Both the
photometric and the spectroscopic results confirm that the object is a red
nova, similar to V838 Monocerotis.Comment: 5 pages, 4 figures, 4 tables, accepted for publication in Astronomy
and Astrophysics as a Letter to the Editor; page 5 is online material onl
Spin vector and shape of (6070) Rheinland and their implications
Main belt asteroids (6070) Rheinland and (54827) 2001NQ8 belong to a small
population of couples of bodies which reside on very similar heliocentric
orbits. Vokrouhlicky & Nesvorny (2008, AJ 136, 280) promoted a term "asteroid
pairs", pointing out their common origin within the past tens to hundreds of
ky. Previous attempts to reconstruct the initial configuration of Rheinland and
2001NQ8 at the time of their separation have led to the prediction that
Rheinland's rotation should be retrograde. Here we report extensive photometric
observations of this asteroid and use the lightcurve inversion technique to
directly determine its rotation state and shape. We confirm the retrograde
sense of rotation of Rheinland, with obliquity value constrained to be >= 140
deg. The ecliptic longitude of the pole position is not well constrained as
yet. The asymmetric behavior of Rheinland's lightcurve reflects a sharp,
near-planar edge in our convex shape representation of this asteroid. Our
calibrated observations in the red filter also allow us to determine and values of the H-G system. With the
characteristic color index for the S-type asteroids, we
thus obtain for the absolute magnitude of (6070) Rheinland.
This a significantly larger value than previously obtained from analysis of the
astrometric survey observations. We next use the obliquity constraint for
Rheinland to eliminate some degree of uncertainty in the past propagation of
its orbit. This is because the sign of the past secular change of its semimajor
axis due to the Yarkovsky effect is now constrained. Determination of the
rotation state of the secondary component, asteroid (54827) 2001NQ8, is the key
element in further constraining the age of the pair and its formation process.Comment: Published in AJ, 28 pages, 4 figures, 2 table
Photometry of the Didymos System across the DART Impact Apparition
On 2022 September 26, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes. Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite’s orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from 2022 July to 2023 February. We focus here on decomposable lightcurves, i.e., those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the postimpact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ∼1 day after impact and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days postimpact. This bulk photometric behavior was not well represented by an HG photometric model. An HG 1 G 2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least 2023 March. Its persistence implied ongoing escape of ejecta from the system many months after DART impact